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標題: Upgrading Marantz 7C capacitors [打印本頁]

作者: alfcat 時間: 2007-12-21 20:49
標題: Upgrading Marantz 7C capacitors
Dear Accphoto and brothers,

My friend now gets hold of my Marantz 7C. He is wondering whether he can make the BASS better by replacing the capacitors.

As Accphoto pointed out once I can upgrade the 0.01uf cap. But in the KIT I got, there is NO 0.01uf cap at all as it is not cater for LP / Phono.

Dear Accphoto, by making us of the photos I posted, can you suggest me how to upgrade the caps for my friend?

Link to the photo: http://www.hififever.com/forum/viewtopic.php?t=1725

CAT

作者: accphoto 時間: 2007-12-23 21:12
There is two ways in improving the bass, change the Elect-Cap , currently you are using RIFA (330U) and BHC, Try to change the RIFA 330U to BHC, You can also change all 0.22U (WIma to other brand) and also change 2.2U to other brand. Personal, I do not like WIMA on tube amp as they will sound "thin" You can try auricap but I do suggest to change 2.2U to at least 3U. Since I only got the photo, it is only a guess and you should post the circuit.

作者: alfcat 時間: 2007-12-24 08:48
Dear Accphoto,

Thank you so much for your help.

I have attached the schematics for this Marantz 7C. Please take a look and give me some of your valuable advice.

This time, I am doing it for my colleague. He said he is willing to spend around HK$ 2K or so for the capacitors. So please advise him on what BRAND of caps he can use as well.

Once again, thank you very much!

CAT

作者: alfcat 時間: 2007-12-24 09:48
Dear Accphoto,

I forgot to attach the file .. ha..ha..

作者: accphoto 時間: 2007-12-24 13:10
I know this schematics, I have done it for my friend but I have change the value as follows :
B+ is too low, M7 is running at +280V in order to sound good.
Add a 3.3K resistor per channel between B+ and R2
Change C3 to a larger value capacitor say 2u to 3U.
Try not to use WIMA, it sound terrible on tube amp.
There are a lot of Marantz 7 circuit but this one definitely is not a good one as B+ voltage is too run. +240V should just be the voltage for T1 before the load resistor.No wonder it sound bad without bass.

The value that i suggest to you is not marantz as the value use by Marantz is too small for modern capacitors. The schematic is based on Sid Smith 7.

作者: Koifarm 時間: 2007-12-24 18:40
Alfcat you must replace C1,2,3,7,8,11 0,22 uF for 0,33 or 0,47 uf and C14,15 2,2 uF for 4,7 uF or 10 uF. Use brands you used for the MHZS mod or if this is to expensive i like to use Clarity Caps SA serie.

http://www.capsandcoils.com/shop ... x&cPath=1_5

Put parallel to C14 and 15 a small Capacitor 10nf to perfect the hightones.

What type/brand of tubes you use?. This is also a issue, tuberolling can improve the sound.

作者: alfcat 時間: 2007-12-24 19:02
Dear Koifarm,

I haven't seen this Clarity Cap before. The Marantz 7 is in the hands of my colleague now. He wants to buy it from me but asked me to help him solve the problem of "loosey" base. He wants more SOLID bass.

Where can I get Clarity Cap? Are they expensive?

Merry Christmas to you!

CAT

作者: alfcat 時間: 2007-12-24 19:09
Dear Accphoto,

Thanks for your valuable advice.

There is nothing I can do with the Voltage, right?

I will follow your advice and change the components once I got the Marantz 7 back.

Thank you and Merry Christmas to you.

CAT

作者: alfcat 時間: 2007-12-24 19:10
Sorry Koifarm,

The Marantz 7C is using Mullard 12AX7 tubes. Blackburn, '60s and closely matched.

CAT

作者: accphoto 時間: 2007-12-24 22:01
For the B+, yes, there is nothing you can do unless there is significant changes. I do not like DIYZONE's kit as they always change a lot and lost the original spirit. At the moment, you can change the caps and this will improve the tone and the bass. However, "好低音難求", sometimes, it is just a little bit of bass and cost you an arm and a leg.

作者: Koifarm 時間: 2007-12-24 23:08
Alfcat here you can order the Clarity Caps,

http://www.capsandcoils.com/shop ... b6f50bb924c136d494d

These caps are not expensive.

