More brightness in the 5E3

[atmars]

Aside from lowering the values of the coupling caps and cathode caps, or raising the value of the treble cap on the tone knob, is there any other way to add brightness to the 5E3?

[Chuck H]

three things I can think of right off.

Try lowering the value of the 22k dropping resistor in the B+ rail. The higher preamp voltages should make the amp feel tighter and brighter.

Add a "bright" cap to the volume control of the channel you use most. This would make the volume controls even more interactive than they already are.

Try a brighter speaker.

Chuck

[MWJB]

5V4 rectifier will give better definition.

[atmars]

I'll give these ideas a try and report back.

Thanks

[billyz]

5e3's are pretty bright amps as is. What speaker are you using ? Celestion 25 w greenback for ex, can make a deluxe seem dark. Try a Weber P12Q style alnico, should be perfect.

[pdf64]

I've AB'ed my greenback against my weber 12A150, and the weber is more middy and quieter. Peter.

[billyz]

I was actually going by my experiments years ago with a pre ROLA 25 w Greenback and a real 220xxx Jensen P12Q. In a real 1957 Tweed Deluxe. I know the new reissues don't sound the same as the originals, so YMMV.

[hasserl]

three things I can think of right off.

Try lowering the value of the 22k dropping resistor in the B+ rail. The higher preamp voltages should make the amp feel tighter and brighter.

Add a "bright" cap to the volume control of the channel you use most. This would make the volume controls even more interactive than they already are.

Try a brighter speaker.

Chuck

The stock Tone control already incorporates a "Bright" cap around the volume control. You can increase it in value to increase the effect.

Also, you could add a high pass filter just before the 2nd gain stage; use something like a 240k resistor bypassed with a 250pf cap for a boost around 2.7kHz, or play with those values to get the results you want. 300k / 250pf = 2.1kHz, 270k / 250pf = 2.4kHz, 220k / 250pf = 2.9kHz, 180k / 250pf = 3.5kHz. Experiment and see what you prefer.

[atmars]

Also, you could add a high pass filter just before the 2nd gain stage; use something like a 240k resistor bypassed with a 250pf cap for a boost around 2.7kHz, or play with those values to get the results you want. 300k / 250pf = 2.1kHz, 270k / 250pf = 2.4kHz, 220k / 250pf = 2.9kHz, 180k / 250pf = 3.5kHz. Experiment and see what you prefer.

Is this inserted in between the wiper and the grid of the second tube or elsewhere?

[Chuck H]

Hasserl...Yup...That's a bright cap for a volume control alrighty. Thanks for being vigilant. Must not have had my thinking cap on. My other two suggetions stand though. Raising preamp volts is good for "clarifying" the tone of these amps. And, going through a speaker search myself right now, I know how much difference a speaker can make.

Atmars, I'm pretty sure you got what he means. But why would you be willing to add another circuit to the amp, but not alter the values of the stock components (ie: decoupling caps and bypass caps)?

Chuck

[atmars]

Atmars, I'm pretty sure you got what he means. But why would you be willing to add another circuit to the amp, but not alter the values of the stock components (ie: decoupling caps and bypass caps)?

the story is: I built one for a friend - a one volume control version with the volume and tone knob wired the "normal" way instead the stock "backwards" way. I have already reduced the values of the decoupling and bypass caps, but this person says the amp is not bright enough with humbuckers. i would like to make adjustments if possible without having to convince this person to buy a new speaker. I was also wondering, form a technical standpoint, if brightening elsewhere was possible.

Also, today I put a another 22k resistor on a switch in parallel with the existing dropping resistor to knock it down to 11k. Although I didn't have the opportunity to give the amp a full volume workout with this mod, the effect seemed very subtle.
What can what expect as far as tonal change by raising preamp voltages? i mean, does a little go along way, or the reverse?

[Chuck H]

The effect of the higher preamp voltages can seem subtle. You may notice more driving the amp a bit louder. Parallel a 10k across that 22k on a switch. Play the amp with the higher voltage for awhile and then flip it back to 22k. What you'll notice is less highs and a loss of bottom end clarity. The higher voltage seems subtle but it's very effective for OD and humbuckers because it tightens things up overall.

Also suggested (by another poster) was the use of a 5V4 rectifier tube. Those are expensive for some reason but if your friend plays the amp cranked alot the higher voltage on the power tubes will help tighten things up too.

Another good trick for tightening up the OD tone is to measure the cathode volts (bias volts) at idle. Get a 5 watt Zener diode with a ZV of about 3 to 5 volts higher and bridge the cathode resistor with the diode cathode on the tube side of the resistor. This will effectively "fix" the bias when the amp is clipping but you'll still get that soft cathode bias attack when playing clean. It's a good trick for humbuckers and a stiffer "rock" tone.

You could also raise the value of the plate and screen filters as well as the cathode bypass cap. Use 47uf for the main filter, 22uf for the screens and 100uf for bypass. While this won't "add" top end it will stiffen the bottom end and add definition which can't hurt.

It's a really simple circuit so it can take a few minor changes to add up to an overall difference.

Chuck

[lowell]

also maybe reducing the initial input grid stopper to 22k or so..? Also won't biasing power tubes on the colder side help?

[pdf64]

If you just want to brighten up the tone a little, the easiest way is to reduce the value of the pre-amp cathode decoupling caps. As a first stab, try altering the one on the 12AX7 section following the Volume controls from 22uF to 0.47uF. If that's not enough, also the one on the 12AY7 shared cathodes. The 12AX7 will have more effect, as it's a higher gain tube (could be wrong as it depends on the various factors).
The above will affect both channels.
Peter.

[atmars]

Thanks gents - some interesting options to explore.