Enquires about Class D Amplifier

Recently, I listened to the Jeff Rowland Class D amplifiers: Capri preamp + Model 102 power amp. The sound is excellent and I love it, but too expensive to me as it is over 35K. For this reason, my idea turns to DIY. But, I do not understand the following notations:
1) UcD 180 ST/AD/HG/HGHXR
2) UcD 400 AD/HG/HGHXR

What do ST, AD, HG, HGHXR mean and the output power at 8 ohms ? Does anyone explain?

At present, I propose to upgrade my amplifier with following goal and objectives:
1) My goal of favour sound is sweet, warm, analytical and deep field effect.
2) Target budget around HK$ 10K either preamp+power amp or integrated amp
3) Target output is 200~300W at 8 ohms for DIY version

I have two choices. First choice is to purchase commercial product with brand name. Second choice is by DIY. Please note my choice:

1) First choice to purchase Cambridge audio 840A integrated amplifier
2) Second choice to do DIY preamp and power amp as below:
=> DIY Preamp (e.g. Audio Note M7, ARC SP-10, or Marantz 7)
=> DIY Power amp. Target class D amplifier is the fever version of UcD 400AD by author la1209 with cost around 6300

Please advise which choice is the best fit to my goal.

I forgot to state my current HiFi system for your consideration:

CD Transport =[1]=> DAC =[2]=> Integrated amp =[3]=> Speaker

HiFi modules:
1) CD Transport:
=> Using Philips SACD DVD player for instead. Still good! No money now. Future upgrade to DIY CD transport of Philips CDPRO 2 from http://www.hifidiy.net
2) DAC:
=> Lite DAC-AM (modified fever version with upgraded audio graded VR, caps, resistors, OPA chip changed from NE5534x4 to AD826x4. Very good at sweet, warm and thick sound. I was satisfied with this DAC.
3) Integraded Amplifier:
=> Using Denon AV amp at 90W/channel at 8 ohms for instead and fix at the Pure CD Direct mode to listen pure music, but feel not professional. Propose to separate AV and HiFi by buying another Hi-end HiFi amplifier to listen music.
4) Speaker:
=> Focus audio FS-688. This is a good speaker with sweet, warm and thick sound.

Interconnect cables:
接線[1] – Digital with RCA at true 75 ohms.
=> Audioquest VDM-5 solid silver digital cable. No money now, future upgrade to silver XLR at 110 ohms
接線[2] – Analog with RCA
=> Cheap OFC cable. No money now,  future upgrade to silver XLR.
接線[3] – Analog fork to fork。
=> Cheap OFC cable. No money now,  future upgrade to hi-end OCC speaker cable. Inside speaker, using Zu Ibis jumpers.

My target is to use full balanced interconnects (XLR) from CD tranport to amplifier in the future.

What do ST, AD, HG, HGHXR mean and the output power at 8 ohms ? Does anyone explain?

KK Ans:
ST = standard opamp at buffer stage
AD = Analog device op-amp at buffer stage
HG = New series of UCD400
HGHXR = New series with seperated preamp regulator.


1) First choice to purchase Cambridge audio 840A integrated amplifier
2) Second choice to do DIY preamp and power amp as below:
=> DIY Preamp (e.g. Audio Note M7, ARC SP-10, or Marantz 7)
=> DIY Power amp. Target class D amplifier is the fever version of UcD 400AD by author la1209 with cost around 6300

KK Ans:
DIY AN-M7 + UCD 400.
If your DIY skill is a very very begineer, you can choose SP-10, it is PCB based. Simple soldering it and complete easily.

KK.Ho

1) CD Transport:
=> Using Philips SACD DVD player for instead. Still good! No money now. Future upgrade to DIY CD transport of Philips CDPRO 2 from http://www.hifidiy.net

KK Ans:
Don't expected too much performace for CD-PRO2 if you are using default components. The SAA7324 is not a best components. As I describe it in CD class.


2) DAC:
=> Lite DAC-AM (modified fever version with upgraded audio graded VR, caps, resistors, OPA chip changed from NE5534x4 to AD826x4. Very good at sweet, warm and thick sound. I was satisfied with this DAC.

KK Ans:
TDA1543 is not for HiFi use, it is design and suit for NICAM decode purpose (for it beginning idea).

We have TDA1541A and Hi-bit DAC such as TI PCM1798. Also with most popular DAC. (cannot say too much as because commerical issue)


3) Integraded Amplifier:
=> Using Denon AV amp at 90W/channel at 8 ohms for instead and fix at the Pure CD Direct mode to listen pure music, but feel not professional. Propose to separate AV and HiFi by buying another Hi-end HiFi amplifier to listen music.

4) Speaker:
=> Focus audio FS-688. This is a good speaker with sweet, warm and thick sound.


KK Ans:
For 3 and 4:
CD Transport --> DAC --> Preamp --> Electronic crossover --> 2 X power amp --> High driver and Low driver.

Perfect. We have this setup at early MARCH.

Interconnect cables:
接線[1] – Digital with RCA at true 75 ohms.
=> Audioquest VDM-5 solid silver digital cable. No money now, future upgrade to silver XLR at 110 ohms

接線[2] – Analog with RCA
=> Cheap OFC cable. No money now,  future upgrade to silver XLR.

接線[3] – Analog fork to fork。
=> Cheap OFC cable. No money now,  future upgrade to hi-end OCC speaker cable. Inside speaker, using Zu Ibis jumpers.

If you are using full balance, you should all system should be full balance, there are some fake balance out CD player in the market.

KK.HO

First of all, thank you for KK Ho sir’s advices. I have more points to clarify:

1) I think that I shall plan to attain some training courses (e.g. UcD power amp, AN-M7 tube preamp, DAC, etc…) organized by HiFi Fever in according to my budget allocation and time available. With electronic background, I think I can handle harder HiFi DIY jobs in your training workshop though I am not an experienced HiFi DIY fever. Do both of your DIY AN-M7 preamp and UcD400 power amp provide true balanced input/output in order to achieve my goal of “full balanced silver interconnect cables from CD transport to amplifier”?
2) In the training course of tube preamp, some models such as AudioNote M7, ARC LS-7, ARC SP-10, Conrad Johnson PV-3, Marantz 7, GG, 禾田茂氏, etc.. are introduced. You selected AN-M7 for me. Why? Is AN-M7 is the best suit to my goal of sweet, warm and thick sound quality with listening to vocal, country or Jazz music?
3) For new modules of UcD400 HG or HGHXR, rather than old version of UcD400 AD, which one shall I select? What criteria to guide this selection decision?
4) For my Lite DAC-AM with true balanced input/output, you said that TDA1543 was not for HiFi use. I am quite in doubt , but not challenge you because the Lite DAC-AM DAC chip AD1853 is also used in hi-end Accuphase CD player with cost around $20K~30K. In fact, used this Accuphase CD player to tune for modification. As result, the sound quality is similar or even slightly better than this Accuphase CD player. But, I shall accept to upgrade to a higher graded DIY DAC if available in your workshop, but set to lower priority. No money!
5) For CD transport, I shall set it into the lowest priority to upgrade to DIY Philips CDPRO2 if you said that the improvement would not be much significant in comparing to my current Philips DVD player. But, my concern is that the DVD player has no balance output. Hence, I still need a CD transport with balance output to achieve my goal of full balance interconnect eventually. In fact, a cheap DIY CDROM with balance output is also OK to me if the sound quality is similar to DVD player or Philips CDPRO2.
6) You mentioned a statement that “CD Transport --> DAC --> Preamp --> Electronic crossover --> 2 X power amp --> High driver and Low driver.” Do you mean a Bi-Amp connection, for example with UcD400 power amp to higher driver of speaker and Denon AV amp to lower driver of speaker? Please elaborate more in detail or refer a website which you did early March. If yes, let me to handle the critical issues first.

