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In Reply to: RE: GM70 OPT update posted by deafbykhorns on May 01, 2017 at 17:08:23
When you changed just the output transformer,that changed the 1khz sq wave that much? If you using some global feedback with a resistor/cap combo,you need to add come capacitance across the feedback resistor. Start with about a 70pf and go up a little until the spike ringing in the corner disappears.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Follow Ups:
Yes, it was pretty dramatic.
No global feedback, SE GM70, 1150v is a little dangerous to starting clipping in caps.
Not so sure this little bit of ringing is important on a sq wave. My Slagle transformers behave similarly to sq waves and they are some of the best opts I've heard to date. I have the leads clipped in right now so it may contribute somewhat at this voltage. Could also be the GM70 tube contributing as well. I might try my copper plates and see what happens.
From what I've heard, ringing sounds harsh and annoying, I don't hear any of this.This is one anomaly we never see in spice.....
The IT gave me some more drive with headroom to spare.
Edits: 05/01/17 05/01/17
The Hammond output transfomers should easily be good for a pure 1khz sq wave but being you have 1150vdc,it is probably breaking down that transformer a bit between the windings.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken
Hipot test is 2kv
Add gain on top of that and yikes! The hammonds were a good starting point, i didn't want to invest more until I was sure with my design. This was my first 1kv+ amplifier
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