anyone add a tone control to their mxr dist +?

[TimWaldvogel]

i am looking to just add a tone control to my distortion +... want to add some bass and mids to that nice trebley tone it gets.
i am looking for a single knob tone stack that works with this pedal very well. i am sure being the diy's your are, you have all tried building one, and you have all thought the same thing as me. what tone controls to add to make this a monster?
please halp. thanks, TIM

[GibsonGM]

Hi Tim,

Given that the Dist + is a single gain stage, I chose to add a "Stupidly wonderful tone control" (search for "SWTC" and you'll find it!) to mine.  It is a simple high cut that doesn't have a lot of insertion loss, so it won't 'add' bass, but will take away a little of the overly high highs, if you know what I mean.
There are other stacks you could add in there, but would probably eat so much signal you'd need to add a gain stage at the output to get the level back - but that might not be a bad thing ;o)
 
You could try the stack from the Big Muff Pi, with some component adjustments to allow a little more mids or what have you. Duncan's Tone Stack Calculator (search Google, it's a free download) can help with figuring out the freq's you want to play with.  Then a transistor recovery stage as the Muff uses, not too hard to implement.
Could be a very cool pedal....

[bumblebee]

I'd like the BMP tone-stack on one I reckon (its my fav tone control), probably need the gain recovery stage though on this one.

[TimWaldvogel]

yea, the latest amz version of the SWTC looks cool, i think i might give that a shot. i have also though about forking the the 30 bucks to buy a concetric pot and the nice chrome knobs for the top of it and using a baxandall tone stack

[GibsonGM]

That could be pretty cool!  I'd maybe try a FMV stack first, though...the baxandall isn't the greatest for guitar purposes.   Get the Tone Stack Calculator and mess around with some values...you can run leads from the pedal to a breadboard, build a tone stack on it with a recovery stage (the last transistor stage of the BMP is good, or an LPB-1), and adjust everything, taking the output from the breadboard until you get it just right.  Then build it in permanently. That way you can tweak to your heart's content before committing! 

[GibsonGM]

...and an afterthought....for a good example of how this is done, check out the schema for a Marshall Guv'nor.  They have a pretty decent tonestack after the clipping diodes...

[jdub]

Given that the Dist + is a single gain stage, I chose to add a "Stupidly wonderful tone control" (search for "SWTC" and you'll find it!) to mine.

+1 to this.  I added this to mine and it works great; simple to add, too.  That box is my favorite overdrive.

[Mark Hammer]

The Dist+ does not have gobs of output.  So, whatever tone control one adds should introduce as little passive loss as possible, unless: (a) you are willing to live with less output and a distortion signal that isn't much louder than bypass, or (b) you add another gain stage post-clip or post tone-control to bring the level up.  One of the reasons why the SWTC works well in this application is not because it is that fabulous a control, but because it takes away very little signal, and still leaves plenty to push the amp.

[GibsonGM]

Well said, Mark....that's what I added to mine, just to take away a little bit of the over-sharpness.  Works great! 
With a full tone stack, you run the risk of not enough input to the thing, and thermal noise due to resistances in it as a result. Then you have to boost it again - so it's no longer really a Dist +.    So if I were thinking that way, I would go for the Guv'nor (which I use as my main 'hard' distortion - but without a tone stack, only a treble-cut cap/pot!!  More CRUNCH).

[TimWaldvogel]

well heres my question, lets say i decide to add a full one marshall tone stack, whats a good way to get the gain recorvery? using another op amp boost? or more like a lpb-1 circuit?....
my idea before was to change the knob labeled distortion to a "pregain control", and add a mxr micro amp or lpb-1 to the output before the tonestack and then call that gain control to post-gain. and then add an overall level control.

[Mark Hammer]

Seems to me that what you probably want to do in that case is to take something like the ROG Tonemender ( http://www.runoffgroove.com/tonemender.html ) and simply mod it to produce distortion.