Again, thank you for your advice!

KK Ans:

1) I think that I shall plan to attain some training courses (e.g. UcD power amp, AN-M7 tube preamp, DAC, etc…) organized by HiFi Fever in according to my budget allocation and time available. With electronic background, I think I can handle harder HiFi DIY jobs in your training workshop though I am not an experienced HiFi DIY fever. Do both of your DIY AN-M7 preamp and UcD400 power amp provide true balanced input/output in order to achieve my goal of “full balanced silver interconnect cables from CD transport to amplifier”?

For the price VS perfomance, I choose AN-M7. But sure you can choice other as you like, we can provide the material and training.
PS : If you need full utlized the UCD balance in, you need balance out preamp. pay attention on preamp, adding a balance driver like DRV136 is not = balance out.



2) In the training course of tube preamp, some models such as AudioNote M7, ARC LS-7, ARC SP-10, Conrad Johnson PV-3, Marantz 7, GG, 禾田茂氏, etc.. are introduced. You selected AN-M7 for me. Why? Is AN-M7 is the best suit to my goal of sweet, warm and thick sound quality with listening to vocal, country or Jazz music?

Same as ANS 1.

3) For new modules of UcD400 HG or HGHXR, rather than old version of UcD400 AD, which one shall I select? What criteria to guide this selection decision?

What is your budget regarding to UCD power amp?

4) For my Lite DAC-AM with true balanced input/output, you said that TDA1543 was not for HiFi use. I am quite in doubt , but not challenge you because the Lite DAC-AM DAC chip AD1853 is also used in hi-end Accuphase CD player with cost around $20K~30K. In fact, used this Accuphase CD player to tune for modification. As result, the sound quality is similar or even slightly better than this Accuphase CD player. But, I shall accept to upgrade to a higher graded DIY DAC if available in your workshop, but set to lower priority. No money!

Sorry, I don't know AM model is AD1853.
You can use AD1855 to upgrade AD1853. Or adding a sampling rate converter inside the box (not outside). Hififever can provide this.
And upgrade it by another DIR IC.


5) For CD transport, I shall set it into the lowest priority to upgrade to DIY Philips CDPRO2 if you said that the improvement would not be much significant in comparing to my current Philips DVD player. But, my concern is that the DVD player has no balance output. Hence, I still need a CD transport with balance output to achieve my goal of full balance interconnect eventually. In fact, a cheap DIY CDROM with balance output is also OK to me if the sound quality is similar to DVD player or Philips CDPRO2.

the balance output is depend on the DAC, not the loader, also if you talking about AES link (balance digital output), this is anoher story.

6) You mentioned a statement that “CD Transport --> DAC --> Preamp --> Electronic crossover --> 2 X power amp --> High driver and Low driver.” Do you mean a Bi-Amp connection, for example with UcD400 power amp to higher driver of speaker and Denon AV amp to lower driver of speaker? Please elaborate more in detail or refer a website which you did early March. If yes, let me to handle the critical issues first.

It is not a bi-amp, it is a electronic crossover. Traditional crossover is at speaker box inside. For ele crossover which remove the loss in the driver since the speaker box don't equip with any RLC.

KK.HO

Refer to your reply point to point as below:

Point 1) Balanced circuit design in AN-M7 preamp
=> I am not familiar with HiFi circuit design. Hence, I do not fully understand your statement “adding a balance driver like DRV136 is not = balance out” in AN-M7 preamp.” May discuss in detail later if I attain the training course. But, I want to know in advance that can AN-M7 preamp provide true balance input/output? Otherwise, need to change.  
=> My requirements of DIY preamp and power amp are that they require one pair each of balanced (XLR) and unbalanced (RCA) of input/output at the rear panel for connection.

Point 2)Selection of preamp
=> Noted.

Point 3) UcD400 Class D module
=> My budget around HK$ 10K~15K totally for preamp + power amp, but can slightly raise which depends on the price vs performance change.
=> For UcD400 power amp, does it requires 2 pcs (left and right) per amp?

Point 4) DAC
=> Noted.

Point 5) CD transport
=> Yes, I am talking about the digital audio connection from CD transport to DAC using XLR connector as per AES/EBU standard at 110 ohm.
=> What is your story?

Point 6) An external electronic crossover
=> I understand! You are talking adding an external electronic crossover between preamp and power amp in an active HiFi system rather than that of a built-in internal crossover inside speaker in a passive HiFi system. Since loudspeaker drivers (internal crossover) are incapable of covering the entire audio spectrum with acceptable loudness and lack of distortion by themselves, an external N-way electronic crossover acts as a filter which can clearly cut the spectrum in into N-passes without any mixing.
=> For 2-way electronic crossover, it requires two mono block UcD400 power amp. Does it require a new DIY 2-way speaker without driver inside? Can we keep my original Focus Audio FS-688 without any change (i.e. remove driver) by using this system?

B. regards,

Dear KK Ho sir,

In additional to the Point #1, I would like to elaborate my concept of “a true balanced stereo HiFi system” to you for review. If something wrong in my concept, please feel free to correct me.
In my concept of HiFi system, every part from source to load in the system is equally important and related to each other with different extent which affects the sound quality. In my goal, I adopt a “Balanced approach” to link each other because a balanced approach will always give you the best sound for the money. Balanced audio technology has been a standard in professional and high-end home audio systems for decades. The advantages are noise and distortion elimination in which the HiFi system can achieve better signal-to-noise performance, greater dynamic contrast, and significantly higher resolution.

In theory of “Balanced signal transmission”, the four signal lines (left - positive and negative) and (right - positive and negative) from source to load must be completely separated and mirror symmetrical such the noise and distortion immunity can be counter eliminated. Please note: (for input voltage “v” and noise “n”)

Left audio channel (+): v (input)  [load]  v+n (output)
Left audio channel (-): -v (input)  [load]  -v+n (output)
Right audio channel (+): v (input)  [load]  v+n (output)
Right audio channel (-): -v (input)  [load]  -v+n (output)

In receiving end (either left or right channel), subtract positive signal to negative signal, we have 2v which can accurately receive the input signal without noise and distortion immunity.

In a stereo HiFi system from source to load, it consists of two parts:
1) Connection cables such as balanced (XLR) and unbalanced (RCA, BNC) cables,
=> In balanced signal transmission in cabling, it uses a 3-pins wiring in which two signals are identical in ever respect with the exception that they are opposite in polarity (+/-). These signals are known by such names as ``inverting and non-inverting'' or ``Live and Return'' - the ``L'' and ``R'' in XLR (the X is for eXternal - the ground).

2) Individual electronic units such and CD transport, DAC, preamp, power amp, etc…

=> In balanced electronic units, it requires to use a balanced circuitry. It sounds simple, but in fact very different in circuit design.
=> Adding a balance driver for output does not mean “completely balanced” if the circuitry in the front is not designed in mirror symmetrical to achieve noise and distortion elimination. This is why KK Ho said “adding a balance driver like DRV136 is not = balance out”. KK Ho, is my interpretation correct?
=> If you want to know whether the circuitry is true balanced or not, by observation, you can see at least 4 OPA chips individually in the circuitry to handle the 4 signals separately. But, it does not 100% guarantee true. Formally, should be tested by complex test equipment, but out of our scope.   

