Tone Bender MKIII schematic template f33d00b52e82

TONE BENDER MKIII: Component Values Table

by

This isn’t a complete reference of every Tone Bender MKIII / MKIV ever made. It’s a working table compiled from multiple online sources and gut shots, so treat it as a guide rather than absolute gospel.

In some cases, it’s difficult to have a definitive set of values for any one pedal, as they are known to change over time, with different production runs.

Where values are unknown or unsure, you’ll see a question mark in the table.

GENERIC MKIII / MKIV TONE BENDER SCHEMATIC

Common components have been left as is, and I know the 100uf cap varies, but it makes no difference really so I didn’t see the point of listing every variation.  Arguably, there’s also no difference between a 220pf and a 200pf cap either, but I put that in any way. 

GENERIC MKIII / MKIV SCHEMATIC

Link to table on google drive


I’ve added the board below as a reference, as most MKIII boards look like this.  I “borrowed” the image from a Antique Electronics file – they have some great products available, including this board.

So if you’re looking at a gut shot online and are not quite sure what’s what, this might be helpful.  A few key things to look for.
  1. Bias resistors R1 & R2 on the base of Q1.  These are conveniently marked with asterisks below – they frequently vary.
  2. The capacitor C3 on the emitter of Q3.  This effects the bass response.   
  3. The treble and bass caps – these are nearly always tweaked on D*A*M builds (which I quite like and frequently use)
The rest rarely change, or the changes are relatively minor in terms of sound.   D*A*M does use a 470k volume pot and omits the resistor R4 between tone and volume controls.  This is primarily a way to boost the output without really changing the tone.

EFFECT OF C3 ON BASS RESPONSE

C3 on the schematic tables above – Darlington pair emitter capacitor 

TONE BENDER MKIII / MKIV ON LTSPICE


C3 on the schematic tables above – same again but response taken at the output



R1 / R2 BIAS RESISTORS

Comparison of different bias resistors on the darlington pair, taken from the 220n cap

This compares 220k/47k,  680k/100k & 1M/100k



Comparison of different bias resistors on the darlington pair

Apart from the output level, the resulting wave is a little different for each one, and of course 100n/47k vs 100n/100k form different high pass filters, resulting in a slight difference in low end.  This can be further tailored with the value of C3 (the capacitor on the emitter of Q2).

So despite some people referring to it as just a boost stage, and that it doesn’t matter that much – choices here do matter. 
Higher bias resistors result in more gated sound, lower bias resistors provide a smoother sound – at least in my experience anyway.   Different transistors in the darlington pair will come into play here as well, depending on how the bias etc – higher gain sets hit Q3 harder.


MKIII TREBLE N BASS VALUES

A lot of the character of the pedal comes from the filter section.   I think it’s fair to say that apart from the fuzz itself, this is the most important tone shaping section of the circuit.

Below are the frequency responses of some of the more common values found, with the tone pot in the centre position and swept to either side.  Increasing C5 lowers the high-pass filter / corssover point of the treble and bass, bringing more high-mids into the mix.  A side effect of this is that the treble side also gets louder, which can be balanced by the bass side to some degree, but it might also be worth increasing C3 to offset the change.






{
“@context”: “https://schema.org”,
“@graph”: [
{
“@type”: “BreadcrumbList”,
“itemListElement”: [
{
“@type”: “ListItem”,
“position”: 1,
“name”: “Home”,
“item”: “https://vero-p2p.blogspot.com/”
},
{
“@type”: “ListItem”,
“position”: 2,
“name”: “Tone Bender MKIII component values table”,
“item”: “https://vero-p2p.blogspot.com/2022/12/tone-bender-mkiii-component-values-table.html”
}
]
},
{
“@type”: “BlogPosting”,
“mainEntityOfPage”: {
“@type”: “WebPage”,
“@id”: “https://vero-p2p.blogspot.com/2022/12/tone-bender-mkiii-component-values-table.html”
},
“headline”: “Tone Bender MKIII component values table”,
“description”: “Component values table and analysis for the Tone Bender MKIII and MKIV germanium fuzz pedal, including schematic, board layout, bias resistor options and treble and bass capacitor values.”,
“author”: {
“@type”: “Person”,
“name”: “Andrew Hopkins”
},
“publisher”: {
“@type”: “Organization”,
“name”: “vero-p2p”
}
}
]
}

Leave a Comment