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Old 15th April 2009, 10:25 AM   #41
diyAudio Member
Join Date: Feb 2004
Location: manchester
if anyone still cares...
the two trannys in this pre mentioned earlier are just there to switch the ouput relays on, as andrew t correctly guessed.
the cause of the noise is definately the dil mosfets, which are in circuit for the buffered output.they are not used as switches, but for gain (oh mine are labelled zvn4206e).
there are 4 of these in total, and they are not in cct when using the passive out.
its a noisy design, but it sounds nice.
the pot is a 50k log btw.lm394s in the phono stage.weird mosfets for the pre amp buffer. all ac coupled with loads of expensive polyprop caps.
pretty sure its a tim de p design, hence its rather non-standard.
the cd section has far too much gain too i think.
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Old 22nd June 2009, 02:53 AM   #42
cchean is offline cchean  United States
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Join Date: Dec 2008
Hey all,

I just bought myself a 3A preamp to partner with my P140 power amp. This setup is working perfectly and is sounding good. However, I am planning on recapping both units, since they're both old enough for that. I was thinking if somebody has the schematics for either one of them, specially the preamp 3a. Does anyone know which caps are crucial for better sound? I want to replace the caps in the audio signal path for audio-grade polypropilene capacitors. Thanks.
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Old 22nd June 2009, 04:25 PM   #43
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Join Date: Feb 2004
Location: manchester
Default caps

i have one of these units.
your pre3a should be chock full of big yellow audio polyprop caps anyway.
all the ones ive seen are.
the unit is ac coupled and has about 25-30 big caps from memory.
i took some of these out to measure and they were perfect, so i've never changed them.

i did replace all the electrolytics a few years ago, theres not many and its easy to do. the preamp doesnt run hot so the caps dont age too badly.

let me know how you get on.

the amp has an audible hiss which is down to the weird dil mosfets in the active stage, but i think it sounds great despite the slight hiss.

i have been after a diagram for this amp for years - no one seems to have one!
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Old 5th October 2012, 09:11 PM   #44
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Join Date: Apr 2005
Location: Cheltenham, Glos.
Shame this thread stopped in 2009 ! What were the conclusions ? Did anyone ever cure their hiss ?

I hope so and if so, perhaps post the outcome as I'm curious !

The older I get, the fitter I was !
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Old 4th December 2015, 10:06 AM   #45
rmgvs is offline rmgvs  Netherlands
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Join Date: Apr 2001
Location: Netherlands
There is another thread here at diyaudio where all aspects of the circuit are deepened. And, I repeat: the hiss can not be solved, they are part of the mosfets used. Don't let you fool yourselves by beter power transformer and fancy caps: this will do nothing at all with the hiss. Only a completely different power supply arrangement does influence the amount of hiss but in no way as to be gone.
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