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**tony sayer** · December 2nd 07, 11:55 AM posted to rec.audio.tubes,uk.rec.audio

In article , GLM labbe-
scribeth thus
adding a bypass cap works up to a point. you seem to have removed all the
ripple a cap could remove.

From the waveform, it sounds like a bad isolation issue: adding caps will
help but you'll need much more than nanofarads to get that slow ripple out.
Use bigger caps if you want to keep it to simple cap patching (something
like 1100uF or 2200uF is nice.

Personally, I prefer the capacitor array method to the simple addition of
single poles.

Power supply would go as such:

XFO - DIODE BRIDGE(tube rect for purists..)- Pi Filter (Shunt cap +choke +
shunt cap)

At equal main's frequency attenuation, the tradeoff is the filter's
inductance vs instant current draw. I usually lift off that limit by using
bigger chokes and a few (BIG) tank capacitors right after the pi filter (I
like arrays of 1100uF,2x2200u,3300u...you can make a nice little square with
1-sided pcb routing if you put 2 together...little footprint, nice instant
draw compensation).

You got a schematic somewhere of that PSU? Tweaking the pi filter should get
rid of the problem

GLM

You can get high voltage switch mode power supplies these days
y'know;-)..
--
Tony Sayer