Single tone knob question

[dehughes]

Originally Posted by imaradiostar

The Big Muff tone circuit (unless scaled) really works best with low impedance drive and a buffer after it. Have any mosfets laying around?

jamie

I do have a few MOSFETs lying about.....

I suppose I don't understand what in a circuit creates "low impedance drive", and I'm not sure what a "buffer" is, technically. I still have a lot to learn with circuits...

[yunger]

this reminds me of when i was endlessly searching for the perfect one knob tone control. i think i went through all the same stacks, in almost the same order as you.
you don't need MOSFETS or buffers if you try my circuit. it's filters are configured around the pot like a big muff but that's where the similarities end. i tried the big muff and thought it was a little too cartoonish and not quite useful in an amp. if you like it, i'll show you how to tune it to your preference. good luck.

[dehughes]

Originally Posted by yunger

this reminds me of when i was endlessly searching for the perfect one knob tone control. i think i went through all the same stacks, in almost the same order as you.
you don't need MOSFETS or buffers if you try my circuit. it's filters are configured around the pot like a big muff but that's where the similarities end. i tried the big muff and thought it was a little too cartoonish and not quite useful in an amp. if you like it, i'll show you how to tune it to your preference. good luck.

You know, I juuuust finished putting your version into my amp. It's close, but still not quite there. I'm running a 500k tone into a 1M volume, at present. I find that there still isn't enough top end clarity, though I like the way the knob shifts things around.

I'm considering putting in a 1M tone and shrinking the .001uf cap to a 500pf, as well as raising the 100k resistors to 150k. What would you recommend, being as this is essentially going into a 6G3 circuit?

[HBamps]

Originally Posted by yunger

this reminds me of when i was endlessly searching for the perfect one knob tone control. i think i went through all the same stacks, in almost the same order as you.
you don't need MOSFETS or buffers if you try my circuit. it's filters are configured around the pot like a big muff but that's where the similarities end. i tried the big muff and thought it was a little too cartoonish and not quite useful in an amp. if you like it, i'll show you how to tune it to your preference. good luck.

What's your circuit? Do you mind sharing?

[dehughes]

Originally Posted by HBamps

What's your circuit? Do you mind sharing?

A sample was posted higher up on this thread...

[dehughes]

Originally Posted by yunger

this reminds me of when i was endlessly searching for the perfect one knob tone control. i think i went through all the same stacks, in almost the same order as you.
you don't need MOSFETS or buffers if you try my circuit. it's filters are configured around the pot like a big muff but that's where the similarities end. i tried the big muff and thought it was a little too cartoonish and not quite useful in an amp. if you like it, i'll show you how to tune it to your preference. good luck.

So, I just finished tinkering with things....

I have a 1M pot in there (maybe a bad idea?) and have tried raising the cap to ground, reducing the value of the .001uf cap to 500pf, as well as reducing the value of the 100k resistors to 56k each. I'm getting closer but also farther from my ideal..... I like the way the channel feels with 56k resistors and the 500pf cap on top, but there's just waaaay too much low end when I turn back the tone knob.

I suppose what I really need to do is understand what each of the components do in your schematic, yunger. I think I get it, but I still feel like I'm stabbing in the dark...

[yunger]

-if you're using a .02 coupling cap on V1's plate(as shown on the 6g3 schematic) your likely getting too much low end with this tone control. c2 on my schematic is .01. is that what you have?
-the larger the value of tone knob seems to drop high end. can you try a 250kb?
-dropping the .001 to a 500pF will scoop the mids a little more. as is the mid scoop is about 6db.
-maybe try changing c4 to .01.

[yunger]

Originally Posted by dehughes

I suppose what I really need to do is understand what each of the components do in your schematic, yunger. I think I get it, but I still feel like I'm stabbing in the dark...

pretty simple:
-R5 and C4 make a low pass filter
-R7 and the series capacitance of C2 and C3 make a high pass filter
-R6 keeps highs from dropping into oblivion when fully CCW on the knob.

[dehughes]

Originally Posted by yunger

-if you're using a .02 coupling cap on V1's plate(as shown on the 6g3 schematic) your likely getting too much low end with this tone control. c2 on my schematic is .01. is that what you have?
-the larger the value of tone knob seems to drop high end. can you try a 250kb?
-dropping the .001 to a 500pF will scoop the mids a little more. as is the mid scoop is about 6db.
-maybe try changing c4 to .01.

Yes...a .02uf off the plate of V1 as per the 6G3 schematic. Could I compensate by adjusting values in the tone setup?

I'll try a 250k pot instead of the 1M.

Okay...the 500pf seemed a bit more scooped, in a way....

I had a .01uf in there, but that was with some alternate values, so I can't say exactly what it did. It seemed to add low end, or raise the low mids overall.

I think I'm (slowly) getting what's going on. I'll see if I can run that SPICE program on my Mac....I think I have a way to do that, but I've never tried.

[dehughes]

Originally Posted by yunger

pretty simple:
-R5 and C4 make a low pass filter
-R7 and the series capacitance of C2 and C3 make a high pass filter
-R6 keeps highs from dropping into oblivion when fully CCW on the knob.

WAIT! So, essentially, that's a TMB EQ network without the bass pot (the 100k resistor R6) and without the midrange pot, yes?

If you removed R7 and instead put a 6k8 resistor underneath C4, wouldn't you have a Fender-ish tone stack, of sorts?

[yunger]

Originally Posted by dehughes

WAIT! So, essentially, that's a TMB EQ network without the bass pot (the 100k resistor R6) and without the midrange pot, yes?

