Rockman Instrument Equalizer

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In a first approach, an equalizer is only an equalizer. Something simple that all the manufacturers should be able to design correctly.

But if you ask someone like Tom Scholz if the common commercial devices fit his requirements, the answer is less obvious.

The Rockman Instrument EQ is just different and better than what's available on the market. Let's see what makes its qualities and differences.

Objective and history

"[...]a couple of years ago we designed a graphic equalizer. Now, how crazy is that?

There are dozens of them on the market, but there was not a single one that could be used with a guitar level signal, was footswitcheable, had a decent signal-to-noise ratio, and could give better than an octave resolution.

We tried to modify existing units, but finally gave up and designed the stupid thing so we would have what we needed."

(Tom Scholz in Guitar World, Feb. 90)

What were these modified EQ's used by Boston, before the Rockman EQ was born? On this picture from the 1987 tour, we can see that Boston used Boss 10 bands EQ's: these were the modified units.

The first Rockman EQ prototypes were certainly reproductions of these modified 10 band EQ's, housed in a Rockmodule enclosure to match the existing Sustainor and Chorus/Delay. The following picture, grabbed from a 1987 guitar magazine, shows this un-issued 10 bands Rockman EQ, the draft of the 12 bands model we all know:

Bob Cedro, now MXR's chief-engineer, was in charge of the development of this 12 bands Rockman Instrument EQ. The first models, made in 1987 had the same blue logo as the Sustainor 100 and the Chorus/delay, as on this ad published in December 1987:

Then the white face series was issued, with the Stereo Echo and the Stereo Chorus: the Instrument EQ was finally a white-face too, and these blue-face models must be extremely rare now.

Inside the Module

The first thing that a tech will see inside the Instrument EQ is... no 4053/4066 chips! These J-FET IC's are everywhere in the other modules, and were not used in the EQ. As a matter of fact, SR&D designed it for the best signal-to-noise ratio, and selected a +/-12V power supply - instead of +/-8V - that prevented from using the integrated switches (the bypass circuit is therefore based on discrete J-FET's).

The higher the power-supply voltage is, the stronger the signal can be, and the better is the S/N ratio: with a total amplitude of 24V, the immediate improvement is 4dB compared to a 9V powered stompbox. The Rockman EQ can thus be used both with guitar level signals, as required by Tom Scholz, and strong line-level signals (up to 14dB): there is a switch on the Rockman EQ that selects the operating signal level (Normal: line level or Hot: instrument level).

Back to the features of the unit. The real difference between a classical EQ and the Rockman Instrument EQ is the presence of 3 additional bands in the mid-frequencies:

  • 62,5 - 125 - 250 - 500 - 1000 - 2000 - 4000 - 8000 and 16000 Hz classical octave bands
  • 700 - 1400 and 3000 Hz additional mid-frequency bands

The range of each band is +/-12dB: all in all, the Instrument EQ is extremely precise and efficient, and allows the best sound sculpture for the most demanding musicians.

This is not instrument gear any longer: the Instrument EQ is a genuine studio-quality device.

Usage and limitations

The Rockman EQ is truly mandatory for anyone who really wants to create and tweak his own sounds. When one starts building a Rockman rig with a Sustainor, it becomes rapidly obvious that two EQ's are necessary: one placed in the loop as a pre-distortion EQ, the second one being placed after the Sustainor.

The possibilities provided by a pair of EQ's are both subtle and endless. Changing a few dB's on a frequency band can alter significantly the sound and the position of the guitar in a mix, and using radical settings can also deliver specific sounds: fuzzy or metallish, fixed-wah effects, etc...

As a matter of fact, EQ'ing can become very complex, and can turn into a real nightmare. Finding the perfect sound is impossible, and the situation was perfectly summarized by UseHerName on the boards of

You are suffering from a condition know as O.A.D. (Obsessive Adjustment Disorder). The good news is that there is help. You are not alone. First you must recognize that you do have a problem. Then you must have a desire to change your behavior. I have devised a three step program to help others like you on the road to recovery.

Disclaimer: Author assumes no responsibility for damage to equipment resulting from users adherence to the recovery program here by known as R.O.A.D.I.E. (Reversing Obsessive Adjustment Disorder Is Easy).

Step one:

Set all EQ sliders flat. Pick up your guitar. Play. DO NOT TOUCH THE EQ FOR 24 HOURS.

Do not go on to step two until you successfully complete step one. YOU CAN DO IT !

Step two:

Find the sliders on both ends of the unit that only dogs can hear. Leave them flat or cut them as you wish. If you have a dog, allow the dog to set those sliders on your behalf. Pick up your guitar. Play. DO NOT TOUCH THE EQ FOR 24 HOURS.

Do not go on to step three until you have successfully completed steps one and two.

Step three:

You must now accept the fact that no matter how many sliders are on your EQ, there are only a few that matter most for guitar. It is generally accepted that those are roughly 500 to 2k. You may now adjust those sliders to your liking. You may re-adjust those and only those as many times as you wish for a period of 24 hours. After the 24 hour adjustment period has expired you must then permanently disable those controls. Break off the sliders with a pair of pliers. If you don't have pliers ask your dog to bite them off for you. If you don't have a dog a wife will do nicely.

Pick up your guitar. Play. Don't look back.....

Collectibility and conclusion

The Rockman EQ is a sort of perfect tool, and is becoming quite hard to find: people always want more EQ's and don't sell them easily.

The problem is that there are 21000 Sustainors and 15000 DG's to equip, while only 5500 Rockman EQ's were manufactured! Rarity makes the price, and it is not uncommon to see EQ's selling above $200.

A genuine classic close to perfection, the Rockman EQ is a keeper. Every Rockman owner has several of them and always looks for more!

Copyright 2008