Please comment!

Alant,

Please me reply for your post balance signal.

1. If the source to power amp (include CD as source) that from pure balance output. That Ok, not problem.

2. If any source are un-balance out, and using the fake method to do the un-balance out, this is the another story.
See the attached photo.

Some DIY web use release this KIT to cheat people as "balance" out.

What do you think ?

KK.HO

Alant,

Let change back the topic with REAL Balance out.
Use DAC as example.


You will see the DAC have I+ and I-, it is easily to config as balance output.

From the diagram, what do you think ?



ADVERTISEMENTS:

We will have PCM1798 DAC, people can choose either to TDA1541A or PCM1798.

Please check with our web later.

KK.HO

Reply to KK Ho,

Again, I am telling you the truth that I am not an experienced HiFi fever. My electronic background is at computer technology in different industries, but not related to sound (i.e. HiFi industry) Hence, I am not familiar with HiFi circuit design. But, I can understand advanced HiFi technology as supported my knowledge with a Master degree in computer engineering from the University of Hong Kong. I love to listen music, thus hope to own a high quality sound reproduction machine (i.e. Hi-end stereo HiFi system). But, commercial products with branding are too expensive. Hope that DIY can provide these items to me with similar sound quality at the lowest cost.

Return to the schematic diagram provided, my idea is that:
1) The circuit of TI audio driver DRV134/DRV135 is not a “balanced signal transmission circuit” design
2) The circuit of DAC PCM1798 is a “balanced signal transmission circuit” design

Remark: 唔好考我吟多HiFi的知識，我不是很有料！

Yes, correctly.

The rule is:
If any one is not the balance I/O (except), this is meaningless.

Execpt the case for DIO in DAC.
KK.

Totally agreed! If the circuit at the heart of electronic device is not designed for "balanced signal transmission", then adding a balance driver with XLR jack at I/O is meaningless.

alant,

One example share to you. It is from a well know brand.

Don't ask me for the model.

Fig 1. DAC output, you will found that it is differential output config.

Fig 2. Differential mode I/V converter + Mixer amp + GIC filter x 2 + output buffer.

Fig 3. Un-balance signal passing to "differential amp" to as a "Balance Out"

Give a question to you, do you know what is the idea from the designer?

If you answer correctly, buy a lunch to you. say < $50 type.

KK.HO

Dear KK Ho,

I am basically not sure designer’s thinking. I just guess as below:

1) Figure 1, from the DAC output, the 4 signal lines (left – positive and negative and right positive and negative) is differentially out and can be separately handled for balanced signal transmission.
2) Figure 2, the designer do not proceed balanced signal circuit design, but mix the positive and negative signals of each left and right channel for amplification, thus the output is unbalanced.
3) Figure 3, the designer again converted this pair unbalanced signal into a pair of balanced signal via driver with XLR jack at I/O, may be due to product requirement from marketing point of view.

Why did the designer do so? I guess that some designers misunderstand the concept of “true balanced signal transmission”. They think that balanced signal transmission refers to cabling only and most of loss comes from long distance cabling. If both sending and receiving end of electronic devices provide balanced driver with XLR jack, then connecting them together by a balanced XLR cable can eliminate the noise and distortion immunity significantly. Referring to the necessity of balanced signal circuit design at the heart of an electronic device, different designers have different viewpoints. Since balanced signal circuit requires double quantity of electronic components at some portion as well as double the material cost, some companies refuse this idea because it will increase the price of product such that decrease the market competition.

However, my idea in DIY, we aims at using the best audio material, but achieve lower cost to the market price of corresponding branding product (i.e. no advertisement cost in DIY) and achieve similar sound quality or even better than this branding product.      

Today, some top models in hi-end HiFi system such as Mark Levinson, Jeff Rowland, etc… use true balanced signal circuit design to their products. In fact, the sound quality is superior to other, but the price is also surprisingly higher too. Ordinary people are difficult to afford it. However, essay in research and development about true balanced signal circuit is not sufficient in oversea journals, or just one to two statements only. (May be, they do not want to disclose) Thus, most people do not fully understand it. In China, it is also not popular. However, I search the WWW website, I find a pioneer supplier from China ( http://www.audio-gd.com/word.htm ) with some journals talking about it. Very good! The price of its completed product is averagely higher than that in China, understandably due to double material cost used in balanced signal circuit design. But, its DIY kit, say C30/C30i true balanced preamp, is just around RMB 1990. Price is reasonable. But, I am not sure the sound character and whether it can fit into your true balance class D power amp. Will you have a review in it and comment to me?  
   
Finally, I have just had my lunch. No matter whether my answer is correct or not. No free lunch is needed. Thank you. My purpose is just to share experience.

B. regards,

It is a strange phenomenon that some music hobbyists prefer audio amplifier in two opposite extremes. One extreme is that some music hobbyists like to look backward to the past technology. These hobbyists are normally tube amplifier lovers and like very old tube amplifier circuit such and Marantz 7 and etc. Another extreme is that some music hobbyists like to look forwards to new technology. These hobbyists are normally solid state amplifier lovers and like to apply new solid state technology in the amplifier circuit such as Jeff Rowland and etc.
Similar to Albert Einstein’s theory of Relativity, there is no absolutely good or bad to the sound character and quality of any audio amplifier, the adjustment is relative to audience preference. For this reason, both of extreme hobbyists, tube amplifier lovers and solid state amplifier lovers go to their road correctly as relative to their sound preference.
As a music hobbyist of mine, I am the second extreme and love to audio amplifier with new technology applied. Would like to introduce the following new information of DIY amplifier using balanced technology:

Preamplifer
1) RelaiXed balanced preamplifier (Ref: http://www.eijndhoven.net/jos/relaixed/index.html )

=> co-designed by Jos van Eijndhoven and Sander Sassen   
=> first published in the Dutch Elektor Audio Special 2 of December 2007  
=> This design employs a new generation of high-end audio opamps National Semiconductor LM4562 to buffer the output signal and add some amplification

Power amplifier
2) ExtremA “Class A” power amplifier (Ref: http://www.hardwareanalysis.com/content/article/1842/extrema-reference-class-a-diy-amplifier/ )

=> designed by Bruno Putzeys and followed up by Sander Sassen
=> Bruno explained that this DIY amplifier was originally used as a demo amplifier to teach Master degree class in university about linear amplifier design (small-signal and power).
=> New “Class A” technology using 2 pairs of transistor Sanken 2SC2922/2SA1216 in a bridged configuration with a maximum dissipation of about 60W per transistor, for an output power of 100W/8-ohm.

3) UcD “Class D” power amplifier (Ref: http://www.hypex.nl )
=> designed by Bruno Putzeys as a commercial module in Hyper Electronics B.V.
=> New “Class D” technology

All these persons, Bruno Putzeys, Jos van Eijndhoven and Sander Sassen are friends in Netherland. Both Bruno and Jos are with past working experience in Philips. Bruno is the designer of both ExtremA and UcD and he now holds the position of the R&D chief engineer in Hyper. I have directly contacted Bruno to ask the difference between ExtremA and UcD. Listed bellows are our emails for your reference.  

Lastly, I have a question if any experienced DIY hobbyist can answer. Please review the circuit design of ExtremA. This question is that what is the difference in circuit concept design between new technology ExtremA “Class A” power amplifier and traditional “Class A” power amplifier?

Welcome if anyone can explain it to me!