You can use one EH 5751 goldpin tube,i like this tube because of his solid bass.
The 5751 has lower gain as the 12ax7( about 20% ), mostly this is not a problem. You get a better range of your volumepotmeter to.

作者: alfcat 時間: 2007-12-24 23:51
Dear Accphoto,

Thanks for the advice. I wise 10 years from now, I could be as good as you are ... ha..ha...

For the time being, we can only stick to KITs .... and learn by trial & error.

I took your advice and changed the Caps inside the Matisse to Auricap. Indeed, they sound VERY different. The Matisse now is much much better and natural. Just run it for around 5 hours and both me and my wife are very satisfied.

Enclosed is the photo of the Matisse after changing to Auricaps.

CAT

作者: accphoto 時間: 2007-12-25 12:40
Since you are already using RMG (or RMA?), It will sound very good if you are using the right caps. You next upgrade will proper cost you more as the elec-caps are worth upgrading but it is really expensive as you can only upgrade to BHC or Blackgate.

Oh, BTW, Auricap needs about 50-100 hours run in before really give the best performance....

作者: alfcat 時間: 2007-12-25 20:52
Dear Accphoto,

Should I suggest my colleague to upgrade the Marantz 7C power supply caps to BlackGate if he is willing to pay?

CAT

作者: accphoto 時間: 2007-12-25 23:40
Upgrade tp Blackgate may not solve the problem. In my opinion, the power supply voltage is too low.

作者: alfcat 時間: 2007-12-26 17:21
Then I can only suggest him to change the capacitors as you have suggested (and increase the uf of some of those as well).

What is the use of adding the 3.3K resistors between B+ and R2?

CAT

作者: accphoto 時間: 2007-12-27 00:09
The last tube is a cathay follower ( 陰極輸出), The original design is that it should work at 280V, the two tubes in front, it is design to work at lower voltage (240V), so the 3.3K resistor is to reduce the operating voltage from 280V to 240V.

作者: steve138 時間: 2007-12-27 11:54
Dear Cat Sir and Accphoto,
Your Matisse is Reference or Fantasy ? What are the sound performance different from Reference and Fantasy ? Which one is better ?
Do you have the schematics ? If yes, would you post it for my reference .
Thank you very much .

作者: accphoto 時間: 2007-12-27 12:24
This one is reference as using 2 tubes, Fantasy is using 4 tubes but each tubes are run in parallel . If you look at the circuit, they are essential the same but two tubes in parallel means more problem on matching the tube. So I think reference sound better. For circuit, you should search the forum as it was posted before.

作者: alfcat 時間: 2007-12-27 17:43
Dear Koifarm,

I registered at the Clarity Cap website. However, I am unable to order items. They just don't have a button that says "Add to Cart".

I can see my shopping cart; just can't get things into it ... :cry:

CAT

作者: Koifarm 時間: 2007-12-27 18:59
Alfcat, this problem i had also. I just send a email with the parts i needed and ask for the amount i must pay to them inclusive the shipmentcost and paymentconditions. If you still have problems contact me. I can phone them and place your order.

作者: alfcat 時間: 2007-12-27 23:26
Dear Koifarm,

No wonder. I will try by first dropping them an email.

Thanks for the info.

CAT

作者: alfcat 時間: 2007-12-27 23:28
Dear Accuphoto,

I would like to take my FIRST trial by changing the C3 capacitor to 3uf for my colleague.

BTW, just need to change C3, no need for C11 which is sitting at the opposite. (Silly Q from people who doesn't know about electronics)

What brand would you suggest? Jensen? Auricap? or Moundorf?

CAT

作者: accphoto 時間: 2007-12-28 13:58
Dear CAT,
Shit, I must quote you the wrong number, It should be C2 which will affect most, it should be 3U, The Sid Smith circuit has corresponding value as follows :

C3 & C11 0.33u  400V
C1 &  C7 0.33u  400V
C2 &  C8 2-3U 400V
C14 &  C15 3.3U 200V

Since you are trial without knowing the result,  I suggest that you go for Aruircap first.  I still have reservation on the power supply.
C14 & C15 is also important, i suggest that you should change it too.
Jensen is certainly good but it will be quite expensive as for a trial.
You need to change both as it is for left and right channel.

作者: alfcat 時間: 2007-12-28 14:07
Dear Accuphoto,

Thank God I take a last minute look at the forum. And thanks for your post right IN time .... I was just going to leave for Mongkok.

I will purchase the items as you described and see how it goes. Will give you a feedback by tomorrow night

Thanks again.

