Question about strange problem...

[turbo5speed]

Hi.

I made this Dumble clone wanna be that gives me a weird sound that its a bit hard to explain but i'll give it a try...

This happens both in the clean and overdrive channel but its more noticeable in the clean channel for obvious reasons. Whenever i play a note and let it ring i get this distortion effect over whatever i'm playing. Its not at the same volume as the note itself, its much lower but i can ear it. The sound is very fuzzy and with more bass.

It's not the speaker because i tried different ones. I have readjusted bias and the same thing happens. There is a little difference of 4mA between the two EL34 but they are more or less matched to think about cross-over distortion. OT? Faulty tubes? Anyone ever experienced this?

And it is not the weed...

Thanks in advance.

[T Wilcox]

If its not the weed it must be the POT
If you built the amp how are the heater wires ran? Above or down on chassis? Inside the amp chassis other than the heaters you should have as much separation between wiring as possible. 1/4 inch is usually enough but any closer and you start getting bleed over and noise.Wireties make everything look neat but can cause these issues.
Can you take pics and post them?
Todd

[turbo5speed]

If its not the weed it must be the POT

Right now the amp is in the rehearsal room but i can take pics latter. The heater wires are running against the chassis and i use shielded cable anywhere there is a signal.

Its driving me nuts.

[T Wilcox]

I have only ran mine above mainly because its easier to keep them away from the other wires. Another forumite here is right now in the process of redoing all his heater wires above rather than below because he was having issues as well, not necessarily the same issues although.
Pics would be very helpful.
How long have you been using the amp before this started?
I would also try different tubes as well, that could be the problem whether the bias is matched or not tubes can go bad. Sometimes brand new ones even.
As a matter of fact when my tubes on my JSX amp went bad it had the symptoms you described. Crackly sounding.
Hopefully some others will chime in as well.
good luck
Todd

[turbo5speed]

Ideas? Anyone?

Thx

[Structo]

Unless it is a tube or component, 9 out of 10 times it is lead dress.

If you don't have much experience it is more likely lead dress.

First though, did you rule out tubes by substituting known good tubes one by one until you tried them all? ( this mainly pertains to the preamp and phase inverter tubes)
4ma between power tubes is not a concern.

Then, if you can take some clear close up pictures of the open chassis I'm sure the guys here can help you straighten it out.

Is this a Ceriatone?

[turbo5speed]

Hi.

I am experienced enough

This is not a Ceriatone. This amp began severall years ago as a JMP50 kind of clone

Later i started to gradually change everything and its almost an ODS except for the output section that is typical Marshall. Believe it or not, after some tweaks it sounds very close to a Dumble but not quite

The OT and PT were custom made.

I haven't tried swaping the tubes because i need to order extra 12ax7. I use JJ's allround with E34L's in the power amp.

Now that i think about it, this problem became more evident when i removed the HRM...

The pics will have to wait since i will be playing this weekend and i dont have any other amp to use so...

Thanks.

[M Fowler]

Perhaps bleed through signal the clean channel and the OD section at the switch, could even be on the return path. Letting a low level distortion through.

Using just switching or relays or both on the OD section?

Mark

[turbo5speed]

Perhaps bleed through signal the clean channel and the OD section at the switch, could even be on the return path. Letting a low level distortion through.

Using just switching or relays or both on the OD section?

Mark

I think you may be right. I use these mini mini mini mini finder relays. Probably thats why both channels are beeing mixed. What do you think?

[talbany]

Perhaps bleed through signal the clean channel and the OD section at the switch, could even be on the return path. Letting a low level distortion through.

Using just switching or relays or both on the OD section?

Mark

I think you may be right. I use these mini mini mini mini finder relays. Probably thats why both channels are beeing mixed. What do you think?

Turbo
Here is the BM layout..make sure you wired the switching network like in the layout..

https://tubeamparchive.com/viewtopic.php?t=12875

Tony

[turbo5speed]

Perhaps bleed through signal the clean channel and the OD section at the switch, could even be on the return path. Letting a low level distortion through.

Using just switching or relays or both on the OD section?

Mark

I think you may be right. I use these mini mini mini mini finder relays. Probably thats why both channels are beeing mixed. What do you think?

Turbo
Here is the BM layout..make sure you wired the switching network like in the layout..

https://tubeamparchive.com/viewtopic.php?t=12875

Tony

It is not wired exactly like that but it is correctly wired. I simply dont use layouts, never got used to them. I work only looking at the schematics.

Next week i will be gutting the amp again and i am counting on your help.

Thx again

[danotron]

you may need a treble bleed

[turbo5speed]

you may need a treble bleed

Treble bleed?

[turbo5speed]

I get it. You mean a treble bypass in the volume pot.

[Structo]

No, the treble bleed is a high pass filter consisting of a .001-.002uF cap and a 500K trimmer that is put on the overdrive volume pot from the right hand lug to ground.
Then you adjust the trimmer to remove the desired amount of highs which help tame the fizziness.