B. regards,
alant

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Reference Email
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----- Original Message -----
From: Alan
To: Bruno Putzeys
Sent: Monday, March 17, 2008 9:07 PM
Subject: Enquiry about power amplifier using either UcD or ExtremA module

Dear Bruno,

Thank you for your reply.

As a music hobbyist of mine, listed as belows are my understanding and difference between UcD and ExtremA. Please correct me if my understanding is incorrect:

1) Thank you for refreshing me the concept of balanced amplifier. With electronic background, I can fully understand it. Your email and the attachment  http://jensentransformers.com/an/an003.pdf are very helpful. I love "balanced" amplifier due to low noise distortion which gives a clear and deep contrast background sound.
2) Both UcD and ExtremA can be constructed with balanced signal circuit design and meet my goal of music.
3) Regarding the size (mechanical dimension) of power amplifier, UcD will be small and compact. ExtremA will be larger, but may be smaller than traditional Class A power amplifier. What are the dimension of two PCBs (amplifer and power supply) of ExtremA? Seeing the photo is diffficult to justify!
4) Regarding the cost, ExtremA suits for DIY purpose and the cost of a set bare PCB (one amplifer PCB and one PSU PCB) is only 150 euros. Are the components sourced easily worldwide? UcD is a commercial module and no bare PCB is sold. In comparison, UcD will be more expensive than ExtremA.
5) UcD provides higher power output than ExtremA. (i.e. more than 100W/8ohm)

It is perfectly to own both amplifiers, but I have basic idea if need to choose from one of them. As you are the designer of both, but from two different business areas. May be, not convenient to advise decision for me. Again, thank you for your reply.


B. regards,
Alan

----- Original Message -----
From: Bruno Putzeys
To: Alan
Sent: Monday, March 17, 2008 4:45 PM
Subject: Re: Enquiry about power amplifier using either UcD or ExtremA module

Hi,

I should start off by a shocking little bit of fact: I've not yet heard the Extrema. I designed the circuit, Sander did the board and made the proto. I debugged that and then Sander made a stereo pair. Before I got the chance of hearing that, though, he managed to sell it before I could try it. I've got a set of boards and parts but no time to put them together. As far as the sound of UcD goes, I try to make it as neutral as possible. My musical tastes align well with yours and so far my UcD based amps serve them well.

There is no fundamental technical reason for building a "balanced" power amp. What matters is balanced signalling between the preamp and the amp (and between the CD player and the preamp etc etc). Keep in mind the difference between symmetrical and balanced. Symmetrical means that the two lines carry a voltage that's symmetrical around ground. Now the whole thing about balanced signalling is to make the connection insensitive to the ground potential, so whether a signal happens to be symmetrical around ground or not should not make a difference. A signal might be symmetrical around ground at one end of the cable, and no longer at the other end due to a ground loop. So symmetry does not define a balanced connection. What does is to have balanced output impedances on the drive end and balanced input impedance at the receive end, and to have a differential input. You can make a perfectly balanced connection using a single-ended driver. See http://jensentransformers.com/an/an003.pdf for more.
This is even more so when driving a speaker. A speaker is entirely floating, so it cannot see the difference between a symmetrical voltage and an asymmetrical one, simply because it only sees the voltage differential between the two terminals. Whether one of its two terminals happens to be at the power amplifier's ground potential is none of the speaker's problems. For a power amplifier, what matters is that it has a differential input and good CMRR.

The reason Extrema is built as a H-bridge was that prior to publishing this circuit I gave a masterclass about linear amplifier design (small-signal and power) and I wanted a vehicle to demonstrate as many of the presented techniques as possible in one go. ExtremA does that very well, but otherwise it is not an elegant design. It would look very different if I had another go at it. It would also have *vastly* lower distortion - the folded cascode arrangement was one of my less intelligent moves.

UcD modules have differential inputs and good CMRR. Using two amplifiers with the load tied between them only makes sense if you need more voltage headroom. There is not going to be any advantage as audio performance goes. By performance I mean both the test bench result and the subjective, musical, outcome. The interconnections should be balanced, but that does not imply the circuit arrangement should be symmetrical. That would only be necessary if building a symmetrical circuit also makes the signal path shorter. As a result, all my converter and preamp designs are symmetrical, but the UcD amps are not. Doubling the UcD circuit does not make the signal path shorter.

The cost estimate of 500 euros is an estimate for the amount the entire project will set you back. The boards sell for 150 euros (for a set of one amplifier board and one PSU board). Incidentally, that is the same as it would cost to have them made to order at the usual PCB shops. Sander has simply ordered a stack of them, using the volume discount to pay back the time and effort his side of the project has cost him (I haven't figured out yet how to get my bit back).

The ExtremA is not cooler than any other class A amp. The circuit board is compact, but the heat sink is not. The PCB bolts onto the heat sink, making for a fairly snug arrangement but it's by no means small or cool.

Cheers,

Bruno
----- Original Message -----
From: Alan
To: bruno@hypex.nl
Sent: Monday, March 17, 2008 7:38 AM
Subject: Re: Enquiry about power amplifier using either UcD or ExtremA module
Missing a word highlighted in RED.
----- Original Message -----
From: Alan
To: bruno@hypex.nl
Sent: Monday, March 17, 2008 2:35 PM
Subject: Enquiry about power amplifier using either UcD or ExtremA module

Dear Bruno Putzeys,

I am a music lover and like to make DIY audio equipment to meet my individual taste because commercial product such as Jeff Rowland is good, but too expensive to me. Recently, I want to make a "balanced" solid state power amplifier for me and have the following two choices:

1) Class D UcD amplifier module
2) Class A ExtremA amplifier module

I have the following enquiries and please clarify my understanding:
1) If goal of my favourable sound quality is clear, sweet, warm and like to listen vocal, country and Jazz. Which of these two choices best suit to this goal?
2)  I have basic knowledge about UcD, but no idea about ExtremA. In order to construct a balanced power amplifier using UcD, it requires to buy a pair of UcD such as UcD180 HGHxR, UcD supply HG, transfomer, socket, On/OFF switch and wiring. Am I correct?  
3) In order to construct a balanced power amplifier using ExtremA, it requires a buy a pair of two PCBs (one for amplifier PCB with heat sink and output transistor, and another for power supply PCB), transformer, socket, On/OFF switch and wiring. Am I correct?
4) From "hardwareanalysis", the total cost of a single ExtremA amplifier PCB, including transformers and heatsink will be around 500-euros. Does it include output transistor and another power supply PCB? If not, please advise total cost as it is copyright and I cannot buy from other supplier.
4) In output power limitation, the maximum output power for ExtremA is 100W/8ohm, but UcD have more than 100W. Am I correct?
5) In traditional Class A 100W power amplifier, the size is big and internal is hot. BUt, ExtremA seems to be small. What is the difference between traditional and new technology ExtremA?
6) Any other advantages or/and limitations for both UcD and ExtremA module?

Thank you your attention in advance!


B. regards,
Alan

I comment that both RelaiXed pre-amplifier and UcD power amplifier are design of product innovation. (i.e. audio relay attenuator, digital microcontroller control technology, power electronics, etc...) Since I just use my hobby leisure time to do it, the original schedule was postponed. I plan that I shall complete these two audio DIY projects later.
In order to present a better understanding for the design of RelaiXed pre-amplifier, I sketched a block diagram of RelaiXed pre-amplifier as attached. After discussion with the designer, Jos van Eijndhoven by email, he commented that my sketch was correct. Listed as belows are the emails about technical discussion between Jos van Eijndhoven and me for your reference.

