#124 Questions

[rootz]

Sounds like dirty tube sockets or a dry solder connection. Did you already wiggle all tubes?
Also, if it’s the power tubes, the amp would behave like this without preamp tubes.

[Bombacaototal]

Sounds like dirty tube sockets or a dry solder connection. Did you already wiggle all tubes?
Also, if it’s the power tubes, the amp would behave like this without preamp tubes.

Good point. I will remove my PI tube and check if this still happenes. Also will wiggle all tubes as suggested. I will report back..

[Bombacaototal]

So, I removed the PI tube and no longer have that interference sound. We can probably eliminate any issue on the Power section. I will check each pre amp tube now and then do the chopstick test.

EDIT: replaced the PI ax7 and no more issues!!! Thanks everyone for the help

As far as the reverb pan hum from the PT the ferrus sheet arrived today but makes no difference if I Place it between the PT and pan or close to the PT

[markusw]

As far as the reverb pan hum from the PT the ferrus sheet arrived today but makes no difference if I Place it between the PT and pan or close to the PT

Maybe it helps if you add a ~470p cap in front of the grid (or grid stopper resistor if there is one) of the first 12ax7 reverb recovery stage of the reverb section to get a high pass filter?
Probably would also need an e.g. 1M resistor to ground after the 470p in case there is no grid resistor.
The high pass might help to reduce the 50 Hz hum.

Regards,
Markus

[rootz]

As far as the reverb pan hum from the PT the ferrus sheet arrived today but makes no difference if I Place it between the PT and pan or close to the PT

Maybe it helps if you add a ~470p cap in front of the grid (or grid stopper resistor if there is one) of the first 12ax7 reverb recovery stage of the reverb section to get a high pass filter?
Probably would also need an e.g. 1M resistor to ground after the 470p in case there is no grid resistor.
The high pass might help to reduce the 50 Hz hum.

Regards,
Markus

Only if the hum is not an consequence of coupling between the output inductor of the pan and the pt.

You tried wrapping around the pan? And good to hear the crackling issue was solved so quickly!

[markusw]

Maybe it helps if you add a ~470p cap in front of the grid (or grid stopper resistor if there is one) of the first 12ax7 reverb recovery stage of the reverb section to get a high pass filter?
Probably would also need an e.g. 1M resistor to ground after the 470p in case there is no grid resistor.
The high pass might help to reduce the 50 Hz hum.

Regards,
Markus

Only if the hum is not an consequence of coupling between the output inductor of the pan and the pt.

Edited: No matter if the output inductor or the input inductor of the reverb pan picks up the hum from the pt a high pass "after" the pan e.g. in front of the first recovery stage (that is "after" the pan) should help to reduce the 50 Hz signal that is amplified by this stage (and the following). At least this is my understanding
A 470p/1 Meg filter would have a Fc of 338 Hz and would attenuate a 50 Hz signal by roughly 16.5 dB.

[Bombacaototal]

As far as the reverb pan hum from the PT the ferrus sheet arrived today but makes no difference if I Place it between the PT and pan or close to the PT

Maybe it helps if you add a ~470p cap in front of the grid (or grid stopper resistor if there is one) of the first 12ax7 reverb recovery stage of the reverb section to get a high pass filter?
Probably would also need an e.g. 1M resistor to ground after the 470p in case there is no grid resistor.
The high pass might help to reduce the 50 Hz hum.

Regards,
Markus

Only if the hum is not an consequence of coupling between the output inductor of the pan and the pt.

You tried wrapping around the pan? And good to hear the crackling issue was solved so quickly!

This is what I ordered

https://uk.farnell.com/wurth-elektronik ... f-00001000

Unfortunately its too small to wrap around the PT or the pan. I also realised it is ferrite instead of ferrous.


Still awaiting on the muMetal. Hopefully it will do the trick

[rootz]

That really is great stuff for shielding! Against high frequencies like in the MHz range Don't want to sound pedantic (but probably will for the last time this year): always read the datasheet.

