strange MASTER VOLUME noise (FIXED)

[richon]

Hi,

i'm wandering what to do to avoid some strange MASTER VOLUME noise:

my amp with master on "0" is DEAD silent... but when increasing the the master volume value appears some little noise... little little that increases as I turn... I know tubes may add some hiss/noise when pushed with many stages but with just one before also?

the noise is present more with master volumen maxed

(NOTE: I have only shielded cables from jack to grids and plates to pots, en pots to grids, also into relays)

[Reeltarded]

The master is a gate. When you open the gate a little, a litte comes through, when you open it all the way, it's like not having a fence at all.

[Structo]

So is it a hissing or white type noise or is it scratchy as you turn the master?

[richon]

like a white noise... I still hear fine the guitarra en everything

but at my home/room when crancked its appears pretty much...

should I record it?

[greekie]

Have you tried doing this while unplugging your guitar cord? Or turning down the preamp volume? This would reveal if the noise is coming from either of these two sources.

[richon]

right now I have the amp in the test bench

NO guitar
NO preamp Gain or Clean pot...

so its just the second stage into the master volume

it seems like a slight ground loop is messing really small in there althogh its all wired into a ground buss into a star ground

[richon]

without the first tube V1 (in a bluesmaster type: V1A -EQ-V1B---> master) ,with the master on full the amps is DEAD SILENT... strike one!

with the V1 connected the noise gets back...

so its from the V1B (and maybe V1A) that the noise comes from

even with the clean level pot on ZERO its there... very small

[Structo]

Try different preamp tubes.
They can vary greatly in noise and hiss.

[richon]

update:

getting the V1B grid to ground makes the amp SILENT full silent...

so by chance I hit with my nail the cable which gets from Clean (Volume) to the 68K resistor into the V1B grid

the cable was noise... is a shielded one... but its is noisy and "microphonic" to touch

so hiting every other cable makes no noise... just this

even when touching "over" or near the 68K resistor the noise increases a little

any idea?

[Structo]

Might be a bad cable.

Most things connected to V1 and sometimes V2 will be sensitive to touch or vibration.

As you found out you can disable a tube by grounding the grid.

If it were me, I would try to find a better piece of cable for the input.

But just to be clear, it is not unusual for things around V1 to be sensitive.

That is why I suggested trying different tubes.
They can vary widely and draw different current and make different levels of noises.

[richon]

Ok

I'm with You with the v1 "thing"

But it's only the v1b which receive the signal from the 1M-A pot (Clean GAIN) which acts as an antenna

Strange is that with Clean GAIN And master volume to 70% each the input cable (from Jack to 22k to v1A grid isn't any noisy or microphonic)

I only have JJ/Tesla tubes to try

[aflynt]

I only have JJ/Tesla tubes to try

I'd recommend trying a few different ones, even if they're the same brand and model.

-Aaron

[richon]

Changing tubes didn't make it any better

When testing I deactivated the V1B grid to ground and shows that even the Overdrive stages are silent too

[richon]

changed the grid stopper of V1B from 68K (1/2w) to 22K(1W) huuuuuge improvement

i mean HUUUGE... now I know where to ATTACK!!!

[richon]

TAKE NOTE:

1W resistor is better than 1/2W of same value to decrease noise into grid


BUT in my case the 68K resistor was an antenna..


although the 22K 1W I had at hand sound even better...