Those audio DIYers who think RelaiXed pre-amplifier interesting can contact Jos van Eijndhoven directly at http://www.eijndhoven.net/jos/relaixed/index.html .


B. regards,
alant


*************************************************************
              Reference Emails as below
*************************************************************

----- Original Message -----
From: "Jos van Eijndhoven" <jos@vaneijndhoven.net>
To: "Alan" <smtam@ieee.org>
Sent: Friday, April 25, 2008 5:52 AM
Subject: Re: Block Diagram of RelaiXed Balanced Pre-amplifier (Dwg Rev#3)

Hi Alan,

thanks for your kind message.
Indeed, sometimes a post is made regarding the relaiXed, or my earlier passive attenuator, in a newsgroup without that I ever see that. Thanks for linking me to that.  Myself, I am also busy currently with building a Hypex UcD-HG amplifier, but my progress is also limited due to lack of time.....
I have heard the combination with my relaixed already (builtin combination by someone else) and I can say that the result is stunning!
To keep you interested :-)  I attach a small text that someone recently posted in a British DIY forum about the passive attenuator. (The DACT switches are -here in Europe- well-known as the ultimate high-end volume control, and is a manual rotary switch with discrete resistors.)

Greetings,
Jos

--------------------------------------
06-03-08
My point is, this is a very good stepped attenuator indeed, it beats the DACT CT2 by quite some margin, which I've been using for some time (2 years). And its fully remote with 64 steps on the gain and 4 inputs all via little relays which are quite audible. (but its no problem, a faint click is all that one hears)

It takes about 1 hour to build (if you take your time, small tip on the iron) and a doddle to install. (follow the simple instructions) Which I did and left overnight as time was running out last night.........today have had a good listen and well well well, very transparent, as if a thin layer of mist was wiped way.

It drives an AD815 chip pre amp very well

Graham

--------------------------------------
07-03-08
Will post more pics over the weekend............it truly is a very transparent device. Now everthing has warmed up again I'm now getting a much clearer picture of the low level information on the CD's. Very good indeed and for less than the price of a 'handomatic'  DACT CT2.

The 64 steps on the gain is a bit of a wind by hand, 2.5 turns to my listening level. Hav'nt counted how many clicks

Graham

------------------------------------
10-03-08
What stands out other than already stated is the low volume level reproduction pin sharp imageing and no loss of detail........

Graham

----- Original Message -----
On Thu, Apr 24, 2008 at 10:16 AM, Alan <smtam@ieee.org> wrote:

Dear Jos van Eijndhoven,

You are welcome! The motivation is based on my interest to your design which is regarded as an innovative product. Hope that every audio DIYer will enjoy it. I am a music hobbyist located in Hong Kong. I discovered your RelaiXed pre-amplifier over internet. After review, I recommended your design at the discussion forum in "HiFifever" organization at http://www.hififever.com/forum/viewtopic.php?t=1783&sid=7f05ce06c2274e97019231d8caff4f55 . My username in "HiFifever" is "alant". "HiFifever" is the biggest and  reputable DIY organization in Hong Kong and he is the sole agent of UcD  (http://shop.hififever.com/index.php?cPath=41_38) in Hong Kong. My goal is to complete the two audio DIY projects of RelaiXed pre-amplifier and UcD power amplifier on or before mid of year 2009. For UcD power amplifier, I shall join the local DIY training course conducted by HiFifever, but RelaiXed pre-amplifer is really a "Do It Yourself" project. Since I just use my hobby leisure time to do it, I cannot start it immediately due to personal reason. It is now under review and preparation process. If I am ready, I shall contact you to purchase the PCB, pre-programmed microcontroller, etc... later. Thank you for adding my name into your potential customer list, please keep me information updated if any.

Hope that every music hobbyist will enjoy your design!

B. regards,
Alan

----- Original Message -----
From: "Jos van Eijndhoven"
<jos@vaneijndhoven.net>
To: "Alan" <smtam@ieee.org>
Sent: Thursday, April 24, 2008 6:59 AM
Subject: Re: Block Diagram of RelaiXed Balanced Pre-amplifier (Dwg Rev#3)

Dear Alan,
yes, all correct.  I think it has become a really nice and clear picture!

Greetings,
Jos

----- Original Message -----
On Wed, Apr 23, 2008 at 10:55 PM, Alan <smtam@ieee.org> wrote:

Dear Jos van Eijndhoven,

One more point, as just want to say more clearly as below:
1) IR remote control indirectly sends instruction to Front microcontroller (U2D) via Photodiode/IR receiver (U3D), but
2) Rotary switch directly sends instruction to Front microcontroller (U2D) without passing through Photodiode (U3D)  
If need to present more concisely, I revised to drawing "Block_diagram_ver3.vsd" (Version #3) as attached to illustrate the difference between instruction sent from IR remote control and rotary switch to front microcontroller (U2D).


B. regards,
Alan

---- Original Message -----
From: "Alan" <smtam@ieee.org>
To: "Jos van Eijndhoven" <jos@vaneijndhoven.net>
Sent: Thursday, April 24, 2008 1:48 AM
Subject: Re: Block Diagram of RelaiXed Balanced Pre-amplifier (Revised dwg)

Dear Jos van Eijndhoven,

I provide you a second choice of drawing with separation of 2 microcontrollers within the Microprocessor Control Unit (MCU) as per attached file "Block_diagram_ver2.vsd". As per this drawing as below, please note:

The Microprocessor Control Unit (MCU) mainly consists of five electronic components:
1) Two microcontrollers, including Front microcontroller (U2D) and Relay microcontroller (U1D)
2) Two IC arrays (U4D, U5D)
3) One photodiode as IR receiver (U3D)

In modelling the logical processes within MCU, it can provide the following six processes:
1) Instruction is activated by either IR remote control or rotary switch by manual option to Front microcontroller (U2D) via photodiode/IR receiver (U3D)
2) Front microcontroller (U2D) directly handles the operation of LCD display unit (L1D, L2D)
3) Front microcontroller (U2D) directly sends instruction to relay microcontroller (U1D)
4) Relay microcontroller (U1D) indirectly drive command to relay in Volume control unit via IC array (U4D)
5) Relay microcontroller (U1D) indirectly drive command to power relay via IC array (U4D)
6) Relay microcontroller (U1D) indirectly drive command to relay in Input channel selection unit via IC array (U5D)

In the logical flow of above processes: when step #1 is activated, both steps #2 & #3 will be proceeded. Depneding on the result on step #3, only one of three steps #4, #5 & #6 will be performed.
In conclusion, you can choose either previous drawing file "Block_diagram_rev1.vsd" or this drawing file "Block_diagram_ver2.vsd". It is subject to your final decision.

B. regards,
Alan

----- Original Message -----
From: "Jos van Eijndhoven" <jos@vaneijndhoven.net>
To: "Alan" <smtam@ieee.org>
Sent: Wednesday, April 23, 2008 9:53 PM
Subject: Re: Block Diagram of RelaiXed Balanced Pre-amplifier (Revised dwg)

Hi Alan,
nice drawing!!!
yes, it is correct, you properly understood how it works. It is nice to see the separation of the power-lines.
The only missing thing might be matter of taste or chosen abstraction....
The diagram does not show the 2nd microcontroller and its responsibilities. - the 'front' microcontroller handles the switch, the IR, the display, and sends results to: - the 'relay' microcontroller which receives commands from the front, and drives all relays (volume-, channelselect- and power-relays)

Greetings,
Jos

----- Original Message -----
On Wed, Apr 23, 2008 at 7:50 AM, Alan <smtam@ieee.org> wrote:

Dear Jos van Eijdhoven,

Forgot to add a 5Vdc power line supplied to LCD display unit. Revised as attached file "Block_diagram_rev1.vsd".

