Increasing Clean Headroom in Fender Tremolux

[rf7]

This Blonde Tremolux amp (6G9-B circuit) starts to break up at about 5 on the volume pot, but the guy wants it to match his Blonde Showman amps that don't break up until about 8 on the volume. Any ideas on how to get more clean headroom out of it? Put in a larger NFB resistor? Pull the tube rectifier diode and put in regular diodes? Anyone have any experience with this type of thing?

[Chuck H]

With only 365 volts on the plate it's simply not going to be as loud, clean, as the Showman. But if the guy just wants the same level of adjustability (and not the same volume) you could always change the volume pot to a different taper. Some guys seem to think this equates to headroom when it really only equates to knob position, if you get my meaning.

To actually make the amp cleaner you could retube it with high value "Groove Tubes" AFAIK GT is the only distributor that rates it's tubes for clenliness

Choose a GT "10" rating and bias the amp a little cooler. That should make the clean tone a tiny fraction louder.

Other than that I might suggest more efficient speakers. But if it's strictly a question of "knob setting" this won't do anything but make the amp louder.

Chuck

[Steve Conner]

Some guys seem to think this equates to headroom when it really only equates to knob position, if you get my meaning.

See the Spinal Tap "Up to 11" sketch for a more detailed explanation.

YouTube- Spinal Tap - 11

[J M Fahey]

Some guys seem to think this equates to headroom when it really only equates to knob position, if you get my meaning.

[2]

I read everyday, everywhere, silly "mods" such as "use a 12AT7/12AU7 as V1", which only mean: "less gain", without affecting one iota of real output or real headroom.
*If* your client is happy with "amp only starting to break up on 8", you can just couple some cathode capacitor or two, or place a one megohm resistor in series with the volume pot.
To improve "transparency" (this time for real) you should parallel it with a low value capacitor, say 22 to 47 pF.

[rf7]

I tried the silicon diodes in place of the tube rectifier and the breakup occurs at the same place, but the amp got a little more output power. I think we're just going to roll with 12AT7's in place of most of the 12AX7's. Bumps the breakup up to 7 on the volume control. I guess it will make the guy happier. The amp actually sounded great as it was, but this guy wants clean headroom, kind of like the CBS engineers at Fender, back in the day.

[tubeswell]

Apart from going to SS rectification with more reservoir capacitance, you can also lower the supply resistors - try halving the values (or putting an HT choke in the filter - i.e. making a CLC filter instead of a CRC filter), or putting a 12AT7 in the PI position.