If you removed R7 and instead put a 6k8 resistor underneath C4, wouldn't you have a Fender-ish tone stack, of sorts?

good call!! but i think without R16 and R5 in the circuit, what your left with is pretty much the treble control of the fenderish stack. bass frequencies will basically stay where they are at all times. with those resistors in the circuit, the tone pot blends high/low frequencies. bass and treble will teeter-totter as you turn the knob (like the big muff stack yet more controled for amp use). the distance between the high/low peaks determine the amount of mid scoop.

for goodness sake, if i'm wrong, somebody who actually knows what they're talking about please speak up.

[simcha]

Here's the modified Moonlight stack( sorry I don't know who originally posted this) Haven't tried it myself, but the author claimed wider tone range. In any case, the original Moonlight tone stack reduces to a bridge network with one cap between 'east' and 'west' nodes. Changing cap value shifts the turnover point without changing much else. It's more a variable-shelf than variable-slope.

Is anyone here savvy enough to add this stack type to the 'tonestack calculator' ? - or do a similar sim?

Also here, a 1-knob EQ of mine. I asked the folks in the shop-front to taste-test several 1-knob EQ's on the same amp, and they all preferred this one. I was running it from a small pentode, so r-source feeding the stack would be somewhere around 50k. It'll work from a triode, but to get exactly the same curves from a typical 12AX with 100k plate resistor, you might need to insert about 20k resistor between triode plate and the .047 cap. Hope this helps, Simcha.

[yunger]

Originally Posted by simcha

Also here, a 1-knob EQ of mine. I asked the folks in the shop-front to taste-test several 1-knob EQ's on the same amp, and they all preferred this one. I was running it from a small pentode, so r-source feeding the stack would be somewhere around 50k. It'll work from a triode, but to get exactly the same curves from a typical 12AX with 100k plate resistor, you might need to insert about 20k resistor between triode plate and the .047 cap. Hope this helps, Simcha.

simcha, scroll up and check out the schematic i posted of the EQ i used in my amp. i think you'll get a kick out of the similarities between your's and mine. the only real difference i see, besides component values, is the wiper connection on your tone pot. pretty cool.

[dehughes]

Great! Thanks to you both. I'll get to soldering...

[dehughes]

So, I tried your Pentode single tone idea, simcha, and it was kinda cool, albeit a bit on the darker, more closed off side.

I also tried a modified version of your idea, yunger, which ended up being nearly a Blackface Fender preamp with my "tone" being the "treble". Sounded cool...but sounded like a Blackface Fender.

I'll give your Modified Moonlight idea, simcha, a try next and see where that lands.

One thought...might it be possible to take the "bass" side of the 6G3 tone knob and turn that into some sort of faux bass/lowmid shift/cut? That is, keep the de facto bright switch side as wired (the 500pf....maybe cut it down to 68 or 120pf or so...) and turn the .01uf side into some sort of fixed "bass" knob (like putting a .047uf cap on top of a 6k8 resistor to ground). I wonder where that would land me....

[dehughes]

OKAY! I think I'm nearly there. Here is what I have.

Normal Volume and Tone (1M, each) controls a la 6G3. The 500pf bright cap is reduced to 68pf (might move it to 100...I'll give my ears a rest and check back in tomorrow). The .01uf cap on the tone control is replaced with a [100k -> .047uf -> 6k8 -> Ground] setup. I like this! The channel has it's Brown Deluxe-y vibe yet isn't nearly as harsh as it was before. I'll tinker some more with the values, but this is getting really close...

See the attachment for what I'm using now (currently have a 68pf cap in there...). It's my first time using the software, so excuse the look...

[simcha]

..... the schematic i posted of the EQ i used in my amp. i think you'll get a kick out of the similarities between your's and mine.....

Yep.... You're right. Very similar end point, by different routes.
It's hard to create anything truly new in tone stack design - Just about everything turns out to have been done before, by someone, at some time. Couple of times I thought I had an original, then later came across much the same the same thing in an old audio amp patent. Ah well......

[benito_red]

I made lot of tests with tone stacks and i also was looking for one with just one knob.
The conclusion (based on my own tastes) is to use the Big Muff that you can tune accordi ng your needs by means the Adam's Amp tone stack (as already suggested above).
IMO another good solution is to use a classical TMB with fixed resistor for mid and bass and pot for treble. I have modified the classical Fender BF ts replacing the 47nF cond with 22nF bass fixed value=82k, mid fixed value=10k and i like a lot because it sounds wormer.
benito

[Natman]

I found this topic really interesting because I just finished building a Dave Hunter 2-Stroke. It had the Princeton style tone control and I HATED it. Way too bright for me and cutting highs is useless because I can do that at my guitar. I did build a Botany Phoenix a few years ago and loved the tone knob.

So last night I went through my parts drawer and improvised with what I had. So I kept the 1 Meg pot (initially a CTS 500k wouldn't fit), I used 100k resistors instead of 150k and a 500pF silver mica instead of 250. Damned if that tone knob didn't do the same thing as the clone! WAY more usable and it's gonna stay this way. Furthermore, my next build has only 1 tone knob too and guess what it's going to use? Every shade of thin and fat is there. It makes a simple amp lots more versatile!

[benito_red]

Natman wrote:
"

... I did build a Botany Phoenix a few years ago and loved the tone knob ...

"

I could not find the Botany Phoenix schematics.
* Is it the same one knob tone stack of Carmen Ghia? (I would like to try your TS)
* do you know where to find schematics of Botany Phoenix?

thanks a lot, benito

[dehughes]

Benito, the Botany Phoenix is essentially a Dr. Z Carmen Ghia.

As for me, I tried out various iterations of the Selmer Zodiac/Gibson GA30RVT/Carmen Ghia tone pot wiring, and settled on what is essentially a Matchless Spitfire tone knob. Ingeniously simple...and perfectly appropriate for my build. Attached is my version.

Thanks to all for the help! I hope this thread helps someone else out in the future...