B. regards,
Alan

----- Original Message -----
From: Alan
To: Jos van Eijndhoven
Sent: Tuesday, April 22, 2008 11:42 PM
Subject: Block Diagram of RelaiXed Balanced Pre-amplifier

Dear Jos van Eijdhoven,

After a preliminarly review of your design, I sketched a block diagram as attached in order to capture my understanding. Hope that you like it too. If any error, feel free to advise me. Besides, I attached the source file "block_diagram_source.vsd" to you which is drawn by Microsoft VISIO software.  You can edit it directly or use for other purpose, such as attach to your user guide if applicable.

B. regards,
Alan

I would like to add some remarks to RelaiXed pre-amplifier as below:

Although RelaiXed pre-amplifier is a solid state amplifier (石機), the design concept of audio volume relay attenuator can be applicable to tube pre-amplifier (胆機) lovers who love the taste of tube sound, but not love to the famous tube pre-amplifier circuit. For this reason, this concept can be re-designed to a tube pre-amplifier. Referring to the diagrams as below, you can change the Part A into a tube based amplification circuit, then it becomes a balanced tube pre-amplifier or just use the audio volume relay attenuator module to do a unbalanced tube pre-amplifier. The Part A includes the audio signal amplification unit with corresponding power supply unit, currently is OPAMP LM4562 and PSU by transformer 7VA, 2x18V.   

Further comments to RelaiXed pre-amplifier as below:

It provides the following advantages:
1) The audio volume relay attenuator provides both functions of input channel selection unit and audio volume control. The application of “relay and resistor” design offers low noise distortion and minimum signal interference when analog audio signal passing through the circuit. The performance of this design is superior to traditional potentiometer which provides the best quality of sound and compatible to hi-end expensive attenuator such as DACT switch.   
2) The selection of OPAMP chip LM4562 is a good choice. Recently, National Semiconductor delivers a pair of OPAMP chips, LM4562 for pre-amplifier and LM4702 for power amplifier. LM4562 is a brand-new dual opamp, which has just become freely available at the beginning of 2007. (Ref: http://www.national.com/pf/LM/LM4562.html or http://www.national.com/news/item/0,1735,1195,00.html ) It is claimed to be a new-generation OPAMP chip with near zero noise distortion rate since THD+N of the chip is only equal to  0.00003%. Besides, audiences can easily change to different OPAMP chips in the IC socket in order to suit their sound preference. Other compatible chips are OPA2134, OPA2604, NE5532, etc...
3) The digital microprocessor circuit, low voltage DC power supply and truly balanced circuit design with left and right analog audio signal completely separated, all these provide very low noise distortion and minimum signal interference.

It provides the following drawbacks:
1) As per Jos’s user guide (page 4), it states that “the clicking of the small relays results in a clear mechanical sound. If you do not want to hear that, you should not build this preamp.” Jos tries minimize it by (a) the attenuator circuitry, and (b) optimized firmware timing in the relay control.
2) In my point of view, this “clicking” sound can be avoidable. You can add an enclosure with sound absorbing material inside to cover the entire area of relay in the PCB circuit as the relays are not heat emission. It is optional and is not critical at this moment. Furthermore, metal chassis with high wall thickness can help to minimize this sound effect.

Lastly, you can see more photos about RelaiXed pre-amplifier in Jos website at http://picasaweb.google.com/jos.van.eijndhoven/BalancedPreAmp .

Hope that every music hobbyists will enjoy this design!


B. regards,
alant

Just drop in.....

Balance input does not mean good sound. I think this is a misconception among a lot of people. If the component of the balance circuit is not of premium grade , it is actually worser than normally RCA input. Basically a balance circuit means both positive signal and negative signal was enlarged. in an ideal world which never exist, this should cancel all the distortion and will have low noise. However, the difference in component made it very difficult to achieve it. I have DIY a balance pre-amp, the transistors need to be matched within 0.2% in order to achieve a good result. matching 0.2% means that you need to buy at least 1000 pcs in order to match within the specification and I have 16 pairs need to be matched.

Please correct me if I am wrong.

[quote:ef0382326e="alant"]Dear KK Ho sir,

In additional to the Point #1, I would like to elaborate my concept of “a true balanced stereo HiFi system” to you for review. If something wrong in my concept, please feel free to correct me.
In my concept of HiFi system, every part from source to load in the system is equally important and related to each other with different extent which affects the sound quality. In my goal, I adopt a “Balanced approach” to link each other because a balanced approach will always give you the best sound for the money. Balanced audio technology has been a standard in professional and high-end home audio systems for decades. The advantages are noise and distortion elimination in which the HiFi system can achieve better signal-to-noise performance, greater dynamic contrast, and significantly higher resolution.

In theory of “Balanced signal transmission”, the four signal lines (left - positive and negative) and (right - positive and negative) from source to load must be completely separated and mirror symmetrical such the noise and distortion immunity can be counter eliminated. Please note: (for input voltage “v” and noise “n”)

Left audio channel (+): v (input)  [load]  v+n (output)
Left audio channel (-): -v (input)  [load]  -v+n (output)
Right audio channel (+): v (input)  [load]  v+n (output)
Right audio channel (-): -v (input)  [load]  -v+n (output)

In receiving end (either left or right channel), subtract positive signal to negative signal, we have 2v which can accurately receive the input signal without noise and distortion immunity.

In a stereo HiFi system from source to load, it consists of two parts:
1) Connection cables such as balanced (XLR) and unbalanced (RCA, BNC) cables,
=> In balanced signal transmission in cabling, it uses a 3-pins wiring in which two signals are identical in ever respect with the exception that they are opposite in polarity (+/-). These signals are known by such names as ``inverting and non-inverting'' or ``Live and Return'' - the ``L'' and ``R'' in XLR (the X is for eXternal - the ground).

2) Individual electronic units such and CD transport, DAC, preamp, power amp, etc…

=> In balanced electronic units, it requires to use a balanced circuitry. It sounds simple, but in fact very different in circuit design.
=> Adding a balance driver for output does not mean “completely balanced” if the circuitry in the front is not designed in mirror symmetrical to achieve noise and distortion elimination. This is why KK Ho said “adding a balance driver like DRV136 is not = balance out”. KK Ho, is my interpretation correct?
=> If you want to know whether the circuitry is true balanced or not, by observation, you can see at least 4 OPA chips individually in the circuitry to handle the 4 signals separately. But, it does not 100% guarantee true. Formally, should be tested by complex test equipment, but out of our scope.   

Please comment![/quote]

There are several concepts involved in your passage. By dividing it into different statements, please note my comments as below:

1) Your statement: “Balance input does not mean good sound.”
Comment: Repeat my philosophy of thinking mentioned previously, similar to Albert Einstein’s theory of Relativity, there is no absolutely good or bad to the sound character and quality of any audio amplifier, the judgment is relative to audience preference. Since balanced and unbalanced signal pair will lead to two different quality of sound, your statement is relatively correct if your sound preference matches to unbalanced signal while it becomes incorrect relatively if your sound preference matches to balanced signal pair. In conclusion, there is no absolutely correct or incorrect to your concept.

