Tube DIY Asylum

That is great news slownlo

76.3.35.245

In Reply to: RE: Push/Pull OPT question... posted by slownlo on May 10, 2008 at 06:47:00

Hi slownlo,

Am glad you are attending to this. All along, I kept on telling you up here "it was non-optimized grounding and layout". :-)

Realize this, with AC heating of the JJ 2A3-40, or any other 2A3 for that matter, there will ALWAYS be some residual hum from the AC filament, a few millivolts on the output transformer's secondary with the speaker hooked up. One totally excellent reason to use a 2A3 is because of its 2.5 VAC filament, where this humm on A.C heating is minimal (versus DHTs with higher filament voltages, say a 300B at 5 VAC or a 6B4G at 6.3 VAC, or a GM-70 at 20 VAC).

You always DO have a choice to go to D.C heating, to buck-out the slight humm you hear when standing near the driver, but you will gain this "dead silence" with a certain real COST, a trade-off.

Because, Clinton, **** with DC heating, not only do you buck-out the humm, but you also buck-out the MUSIC and the sensitivity of the amp to the audio signal. ****

So, now we make a design judgment call, (dealer's choice) buck the humm totally, (the very last vestiges of the 2A3's humm), or ..... buck-out some of the music.

Lets KEEP THE MUSIC!!!! A 2A3's 2.5 VAC filament ALLOWS us to use superior sounding AC heating. If you lived and listened to it both ways, DC versus AC, I know you will want to keep all the music intact!! There my friend, now you have it !! This further reinforces the use of a 2A3, doesn't it. Capish??

Congratulations for hanging in there on getting this DC amp build done, I commend your effort and tenacity. Yes, I can imagine it sounds quite good on those K-Horns fella !! Its totally IM-possible to eclipse a L-S.E.S. supply and proper layout, in my humble opinion. Enjoy your build and all your music now slownlo!

Jeff Medwin

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