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6av5ga distortion spectrum

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Hi all.

I'm throwing together a push pull amplifier with parts from my stash. It's got the cheapest danbury 6k6 20 w opt in at is but these will be replaced next month. This amp is going to be a test bed as 310v and 6k6 seems to be ok for lot of tubes 6c4c 6av5 6p13s 6p20s el360 etc

Any how, its got 12av5's in at the minute triode strapped g2 to anode with 470r ad a soft bias of -60 for now, and d3a diff pair input/driver.

Anyhow.... The spectrum seems to be dominated by 3rd harmonic, anyone else found this?

Also any recommendations re opt, nothing too boutique as this is not my main amp, I was thinking of the better danburys or hammond 1650 etc

Enzo
 
This is obviously not a popular thread, but please indulge me sharing some results?

After a lot of bias fiddling and tube swapping (only have 4 12av5, 15 6av5 on their way from states) I seem to have hit a sweet spot, i think some cancellation or something in the mix.

6P52s 10ma 12k5 load 300vht, 12av5 -65-67v 310vht 6k6 load

1W 0.076% 3rd harmonic 4 db higher than 2nd
8W 1.28% using same driver ballance setting as the 1w or 1.1% if adjusted.

the 1W figure impressed me zero feedback.

enzo
 
I managed to get visual analyser working again tonight...


1% @ 8W
12av58w10.jpg




0.065% @ 1W
12av500651w.jpg



1khz

12av5sqrwave.jpg
 
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Thanks for your replys, I have MJ 1,2&3, not sure i'll be getting 4:)

Sounds ok, difficult to tell with just the one channel running, second opt will have to wait till payday friday!
It is less smooth and relaxed than my SE GM70, maybe more dynamic. Not too bad considering i only had to buy 4 tubes @$3/each and the rest was from my parts bin, worth developing i think. Best use i@ve found for 6j52p's sofar.

enzo
 
I just had the 'super' 6k6 danbury opt delivered, its smaller brother i already had. From looking at old posts i saw Andy Evans rates the smaller opt more highly but i thought i'd get one of each and compare. Specs say 10hz-70khz, ~$100 delivered. Just need to wire it up and start listening, oh and cut and plane the yew side panals, settle on a design and layout and replace cheap alloy top with thick copper. er and then start tube rolling output tubes, el36 6n21 6b4g etc




2013-01-29220305.jpg


enzo
 
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