Tym "Op Amp" Big Mud

I seem to start a lot of my blogs with "this has been a long time coming" and this one is no different. It's not because I'm slack or lazy (although I can be) but because I have so many ideas bouncing around in my head and I'm so busy trying to keep this place going, things tend to fall by the wayside until I can find time to get onto them. Having said that, this one has been a long time coming ...........

This version of the BM is commonly known as the "version 4 and 5" and ran simultaneously with the version 3 which is the famous red/black transistor version with ON/OFF or tone stack bypass switches which this version also had. From the outside it's impossible to tell which version you have but plugging them in will certainly let you know. As the nick name suggests the op amp version was supposed to be the famous sustainer using op amps instead of transistors and they did a pretty good job of "simulating" the BM tone with this circuit.

Since I don't use batteries this is obviously a copy of the version 5 which was exactly the same pedal with the tone stack bypass instead of the battery ON/OFF switch. Like all my BM clones with a TS bypass I work it a little differently to give more options but keeping the original idea fairly intact. The classic BM has a substantial and very noticeable mid scoop and the tone stack bypass does exactly what it says, it bypasses the tone stack and makes the pedal have a flat frequency response in the mids (ie: no mid scoop) and also gives a slight boost in signal as the tone stack is no longer "pulling down" on the signal. My switch makes the flat frequency response while keeping the tone stack in the circuit, therefor giving you the option of still using the tone knob, but without the mid scoop. I find this much more usable as it's a significant mid "boost" (on most versions) but you can still dial in treble/bass as you like. With the original you get NO tone options once the switch is engaged.


This version was not particularly sought after, and was in fact avoided by many for straying a bit too far from the classic BM tone but was given a big kick in interest when Billy Corgan revealed he has used one on the recording of Siamese Dream and suddenly everyone wanted one. The prices increased and they became sought after for their thicker, fuller sound. Personally I'm not a huge SP fan and it's pretty obvious that record has a million layered guitars on it giving it that sound so the fact that Billy used one never really appealed to me. I've had an original version for years that I never paid much attention to because the consensus was it wasn't really worth the effort.

A few years later a friend gave me a Deluxe BM which is the op amp version in an enclosure with a compressor built in. They never really caught on and have become quite collectible because of low numbers made and sold. They were cheaper even in the "pre vintage stompbox" market as not only were they the "bad" BM circuit, they had a comp built in AND they were hardwired power (110 or 240V) making them more trouble than running a battery or daisy chain.


I was talking to J ages ago and I mentioned the Deluxe BM and he said "That's what I used on the first three Dino records .............. before I got the Ram Head" Being a Dinosaur Jr fan my ears pricked up and I instantly thought I should probably go back and visit this version ?

I plugged in the Deluxe and standard version 5 I had and.......... they were pretty cool. They didn't sound like a Ram Head, or a nice Civil War, but they had a sound all their own and it was pretty cool. I had friends who rated them as well so I started looking into it a little more. Like all old EH stuff there seemed to be good ones and bad ones and I borrowed one off a friend who didn't use it because he thought it sounded terrible. It did sound pretty bad. I compared it with mine and much preferred the sound of mine. I repaired one recently that also sounded pretty good.


The original design runs two op amps instead of the transistors and both are one's I use in other pedals I make so it was time to work out what made these tick. The famous 4558 dual op amp is used as the first two gain stages but without diode clipping on what would normally be the second stage on a standard BM. The great little LM741 op amp is used to clip 6 (yep SIX) diodes in symmetrical clipping and then sent out via the tone and volume pots. It's a pretty simple and great little design and achieves a pretty authentic BM tone.


I've added a clean transistor stage after the 741 towards the end to boost the signal in the tone stage which keeps the signal up and gives more output that is lost in the original circuit from the 741 having to drive the diodes AND go through the tone stack. This gives a slightly higher output than the original in TS bypass mode with the advantage of scooped/flat mids with the tone control still active. The original tone is still in there with the volume and sustain level slightly backed off. 

Tone wise this version sounds like a BM but with more saturated gain and more "fizz" around the edges, and more "wall of sound" bottom end. It's certainly not subtle, but neither was the version 3 it ran simultaneously with in the mid/late 70's. It's a full, thick fuzz with some really nice harmonics going on and LOTS of sustain. Good, clear bottom end that gets a little messy on full sustain setting but still cleans up nicely with lower setting and/or dialing in more treble but not good for palm muting crunch. The mid scoop is, like most BM's fairly pronounced but fizzes up nicely when flattened out. Having the tone control still engaged with the flat response means things can get a lot more interesting than the original version. 


Compared to my early original op amp BM (with the EH3003B PCB) I can pull exactly the same tones and it reacts differently to pick ups just like all good BM's. It gets big and muddy with humbuckers and P-90's and cleans up with single coils. It's much thicker with all pick ups than my other favorite BM's like Ram Heads and Civil Wars and is closer still to distortion, as apposed to fuzz than all the standard BM's. My Deluxe BM has a slightly different tone but can be dialed in to match both my standard original and my Big Mud version without, obviously, the comp involved. As mentioned my Mud has more overall output than both (the Deluxe is slightly down on the Std) but behaves and sounds just like them in most settings.

It's easy to see why people relate these to that SP sound as it is much thicker and less "fuzzy" than any other BM and really does get that "wall of sound" even more than the version 3, but for me it will always be the first three Dino albums bt maybe that's just personal preference.


Aug 05 2014 Written By: Tim Brennan