From my side of the pond: happy new (amp) year!

[Bombacaototal]

That really is great stuff for shielding! Against high frequencies like in the MHz range Don't want to sound pedantic (but probably will for the last time this year): always read the datasheet.

From my side of the pond: happy new (amp) year!

Yes, totally my fault on this one.

Happy new amp year!

[Bombacaototal]

I think the nice washers for the toggles are not creating a tight enough connection to the chassis. I rewired the deep like Dumble and still having the same issue, of getting some interference when I touch the toggle.
Now same is happening to the bright.

I might change back to the normal washers...

[rootz]

Might, or might not be tight enough. Which would suggest that a jumper wire to chassis earth from the toggle would kill any interference. Did you test that first?

Tightening from the inside of the chassis should be enough. I suppose the is a small nut on the inside? You just need a small enough wrench, probably even an angled on to get between the switch and the chassis.

By the way: where did you get those beautiful nuts for the switches? Looks like the stuff Two Rock uses and really gives it that high end finish.

[Bombacaototal]

Might, or might not be tight enough. Which would suggest that a jumper wire to chassis earth from the toggle would kill any interference. Did you test that first?

Tightening from the inside of the chassis should be enough. I suppose the is a small nut on the inside? You just need a small enough wrench, probably even an angled on to get between the switch and the chassis.

By the way: where did you get those beautiful nuts for the switches? Looks like the stuff Two Rock uses and really gives it that high end finish.

So I went with an alligator clip, one side at the buss bar and the other touching the toggle, no noise at all. As soon as I stopped touching the toggle the noise was back.

I tried to remove the toggle and add another washer on the other side, but then there is not enough lead. I tried to tighten them as much as I could and the bright is better but the deep is still an issue. Should I solder a lead on each toggle and the ground it?

I don't have enough lead to add a nut inside unfortunately and the chassis is bent so it would be a real mission to try to tighten it from there

Edit: just swapped the deep to the normal nut and no more issue, I guess looks will take a step back

Edit2: So I realised I had different length toggles. The 3 which had no issues were slightly longer and adding a nut on the begging of the thread made them perfect length for those fancy nuts. The two that had issues are about 1mm too long and hence why not being grounded properly. I think if I add 1mm washer on the inner side of the chassis should be enough. But to be honest ai prefer the peace of mind of knowing the toggles are vert tight and secured via the normal nuts, even if they look a tad less nice...

Thanks, I bought them here https://uk.rs-online.com/mobile/p/push- ... s/7874801/

[Bombacaototal]

Different amp, different issues.

The attached is me going from zero to max in my master with volume at zero.
I am finding this amp more noise than any of my others. Can anyone pick up on what may be the source of this extra noise?

[rootz]

Is this with the reverb tank in the chassis? This is 50Hz hum, with some overtones. So not noise, hum it is. Still sounds like coupling between the PT and other components or a ground loop. Is grounding done per layout?
FWIW, I do not hear a lot of hiss.

[Bombacaototal]

Is this with the reverb tank in the chassis? This is 50Hz hum, with some overtones. So not noise, hum it is. Still sounds like coupling between the PT and other components or a ground loop. Is grounding done per layout?
FWIW, I do not hear a lot of hiss.

Thanks rootz, no reverb in this case, but with the volume at zero, in the circuit are the filters and the PI.

So it’s a ground loop..I spent weeks moving grounds around, first I got each part of the circuit (tonestack, filters, PI) to have all the grounds jumpered together, and then with alligator clips I started moving them around between the 4 options I had (FX Loop, pre amp, power tubes, and power supply). My fx loop is isolated via washers so they are part of the variables that can be moved.

This is the quietest I manage to get but seems the ground loop is still there. Only thing I didn’t try was the speakers jack, as they are not isolated and the bias pot, for the same reason.

I will need to work harder on this one it seems...