Taming the brightness

[Matthews Guitars]

I've observed that my Express clone is quite a bright sounding amp. I run low treble settings, don't use the bright switch, and presence is usually at zero, and I still use the tone control of the guitar to trim the high frequencies so the feedback is just right and not killing eardrums.

I could experiment but I'd rather ask the veterans. What's the preferred way to tame that excessive brightness without compromising the soul of the Express circuit?

Yes, I have a variety of speakers and cabinet combinations to choose from. And some I have to avoid with this amp. My darkest sounding cabinets are the best balances, such as my 4x12 full of EVM-12Ls, and yes, those ARE relatively dark speakers compared to some.

[Roe]

try a high-capacitance cable from the guitar, turn up the volume a bit and consider a warmer bias on the el34s. turning up the bass may also help as well as turning down mids and treble a bit

[Matthews Guitars]

This kind of brightness is beyond mere control adjustments to handle. Looking for suggestions on taming it by adjusting certain component values or adding a treble bleed at just the right spot in the circuit.

Yes it warms up at higher volume but even then it's still pretty bright. Loud and bright is a bad combination for my ears.

[Roe]

This kind of brightness is beyond mere control adjustments to handle. Looking for suggestions on taming it by adjusting certain component values or adding a treble bleed at just the right spot in the circuit.

Yes it warms up at higher volume but even then it's still pretty bright. Loud and bright is a bad combination for my ears.

start with the guitar cable, get a curly coil or a similar hi-capactance cable. these amp were designed before low-capacitance cables became widespread

[Matthews Guitars]

Respectfully, that's two people who suggested curly cables and that's not the fix I'm after. If you don't have a component related suggestion to make, within the amp chassis, then you're not making the suggestions I will consider implementing.

[Colossal]

You can try increasing the 50p across the PI plate load resistors (the so-called fizz cap) to 250p. You will hear that as a high cut.

[Roe]

Respectfully, that's two people who suggested curly cables and that's not the fix I'm after. If you don't have a component related suggestion to make, within the amp chassis, then you're not making the suggestions I will consider implementing.

so you are not willing to try it? Consider a 470pf snubber then from the grid of the first gainstage to ground or the cathode

[martin manning]

What about a larger grid stopper on the input stage? That will accomplish about the same thing as a high-capacitance instrument cable.

[Roe]

What about a larger grid stopper on the input stage? That will accomplish about the same thing as a high-capacitance instrument cable.

yes but it adds resistive hiss. try a 470k-1m grid resistor on v2 instead?

[Matthews Guitars]

Yes, I'll give that a try.

I don't want the "fix" to be something external to the amp. If I make another one like this and sell it to somebody, the last thing I want to do is tell him to find and buy a specific kind of instrument cable to get his desired tone.

I guess I'm going to have to experiment with treble bleed caps to ground at certain points in the circuit, at various values.

[wpaulvogel]

The trick to a Trainwreck is to bias the output tubes hot, at least 75% dissipation, use a 50 foot instrument cable and play it loud. The midrange will swamp the brightness.

[Matthews Guitars]

It definitely warms up when run pretty hard. I set the volume to about halfway which IS loud and leave it there. And that's the tonal sweet spot. I run it through an attenuator and use the attenuator as the volume control.

[Matthews Guitars]

Another answer that works well for me....I just use my Mesa horizontal 2x12 cabinet with V30s in it. The darkness of that cabinet has a synergy with the brightness of the amp. It sounds killer....despite them being V30s.

[Mark]

Another answer that works well for me....I just use my Mesa horizontal 2x12 cabinet with V30s in it. The darkness of that cabinet has a synergy with the brightness of the amp. It sounds killer....despite them being V30s.

If you have a look at pictures of the various Express and Liverpool amps, there was an amp possible Maloo which had a largish cap in series with a pot across the plate resistor of the second triode stage. I did experiment with 2200pF and a 1000pF coupling cap and the amp sounded bassier to me. There is a limit to the value of the cap before the amp sounds lifeless.

IMG_2502.jpeg

http://www.amparchives.com/folder/1854/

[bcmatt]

I've continued to experiment trying to address this issue because I also like the eq/gain affect of having the bright switch on. Currently in my Liverpool and Express I have either no presence or a preset wired in amount and use that pot position for a cut control. In my Express, I keep upping the cap value for the cut... I think I'm currently at a 0.01uF.
Cut control seemed to work better when I removed NFB completely, but I want the faster transition from clean to mean that NFB provides.