Strange noise from (ceriatone) Express itself, not speaker

[larseko]

Some time ago I received the complete (assembled) kit from Nik with the PPIMV(?) mod. It works well, but lately I have discovered a noise when running the amp with a Webe Mass attenuator.

When I have the Volume on about 1 o'clock, the MV cranked and the attenuator on bedroom level (almost 0, in other words), there is a slight hissing sound coming from the amp itself (I can hear it because the attenuator is turned way low, but I'm sure it's there when cranking up too). I don't know how to describe the sound, but it's kind of buzzing, like a headset with some heavy music inside. The sound appears only when playing, and it sounds like it comes from the power section (power tubes/trannies).

There is one thing I should mention. Just some time after I received the amp I managed to turn it on (very low) without plugging in the cab. Of course I knew not to do this, but I also have lousy short term memory, and forgot that I had plugged the connector out for some reason. It was just standing on standby for a few minutes, and then it was on for a short while (still with MV turned way low, about 0,5) before I became aware of my horrible mistake and switched the amp off. I started it up again afterwards, and it worked nice. I thought maybe it was sounding a tad darker than before, but that might have been just a psychological thing (I was expecting something to be wrong). I don't know whether this incident would have any such effect as the noise I've described here, but thought it better to describe the whole picture.

So, do you have any suggestions as to what might be wrong, if anything - maybe it's just normal? I'm still pretty noob with tube amps, but have built a small kit and know how to solder and make necessary precautions to work inside the amp. I just don't really have the grip of the amp circuit design yet.

Any help is greatly appreciated.

[tomrasdf]

I have the same thing happening to a 5f1 champ kit. Your description of loud, buzzy music through headphones nails it. I believe its resulting form the same dumb mistake (power with no load). I've since replaced about everything EXCEPT the OT and the problem remains. That's next in line. Anyone else heard of this?

[larseko]

I have the same thing happening to a 5f1 champ kit. Your description of loud, buzzy music through headphones nails it. I believe its resulting form the same dumb mistake (power with no load). I've since replaced about everything EXCEPT the OT and the problem remains. That's next in line. Anyone else heard of this?

That doesn't sound good, but makes sense, I guess. It sounds like it might be coming from the tranny... thanks for the reply.

What might the explanation be?

[Dai H.]

if it's coming from the OT (sort of a "zizz" or buzz), that would be normal. You usually don't hear it because you usually aren't in the situation of having the output section on full but acoustic volume near zero (IOW the speaker signal would normally mask the sound coming from the OT).

[larseko]

if it's coming from the OT (sort of a "zizz" or buzz), that would be normal. You usually don't hear it because you usually aren't in the situation of having the output section on full but acoustic volume near zero (IOW the speaker signal would normally mask the sound coming from the OT).

Ok, and that still makes sense when it only buzzes when there's a signal that is being amplified (ie I'm playing)? In that case, I'm relieved. Anyway, I don't think there's anything wrong with the amplified signal, so I guess I should just leave it at that

Edit. But... an OT from Tonesluts might be a worthwhile upgrade anyway? I have Ceriatone's latest and improved trannies.

[Dai H.]

sorry I have no idea. I have experienced a tonal change on a Marshall 50W going from the stock JCM800 OT to an OEI (for the better--which told me that a different OT can make a difference), but I don't have any experience with an Express or a clone.

[ren]

Correct, that noise is more than likely the OT.

[larseko]

Thanks, I'll just leave it there if that sound from the OT is normal.