Single tone control for cathode follower.Anyone use one?

[phsyconoodler]

I'm trying to figure out a simple one pot tone control in place of a TMB stack driven by a cathode follower.
  There must be some way to do it with one control.I know I need to get Merlins book and read up on it.
I just don't have room for a TMB stack in this chassis.It's a single ended hot-rod marshall style preamp with a cathode follower.It sounds killer good as is,but some tone shaping would be welcomed.
  anyone have a design they want to share?

[tubenit]

You have options .......................

5E3 tone control  (I use a psuedo 5E3 tone stack after the CF behind the 5879 pentode in the OD of the D'Mars ODS)

Dual gang with James tone stack

Dual gang with TMB with fixed mid resistor.  Use 500k and put a 470k across the pot that you would use for treble. Try a 18k-33k mid resistor.

With respect, Tubenit

[jjasilli]

Especially checkout the Garnet / Gibson GA-30RVT:  http://amps.zugster.net/articles/tone-stacks

Also Big Muff:  See Duncan Tonestack Calculator  
A schematic of a cathode driven Big Muff circuit is here:  http://psg.com/~dlamkins/dbl/Archive/amp-1/amp-1-build.html

[phsyconoodler]

Hey Tubenit,you have a layout of the 5E3 tone control after the cathode follower?

i don't see that at all in the Gibson GA-30RVT.They all have TMB tonestacks.
The Garnet one I can't find anywhere.

 My issue is where to insert the control.From pin 8 of the cathode follower,to the control, and then to the grid of the power tube?

[HotBluePlates]

You could use a contour control which varies resistance values in a bridged-T-filter, but you'll need a dual pot (I used a dual 1MΩ pot).

Depending on your chassis design and control placement, you may not have room for the pot's depth.

The standard T-M-B tone stack is essentially a bridged-T-filter; Treble is controlled by varying the resistance of one of the resistors forming the "T", and bass is controlled by essentially varying the size of a cap in the T-filter circuit (but done using a pot). Amount of mids are controlled by lifting the "T" off of ground.

In my Standel build, I used a contour control to sweep the mid-notch of the T-filter higher/lower, and added a Mid control to get anything from very deep notch to none (which sound to us like a lot of mids).

Yeah, that's 2 controls, but you could make the mid setting switchable.

[tubenit]

Layout for a 5E3 tone stack?   The schematic and layout are for different amps.

[kagliostro]

A bit of documentation about Tone Control

http://amps.zugster.net/articles/tone-stacks

If the problem is a single hole in the faceplate you can use a double pot like here



A good two knob Tone Control may be the Bone Ray Tone Control

that is an improvement of the Big Muff Tilt Control





K

[Colas LeGrippa]

Here's a simple very effective tone control`

Colas

[phsyconoodler]

Thanks tubenit! Now I see how it works! The cathode follower to the tone control,a different placement of the 5E3/5F2A values and then on to the next stage or grid of the power tube in my case.

 Apparently the two knob control doesn't work well with high gain amps,and believe me,this amp is hi-gain!

[jojokeo]

Extra caps...

[phsyconoodler]

So it will work without that .01uf cap I'm understanding?

[HotBluePlates]

Here's a simple very effective tone control`

And a variation of the adjustable bridged-T filter I was talking about earlier. However, this one is a fixed midrange notch.

[jojokeo]

So it will work without that .01uf cap I'm understanding?

Of course - the 500pf cap does that on it's own and only allows a small amount of signal through based on it's value. The signal path currently goes through the .01uf then the .0005uf (500pf) then again through another - the .02uf cap before it reaches the pi input...

[phsyconoodler]

I tried the tone control,and it works,but it's  deadly tone sucking monster! All the character and drive the amp had without it is pretty much squashed.
  The tone works fine,it just sucks the tone and life out of the amp.
 So......I have to come up with a use for the extra pot on the faceplate now!

The amp sounds absolutely killer good without the tone control,so I've decided to leave it out.I tried adding some gain in different places but it seems the tone control just squashes whatever I add.When you crank it all the way up the gain is back but it's icepick bright enough to rattle your teeth!
 Hmmmm........the game is afoot!

[kagliostro]

You can use a trimmer inside the amp (if you have no further holes)

as to have a raw control

Using a trimmer or <resistor + switch> (but this requires a disposable hole) you can lift the ground reference of the Tone control

and may be you can find an acceptable compromise between Tone control and gain

K

[tubeswell]

A good two knob Tone Control may be the Bone Ray Tone Control

that is an improvement of the Big Muff Tilt Control

I did this one in an amp a while back using 1M pots and appropriate cap values - quite liked it. However its not a 1-knob control, but a big muff style tilt control on it own works well using 1M pots and appropriate cap values.