2) Your statement: “Basically a balance circuit means both positive signal and negative signal was enlarged.”
Comment: (Ref: Wikipedia at http://en.wikipedia.org/wiki/Balanced_line and Bill Whitlock in Jensen AN-003 at http://jensentransformers.com/an/an003.pdf ). By definition, balance is defined in terms of the impedances of the two signal conductors with respect to a reference, which is usually “ground”. As a result, the output signal will normally be enlarged in corresponding to input signal after signal differentiation in balanced signal pair.

3) Your statement: “this should cancel all the distortion and will have low noise.”
Comment: Yes! In balanced signal pair, signal distortion and noise immunity will be smaller in comparing to unbalanced signal.

4) Your statement: “If the component of the balance circuit is not of premium grade, it is actually worser than normally RCA input.” and “However, the difference in component made it very difficult to achieve it. I have DIY a balance pre-amp, the transistors need to be matched within 0.2% in order to achieve a good result. matching 0.2% means that you need to buy at least 1000 pcs in order to match within the specification and I have 16 pairs need to be matched.”
Comment: I am not sure what your term “premium grade” exactly means since it can be explained in terms of different meanings such as expensive high graded, high quality, etc... I prefer to use the term “material consistency”. Material consistency refers to characteristic of material to achieve same performance of operation. “Tolerance” is one of index to represent the material consistency of a group of similar component. Since balanced signal pair requires double quantity of components running in parallel in comparing to unbalanced signal, the material consistency of components in either positive signal side or negative signal side becomes important. Otherwise, inconsistency of material will lead to drawback at output operation. However, component with high material consistency does not mean expensive high premium grade material. Cheap material can offer high precision of tolerance such as copper conductor, resistor, etc... Take signal cabling for example, the goal of signal transmission in cabling is to minimize signal distortion and noise immunity due to interference. In balanced signal transmission using XLR connection, cheap audio grade OFC copper conductor can achieve this goal well and does not require expensive premium grade conductor material such as silver, gold alloy, etc... It is because cheap copper conductor can provide a good material consistency. Hence, the difference in material used between copper and silver conductor becomes insignificant. In unbalanced signal transmission using RCA connection, it highly depends on the nature of material used. Hence, expensive silver conductor performs highly superior to cheap copper conductor. Same principle applies to electronic components such as resistor, capacitor, etc... In referring to your example of transistor with 0.2% tolerance requirement, I am in doubt since the 0.2% operating voltage tolerance in transistor is a very high precision in which it seems to out of process capability in transistor component manufacturing. If the design requires such high precision tolerance, then it is a poor design. Take Jos RelaiXed pre-amplifier for example, Jos suggests two components for voltage regulator used in position U3P & U4P. One component is TL431CLP (Farnell #1106038) with 2% tolerance in operating voltage and another alternative is an “A” grade component TL431ACLP (Farnell #9593543) with 1% tolerance. Generally, the tolerance is 5~20% for capacitor and 5% for resistor, etc... Hence, 1% tolerance seems to good enough in most components. In conclusion, balanced signal pair emphasizes the importance of material consistency which is normally measured in term of “tolerance”. It does not mean that it requires expensive premium component because cheap material can also offer good material consistency.

In summary, the purpose of this discussion aims at providing a better understanding of balanced signal pair design as its impact to sound quality. It does not mean that you are wrong if you are currently using unbalanced design, and should change to balanced design. Once you understand the difference in sound quality between balanced and unbalanced design, you can make final decision in product selection in referring to your sound preference.  

Lastly, it is more practical to do listening testing when you decide your choice. In Chinese, it states “聽聲後付錢才最實際“. Last week, I had a walk-in to big shopping mall in Langham Place (朗豪坊). I entered to an AV shop called Digital Pavilion (數碼坊) to have a listening test of the newest model of Jeff Rowland. The sales, Mr. Danny Wan is a kind person who perform the sales function with high professionalism. The configuration in listening testing are: Jeff Rowland Power conditioner (Retail price over HK$10K), Jeff Rowland Model Continuum 250 Integrated amplifier (Retail price over HK$50K) and speaker Martin Design model Miles 3 with ceramic speaker driver (Retail price over HK$90K). My comment is that the sound quality is excellent and matches very well to my preference. However, it is too expensive. I prefer to spend a total budget cost below HK$20K to do DIY of RelaiXed pre-amplifier and Hypex UcD-400HG/HXR power amplifier. Furthermore, I prefer to separate into two blocks of pre-amplifier and power amplifier rather than an integrated amplifier because I want to use power amplifier as a common connection between RelaiXed pre-amplifer and Denon AV amplifer because it does not require to change plugs of front (LT/RT) speakers frequently. The Hypex UcD power amplifier offers two pairs of signal input, one balance (XLR) and another unbalance (RCA). The RelaiXed pre-amplifier connects to XLR input of UcD using balance connection while the pre-out of Denon AV amplifier connects to RCA input of UcD using unbalance connection.

Hope that every music hobbyist will enjoy this design!


B. regards,
alant

Audio volume relay attenuator with IR control

Apart from Jos’s audio volume relay attenuator, I find following two China suppliers have similar module:

1) REIZ Audio in DIY kit at http://www.audio-gd.com/Pro/diy.htm . (photo exists in Chinese version, but does not exist in English version)
2) LITE in DIY kit at http://www.lite8.com/index.asp?sortsid=8 and http://www.lite8.com/index.asp?sortsid=11 . (only Chinese version)

The design of REIZ and LITE is similar. But, it is quite difference from Jos’s design. In China supplier design, each relay located with one transistor at back. Hence, there are many transistors in the PCB module. (e.g. 17pcs of 2N5401 and 17pcs of 2N4148) In Jos design, there is no transistor. There are only 8 transistors mentioned in the photo below which are used for PSU to supply 16Vdc to OPAMP LM4562.
It should be emphasized that analog audio signal enters into pre-amplifier from XLR/RCA jack to the point just before OPAMP, it is totally free of semiconductor components. It only involves three components of jack, relay and resistor only. Hence, it should be free of noise which provides a very clear sound quality. Transistor is a kind of semiconductor device, it can emit noise when operates. I am not sure whether these transistors will have any impact to noise interference around the audio signal.

Just for reference!


B. regards,
alant

Your response is quite typical engineering people response, who quote a lot of theory with the real world experience. I have a DIY passkab per-amp with full balance driving a full balance Mcintosh MC275 for at least one year of intensive listening.

My friend using a Mark 380 driving 438 power -amp, they have both balance and unbalance input.

We finally still using unabalance output .


1. For balance circuit, it will have higher distortion and time delay because all the component in the circuit need to be prefecty matched ( that is what I mean premium grade), Given the general compnent is normally withn 5% tolerance, ithen it will means that you have a 5% chance distortion .You can ask a lot of person , 5% distortion is a lot. It is the reason why DIyer have difficult to build distree amps as the transistor need to match to a low tolerance. I built the per-amp based on  1% matching on transistor.We found that the distortion in the upper and lower half wave will not good enough  because differences in component tolerance.
2.  You normally found that the sound of balance is different from unbalance because the output level of the balance circuit is normally double the unbalance level. If you are not using full balance, that means from CD-->pre-amp-->power amp, you are not really enjoy the benefit of balance circuit. I have both balance and unbalance equipment in my system, I did not find balance sound better. My purpose for this responses are to correct misconception that balance will sound better.

I respect your computering knowledge but HI FI is sound, which is quite difference from what you are expert at.

Yes, your guess is correct. I start my career as a practical engineer and have been over 20 years after graduation. During work, I only deal with very high level senior management and now seldom touch with routine technical issue. Thank you for your information sharing. Lastly, I would like to conclude that this forum is an open platform, everyone should learn not only to accept the tolerance from electronic component, but also to accept the tolerance from people from different comments.

