how can i add a mids control to a tube screamer circuit?

[GibsonGM]

I don't think I'm being clear enough, LOL.   You would remove R8, and ALL that comes after it, but then put the 100k pot where R8 is (your schematic), as an output level control, wired as it currently is.   that is one way to simplify the design.  The buffer is only there because of how Ibanez/Boss etc. do their switching.


OR - you could do like Iaian suggested, and put the volume pot before the mid/treble controls, which will allow you do reduce level before the signal hits those stages, giving you control over how they distort (or not).

OR - neither, if you are happy, solder up and box it! 

[snow123]

I don't think I'm being clear enough, LOL.   You would remove R8, and ALL that comes after it, but then put the 100k pot where R8 is (your schematic), as an output level control, wired as it currently is.   that is one way to simplify the design.  The buffer is only there because of how Ibanez/Boss etc. do their switching.


OR - you could do like Iaian suggested, and put the volume pot before the mid/treble controls, which will allow you do reduce level before the signal hits those stages, giving you control over how they distort (or not).

OR - neither, if you are happy, solder up and box it! 

no, i had removed that resistor AND the output buffer, but it increased the distortion a little bit.

[snow123]

that resistor just (slightly) decreases the distortion to where I'm not bothered by it.

[bartimaeus]

if you don't want any distortion, why did you include LED clipping diodes?

[GibsonGM]

Bartimaeus is onto something.  We're all assuming (and I mentioned before) that the distortion you speak of is due to overwhelming a stage with too much signal, resulting in clipping due to lack of headroom...exceeding power supply's ability to amplify due to this limitation (asking for 12v when only near 9V can be supplied). I mentioned in a prior reply - there is overdrive/distortion occurring normally in the clipping stage (hence its name).    You may not be aware of this (that 'assumed knowlege' thing), but how you shape the tone will make that distortion more or less apparent down the line.

If you cut highs after distortion, it decreases the apparent level of that distortion; it makes it 'wooly' and less biting.  Adjusting mids changes its character quite a bit.  And so on.  Low end has the most energy, so overdrives following stuff more, requiring more from the power supply. So, when you increase the mids above a certain point, and you 'get distortion', I am assuming this is due to overdriving its associated opamp.     This is exactly why I asked you to listen to each stage with an audio probe to determine what is 'normal', and what is being caused by your adjustments.   I don't know if you did that or not (and should be doing it at every step here), but that's our working assumption.   

Not an easy task to undertake, is it?     My preferred route for this is 'dirt box >  EQ pedal' and done.  I rarely bother with anything more than a high cut to knock back some shrill.  Or,  guitar>EQ>interface>DAW>sim>EQ...

TS is a one-trick pony, and there isn't much special about it.  Most any feedback clipper followed by some form of EQ circuit would get the job done, IMO (ROG's "Tone Mender" comes to mind).   But this is (hopefully) a learning experience.

[GibsonGM]

Are we sure that a lot of this 'distortion' isn't what we get from the clipping stage, and messing w/the tone shaping making it more prominent? 
WHERE you are hearing the distortion is the key. 

Sound at the output isn't giving much info..."Right at R1 is has a lot of low end and is distorted; it's not like that before R1" is much more valuable than what you hear on the output...to help we have to know where it is happening, specifically, every time.

BTW, R1 with R2 sets the 'volume level' of the signal hitting your tone controls - I'd say that's 'doing a lot' lol.    C1 adjusts how much high end gets thru that network to the tone controls.   If they're adjusted equally (2x R1, 1/2 C1) then ideally nothing changes except signal level, loading and resistor noise.

[snow123]

if you don't want any distortion, why did you include LED clipping diodes?

i still want it to get a bit dirty and break up a bit, but i dont want it to distort from maxing out the mids and volume control. i just want to a have a consistent amount of dirt/breakup regardless of where the mids control is.

[GibsonGM]

I dunno, changing the composition of a complex signal will change how the distortion sounds just by definition - the distortion really does change character with different settings of tone controls.  Some is TAKEN AWAY (so it's GONE). Distortion is composed of a lot of highs, harmonics of fundamentals that were clipped.  This is true for a tone control or an eq pedal, which are active controls like the mid control here.    All I can think of that actually is somewhat consistent in this way would be an eq BEFORE clipping, tho that too does assert an effect on how your distortion comes out.

The only way to not "distort from maxing out the mids and volume control", literally overdriving them, is to take my advice and listen with a probe, and adjust the level of signal hitting the stage accordingly. that's 'gain staging' that others were talking about.  ANY design will distort in unintended ways if you overdrive it.

Iain suggested you put the volume before most of the tone shaping - that could be a solution for you.

[snow123]

I dunno, changing the composition of a complex signal will change how the distortion sounds just by definition - the distortion really does change character with different settings of tone controls.  Some is TAKEN AWAY (so it's GONE). Distortion is composed of a lot of highs, harmonics of fundamentals that were clipped.  This is true for a tone control or an eq pedal, which are active controls like the mid control here.    All I can think of that actually is somewhat consistent in this way would be an eq BEFORE clipping, tho that too does assert an effect on how your distortion comes out.

The only way to not "distort from maxing out the mids and volume control", literally overdriving them, is to take my advice and listen with a probe, and adjust the level of signal hitting the stage accordingly. that's 'gain staging' that others were talking about.  ANY design will distort in unintended ways if you overdrive it.

Iain suggested you put the volume before most of the tone shaping - that could be a solution for you.

yea, im probably gonna try that at some point, but rn im super happy with how it is, and just kinda want to be done with it lol.

[snow123]

nvm, i just tried putting the volume before the tone stage, 'cause i just had to move a few things around, and the tone control doesn't really seem to do a whole lot with the volume before it, and i dont really like it. but it doesn't distort as much, but i also dont really like how it sounds.

[bartimaeus]

honestly, i'd just reduce the amount of boost from the first stage. decrease the value of R9 until it stops clipping, then call it finished.

another option is to reduce volume before the tone control. but if you're reducing volume anyway, better to reduce it at the root of the problem (by reducing the boost of the first stage).

[GibsonGM]

^   That's pretty much the only thing that can be done.  A boost with tone controls is a little different than something with clipping diodes AND which can overdrive the stages that have been tacked in.    The 'secret' to that level issue is R divider after the 1st stage - oh well....   

[snow123]

guess im done for now.

[marcelomd]

You can always use a voltage doubler/inverter to increase the headroom of some stages, like the Klon.