Need help with something wierd

[RoninAudio]

Hey all.  I am designing and building an amp circuit that is giving me all kinds of fits.  Firstly, I started with a build that worked just fine.  It was a 6SJ7, 6SN7 fx loop, and SE 6V6.  The sound is amazing. BUT, it was pretty much clean,...really clean and didn't have a good stage volume level.  Great for a studio, not for live performance.

So, I decided to up the power section to SE parallel 6L6's in triode configuration, and add an additional 6SN7 in parallel for a driver.  The problem I am having is that when everything is in one chassis, I have pretty loud noise created somewhere in the preamp.  When I say noise, I mean it sounds like you're trying to tune in a radio station.  Static and hiss.  The noise is not filament or PT related at all.

Oddly enough, I can jumper in the preamp from the original build directly to the output section and get AMAZING tone, drive and overall sound with virtually no noise at all.  It would seem that this would be the noisiest thing in the world, but not.  I have built the new amp identically to the first version, layout included.  But, even when I bypass the second 6SN7 and go from FX loop recovery stage to output stage, noise is still there.   

I've racked my brain on this, and am sure it's something stupid.  For some reason my eyes can't see it, and my mind can't think of it.  I'd appreciate ANY thoughts or advice on this one.

[pdf64]

Schematic and layout designs, and good photos of the build, would be helpful.
In the meantime, just like an uncompensated opamp, you may wish to consider limiting the amp's gain bandwidth product, eg roll off the ultrasonics.

[shooter]

^^ we like schematics here


your description sounds like there is either, high power signals getting too close to sensitive signals, iffy/sketchy grounding, including things like input jacks, FX jacks.


does the "noise" exist with nothing plugged in, just sitting idling?
If so;
does it change with knob playing, Vol, TS?

[sluckey]

I have built the new amp identically to the first version, layout included

I suspect something is not identical.

[RoninAudio]

Schematic and layout designs, and good photos of the build, would be helpful.
In the meantime, just like an uncompensated opamp, you may wish to consider limiting the amp's gain bandwidth product, eg roll off the ultrasonics.

I'm working on making the schematics accurate and will upload shortly.

[RoninAudio]

I have built the new amp identically to the first version, layout included

I suspect something is not identical.

You're correct,... the identical refers to the original values and layout of the 6SJ7 and 6SN7 effects loop.  The problems have only come in by trying to add another gain stage, the additional 6SN7 in parallel.  I'll get some photos up in just a few.

[RoninAudio]

Well, all, thanks for the help.  As it turns out, one of my NOS "certified perfect" tubes was bad.  Preamp tube was gassing a bit.  Put in a red metal 5693,.... perfection.

I'll share the build with you all once I get a few things finished up.  Thanks again.