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Old 25th May 2011, 12:18 PM   #101
PMA is offline PMA  Europe
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Thanks for your comment, chlorofille. Very interesting customer's feedback to me

Cheers,
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Old 5th June 2011, 05:46 AM   #102
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P3A now running at 225mA bias. The sound is a little smoother, less grainy and soundstage seems to have opened up. Bass seems to have more control and impact as well.
I played "My Parties" from Dire Strait's album - On Every Street. The triangle, hi-hat, saxophone and bass/rhythm are etched precisely in the 3D soundstage, vocals dead on centre. The crack of the snare drum is reproduced with so much transient attack that it's frightening!
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Old 5th June 2011, 07:12 AM   #103
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Quote:
Originally Posted by sakis View Post

here is my 2 cents in your question ...before you make your choise remeber to read that the p3A the way i make it has a few changes (minor ) than the standard version ...Since class AB amplifier is no more than 10 topologies (at this range of power ) remember also that all these small details and the way implmeneted make a lot of diference ...
Hello Sakis,

why dont you share these changes with the forum, do you consider it IP you wont share or because Rod may object?
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Old 7th June 2011, 07:41 PM   #104
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well no ... since the circuit is free on the internet any one can do anything with it ...

through the post though all the things i ve done and changed have been reported more than once but let me refresh for you ...
--- i use my own pcb ( i ve been trying a few and setled in a specific one )
--- yet never heard an original version with an original pcb hell it could be by far better than mine but still dont know
----i use very carefully matched ltp stage
---- my ltp has thermal junction
---- my pcb features 4 R68 5W vitrohm resistors (paired in two per transitor )
---- been working so far with BD139-140 pairs but i found BD829-830 to sound better and with even less bias
---- been playing with 30-120ma of bias .... found that with slow drivers more is needed while faster ones will happily work with less
---- Drivers 829-830 are common heatsinked and feature also the VBE multiplier on the small heatsink
---- Been using mostly styroflex caps and i was happy and stable enough with 68of on the VAS next to the 100 that was placed originally
---- i use silver mika input filter capacitor
---- my pcb features rail capacitors on board ( 10.000 mfd X2 )
---- and finally on most of the P3A amplifiers i make i use the impossible to find 2SA1302
2SC3281
pairs since i have about 100 more original pairs available ....


be sure that very against to what Rodd says about the "amplifier being very tollerant to change or choise of parts" which is partially true since the amp will happily work very well with a bad choise of ltp but as i said be very very sure that small changes like the above will of course alter the performance of the amplifier ....

working with this amplifier for more than 4 years now and playing arround from time to time the above is my results in a nutshell ...

For the rekord i will state that eventhough latest times and with the economics world wide i am way to busy to update the thread too often but for you information rates remain as was in the first post and none of the comercial hifi i repair ( now days about 250 amplifiers per year ) has been able to beat a well made P3A from any aspect at the same power class ...

Finally i will have to state once more that i think the DX amplifier is technically a better amplifier than the P3A still the P3A remains more warm and musical ( benefit of the sziklai topology i think ) for my ears

happy regards
Sakis
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Last edited by east electronics; 7th June 2011 at 07:44 PM.
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Old 7th June 2011, 08:11 PM   #105
wahab is offline wahab  Algeria
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Quote:
Originally Posted by sakis View Post
---- and finally on most of the P3A amplifiers i make i use the impossible to find 2SA1302 2SC3281 pairs since i have about 100 more original pairs available.
Surely the most interessant feature in the list...



Quote:
Originally Posted by sakis View Post
still the P3A remains more warm and musical ( benefit of the sziklai topology i think ) for my ears
Yet, P3A is better with a classic double emitter follower and can be improved a little step further by using an adequate TMC compensation network.
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Old 7th June 2011, 10:10 PM   #106
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Originally Posted by wahab View Post
Yet, P3A is better with a classic double emitter follower and can be improved a little step further by using an adequate TMC compensation network.
Then, perhaps, it is no more a P3A.
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Old 8th June 2011, 10:02 AM   #107
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Thanks Sakis, I am always interested to read peoples enhancements to amps.
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Old 8th June 2011, 10:47 AM   #108
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small thing to to add and reverify the above is like that :

I made for a costumer a mod and installed two of my pcb in a specific very small size box the power supply ( existing ) could produce 24+24 volts after rectification ...obviously low ...specific board also was made with BD139-140 pairs and fairchild 1943-5200 and after carefull listening low bias is not the best for these pairs
higer somethink like 100 ma and everything is a bit warmer but sounds really fine

Kind regards sakis
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Old 8th June 2011, 10:50 AM   #109
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Yes, exactly my findings as well.
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Old 8th June 2011, 01:23 PM   #110
wahab is offline wahab  Algeria
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Quote:
Originally Posted by Ian Finch View Post
Then, perhaps, it is no more a P3A.
Well, the output stage would still use the same components
while TMC would require adding a little cap and a resistor.

Hardly a big change in the topology..
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