still slight noise in latest build.

[axpro]

Hey guys, still fighting a few problems in my latest build.

It WAS a 5e3x2, which became more of a Proluxe with the s2 changes to the pre to give less interaction.

fixed bias, paul c mod, 6l6's. new tubes. it souns ok (havent really tested too much yet)

Heres the issue. the amp hums a little with the volumes off. crack either one just a bit and the hum goes away.???

I am not looking for a totally silent build, but the issue is driving me nuts!

Any ideas?
I've tried moving the signal wiring, but still no change.

[txstrat]

Sounds like a grounding issue.
Where have you grounded your 1st filter, screen filter, preamp and OT secondary?

[axpro]

hey tx

I have a grounding buss, the preamp is tied together, and runs to the buss, power supply caps go seperately to the bus, and the bus goes to the chassis ground point where the CTs and output section is grounded.

The noise also goes away when i pull the PI, so i guess it isn't in the Power Amp Section

[MWJB]

Ground the preamp filter to the input jack ground, ground main & screen caps directly to the same place as the CTs/output.

[axpro]

This is the part where i hang my head in shame....



So, after listening to all the advice, i decided to look it over again...

and realized a la "old skool" i had run the ground from the input to the back of the volume pot (In my defence i AM a guitar tech...lol thats where grounds go!)

Totally eliminated the wierdness of the hum, it is now normal... though there is still some noise with the volumes at zero. but the concern i had where the noise went away when you turned it up a little is gonel.

I think i may just live with it. I am in a noisy basement workshop. flourescent lights, computers/soldering irons and this week power tools!

My champ had a little noise at work (where i do my modding... since i don't have a good home shop) and i can't hear a thing at home.

I will continue and update people when changes occur.

Amp is sounding much nicer now though... though it certainly isn't "tweed" anymore.

[Bruce / Mission Amps]

Do you mean you ran the ground from the back of the pot to the input jack or do you mean you ran an isolated input jack's ground to the back of the pot and where is the pot grounded?
Or do you mean you ran a ground wire from the cathodes of the first preamp tube to the back of the volume pot which isn't a very good ground and a different ground for the input jacks... ha ha ha
I'm confused as any of those would not generally create much of a ground loop and create a bad hum.

[axpro]

I had the input jack grounded to the ground bus on the back of the pots. I switched to grounding it to my central ground point. it didn't get rid of any hum really, but it DID clear up the wierdness of the volume controls (Hummed at zero, hum reduced at .5-1, then returned) now the hum is consistent.... don't know if that is any "better" but its one problem to fix instead of hum+ volume control weirdness.

The amp is at my workshop (which is turning out to be a nice way to get away from a build for the weekend) and i'll be looking at it in the morning. I'll update any changes

[axpro]

OKALEEDOKALEE!

Got the amp home and hooked up to my 4-12.

First impressions? Sounds pretty good, nice tone (i thought it was quieter than it should be until i realized i had plugged into the attenuated inputs )

but


I am getting a buzz/hum when the volume is off. nothing plugged in.
It's not Loud, not a sharp audiable buzz, just a background hum. even with nothing plugged in. BUT if i turn up the volume, it goes away.?!?!?!?



Even with a guitar plugged in, it is a little hummy at zero, but it is pretty quiet at 4-7!!! at least background noise wise. wired as a fixed bias proluxe type, it is ANYTHING but quiet when i turn it up to 4!!

Any ideas?
Bruce?

anyone? anyone?
Bueller?

[olddawg]

Is there a hum if you use a shorting jack?

[axpro]

Switchcraft jacks, plastic bodies, short to ground when not in use. grounded with V1a's cathode resistor.

[MWJB]

"Switchcraft jacks, plastic bodies, short to ground when not in use. grounded with V1a's cathode resistor."....and the preamp filter cap?