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Solens and power supply ghosting

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5/18/2005 7:51 PM

Michael Polutta

Solens and power supply ghosting

Like nearly everyone on this board (it seems ;-)

;-)

I have a Bandmaster Reverb chassis as a prototyping amp. One thing I'm trying right now is an ALL-Solen PS cap arrangement. However, I'm getting some pretty significant ghosting. I have 44uF as the 1st (plate) filter, 22 as the 2nd (screens). This is more filter capacity than the Bandmaster Reverb came with stock.

Has anyone else experienced this phenomenon? Could it be a Solen-caused issue? Could a ground loop cause ghosting? It does not happen at lower volume.

Any guidance is appreciated.

5/19/2005 12:31 AM

I've got three amps with solens installed and I have no problems with ant sort of oscillations.
Kevin O'Connor says you can use less capacitance using the solen type caps and still get good filtering.

Are all of your filter caps Solens, or just the first two? You might want to check any electrolytic filter caps for leakage and ground connection.

You might check your layout, especially grid leads, shielding those is good.

Db

5/19/2005 5:43 AM

Michael Polutta

Except for the last stage for one channel, every PS cap in this amp is a Solen.

44uF on the plates, 22 on the screens, 15 on the PI, 15 on the effects loop, 10 on the clean channel.

I've also tried a SS rectifier just in case the Copper Cap wasn't sending enough current to keep things charged. Going to try different power tubes next - have the Sovtek 5881s in there now. Then I'll triple-check the grounding scheme...

5/19/2005 9:28 AM
Michael Polutta	Well, I changed one ground in the PS. The screen filter is now grounded with the plate filter, and things seemed much better, but I didn't get to test it for long. I'll try to update later this evening when I can give it a loud workout...

5/19/2005 11:15 AM
jaysg	Q: Solens Do the big solens actually fit in the doghouse? Nice to see you back after too long an absence. Now if Gil Ayan and Jack Zuker would drop in more often...

5/19/2005 11:43 AM
Michael Polutta	Thanks. No, I am sans-doghouse for now. These are nowhere close to fitting in the standard doghouse. The one I would need would have to be bigger in 2 dimensions - height and length.

5/19/2005 7:03 PM
Michael Polutta	Update - and Parasitic oscillation? Could that be what I'm hearing? It only happens when I really crank it up. Doesn't parasitic oscillation manifest itself at most any volume? BTW, the ground rerouting did make it significantly better - but not yet all the way to "good".

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