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Old 20th February 2011, 05:24 PM   #1
tubemax is offline tubemax  Netherlands
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Join Date: Oct 2010
Location: Heemskerk
Default New build of P-P PCL86 Amp

Hello everybody!

This is my first post, I wish to show my latest build of very fine sounding PCL86 PP amp which is fully based on Dissident amp ( Yvesm ) & Gingertubes ( Giant Killer ) designs but with some changes on biasing of output tubes ( I used LM317 as CCS instead of resistors per channel ), power supply ( 2 x toroid 12V power transformers with secondaries connected together ) and fitting a complete pre-amp stage with RIAA from Audio Innovations 300 series amp.

My goal was to build practical, compact en cheap integrated amp. Total cost is about 200,-Euro in parts with Toroid power transformers, Hammond 125D output, Philips NOS PCL86 & new JJ ECC83S.

What can I say - very musical & sweet sounding amp with great stereo and pin-point presentation. I used pentode mode connection mostly because of Hammond 125D limitations - btw. considering how small it is - it sound really good, except for very limited low-end.

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File Type: jpg Image012.jpg (77.4 KB, 425 views)
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Old 20th February 2011, 10:57 PM   #2
Matt BH is offline Matt BH  United Kingdom
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Join Date: Jul 2009
Location: Cheltenham
Nice looking build

Got any photos of the innards?

Cheers Matt.
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Old 20th February 2011, 11:05 PM   #3
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aardvarkash10's Avatar
Join Date: Mar 2007
Location: Auckland, NZ
niiiiiice! Schematic?
"It may not be easy for some to not hear differences, even if they are not there." - Vacuphile,
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Old 21st February 2011, 08:17 AM   #4
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Looks nice, well done! What are the measurements on the frequency response? That always worries me a bit with the Hammond 125's, especially since you remark that the low end is limited. I'm kind of curious as to how this actually works out in a practical implementation using this kind of power tube.

I find that when using power trannies for OPT's (yes, it's filthy, but it's an option...), the low end tends to be quite well-represented, extending to about 40Hz in a 6AQ5 PP triode-connected amp I use daily. However, above 10kHz, performance tends to degrade quite badly. How do the Hammonds perform in your amp for high frequencies?
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Old 21st February 2011, 11:02 AM   #5
tubemax is offline tubemax  Netherlands
diyAudio Member
Join Date: Oct 2010
Location: Heemskerk
Default PCL86 PP


Thanks for kind words, to be more specific I used cheapest Hammond PP-output transformers model-125D for output duty and two standard toroid power transformers 220V/12V 200 WATT connected with secondaries together to form one high voltage ( about 230VAC ) transformer. It works very well with about 285 Volts on anodes of output tubes.
Only Hammond 125D are not really made for hi-fi use, there is not much power in the low-end, but mid & highs are excellent!
I based amp on proven design from DIY audio members ( look for Giant Killer or Dissident ECL86 amp ) and is probably best pentode sound I ever heard.
I used first two drawings to combine one that works for me and from third I picked LM317 CCS biasing...
At the moment I can't measure linearity of output transformers... I have no means to do so...

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File Type: gif PCL86-differential-PP-4.gif (18.3 KB, 286 views)
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