[jojokeo]

I tried the tone control,and it works,but it's  deadly tone sucking monster! All the character and drive the amp had without it is pretty much squashed. The tone works fine,it just sucks the tone and life out of the amp.

Yes - BUT where it's used w/ Tubenit's extra gain stages it assuredly "needed" some softening and gain reduction since there was so much.

So......I have to come up with a use for the extra pot on the faceplate now!
Hmmmm........the game is afoot!

Oh boy - LOVE that too! I'm always fine with that just make sure it's useful not gimmicky

When you crank it all the way up the gain is back but it's icepick bright enough to rattle your teeth!

Hard to say anything w/out knowing what you're doing, sounds like just a wee bit of resistance in the right place or very small cap on something just to take the edge off.

[phsyconoodler]

The trouble with it is it sucks gain right out of the amp.It's sweet and gainy as all get out with no tone control but you wire up the control and it sucks the gain right out.
  I have three stages of gain and a cathode follower/two 12AX7's.It's juicy and lovely without any tone control at all.Will a tone cut control work on a single ended amp?
 I may just move the controls over one slot and add a low input that bypasses one gain stage like a JCM800.That would solve the extra hole issue.
  This amp is so fat and gainy and loud that it's hard to believe it's one 6V6.I think I'm also going to scale just the power amp too so the preamp stays tight.It's a wee bit loose when you turn down the VVR right now.I plugged it into a 2-12 cab with Zack Wilde EVM12L's and it's absolutely HUGE sounding!
  This little bugger is fun to play around with.
Thanks for all the tips guys!I don't suspect I'll be satisfied until it's all buttoned up in it's cabinet.

[jojokeo]

You're liking the "Tweed effect" - full toned w/ all the mids. Tone stack inherently load the signal down and most provide a mid cut which cleans up the tone while at the same time removes some harmonic content and gain too. Tone stacks in smaller/simpler amps like this makes a huge difference on where as well as what you using and doing. Does the CF stage utilize a bypass cap? If so, lower the value way down and remove the cap keeping gain but losing the very high-end range (easy to try). I'm guessing you have no NFB? If not, it's simple & non-invasive to try a very small amount (creating a high ratio such as 100k on 8ohm tap : 2k2 on 12ax7 = ~45 instead of the usual 20x or so) There's a ton more things which can be done.

[Jack_Hester]

I'm trying to figure out a simple one pot tone control in place of a TMB stack driven by a cathode follower.

This tone stack works quite well, after a CF:

http://www.el34world.com/charts/Schematics/files/gibson/ga40_2.pdf

Jack

[tubeswell]

The trouble with it is it sucks gain right out of the amp.It's sweet and gainy as all get out with no tone control but you wire up the control and it sucks the gain right out.

The reason I used 1M pots on this version of the tilt control was to decrease the AC load. And it works quite nicely.

[phsyconoodler]

I moved the pots over one space and installed a 'lo' input that bypasses one gain stage just like a JCM800.The cleans are great too!All the drive is still there when you plug into the high input,just like before.
  There is a lot of gain on tap in this amp;just wondering why that one tone control sucked so much of it out?I have built lots of 5E3's and they don't suck the gain out that much!
  The tone was really wide ranging;going from pretty dark to searing treble,just by turning that knob.
The coupling caps I have in the amp right now seem to right in the 'sweet spot' for humbuckers and my strat too. Funny how that worked out!
  Cool thing happened when I wired in the control:forgot the ground wire and when I turned it on I got a really cool rock radio station when I plugged in the guitar! Hahahaha!
  Fun with little amps! Little amps that roar!

[clyde]

Cut control?

[fuzz]

There's a thing I did on one of my amps. I put a selmer TnB tonestack but keeps only the treble pot (the bass pot didn't do much anyway so changed for a fixed resistor) , and it works really well that way !  much better than with two pots or three . The only thing is that the tonestack cuts out mids so you have to like that kind of sound...

I've also tried the big muff tonestack which is simpler , works well too .

I've also put a rotary switch to add cap in // with the miller effect of the EL84 to make a "cut" control (the filter works in the grid resistor)

Making simple RC filter is also a nice subtle way to add tone control. You cut off only small part (ice picking treble for instance) and keep the sound how it is instead of putting the TMB tonestack which gives its own color to the sound.

this link may interest some of you :

http://www.freewebs.com/balijukka/variouscircuits.htm