Brown sound voltages

[Tone Junkie]

Anybody variaced there marshall down to 90 volts to get the brown sound and then took voltages on your power tubes or first position cap to see were you were at. I was thinking of doing marshall based build and try to get dual voltage transformer and switching between the two b+ voltages. thanks Bill

[DummyLoad]

flaw in plan: filament supply voltage will have a great effect on the variac modeling for "brown tone" - e.g., the filament voltage will fall proportionately when the whole amp is run at 90VAC mains with variac control, whereas the the switched secondary will have a more steady-state filament supply.

respectfully,

--pete

[Tone Junkie]

I guess Pete i was thinking the whole lower B+level  to the tubes had more of a effect on the sound than the lowered heaters and thought possibly the lowered heaters would actually be hard on the tubes. But that is a definately a fly in my ointment. I should rethink the whole thing . But maybe someone has tried it.
Thanks Bill

[tubeswell]

tube filament voltages are designed to operate within +/- 10% of the target voltage. For a 6.3V filament, this would be between 6.9 V and 5.7V with a preference for the mid-point (6.3). Anything outside that range is generally not good for tube operation.

[sluckey]

I think EVH tried it.

[SILVERGUN]

I think EVH tried it.

Right around the 20:00 mark he gets into it:
https://www.youtube.com/watch?v=yb26D8bBZB8

[bmccowan]

TJ - when you say a dual voltage PT, I assume you mean one of the PTs that has two sets of secondary voltage leads, and you wire one set or the other to the rectifier? If so, have you considered a VVR? With a VVR you will have a wide range of B+ voltages at the twist of a knob. Many threads here and many opinions about the tone and longevity. I've used it on one cathode biased amp and two fixed bias amps. I like it, but probably don't play enough to comment on longevity. Modules for cathode bias are available, but I do not think anyone is making a fixed bias model these days, so you'd need to modify or build. Heater voltage is not affected.
Like others I would not suggest restricting the primary voltage. EVH probably did not care how many tubes he tossed in the trash.

[SILVERGUN]

Anybody variaced there marshall down to 90 volts to get the brown sound and then took voltages on your power tubes or first position cap to see were you were at. I was thinking of doing marshall based build and try to get dual voltage transformer and switching between the two b+ voltages. thanks Bill

None of this is exact science, but...
When I first hooked up my variac and had my breadboard cooking I was like a kid in a candy store. I was able to vary the B+ independently of the filaments.
The secondaries reacted exactly as you think they would.

So if  90V is approximately 25% off of 120V then you can guesstimate a result of approx. 25% off of the usual B+ for a Plexi.
If the original B+ is around 460-480VDC, then 25% off gets you to approx. 340-360VDC

My guess would be around a 350-260-0-260-350 transformer would get you in the ballpark. Is there such a transformer?
But again, because this isn't exact science you have a wide margin of error....kinda like using a Variac as a "volume control" (per Eddie)