Ha Ha, I always have problems in discussing with engineer with Hi Fi as I found it very difficult to tell them my experience, which may be conradict to a lot of "engineer' belief. Interestingly that Hi Fi is not something that can measure by instrument only or specification only. You can build a top speciifcation machine but sound awful.  The secret of good sound seemed to be much more than those seen on the scope and specification.  I do not mind whether you will accept or not as it is your money and your system. You can take you own route and spent your money that way. I am just here to share  my years of experience in DIY wth people  and hope them they can spend their money wisely.

Please excuse me if this topic “balanced technology” makes anyone felt displeasure. My philosophy is that work is different from hobby. In work, you receive salary and you should follow instruction from your boss. In hobby, you usually do not receive money (excluding some exceptional cases), but in contrast you have to pay for your hobby. For this reason, people usually decide to pay for hobby what they feel happy, but not they think correct or incorrect. In Chinese, it states “工作是為錢，愛好不單只沒有錢收，反而要付錢。所以人們決定對其愛好付錢，在於他們喜不喜歡，不在於所做是對或錯。”

OK! May be, discuss this topic later once my DIY kit completed. If this topic “balanced technology” make you felt restless, then my next topic “power supply unit (PSU)” may make you felt shocking. In Chinese, it states “如以下內容令你感到不安，請不予理會。” It is because my mind is innovative and creative.

Power supply unit (PSU) is very important to any audio electronic devices such as CD player, DAC, pre-amplifier or power amplifier. The goal of PSU is to provide a sufficient, stable, reliable and high purity DC power supply to an electronic device from an AC source. There are two kinds of power supply unit:

1) Linear power supply
2) Switch mode power supply (SMPS)

I think that they are well known to all of you and do not need to explain anymore. The comparison of these two units is stated as below:

1) Comment in HiFifever at http://www.hififever.com/forum/viewtopic.php?t=876
2) Other comments at
http://www.acopian.com/linear-power-supply-vs-switching-power-supply-vs-unregulated-power-supply.html and  http://power-topics.blogspot.com/2007/08/linear-vs-switch-mode-power-supplies.html

However, I would like to discuss a third type PSU, the Hybrid power supply unit (HPSU) which takes the advantages from both of linear and switch mode power supply. (See drawing as below) HPSU consists of two units. The first unit is an external PSU made from SMP and like a notebook adapter which convert AC to DC. The second unit is an internal PSU made from linear power supply which converts high voltage DC to low voltage DC for use.

My goal is to do an extra low noise audio device. HPSU is free of AC interference and only quiet and pure DC power exists within the circuit. As a result, it provides minimum interference to the audio signal. (i.e. extra low noise) It is applicable to low power consumption of solid state audio devices such as DAC and pre-amplifier. For power amplifier, it may be only suitable for class D amplifier for its highest power efficiency. Power efficiency of different class of power amplifier is listed as below:
Class A: 25~50%
Class AB: up to 78.5%
Class D: up to 95%
   
Ref. at http://en.wikipedia.org/wiki/Electronic_amplifier#Power_amplifier_classes

It is not a theory of concept, this product now exists in market as below:

1) Jeff Rowland Power conditioner Model PC-1
=> It is an external PSU, like a notebook adaptor which convert 120/230V AC source to 385V DC source. (See photo as below)
=> Ref. at http://www.myav.com.tw/forum/showthread.php?s=&threadid=328827

2) DACT - CT102 Audio Power Supply
=> It is an internal PCB based DC to DC power supply. It includes another commercial external power adaptor to convert AC to DC and then supply to CT102 for use. (See photo as below)
=> Ref. at http://www.dact.com/html/power_supplies.html#Toni-DAC and http://www.dact.com/DIY_DAC_BOM_and_connections_diagram.pdf

If DIYers feel not comfortable with existing PSU, it is just a reference for “upgrade” purpose. For other DIYers who have previous experience in this Hybrid power supply unit, may share their experience here. Good or Bad?


B. regards,
alant

Alant,

My approach is quite different and I am a practical man. For my hoddy, i just want to achieve the best possible sound for a sum of money that I can afford. Being play with factory made machnes for about 10 years, I decide go to DIY because I really frustrated with those factory made machines. For those factory made machines that I like it, I cannot afford it. In 80's, I am already playing wiht mark's 30.5 + 30.1 and cello performance driving a Duntech. As a result, my ears are very critical. Therefore, I always use listening test as my final decision making criteria. No matter how good a certain technology or products appear on paper, it will be of no value to me if it does not pass the listening test. I hope this will ease your feeling that I am finding trouble with you, it is just our evlauation criteria may be difference.

Go back to your discussion of the power supply unit, both power supply , tranditional transformer and switiching power supply are of different sound characteristic, and it is really important that material like caps, resistor and transformers  that really make up the power supply. I suggest that you should take some time when Hi Fi Fever has a demo of UCD ampifier, you can distinguish the difference in sound characteristic so that you can decide your personal preference.

Dear accphoto,

I respect your DIY experience. You may feel me quite theoretically because I had a very strong practical experience in research and development (R&D) over ten years in the past, but not related to audio product. Hope that it is not a barrier between you and me. In hobby communication, don't concern too much about the differences from other people because we are looking for happiness, but not argument. The most important is that you enjoy your task and I enjoy mine too. Lastly, thank you for your comments about PSU for UcD and I totally agree with it. I met KK Ho once in a listening demo of Hypex UcD180 using SMP, but not try linear PSU yet. He is a kind man. If my time available, will appreciate further opportunities in the future.


B. regards,
alant

Agreed , no worry, audio is quite an amazing hobby. One had to pass the listening test. Nice to talk to you.

Noted!

Dear alant & accphoto,

Hmm...we get a lot of information from your discussion.

Playing HiFi is really very different from other hobby...the best woman doesn't mean will match the best guy....

Your best sound may not be my best sound. Anyway the most important thing is to enjoy the process.

Alant,
Hope you can completed your DIY project soonest and achieve your target of the latest best technology will produce best sound for you...

I myself like the low/old technology which can produce good sound --> low technology normally less complicated, lower cost and easier to be done by DIYER : )

Dear WINDWSS,

People may have same hobby, but with opposite taste. Can they be friend which depends on individual personality and character?

New technology or old/traditional technology, it doesn't matter. No distortion amplification circuit does not guarantee good sound, it just provides a deep sound contrast. The nature of sound is tuned by the secret of circuit design or/and wiring. It is because some people like sound with few distortion (音染) such as tube sound with warm and soft voice. Personally, I keep on my preference, but admire the result and effort from others even with opposite taste or preference. Then, no argument or conflict.

In DIY, people feel happy with their effort spent, rather than an outstanding achievement because it is not their professional. (首先有聲出已很開心, 要好聲就须長年的實際經驗)


B. regards,
alant

Dear Alant,

I will say they can be very good friend..even personality & taste is different if they have same hobby.

I got a friend who also keen in HiFi, we are classmate since primary school but his taste & personality very different from me but we still keep close to each other on dicussing the same hobby.

Frankly speaking the song he like and the tone he look forward very different from me, he listen to song for relaxing so he like slow & soft especially vocal. I listen to music to refresh & obtain energy so i like instrument especially with drum.

Anyway we make use of each other's strength & felxibility, as he always travel out so he is taking care of buying part, i will do thel DIY job like sodlering, assembling....

I very agree with you that we DIYER really enjoy the process of DIY especially when a product is completed and working....