My DIY 2A3 amplifier

Folsom

VIP/Donor
Oct 25, 2015
6,024
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Eastern WA
Looks nice so long as you have banana plug speaker cables.
 

bazelio

Well-Known Member
Sep 26, 2016
2,493
1,745
345
California
Nice! Winding your own trafos!! Big props there.

Any hum as a result of using AC heating? Did you consider interstage trafos instead of coupling caps?
 

bigbulb

Well-Known Member
Jan 26, 2019
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Hi all,
Thanks! I have no hum problem because I'm using DC filaments. I tried AC and need a multi-turn balance pot to null out hum .
Yes, I love interstage transformer. I'm winding my own interstage transformer now, prepare to build another 4P1L single ended.
 

bazelio

Well-Known Member
Sep 26, 2016
2,493
1,745
345
California
Ok, I wasn't sure from the schematic, but I guess that F1 box is a rectifer. Have you tried a filament regulator?
 

bigbulb

Well-Known Member
Jan 26, 2019
7
4
83
54
Ok, I wasn't sure from the schematic, but I guess that F1 box is a rectifer. Have you tried a filament regulator?

Hi. Sorry , I should mention thats a rectifier. will edit it now. thanks for pointed out my mistake! I have filament biased board I built my own. It was in my other 2A3 , In fact, I built 6SN7-2A3, 717A-2A3, and 6C45-2A3 , and now 6E6P-2A3. filament bias board ( filament constant current + capacitor multiplier , just like Rod Coleman DHT filament regulator )
The filament regulator did provide good dynamic, and this amplifier is just to try out plate choke loaded driver stage.
 

bazelio

Well-Known Member
Sep 26, 2016
2,493
1,745
345
California
Great!! It's a lot of fun to tinker with this stuff. I wish I had time for it. Speaking of Rod Coleman, have you seen his shunt cascode design? I'd love to hear an amp based on that very interesting topology. He found a Russian 6E5P DHT (I think) makes a great driver for 2A3 or 300b - very high gain and linear. Maybe I should commission a build from you! ;-)
 

bigbulb

Well-Known Member
Jan 26, 2019
7
4
83
54
I have bunch of 6E5P as well, its nearly the same as 6E6P, both are very linear. 6E5Ps RP are slightly lower than 6E6P but I choose 6E6P because it last longer than 6E5P , This amp will ship to new owner one day, ( have to go, to fund my others project ) thats why I hope it can last longer. Thanks for the info about the shunt cascode design. I haven't try yet, but I did built something like constant current load for vacuum tube, a lot of fun to play with it.
Too many projects, too little time.
The new external microphone still on its way , I bought from Ebay, takes a long while to cross the pond. Hopefully it can provide me with better recording. Sure I will post an update here, thanks !
 
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