ENGL Savage output level issue

[Heabow]

Hi

I'm reamping some guitars right now and I get a weird issue about output gain of my Engl Savage 120. When I record, the signal is louder (about 3db) at the beginning and progressively returns to its normal level. I can clearly see it on the screen. It's normal when it's playing for a few sec but when I stop a while and play it again the problem occurs again.

All the tubes are brand new (actually first time I use the amp since they get changed) and no problem with other amps.

Any idea?

EDIT - Here's a screenshot of the waves: https://dl.dropbox.com/u/36870048/Level issue.tiff Note that each time there's a silence, the level tend to be louder when it plays again. Also I find the amp make 'a lot' noise for new tubes, check it out: https://dl.dropbox.com/u/36870048/Noise.mp3

 

[Heabow]

Anyone?
Problem should come from the power tubes I guess and/or bias although I paid a tech to do that properly.

 

[aortizjr]

Sounds like bad tubes to me. Even if they are new, they often fail right out of the box.

Buying them from a place that does a burn-in helps. But even then they could still fail really early.

So I would start there. After that, take it to a tech. Could be a few things wrong.

 

[Heabow]

Yeah that was my first idea although there's no problem with the sound. I brought it to the tech who changed the tubes and set the bias. He had no idea what's the problem, first time he heard about such a thing!?

 

[aortizjr]

Yeah that was my first idea although there's no problem with the sound. I brought it to the tech who changed the tubes and set the bias. He had no idea what's the problem, first time he heard about such a thing!?

Well how much faith do you have in your tech?

I assume you have done all the stupid stuff, changed guitars, cables, etc. I have had similar symptoms with a bad cable. You could squeeze it at the jack and the volume would come back then slowly fade away.

Did he clean the jacks and tube sockets? I had a dual rec that would fade in and out while playing. Turned out to be a bad input jack. FX loop jacks (run a cable from the send to return).

Really could be the pre-amp or power amp. Short circuit that by running the FX send into your DAW and/or running another pre-amp or pedal into the power amp section. Obviously will determine one or the other.

Then at least start by swapping tubes.

If both, then it is likely a power supply issue (symptoms do point there also). I can't remember if the Savage has a tube rectifier. Based on the noise I heard, could be filter caps, rectifier, or another cap in there somewhere not doing its job. Bias circuit could also be having issues.

As far as the sound goes, I have had amps come in that sounded better broken. Crate's SS amps in particular sound that way to me... the silence is better

But seriously problems like this are a bitch to track down. A scope helps and detailed schematics with voltage check points. ENGL is a bitch since their boards are upside down too. So by the time you get into it for inspection, you might as well start swapping even slightly suspicious parts. The extra $10 in parts will save you tons of time.

Best of luck!

 

[Heabow]

Thanks a lot man! I will inspect all these things. I hope this is only a tube issue.....