Question on tube load resistant & output trans (need adv

Dear all especially accphoto,

need advice from u all...

Example 2A3's load resistance is 2.5k ohm, so we will use 2.5k ohm output transformer(at primary),

my question is if, we parrallel 2 piece of 2A3 at 1 channel--> do we still use 2.5k output trans or we shall use 1.25k ohm output trans???

besides, i'm also doubt on the type of output trnsformer?


what is the different between SET output trans and push pull output trans?

can i use the push-pull output trans for a SET equipment?

thank you very much autumleafcat!!!

If i were DIY a 300B SE as the AN kit 1 in the attachment, is a 12w output trans, max 100mA (balance dc 60mA) sufficient??

besides, instead of 2.5k primary can i use the 3k primary?

Anyone here had experience with SAC silk transformer? any comment?

thanks!

The transformer i'm thinking to use is the silk S-303 from www.sacthailand.com it is a SE output trans.

On behalf of my friend, i have another question, he is keen to know whether a 8-10w SET is able to push his proAc 1sc (86dB)?? he mainly listen to sentimental song & vocal.

Thank you very much for your info.....

Last weekend, my friend and i is testing a meixing 300B (4pcs) SE rated 20W on his Proac 1SC... result is dissapointing.... it can't release the real strength of 1sc then we test another amp (Ella, 50W push pull - can use KT 88, 6550 & KT 90), this Ella can really drive the proAc and it had really show the strength of the 1sc.....

Do you have any experiece in hybrid amp?
Since a good output transformer is expensive, i'm looking into the alternative to use mosfet to replace the output transformer, is it can be done?

i wondering other than output trans, any other buffer circuit can be use to convert the ouput of the tube to the speaker?

How does OTL(output transformerless) amp functioning?

what kind of circuit the OTL use to convert the high impedance load to a low impedance load(speaker)?

Do you think the circuit attached can be work out?

i have several 2C51, 5687 & 12A6 tube.... tinking of make use of them to DIY a OTL...but i'm not so understand the way the OTL work, are you familiar with OTL circuit?

Wow, thank you very much for the info.

Just bought a 2nd hand Monitor audio 9 gold speaker and modified with OIMP. My previous speaker MA R100's bass is too soft as its low pass filter is using single inductuctor only.

dear accphoto,

Do u think changing the iron core inductor to foil inductor in crossoverr will give more improvement compare to changing the cap?

any of you had experince on the obligato film cap?

I have a doubt, my orginal bipolar cap for low pass filter is written as 6.8uf but it read/measured as 7.2uF, shall i use 6.8 of 7.2?

currently i found my HF is very good, bass also plenty but mid seems like a bit lacking, if i use 6.8uf do you think the mid will be better?

Thank you. U had solve part of my doubt.

For the inductor, is the internal resistor only affect the bass energy, would it affect the frequency cut off point?? (this is what i'm worry). Does it mean that using an inductor with less internal resistor, the sound will be faster will have more energy??

I had some experience with solen cap, it is quite smooth & warm but blur, poor imaging & sound stage.

For the tweeter (HPF) i will recommended to use Vcap OIMP if affortable. For cheap replacement Mcap MKP is not bad.

For mid bass, i'm still searching for nice & cheap cap, Mcap Zn is quite warm but not so cheap. Hovland Musicap not yet try as also not cheap at my place and heard that it not easy to match...

Hi, do u have any idea the purity of the copper wire in the inductor use by monitor audio in 1990s? is it 99.9% or 99.99% cu?

I have a problem here as my multimeter is not so good it can't really measure accurately the resistance which < 1 ohm.

I'm planning to use Jantzen 99.99% cu air core inductor, if my original iron core is 99% or 99.9% pure then i guess the internal resistance might be similar even i use a air core coil.

If possible i try to avoid using the foil air core as the price is double of the aircore wire coil...

ok, thanks for sharing.

By the way, what is your opinion on using combination of 2 or more cap to reach a desire value for speaker cross over cap?

e.g 3.3+4.7uf or 6.8uf+0.2u to become 7uf compare to 1 pcs of 7uF.

Often i prefer to use a single cap compare to multiple cap.

In my case now my measure value is 7.2uf, it is really difficult to get a 7.2uf single cap.  So i'm wondering i shall just use a 6.8uf or use 6.8+0.47uf??

lastnight i replace my 7.2 bipolar cap(at woofer) with (6u+1u) mkt cap, mid & bass become very transparent, clear & better imaging but need to sacrify some warmness & bass quantity....

Any suggestion of cap which can give good imaging, resolution and bass and still having warm sound?

hmm... will try a 6.8uf as you suggest, if not ok then only parrallel in some cap....
i think the requirement for cap use in woofer is not as critical as in tweeter, thus shld be able to try cheaper cap to get decent sound...

Hmm, i had just get my brother to buy me the Jantzen foil inductor in order to replace the iron core inductor in my MA 9. Hopefully the foil inductor have low impedance enough to further boost up/ equall my current bass.

Dear ALC, acphoto,

If u you 2 choice for inductor below with similar price, what will u choose for the series inductor in woofer and why?

1) Foil inductor, air core, 16AWG, DCR = 0.34R
2) air core wire inductor, 14 AWG, DCR =0.25R

Thanks, your analysis make sense....

My system is 2way speaker.

So this round is try & error =  gambling. I hope my newly purchase 16AWG foil inductor will have equal or lower DCR than my original iron core inductor, then sound quality & bass will be better than current.... then i'm already satisfy...

dear ALC,

Another doubt need your advices.

Do u ever try to DIY a preamp/tube buffer using power tube?

can we actually build preamp use power tube like 2A3, 12A6, 6550 and so on? what will be the impact?

Hi, a question.


The LF hum in tube preamp is cause by the unsufficient capacitance in power supply filtering right? This LF hum will increasewhen voulme level increase.

U r right, by just changing the connection point of 1 ground wire, i had reduce a lot on the hum.....