CAT

作者: alfcat 時間: 2007-12-31 22:58
Dear Accphoto & Koifarm,

I changed all the caps of the Marantz 7C as the first trial. However, the Marantz 7 had been gone for too long and I can't exactly recall HOW it sound.

After upgrading, I "think" it gets closer to the Matisse but the Matisse seems to be a bit better. Unfortunately, my colleague is tooooo eager to get it back and I haven't got the chance to really compare the two.

I also changed the Volume switch as he doesn't like the Ladder one and I installed a TKD selector for him as well.

CAT

作者: accphoto 時間: 2008-1-3 23:15
ALPs is already very good. Hope your friend like the upgrade.

作者: alfcat 時間: 2008-1-4 09:02
Dear Accphoto,

Thanks for your help along the way

My colleague is now using the Marantz 7C but he said the Auricaps haven't yet run in. The sound is a bit dull for the time being.

I also changed some capacitors of my Antique Sound Lab amplifier. Will post the photos here later for sharing. However, the improvement is NOT good as expected. Maybe you can give me some advice as well.

CAT

作者: accphoto 時間: 2008-1-5 19:42
Yep, you can only listen it after 50 hours of running.

作者: viewer 時間: 2008-1-5 20:05
HI ALFCAT,

PO SHU (CENTRAL) HAVE "Black Beauty" VOLUME CONTROL FOR SELL.
I TAKE ONE BEFORE.
AROUND $200 EACH FIVE YEARS OLD.

THANKS.

作者: alfcat 時間: 2008-1-5 20:56
Dear Viewer,

Long time no see la ... wish you the best for 2008.

I went to Po Shu right before New Year. They don't have the ALPS Black Beauty anymore. The old man said it had been sold out for some time.

On the contrary, I picked up TWO rolls of 100m hook up wire from them. They are from RS; should be pretty good wires. Only $ 110 each roll.

CAT

作者: viewer 時間: 2008-1-5 22:51
hi alfcat,
happy new year,
宝樹有東京光音volume control. It is better than alps "Black Beauty".

thanks.

作者: viewer 時間: 2008-1-5 22:55
alfcat,

blue colour alps volume control 誤差是 4 to 5%
"Black Beauty"誤差是2%
東京光音volume control 誤差是1%

thanks

作者: accphoto 時間: 2008-1-6 00:11
東京光音 volume 好貴！600+不如用 Holco volume 啦，俾多兩百元好聲好多。東京光音的聲偏薄。

作者: alfcat 時間: 2008-1-6 09:06
Dear Accphoto & Viewer,

What do you think about the "ladder" volume I DIYed? Assuming that there is NO cold soldering, is that a good one? For this type of Ladder Volume control, what makes it good? The design? The materials? I got the thing from DIY zone.

The problem with that Ladder volume control is, it is step by step. Turn to step 4 is too low the volume, turn to step 5 it is too loud .... There are 24 steps, I never use more than 5 .... just don't know what is the use of the rest ....

CAT

作者: accphoto 時間: 2008-1-6 10:51
Ladder volume is certainly better than other volume as the sound signal only pass through one resistor. However, the type of resistor had significant influrence in the sound, normally , the best sounding resistor is RMG, than Holco, than Dale . AB had too much noise and is not suitable for such application. If you find the step is too loud, actually, you can modified the value of the resistor in the first few steps so that it suit you needs.Other volume like ALPS using carbon film, the sound is ok but in terms of music definition, those ladder volume will definitely win. One of the reason why Matisse sound so good is its volume is made of a pair of Holco Ladder Volume. the others are BHC caps .

作者: alfcat 時間: 2008-1-6 16:30
Dear Accphoto,

The one I DIYed has 4 layers. Two Rin and Two Rg. That means the signal will go through TWO resistors for each channel, right?

So if I increase the Ohm value of the resistors, the sound will be lowered. Am I correct? If my logic is right, I should have the value (ohms) of the steps narrowed if I want small increment steps by steps.

You are very helpful ... many thanks.

CAT

作者: accphoto 時間: 2008-1-6 19:52
Actually, one resistor is on the signal path and one resistor to the ground. Change the value of the resistor to the ground (Rg) in the daigram will affect the loudiness of the sound. The below web will certainly help you

http://home.so-net.net.tw/chufamily/StepVR/Calculation/StepVR.htm

You can use the appropriate value on trial and error.

