Silverface Bassman Hiss (Oscillation?) Problem

[AtomicMassUnit]

It does sound like normal hiss at this point, but MUCH louder than it should be. I've owned dozens of bassman heads, and side by side with my vibrolux reverb, it is way way louder. All the power supply resistors and plate resistors have been changed to metal film. At this point, the preamp is basically rebuilt with good parts, and still hissing like a beast.

Here's a link to the schematic I'm using. http://www.thevintagesound.com/ffg/s...b165_schem.gif

I notice if I pull V2, the amp plays clean and sounds great, hiss is gone, of course at a loss of that gain stage. Could it be that the gain reduction from not having that tube in is quieting it down? Because I thought if the volume control turned the hiss down, it was happening before that control.

[AtomicMassUnit]

I have been doing all kinds of research on these heads, the different circuits, etc. I noticed the older AA864 model has the normal channel going straight to the PI and not getting the extra gain stage. With this amp, each channel sounds perfect when bypassing that extra stage, but hisses super loud when it goes through that. Could it somehow be the tube socket itself? I have changed every part in that stage, so what gives? Is there any step by step method I could use to figure this out?

[AtomicMassUnit]

I have been doing all kinds of research on these heads, the different circuits, etc. I noticed the older AA864 model has the normal channel going straight to the PI and not getting the extra gain stage. With this amp, each channel sounds perfect when bypassing that extra stage, but hisses super loud when it goes through that. Could it somehow be the tube socket itself? I have changed every part in that stage, so what gives? Is there any step by step method I could use to figure this out?

Update: I changed the tube socket and it did reduce the noise a bit. I'd say it's pretty tolerable now. I'd like it to be quieter, but I don't know any other methods of reducing it further.

One thing I noticed, comparing the amount of hiss to my Super Reverb, at full tilt they're about the same, but the Bassman gets louder faster (both noise and guitar signal) Both volume controls on the bassman seem to have a different taper to them than most, and even looking at the control. I think what I'm hearing is that the Bassman is about as loud on 3-4 as the Super Reverb is on 6-7. These are audio taper pots, though.

I'm really thinking about converting the normal channel to AA864 specs just so there's one that is super clean and low noise, and leave the bass channel as is, unless you guys have any other methods of quieting down the bass channel?