So, you can see here that the circuit uses a dual op-amp.  Stage 1 is set for unity gain.  If the path connecting pins 1 and 2 were to be replaced with a 1M resistor and parallel 47pf cap, and a 100k pot, 4k7 fixed resistor and .1-.22uf cap was run from pin 2 to ground, you would have replicated the gain stage of a Dist+ for the most part, albeit with a little less frizz and a little more bass.

Stick a 10k resistor on the output of stage 1, with a pair of diodes to ground, just before you reach the tonestack, and there you have it.  Normally, there would be a cap on the output of the clipping stage to block DC, but we have plenty of those downstream, so we can skip that one.  As well, there would normally be a cap in parallel with the diodes to tame frizz, but we have plenty of EQ downstream as well.

Do we need all the gain that stage 2 is poised to give us?  Not really.  My gut says that a 50k-100k level pot is going to provide plenty gain.

And that's it.  Is it a "pure" distortion+?  Not really, since the biasing is different, the op-amp is different, the tonestack changes everything, and I goosed the bass a bit.  But then what you had planned was going to disqualify it from the Dist+ purebred olympics anyway.

[wampcat1]

well heres my question, lets say i decide to add a full one marshall tone stack, whats a good way to get the gain recorvery? using another op amp boost? or more like a lpb-1 circuit?....
my idea before was to change the knob labeled distortion to a "pregain control", and add a mxr micro amp or lpb-1 to the output before the tonestack and then call that gain control to post-gain. and then add an overall level control.

honestly, there is no right or wrong answer. This is where your ears come in... you could do it a number of different ways.
Breadboard!!!!
bw

[TimWaldvogel]

wow thanks mark, i appreciate the help, so since i will be raising the gain at the end anyways, anybody have tone stack connections, or character shaping ideas for this thing?

[GibsonGM]

If you build the above circuit, as Mark described it, you'll have tons of tone-shaping possibilities!  There is a switch that modifies the tone stack response, too, so you'll get a double stack!  You'd end up with essentially a Marshall Guv'nor (once again, my favorite) with a full tone stack, and a switch to change its range.  You can get Marshall or Vox-like tones with that.
Head over to Runoffgroove.com and look up Tonemender, there is a write-up that tells you how they came up with this. It emulates various amp's stacks....

[TimWaldvogel]

can i use a jrc4558 for th dual op amp? what does rail to rail mean in the description on ROGs description?

[Mark Hammer]

can i use a jrc4558 for th dual op amp? what does rail to rail mean in the description on ROGs description?

Use a socket and then you can use whatever op-amp you have on hand and sounds "best" to you.  The primary difference between the TL072 shown, and a 4558, will be hiss and maybe clarity of top end (maybe).  But that's it.  And of course, if you turn the treble down, you won't notice it, will you?

Op-amps are able to produce output voltage changes (or "swing") extending from some point close to the most negative supply voltage to some point close to the most positive supply voltage.  In a great many instances, one should expect that an op-amp won't do much better than getting within a volt of either "rail".  So such an op-amp powered by, say, a +/-9v supply would hypothetically be able to produce a maximum output that "swung" from -8v to +8v.

"Rail to rail" simply means that the chip can produce outputs that can go right up to the most positive and negative values of the supply voltage/s.  Why "rail"?  Simple, the derivation is likely from electric street cars and subways (and maybe even model trains), where the power is supplied through the rails, with one rail being positive and the other negative.

[WGTP]

From the simple is good (you all are more ambitious - less lazy - than I) school of thought, try a 22n-220n capacitor between the diodes and ground.  This allows less bass/mids to be clipped (which means less distortion) and boosts their output (and the overall output).  The more clipping that occurs (the higher the gain) the greater the effect.  This also provides more relative distortion/sustain to the Treble frequencies, which to me is a good thing.  The lows are less compressed by distortion and retain more dynamics.

This can also be used with the other suggestions.

This is a far from perfect solution, but simplicity is one of the appealing aspects of the Dist+ design.  Try GE diodes if you need more distortion.  I like an SI/GE combo.  If your running into a SS amp, you probably don't need huge output.

P.S.  I like to add an SHO at the end...

Something different anyway...

[superferrite]

Great discussion, guys.
I've got most of the parts on hand except for the pots, so I might try this some time soon!