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Unexpectedly good EL84 amp
Unexpectedly good EL84 amp
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Old 26th March 2011, 06:55 PM   #11
andyjevans is offline andyjevans  United Kingdom
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No global feedback I see. I did much prefer my EL84 amp without.

I originally tried UL with no global feedback. It was better than with feedback but I felt that there was a hint of sharpness so didn't pursue it

Andy.
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Old 26th March 2011, 07:21 PM   #12
Poindexter is offline Poindexter  United States
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Quote:
Originally Posted by Eli Duttman View Post
I would think power O/P is less than 8 WPC. Look at page 3 of the GE 6BQ5 data sheet, where some PP AB1 triode mode conditions are given..
Whut Eli sez. You are going to get four watts, maybe five max, from this circuit. If you load down the outputs with a lo-Z output transformer in the attempt to get a little more power, you'll get that late tube soft sound.

That said, you'd be surprised what five watts can do, as long as you're not trying to drive Acoustats with 'em.

Aloha,

Poinz
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Old 26th March 2011, 07:58 PM   #13
Shoog is offline Shoog
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I really would be inclined to try an experiment of disconnecting the bypass cap on the outputs and seeing how it sounds. It shouldn't make much difference to the output power.

Shoog
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Old 26th March 2011, 08:35 PM   #14
cjkpkg is offline cjkpkg  United States
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I have built this one too!

I made a couple tweaks so far...I implemented a CCS for the EL84 cathodes using an LM317 to hit 80mA total per channel.

I also implemented some red LEDs for the front cathodes of the 6n1p's in lieu of the resitors.

This amp really rocks! and is very tweakable...
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Old 26th March 2011, 08:42 PM   #15
woodturner-fran is offline woodturner-fran  Ireland
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Shoog - you mean the 1000uf on the cathodes of the 84s?

Cjkpkg : would you post some schematics?


Fran
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Old 26th March 2011, 08:47 PM   #16
Shoog is offline Shoog
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Yes that one. It would become semi-differential. If it worked then replace the 400R with a LM317 CCS.

Shoog
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Old 26th March 2011, 08:55 PM   #17
Wavebourn is offline Wavebourn  United States
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Unexpectedly good EL84 amp
Nice amp. Very optimal, and should sound nice.
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Old 26th March 2011, 08:58 PM   #18
6L6 is offline 6L6  United States
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Unexpectedly good EL84 amp
Hmmm..... I think I should use my old Fisher guts/chassis and make this amp...
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Old 26th March 2011, 09:33 PM   #19
Lingwendil is offline Lingwendil  United States
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I've built this amp up, but with 6CG7 drivers and Sy's led output stage biasing scheme. Very nice amp, and plenty of volume from every speaker I've tred, even low efficiency types. Very nice sound, tryed a led on the 6cg7's cathode, and it seems like slightly more usable volume before breakup. All in all, a great amplifier.
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Old 26th March 2011, 10:02 PM   #20
woodturner-fran is offline woodturner-fran  Ireland
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This is how she turned out:

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