5E3 whistling noise until warmed up

[rdh006]

Hi guys,

I have a 5E3 clone that I built from a Mission kit a few years back. It's a good sounding amp, which has served me very well. I've used it mic'ed up at gigs for several years and it has been completely reliable. Somewhere along the line I added power scaling for small gigs, which has also been in there for a long time with no problems, except for a little residual hum which I couldn't filter out.

The amp has started making strange noises -- difficult to describe, someone said it sounds like the noise you get when you stretch the neck of an inflated balloon and let the air out. If that rings any bells, it's actually a good description of the noise. Like a scratchy whistling sound that goes up and down in pitch.

After a few minutes, when the amp is thoroughly warmed up, the noise goes away.

I am not an expert in amp building. I have built a few, but mostly from kits, where the design/layout/troubleshooting expertise came from someone else. I don't have a scope or any advanced testing tools, just a multi-meter.

I have chop-sticked throughout the amp without coming up with anything. In terms of layout, I have moved wires about with the chopsticks, in terms of components I have examined everything and tapped everything. I have replaced the preamp tubes with new TAD 12AX7s. (The amp has had a 12AX7 in V1 from the word go). I changed the power tubes a short while ago and the noise was there both before and after.

So I wondered if anybody might have a clue where I would start to look for the cause of this -- perhaps there is an application of logic which can narrow the field?

Any help appreciated.

[The Dude]

Is the noise from the speaker or from the amp internals? From the description of the noise, it sounds like a cap with a popped top.

[m1989jmp]

Hi guys,

I have a 5E3 clone that I built from a Mission kit a few years back. It's a good sounding amp, which has served me very well. I've used it mic'ed up at gigs for several years and it has been completely reliable. Somewhere along the line I added power scaling for small gigs, which has also been in there for a long time with no problems, except for a little residual hum which I couldn't filter out.

The amp has started making strange noises -- difficult to describe, someone said it sounds like the noise you get when you stretch the neck of an inflated balloon and let the air out. If that rings any bells, it's actually a good description of the noise. Like a scratchy whistling sound that goes up and down in pitch.

After a few minutes, when the amp is thoroughly warmed up, the noise goes away.

I am not an expert in amp building. I have built a few, but mostly from kits, where the design/layout/troubleshooting expertise came from someone else. I don't have a scope or any advanced testing tools, just a multi-meter.

I have chop-sticked throughout the amp without coming up with anything. In terms of layout, I have moved wires about with the chopsticks, in terms of components I have examined everything and tapped everything. I have replaced the preamp tubes with new TAD 12AX7s. (The amp has had a 12AX7 in V1 from the word go). I changed the power tubes a short while ago and the noise was there both before and after.

So I wondered if anybody might have a clue where I would start to look for the cause of this -- perhaps there is an application of logic which can narrow the field?

Any help appreciated.

I had a similar problem when flipping the standby switch to playing position with my 2204 clone. I was running JJ EL34's at the time and switched other EL34's in without help along with all preamp tubes.

Also, I tried cleaning every damn pot, socket etc. before that and still the noise was there.

It would start like this, but a lot less severe, barely audible, and would turn into that air balloon type of thing (or long tearing with pitch shifting) you mentioned until finally disappearing:

https://www.youtube.com/watch?v=-CBJSzC88Lg

I had some Mesa 6L6's laying around so I adjusted bias range and popped them in. To my surprise the noise stopped; I figured thicker pins did the job since tubes were a lot tighter in the sockets.

I hope someone knows exactly what's the cause of the problem, but everybody I asked couldn't give me an exact answer. Everyone said dirty pins/sockets/jacks etc.

[rdh006]

Is the noise from the speaker or from the amp internals? From the description of the noise, it sounds like a cap with a popped top.

Thanks for helping out. The noise is definitely coming through the speaker.

Do you mean filter caps?

[rdh006]

I had a similar problem when flipping the standby switch to playing position with my 2204 clone. I was running JJ EL34's at the time and switched other EL34's in without help along with all preamp tubes.

Also, I tried cleaning every damn pot, socket etc. before that and still the noise was there.

It would start like this, but a lot less severe, barely audible, and would turn into that air balloon type of thing (or long tearing with pitch shifting) you mentioned until finally disappearing:

https://www.youtube.com/watch?v=-CBJSzC88Lg

I had some Mesa 6L6's laying around so I adjusted bias range and popped them in. To my surprise the noise stopped; I figured thicker pins did the job since tubes were a lot tighter in the sockets.

I hope someone knows exactly what's the cause of the problem, but everybody I asked couldn't give me an exact answer. Everyone said dirty pins/sockets/jacks etc.

Thanks for replying. The noise in your youtube link is more of a crackle than mine. I saw a post where someone talked about the noise from a tea kettle -- it's a bit like that, but varies in pitch. Also reminds me of the interference/squelching noise you'd get with old radios.

[rdh006]

Does the fact that the noise goes away when the amp warms up give a clue?

[The Dude]

Yep. I meant filter caps. You'd be more likely to hear the noise from the chassis than speaker, but I suppose it could still be a cap. Did you use radial caps for the build? If so, inspect them and see if the tops of any are split.

[m1989jmp]

Thanks for replying. The noise in your youtube link is more of a crackle than mine. I saw a post where someone talked about the noise from a tea kettle -- it's a bit like that, but varies in pitch. Also reminds me of the interference/squelching noise you'd get with old radios.

See my post; it would start as ripping/crackle but would turn into the sound you described. Mine would go from higher to lower pitch a couple of dozen times and then stop.

[rdh006]

Yep. I meant filter caps. You'd be more likely to hear the noise from the chassis than speaker, but I suppose it could still be a cap. Did you use radial caps for the build? If so, inspect them and see if the tops of any are split.

The caps are inline. I can't see any cracks or blisters.

[rdh006]

See my post; it would start as ripping/crackle but would turn into the sound you described. Mine would go from higher to lower pitch a couple of dozen times and then stop.

Right. Sounds like a similar issue, then, except that changing tubes has not fixed it for me.

[nickb]

What effect do the controls have on the problem?

What happens if you allow to warm up, turn off and then on again?

[dstrat]

that sound in the vid is usualy leaky coupling cap or caps.
very small dc hitting a tube grid sounds just like that and its common for it to go away when it heats up.
seems to get worse in the video!

[rdh006]

What effect do the controls have on the problem?

What happens if you allow to warm up, turn off and then on again?

The Normal volume has little effect on the noise.
The Bright volume has much more effect on the noise.
The volume controls are somewhat interactive on this amp which confuses the issue to some degree.
The noise goes away altogether with the tone control turned down -- but then the whole amp is shut off anyway.


If I allow it to warm up, turn off and then on again, it is the same before and after -- the noise is still there, to the same degree, as far as I can tell. If I turn it off and back on while the noise is there, the noise is still there. If I turn it off and back on while the noise is gone, the noise is still gone.

Thanks for helping.

[rdh006]

that sound in the vid is usualy leaky coupling cap or caps.
very small dc hitting a tube grid sounds just like that and its common for it to go away when it heats up.
seems to get worse in the video!

Thankyou. Is there a way to test, or is it a question of replacing caps?

The answer to nickb's question above may be highlighting something about the Bright channel -- would that narrow down your focus at all?

[The Dude]

Do you have a scope?