Nick Gorham wrote:
Andre Jute wrote:
Nick Gorham wrote:
Andre Jute wrote:
The "KISS Amp WE300B SE Ultrafi" (1) has been finalized. This is a
project that was designed step by step on rec.audio.tubes. The
This may have been covered, in which case, sorry, but why is the signal
ground point taken back at the rectifier? Doesn't that make the output
stage signal loop include the choke and snubbers in the supply?
--
Nick
Aha! At last, a substantive point. Where in my amp would you take off
the ground for the power supply, Nick? Same question to everyone who's
ever built a tube amp; don't just assume Nick will give the same answer
you will. Grounding is one of the last, possibly the last, unexplored
frontiers in hi-fidelity tube amplifiers.
I'll explain what I actually do, what I consider optimum when possible,
and what others have done when we have your answer and reasoning to
hand.
Well, its a loaded question, as without building and testing, I am not
certain that I would use the common mode choke. Or if I did and found it
offered improved noise performance I would use a WE or ultrapath bipass
arangement to avoid the problem. Without that, I would see what the
issue was with grounding after the choke, with the expectation that it
would possibly introduce switching noise from the mains TX, which may
well defeat the use of the CM choke in the first place.
Personally I would use a series regulator in the supply (either
referenced to a voltage ref, or just as a shunt) and not the CM choke,
as I have found that they sound better than anything else I have tried.
So, what was your findings?
--
Nick
Nick
I wrote you a long letter which fortunately was not delivered and then
actually looked at the circuit. What happened is that I added the
snubbers over the chokes at the last moment, before sending the circuit
to the net. Before that the power filter had a star ground, the input
had a star ground, both were the same star ground, so it didn't really
matter where I parked the earth while I did major surgery on the
schematic to make space for the snubbers (1), and then I just
overlooked moving it again. It is exactly for this kind of correction
that I post the schematic to RAT and UKRA before making any other
public announcement. (It's a pity that some resident quarterwits take
that as a license to indulge in childishness, but strictly for such
self-selecting fools I do a little sleight of hand with (Gain) cards
and simple stuff about bike computers they can look up, then they go
off on a wild rabbit chase and fall over their own feet at the same
time, as intended, much to the amusement of the rest of us.)
In more "normal" or simple supplies I routinely use the earthy end of
the bleeder at the end of the supply as a star ground. You can see a
one here,
http://members.lycos.co.uk/fiultra/K...0T68MZ417A.jpg
where the bleeder is the ali-cased resistor behind the right-hand
battery box and its right end is the star earth for all sections.
Thanks for your help. I'd like you to contribute when we discuss my
next project.
Andre Jute
Visit Jute on Amps at
http://members.lycos.co.uk/fiultra/
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(1) The choke snubbers seem to have little sonic benefit. They protect
the longevity of the chokes and the power tranny, all of them expensive
items.