Single tone knob question

[dehughes]

Hey all,

So, I've given the typical Brown Deluxe tone knob setup a chance, but I find that for the most part it seems to impart a honky tone (think the letter "R") to the channel, and I'm wondering if there's an appreciable difference between the 6G3 and 5E3 single tone knob setup. Or, perhaps there is a more versatile single tone knob wiring? I'm mostly looking to add and subtract upper mids instead of the more growly, lower midrange. Any suggestions?

Or, perhaps this "R" tonality is just part of the Brown Deluxe vibe...but I fail to see on the schematic why this would present itself....or is it just a result of there being no typical TMB tone stack between the triodes???

[tubeswell]

Maybe try Stephen Delft's 'Moonlight' tone control here:

Adam's Amplifiers: Tone Stacks

[Robert M. Martinelli]

I would also give the "EH Big Muff Pi" tone control a try, very versatile for a "single knob" tone control, as it can also create a sort of "mid scooped" tone.

Hope this helps

Best regards

bob

[txstrat]

I've given my brown Deluxes normal channel a mid scoop filter. I replaced the .02 coupling cap (at the first triodes plate) with a .1 cap and a 120k resistor in series. The resistor is bypassed by a 150pF cap. This gives me a tone in between blackface and brown Deluxe. I like it. That way you might lose that honky "R". And it's undone very easy if you don't like it. Doesn't make the tone control more versatile, though.

[yunger]

dehughes, if your feeling adventurous, try this out. it's similar to the big muff control only with usable ranges from open to closed. c2 and r6 keep low and high frequencies from dropping off to no man's land. i love it. i can dial in almost any sound i want from it. just keep in mind that it was designed around my circuit so some values will change if you use a bypass cap on v1 for instance. that's just one example. your preamp configuration may be completely different from mine.

[Mark Hammer]

The classic Fender Tone control has a reiprocal action. In one direction it bleeds treble, while in the other it provides a variable degree of treble bypass across the Volume pot. Naturally, like any Volume pot treble bypass, the treble boosting effect of that cap is most evident at lower volumes, and disappears as the volume level is increased. Of course, the big difference between guitars and guitar amps is that one is likely to leave the volume up full on the guitar (such that the bypass cap "fixes" things when you turn down below that), and more likely to have the volume at less than full on the amp.

That bypass cap essentially duplicates the role that a "bright" switch fills, and the thoughtful reader will note that there are simply no Fender amps that use a single Tone pot yet also have a "bright" switch.

More recently, I was thinking about the tone control on my guitar, and realized that while I liked the reciprocal tone control on my tweed Princeton, it could be made more flexible. I tried out an experiment and it worked. You can read about it here: http://music-electronics-forum.com/t15821/

I see no reason why the same principle could not be productively applied to a guitar amp tone control, albeit with changes to component values. I may well give it a whirl on my Princeton too.

[imaradiostar]

I'm a big fan of the old gibson style single control. It gives scooped mids in the middle positions and treble or bass rolloff at the extremes with a nice smooth slope. At the front end of a cranked up amp it has a neat effect on distortion character, at the front of a cleaner amp it serves well to produce useful clean tones of different kinds (top boost, blackface mid scoop or jazzy treble rolloff).

here's a gibson amp with the circuit:
http://schematicheaven.com/gibsonamps/ga30rvt.pdf

I think you'll find it works better driven from the plate of a triode. There are modern amps that seem to support this theory.

jamie

[imaradiostar]

I thought I'd add- it's pretty low loss- only around 6 to 8 dB at the bass side and less on the treble end. You can reduce the loss and improve the action a bit by using a 500k or 1M pot. The mid scoop is down 15 to 25 dB depending on position. Here's a plot:



jamie

[HBamps]

I'm a big fan of the old gibson style single control. It gives scooped mids in the middle positions and treble or bass rolloff at the extremes with a nice smooth slope. At the front end of a cranked up amp it has a neat effect on distortion character, at the front of a cleaner amp it serves well to produce useful clean tones of different kinds (top boost, blackface mid scoop or jazzy treble rolloff).

here's a gibson amp with the circuit:
http://schematicheaven.com/gibsonamps/ga30rvt.pdf

I think you'll find it works better driven from the plate of a triode. There are modern amps that seem to support this theory.

jamie

Which control are you referring too? The MID control? I have used similar along with a CUT in the PA. Works really well.

[imaradiostar]

Yeah, that's what I prefer too- just the mid control from the 30rvt. The plot I posted was that control with a 500k pot instead of the 250k in the original schematic. You can easily scale it to make it work a little better with higher plate loads like a pentode.

I think it works well with a phase inverter and power section that's breaking up just a little bit. The cut control can serve to take the edge off of things- really a great combo for natural sounding low gain amp distortion tones. Not so much gain that it doesn't work with a few pedals out front...but enough to make it obvious that it's not 100% clean and add some interesting harmonic content.

jamie

[HBamps]

Yeah, that's what I prefer too- just the mid control from the 30rvt. The plot I posted was that control with a 500k pot instead of the 250k in the original schematic. You can easily scale it to make it work a little better with higher plate loads like a pentode.

I think it works well with a phase inverter and power section that's breaking up just a little bit. The cut control can serve to take the edge off of things- really a great combo for natural sounding low gain amp distortion tones. Not so much gain that it doesn't work with a few pedals out front...but enough to make it obvious that it's not 100% clean and add some interesting harmonic content.

jamie

Like I said, I have used this type of control and have tried tweaking it some. Problem is when I change values, I am doing it blindly and never know what to expect and it can be very time consuming. What program did you use to plot that curve? it could prove VERY handy!

[imaradiostar]

5spice- google it. I just found it the other week. I'll send you a few of my own simulations to get you started.

jamie

[dehughes]

Wow. GREAT info, all. Thanks so much. I'll get my soldering iron out and see what happens...

I'll start with trying the Gibson Mid/Matchless Chieftan Mid pot thing and see if that does it (I have a Cut control already wired in, which is supposed to make a good pairing). If that doesn't do it, then I'll give the Carmen Ghia tone wiring a try. After that, I'll give Steven Delft's Moonlight tone control a try. If that still doesn't do it, then I'll try your idea, txstrat, and try some sort of filter setup to drop some mids.

[imaradiostar]

this gibson 30rvt thing is the carman ghia tone circuit.

I really like Dr Z amps and I'm torn between outright copying his ideas and knowing that most of his designs are really great ways of implementing old ideas. I've lived in Nashville for the last 12 years and it's hard to miss how many great Z amps are in Nashville. They work and sound great in the real world of clubs and churches where Marshalls and Mesa don't do the trick. Of course...that makes them great in the studio too.

jamie

[dehughes]

this gibson 30rvt thing is the carman ghia tone circuit.

jamie

Huh. I have a "Phoenix" layout (a copy of the Carmen Ghia, I assume) and it is wired a bit differently than the Matchless Chieftan and Gibson 30RVT in that all three lugs are used in the Carmen Ghia, whereas only two are used in the Chieftan and 30RVT. Perhaps I have an incorrect schematic...