作者: alfcat 時間: 2008-1-7 09:24
Dear Accphoto,

I see. I will try to get some DALE resistors and change the values of probably third to six / seven stages.

The one from DIYzone has small holes. I think it is not very possible to use RMG resistors as their leads are quite thick.

Still waiting for the Matisse and the ASL amp to get to their Normal stage after changing the caps.

Too busy helping my daughter to prepare for her exam yesterday and no chance to post neither photos or schematics of the amp. Really would like to seek your advice on whether I replaced the right materials inside the ASL amp.

CAT

作者: SSWONG 時間: 2008-1-7 15:53
Dear Cat,

If u step volume control, u can actually save cost by using very good resistor (e.g RMG or tantalum resistor) at the range you often use. then other range use cheap resistor.

Or u can use different brand of resistor so that can enjoy different type of sound....

作者: alfcat 時間: 2008-1-7 20:24
Dear Accphoto,

I managed to get the Antique Sound Labs 6L6 Mono Block Schematics and post it here. Hope that you can give me some advice on upgrading it.

Following another link by an American, I upgraded TWO capacitors as indicated in the photo. The person used Moundorg Supreme Gold / Silver but I used Jensen same value 0.22uf / 650V. I also changed the other one to an Auricap as the original one is a bit cheap.

For resistors R5 & R6 (I guess), that person used DALE / Vishay but I used RMG with same value.

Do you think the modification makes sense?

CAT

作者: alfcat 時間: 2008-1-7 20:29
Strange ... cannot upload the Schematics?

Converted it to JPEG and try again.

CAT

作者: alfcat 時間: 2008-1-7 20:31
Dear WINDWSS,

As I have said before, the one I got from DIY got pretty small holes. I am not sure whether I can use RMG as their leads are pretty thick.

CAT

作者: accphoto 時間: 2008-1-7 22:10
Basically, i hatre those Japanese Electic-cap, If you really want a firm base, you should consider to upgrade those elect caps to black gate C1 and C2. If you do not want to spent a lot of money, consider Jensen elect caps. C9 is also important as it is for the -Ve, consider blackgate as this will not too expensive. The circuit is so small that i cannot really read. The feedback resistor (R11 or 13??? ) is also important, suggest to change to RMG 2W.

作者: alfcat 時間: 2008-1-8 09:57
Dear Accphoto,

Thanks for your ultra fast response. I am not sure whether this is my 心理 problem or what ... the whole system does NOT sound as good as before after changing the caps.

I have thought of two possibilities: ONE, of course, is the capacitors need time to run in. I just run them in for 20 hours or less.

Second, a Mis-Match or need to upgrade some other components to match those newly installed.

I will seriously consider your suggestion and will enlarge the Schematics later today when I got home.

Many thanks.

CAT

作者: viewer 時間: 2008-1-8 11:01
hi alfcat,

In my feeling, changing the resistors are better than caps.
i just replaced a lot of the resistors of dac and sound parts in my mhzs cd33.
sound become clear and solid.
low costs and got high gain.

thanks for sharing.

作者: alfcat 時間: 2008-1-8 13:41
Dear Viewer,

Can you post a photo showing the resistors you have changed?

I will see if I have time tonight and post my modified CD 33 with the DAC incorporated into it.

CAT

作者: alfcat 時間: 2008-1-8 17:22
Dear friends,

I attached here a better schematics of the ASL AV-25. Hope this can help. I really would like to upgrade this Amp as I "think" this is a good amplifier at this price of HK$ 3K only.

CAT

作者: alfcat 時間: 2008-1-8 17:32
Dear Viewer,

I didn't realise that I already posted the modified CD 33 with the DAC incorporated into it. I just made it a bit better by:

1. squeezed out some of the blue stuffs inside the cold / hot pad to make it thinner.

2. drilled a hole on the DAC PCB and installed a pole to stablize the board.

I have compared several songs with my CD 33 and the CD 88 unmodified. My CD 33 for sure sounds better than the CD 88.

CAT

作者: viewer 時間: 2008-1-8 18:00
hi alfcat,

i enclosed my cd 33 for your sharing.
white colour areas which replaced the 東京光音resistors and dale resistors.

thanks.

作者: Koifarm 時間: 2008-1-8 18:00
Dear alfcat, looking at the schematic of the amp. I like to tell you some things.

Not every change or mod give a better sound sometimes it is better to leave it.

Before you got modding set a goal of the things you like to improve.

