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If I say that it was horrible with San Audio 2A3 driven with buttery biased 6E5P then I really meant it.  I got home today tune it on and it was so bad that decided that it shell not use it as is. Even though it an experimental amps but still it beyond any acceptance. I run Tannoys from full-range Milq. With all imperfection of Tannoy RD it was Sound instead of the crap that 2A3 outputted. Could the 6C33C be so much superior to 2A3? I do not think so. The sound from 2A3 was truly broken – it was flat, blended and extremely boring.  The 2A3/45 that I heard out there did not sound like this. It was obviously a bug somewhere in it.

Then I begin to rollback in memory what I got this sound. Evan the original San Audio 2A3 with 6SN7 was more exiting in my view. I concluded that I got that sound when I introduced my 6E5P to San Audio 2A3. Does it mean that a pair of 6SN7 stage is better driver for this amp? Hm, I would argue with this assumption.

When I put the 6E5P in the game I used battery bias. I used very briefly a fixed bias with original San Audio 470R resistor and the garbage bypass caps that they supplied the kit. It was not good and then I move for Able Lithium 3.6V battery sitting on the grid. I did not go got a full scale Milq bias in San Audio as I did not want hassles with negative supplies, gas tube, dividers  etc.... Still, right along with introduction of 6E5P the indifferent sound came along…

I was thinking about this: how come that driving 6C33C (in fact driving anything one can imagine) the 6E5P was very fine but driving 2A3 it was dull like hell. I opened the amp and tested all – everything was perfect but there was no sound. I desired that before I put in there the full scale Milq bias I need to try one more time a cathode bias only with good parts. I kicked off the Lithium battery, leaving only 100R resistor as grid stopper (the 6E5P is very fast tube). In cathode of 6E5P I put 562R very good resistor and bypassed it with unavoidable 25V/1000uF Nichicon Muse KZ. The whole procedure took 15 minutes. I measured what I got. It was 4.1V on 6E5P’s cathode and 170V on plate – perfect. I closed the amp and plugged it in.

Abracadabra!

Well, the very first note I hear I immediately knew that the sound went back. I do not want to describe what got better – it was just very different sound – better or worse but it was already the Sound that might be worked with.  So, it was the battery bias that screwed me up. In the past what I true it did not like the result but it was not even close in misery to what I go now. Perhaps it was the brand of the battery or it might be that all battery bias work this way. I do not know that answer but I do not care now and I do not use battery bias anymore…

I still do not know if I like the San Audio amp but now it does not have the revolting sound. Back to business to make the amp to sound “interesting”…

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