buzz on volume control from about 0 to about 2-3, quiet when higher

[isaac_teller]

What would cause this? Thank you.

[Latole]

Buzz or scratchy volume ?

Wich amps ?

I had a scratchy volume pot on vintage amp ; answer : bad filter caps
A DC leaky signal cap could be a issue too

[sluckey]

Do the simple stuff first. Test the pot. Ohm meter connected to ground and wiper. Set the pot to zero. Resistance should be close to zero ohms. Now turn the pot up slowly. Resistance should smoothly increase. If you don't have an analog meter you will have to turn up very slowly so the dmm display can do it's sample/update.

Or you could just replace the pot and re-evaluate.

[PRR]

Buzz on zero?

Pot "ground end" is not at same potential as next-stage's ground reference.

[pdf64]

It’s unhelpful to ask technical generic questions, as generic answers are impossible. Or at least are rather more complex than necessary.
As the particulars of any scenario are critical facts.

Buzz on zero?

Pot "ground end" is not at same potential as next-stage's ground reference.

Need the schematic or at least some specifics on the amp in question.
As with some, eg 5E3, the volume control isn’t wired as a pot, so the issue could be due to poor lead dress or a hummy tube with unbypassed cathode.

[isaac_teller]

The amp is a 50 watt Marshall JCM800 style with reverb.

[Latole]

Buzz or scratchy volume ?

[isaac_teller]

Definitely a buzz(50 Hz)

[pdf64]

Schematic - there lottsa jcm800 models?
Is it a DIY?
Was it ever buzz free?
What controls affect the buzz? Has a tube issue been eliminated?
What’s the resistance between any part of the heater circuit and chassis 0V?

[Latole]

Schematic - there lottsa jcm800 models?
Is it a DIY?
Was it ever buzz free?
What controls affect the buzz? Has a tube issue been eliminated?
What’s the resistance between any part of the heater circuit and chassis 0V?

IMO, with reverb, it is a DIY 

I built from scratch a Marshall Master volume  model 2204 with reverb "a la Fender"
Work great

[2deaf]

IMO, with reverb, it is a DIY 

I have two Marshall JCM800's with reverb, so reverb is not a distinguishing feature of DIY.

[Latole]

IMO, with reverb, it is a DIY 

I have two Marshall JCM800's with reverb, so reverb is not a distinguishing feature of DIY.

Always something to learn here, thank you

[aabbs20]

Schematic - there lottsa jcm800 models?
Is it a DIY?
Was it ever buzz free?
What controls affect the buzz? Has a tube issue been eliminated?
What’s the resistance between any part of the heater circuit and chassis 0V?

I don't mean to hijack this thread, but this is interesting to me. Where did you insert the reverb?

IMO, with reverb, it is a DIY 

I built from scratch a Marshall Master volume  model 2204 with reverb "a la Fender"
Work great

{EDIT -- untangled quote -- PRR}

[Leevi]

Based on the similar cases I have had it can also be a wiring issue.


Try to move the signal wires and listen if there is any change.

/Leevi