In your case with the amp for example:

1 - change overall sound: just change C4 and C5 for other types like PIO or change tubes.

2 - If there is humm: replace R1 for a big inductor like 10 or 50 Henry

3 - Got more or less bass control: Change R13 for another value ( between 4K7 and 100K )or replace it for a variable resistor of 100K with in serie a 4k7 resistor. Now you can change feedback ( bass controll ).

Changing resistors with ones of the same value is only use full in low signal voltage amplifiers like phone stages or I/V conversion of DAC's. In power amps this is a waste of money.

Reading about mods is one but listening is the real thing.

作者: alfcat 時間: 2008-1-8 21:50
Dear Viewer,

Where did you get the DALE resistors? I know that you can get 東京光音 from Mak's.

If you use RMG, it is going to cost you a lot of money I guess. How much it cost you this time?

CAT

作者: viewer 時間: 2008-1-8 23:35
Hi alfcat,
I used around $160 for this time.

I get 東京光音 from 寶樹. $5.00 each 1/2w $10.00 each 1w
I get DALE from 電子館 . $3 each 1/2w.
total costs $150.00. = one good film cap's amount.

can get it at 永盛 same price.

thanks.

作者: accphoto 時間: 2008-1-9 15:16
On the power amp mod, you do ask yourself a few questions that what you are not happy about ?

1. If you need more details , then change the resistor on the signal path,
2. If you need more smooth sound, change the electric caps and perhaps add a choke will improveit
3. If you need a different sound, change the C3,4 cap into some other type will improve it.

So it all depends on what you really need.

作者: alfcat 時間: 2008-1-9 19:03
Dear Accphoto,

Actually there is little story about this modification I am looking for. After I got this ASL AV 25, another user "Viewer" forwarded me a link from another forum in the States. That owner of the AV-25 said the sound quality of the AV 25 can actually be improved by a few simple modifications. Unfortunately, when I send him a message, he said he already SOLD the AV 25 and can't recall about the modification.

I then sent another message to ASL, they replied saying that changing the Signal Path Resistor and the Capacitors will do the job.

1. If you need more details , then change the resistor on the signal path,
2. If you need more smooth sound, change the electric caps and perhaps add a choke will improveit
3. If you need a different sound, change the C3,4 cap into some other type will improve it.

And that is exactly what you are telling me here.

What I want to know more are:

1. Change the Resistor on the Signal path = change the VALUE of the resistors or change the BRAND to a better one?

2. For an idiot like me, which resistors are they referring to? R5? R6? R13?

For me, I would like to add more details / clarity to the system and hopefully just a little more bass.

And finally, if you have time ... can you explain a bit why changing the resistors will improve the details?

Many thanks.

CAT

作者: accphoto 時間: 2008-1-9 23:26
Basically, change the material will change the sound quality. It is very difficult to explain but if the design is good enough, then change some better brand resistor on the signal path normally will improve the sound quality like details sound stage etc. Resistor in the signal path means any resistor that pass through by signal from input to output. In your case, it should be R6 & R7 ( sorry, it is still very diffuclt to read). two resistors that after the signal caps. It is a common sense that Holco & RMG will yeild better details with sweet sound , dale are more neutral and AB resistor are more musical. Normal carbon firm resistor will sound a little bit dull. Some wire-resistor ( white in color) will sound terrible.
Using different resistor like using salt and suger in cooking.
Normally change the caps and signal path resistors will change the sound quality as signal pass through these materials. If you want to improve the bass, then it will be another story
To get good bass, you really need to look at the power supply ,the frequency response of the transformer, and finally the design of the circuit. Since the transformers and the circuit are fixed, you can only modify the E-Caps on the power supply to provide a bigger supply of power or change the feedback resistor to a different value. Changing the feedback will change the characteristic of the amp. For the E-caps, change to different brand of E-caps will yield different quality of bass. Someitmes, you can increase the value of the E-caps but it really need to be an experience mod. Premium brand like blackgate or Jensen should be able to do the job. Changing the value feedback resistor requires some calculation. It can also be done by trial and error but just make sure that you do blow the speaker by the oscillation if the feedback is too large. As i say before " Good Bass is difficult to get" A lot tube amps is lack of bass as it is limited by the output transformer and the design itself. I had built a 300B amp 10 years ago and try to improve the bass without success. Finally, I find out that there is some limitation on the design of driver stage so it does not provide enough power to drive the 300B.

