Noisy amp

[HeimBrent]

Hello!

I've gotten myself an OLD Earth Bass Travler-amp(BT-2000) for the fun of it, but it seems to be a slight problem regardig noise. It almost sounds like a guitar with a really bad fretbuzz when I play through it. One thing is that's noisy when turned on, but the fretbuzz-kinda noise while playing is bugging me. Any ideas on what it might be?

And yeah... It ain't the guitar having fretbuzz

[Enzo]

Have you tried more than one speaker? it almost sounds like a bad speaker with a rubbing voice coil from your description.

[Sir Cuitous]

I would have said tube socket rattle, but then I read this Haramony Central review which mentions buzz:

http://reviews.harmony-central.com/r...ss+B-2000/10/1

[HeimBrent]

I have tried several speakers, and that ain't the problem. And the tubesockets can't be loose as... Well; it's a SS amp

[HeimBrent]

And it looks like the one that have gotten that HC-review is a bit more complicated then mine. Mine have 2 channels, 2 inputs per channel, one volume per channel, one treble-pot and one bass-pot. That's it. And it's "only" 45 watts.

[Enzo]

Does this one use a small transformer to drive the output transistors?

Unplug the speaker, is there a DC offset at the output terminals? More than a quarter volt anyway.

In any case, it could be numerous things, but considering the age, I would explore the power supply first. Are both the positive and negative main power rails both up to voltage and are both CLEAN? SCope them for ripple. Watch them as the amp cranks power. The caps might be OK when nothing is happening, but they cannot hold up under load. SO apply a stiff signal and see if the rails sag and get ripply.

This has a couple op amps? One op amp? If so, check its power rails too. They would likely be dropped to zeners - likely 12 to 15v zeners. Are both rails the same? A collapsing zener would leave a low rail and that would distort things.

If this has the drive transformer, what does the signal look like on its primary. One end goes to B+, while the other end is driven by a transistor. Look at that end - or the transistor collector. The NFB only goes as far as the output driver, so looking at the waveform stage by stage will see if there is distortion anywhere there.