Tone Shaping

Links here to some of my favourite sites regarding tone stacks.

Page to be updated with standard template…
20230612/20190330 – Updated broken links with Wayback Machine Archives.

Relax, this is only a draft!

If links show up as videos or images then I’ll remove the link WP puts straight in.

Tone Control Links: Webpages

“How to Voice a Tube Amplifier” and “How the Tone Stack Works” by Rob Robinette
Andrew Waugh (aka Stratopastor / PR11) got me looking at this site again after a four-year hiatus and there is plenty of good information on this website about guitar amps and especially Fender Designs relating to the AB763 BlackFace (BF) series from the early 60s onwards.

See Also: http://www.angelfire.com/electronic/funwithtubes/Amp-Tone.html

“The Tone Stack Explained in English for Humans” One of the best explanations of the TMB tone stack for musicians: it’s a bass control with tweaks. The original link that has been archived:
http://pickroar.com/1003/the-tone-stack-explained-in-english-for-humans/

And 38-page PDF file archived from the defunct AX84 website that is linked from the PickRoar blog.

Adam Alpern’s 1-2-3 Knob Tone Stack comparison.

GuitarPedalX (Stefan Karlsson with Adrian Thorpe) compares tone stacks in effects pedals.

“The truth about EQ controls on amps” Brian Wampler from Wampler compares EQ controls on amps with SPICE software

“6 ways to use an EQ pedal for better tone, & Fender Hot Rod amp tips” In a 12m30s video about using an EQ pedal (pre&post distortion), Brian Wampler talks about EQ tips for a HRD from 9m30s. Brian’s HRD had been modified; for a stock HRD Brian suggests tweaking a graphic EQ [100Hz smidge-up; 200Hz boost; 400Hz smidge-up; 800Hz cut; 1k2 cut; 3k level; 6k4 up; use HRD Drive (distortion) channel].

Some more videos, in two or more parts, about tone stacks in guitar and harmonica amps and effects:

Uncle Doug’s two part series (with guest spots from his cats and dog)

DeepBlueHarp’s series; it began with five parts, then went to eight parts plus. (Jim Whiteside)

Effects Loop Links
Having an Effects Loop offers many more possibilities for tone shaping: I’m not talking about going from steel-guitar clean to metal djent; but you may have favourite settings attained in a quiet environment that you’d like to replicate in a noisy room. That can take a bit of figuring out until you master how we hear a mix of sounds differently depending on the volume.

“The Amp’s Effects Loop” Andreas Möller suggests that if you only run the amp clean, or if you are dropping the signal level for stompboxes then reamplifying it, may be good reasons to give the Effects Loop a miss. Or not!

Video: “Easiest “modification” for Fender Hot Rod amps (and others) to make it better for home use” – Andreas Möller Volume Box design built by Brian Wampler
As a 17 year-old I built my first Volume Pot in a Box with a plastic utility box, using solid-core doorbell wire, and a cheap plastic footswitch attached externally to the box with standard 15-amp three core power lead! I got the parts from a local domestic and industrial electrics store, along with a pencil diagram showing what to make on the back of the bill of sale from Arthur the sales assistant. This was in the late 70s when solid state effects into solid state amps were being marketed by manufacturers and they were about all we could afford. A cranked Big Muff into a Yamaha 100 G212 may hardly have been tone nirvana but that’s where we thought we should be heading. In this video Brian Wampler shows how to build a Volume Box for the HRD from the design by Andreas Möller on the Stinkfoot website. The HRD Effects Loop is all solid state (the 93 Super and 93 Concert is all Tube) so Andreas Möller prefers to use a 25k audio pot to control volume; but up to 100k should work fine. Higher value volume pots aren’t always better in this situation: really high value pots, such as 1M ohm may be robbing your signal of bass frequencies (fundamental notes; second harmonic; low end…); it all depends on the combined capacitance of the leads and circuit leading up to the volume pot (see High Pass Filter from How the TMB Tone Stack Works ).

The Roland Bolt 60 Amp
My first (tube) amp came with an Effects Loop: it was a great little Roland Bolt 60 that I bought second-hand in 1980 and sold in 1982 to raise funds for travel. Around the same time I owned a Roland 501 Tape Echo – Chorus that I plugged into the effects loop; and in the preamp-out – power-amp-in I used my home-made plastic volume control box with its ground lift switch (to take the Volume Box out of circuit) that had been designed for me by a gentleman called Arthur in 1977. I used the control because the preamp of the Bolt 60 was all solid state and it used fuzz-box-style back-to-back diodes and three volume controls to achieve a compressed or saturated sound in the distortion channel of the preamp; so it sounded best with the preamp dials wound up and the volume control box plugged in, post-onboard reverb and preamp, to act as an overall master volume control and lead-volume or rhythm-volume selector. Roland Bolt 60 website archived 20190330 (https://bolt60.no.sapo.pt/)

OVNILAB “compressor reviews”
Cyrus Heiduska at OVNILAB has done a great job of comparing and reviewing many of the recent and current Stompbox Compressors. He notes how they fall into families of roughly three to five different designs, and how the overall design makes one Compressor best-in-class compared to others from the same family.
Cyrus emphasises that his reviews are for Bass Players; but as a guitarist and sound engineer I still turn to Cyrus’ reviews because there is so much to learn from them. Two of my favourite stompboxes I learned about first here are a large box Origin Effects Sliderig and a compact Cali76; both work ideally in the Effects Loop of the Super Amp when I have the Mix Control set at ’10’ (more like a series loop).

The OVNILAB Compressor FAQ should answer many of the questions that arise about Compressors and their use: http://www.ovnilab.com/faq.shtml

Phase Splitter / Phase Inverter
A lot of tone adjustment can be done in and around the output stage. There is some debate on whether the Phase Splitter (aka Phase Inverter) is part of the preamp or part of the power amp: I won’t get into that debate here. In push-pull output tube guitar amps we really need two triodes to perform the duties of phase splitting and phase inverting due to insertion loss with this stage (some designs have a gain of less than one). Phase Inverter? OR Phase Splitter?

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