作者: alfcat 時間: 2008-1-11 09:35
Dear Accphoto,

I agree with you that using different materials will yield different sound effects. However, if the circuit is poorly designed, using better materials will just give opposite results --- magnifying the errors.

So far I have been running the 6L6 and the Matisse each and every day for 3 hours / day. The results of changing the capacitors are getting more obvious now. As I asked my wife and my girl how do they feel about certain piece of music, they like it more tho' they don't in the past.

In the past, I don't believe that a "good" power supply is that important. Now, I am a believer. I think a good power supply / source is even more significant for Tubes Amps and Players, am I right?

I still got a funny problem with my CD ... sigh ... The Left Channel is significantly louder than the Right channel. What could have gone wrong? I checked my soldering points, they are all okay. And the difference is pretty obvious ...

CAT

作者: accphoto 時間: 2008-1-12 00:32
Most circuit is basically a switch , to reduce the power from the power supply to drive the speaker. In that sense, the power supply is important in all HiFi equipment. Pre-amp , power-amp, CD and DAC, the quality of power supply will determine basically it is a good or bad sound.

作者: alfcat 時間: 2008-1-12 18:38
Dear Accphoto,

If I would like to learn circuit designs, should I therefore learn about how amplifiers are constructed? Should it be the simplest type to start off with?

CAT

作者: kkwan18 時間: 2008-1-13 01:23
Hi Cat,

have you try to swop the valves around in your cd player.....

kkwan

作者: alfcat 時間: 2008-1-13 10:46
Dear KKWAN,

Yes, I have tried that before. Actually I have 3 sets of 396A tubes. I marked them and swapped them once in a while, using different combinations. Still the output on the Right Channel is still lower.

BTW, your remote works okay or not?

CAT

作者: kkwan18 時間: 2008-1-13 12:05
Yes CAT the remote works, but not all the time i don't know why, when i open the case of the cdp it works better or when its warmed up. anyway it better then not working.
Cat what audio setup you got? like what power amp connect to you marantz 7c etc.....

Thanks

kkwan

作者: accphoto 時間: 2008-1-13 22:14
[quote:212449ba8c="alfcat"]Dear Accphoto,

If I would like to learn circuit designs, should I therefore learn about how amplifiers are constructed? Should it be the simplest type to start off with?

CAT[/quote]

Got to learn some basics on electronics and then you should be able to learn more. I am not a engineer and all my knowledge are from self-study.

作者: alfcat 時間: 2008-1-14 08:35
Dear KKwan,

That is really interesting. Maybe there is a poor soldering point or so in your CD's PCB. I tested it out a number of times, inter-changing it with my remote on TWO different CD 33. It worked all evening.

I don't have the Marantz 7C anymore. I sold it to my colleague and I changed the WIMA caps to Auricaps, changed the ladder type volume control to Alps for him as well.

Under Accphoto's advice, I changed the Matisse caps to Auricaps as well. After around 40 hours of running in, the Matisse sounds much much better than before. The base is more solid and the sound is "thicker" than before. Also, it is not that "fast" (Hi Fi sense). As I listen to female vocals relatively more, the ladies sound "sweeter".

I connect the modified CD 33 to the Matisse and then to the Antique Sound Lab AV25 Mono Blocks. I changed two capacitors and some resistors in the AV25 as well. More details and better base now I have.

The speakers are just Chinese clone ProAc 1SC. Low price (HK$ 2200) resting on a beautiful but not heavy pair of stands. My next modification will be the cross-over and alike of the speakers.

CAT

作者: alfcat 時間: 2008-1-14 08:42
Dear Accphoto,

In the past, I should be called an "Arts" student as well. However, some of my classmates in my class were constructing amplifiers even at the age of 15. They eventually went overseas and became engineers.

I am doing self - study as well. Actually I also learned a lot of stuffs through this method; computers, cats raising, aquatic plantation, etc. Nice to see people going through the same route.

Sorry to bother you but I will have another question to ask you later this week. It is about an EL34 Mono Block amp I am doing for my colleague. I followed all the procedures carefully but when I turn the amp on, one capacitor (known as C12 -- 47uf/63V) explodes. This happends for BOTH mono block but I couldn't figure out why.

The schematics had already been scanned (this time should be able to read clearly, ha..ha). I will take some photos as well. Hopefully you can help to show me some hint or help me to solve the problem.

Thanks in advance.

CAT

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