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Old 16th November 2012, 06:40 PM   #321
mkusan is offline mkusan  Croatia
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Hi blackdod,
thank you for pictures, I don't believe uploaded schematic applies to your version of the board. If you are worried about those lifted tracks check for continuity with DMM to be sure , however I don't expect problems there. Cleaning the flux from the board with some alcohol wouldn't hurt either. If you feel confident and you are good at desoldering change input ceramic cap to 1uF film type, not sure if WIMA would fit here because lack of space, if not try Panasonic ECQ-V series. If all goes well replace two Zener diodes on the board each with 4x1N4148 connected in series, observe the polarity it is opposite to the zeners.

Regards
Marko
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Old 16th November 2012, 07:42 PM   #322
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Thanks Marko

I followed all scheme and is not compatible with my amp on some points.

I'll think I do. I did not want to spend much time on this amp because it is a "smaller" project and I have other amps outstanding.

Thanks for your patience
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Old 16th November 2012, 07:51 PM   #323
oz7aff is offline oz7aff  Denmark
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Hello blackdod

The biggest difference between your green PCb and my blue PCB, is that my heath sink is at least twice the size of yours.
But if you mail me your postal adress, then I will send you a blue PCB at no cost.
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Old 16th November 2012, 08:08 PM   #324
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Quote:
Originally Posted by oz7aff View Post
Hello blackdod

The biggest difference between your green PCb and my blue PCB, is that my heath sink is at least twice the size of yours.
But if you mail me your postal adress, then I will send you a blue PCB at no cost.
Thanks Max but I canīt accept that. Let me pay you the plate and sending.

I will change the input ceramic capacitors and some bridges because are rusty only by test.

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Old 16th November 2012, 08:24 PM   #325
mkusan is offline mkusan  Croatia
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Quote:
Originally Posted by oz7aff View Post
Hello blackdod
But if you mail me your postal adress, then I will send you a blue PCB at no cost.
This is why I love this forum so much, indeed a true DIY spirit.

Regards to you Max

Marko
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Old 16th November 2012, 08:32 PM   #326
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Quote:
Originally Posted by mkusan View Post
This is why I love this forum so much, indeed a true DIY spirit.

Regards to you Max

Marko
Of course
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Old 18th November 2012, 07:13 AM   #327
oz7aff is offline oz7aff  Denmark
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Hello blackdod

I forgot to say that you can send mail to me via my homepage www.sandcastle.dk
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Old 19th November 2012, 11:15 AM   #328
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If output coupling caps are added to protect the headphones from the output dc offset, is there any reason to aim for 0V dc offset upstream of the cap?

I have a pair of ASC GLY513 600uf fim caps that I'm mounting in a separate enclosure with 6.35mm stereo in and out to allow me to use these caps with any headphone amp I'm using. With these film caps it won't damage anything if the offset is positive or negative, but I wondered if setting the offset to +1vdc (making the signal vary from 0-2vdc in normal use) would be best.

In the meantime I have a pair of black gate 1000uf 16v standard polar caps at the output, so setting the offset to +1vdc keeps the polarity of the signal correct for the polar cap.

Any thoughts?
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Old 19th November 2012, 11:48 AM   #329
oz7aff is offline oz7aff  Denmark
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Just remember that the original JLH class A amp from the sixties had single supply, and there for 1/2 Vcc as offset and only a standard electrolyt in the output, and this arrangement works very well. I think that the answer is, lisent to it, does it sound good, then it is good.
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Old 19th November 2012, 02:42 PM   #330
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If you use a capacitor at the output , it might be better to use a single supply circuit. That would bias the output cap at 1/2 Vcc. Electrolytics with no dc voltage across them aren't really operating in a comfort zone. Even a non polar electrolytic might not be the best solution here.
Like oz7aff said. Try out the way you want to do it and see how it sounds. It finally depends on if the sound is acceptable to you.
Have fun !
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