Tym Overdrive Preamp/666 part 2

If you read my first part you'll know I'm a huge fan of these pedals. I'm actually a MUCH bigger fan of them now after developing my own clone of it. I remembered it was good, but I didn't remember it was this good.


Back in the eighties these were the "go to" overdrive, especially for Marshalls which seemed to come to life when pushed with these little yellow boxes.

That's not to say they don't work with other amps at all. I have been playing them through nearly anything I can find while developing these and they sound great through nearly everything, including solid state amps. They sound AMAZING through my Matamps.

These can be used as a thick overdrive using the gain knob and setting the volume where you need it or, as a preamp by running the volume high and setting the gain to give you the overall volume you're after. Even with the gain at zero and the volume at full you get a boost.



Because I'm not interested in just downloading a schematic off the net and hitting some message boards (REALLY not interested in that) when I start work on a new pedal for my line, I needed to "re-buy" one, or two of these to get my bearings and have something tangible to compare to.

I own, or have owned or borrowed every pedal I have made a clone of and preferably need to get several for comparisons where possible. I like to reverse engineer by ear and on the scope as I'm a visual person and the scope makes a lot of sense to me when it comes to replicating a signal. In the end though, it's got to do with ears, and not just mine.


All my audio testing is  done through a Matamp into an old early 70's Orange 2x12 with original Greenbacks and I use as many guitars as possible to get different pick up responses for each pedal. Sometimes stuff sounds great with single coils and bad with humbuckers, or the other way around. This pedal is VERY pickup sensitive which I find essential in a good overdrive.

It has great bass response and really nice, but slightly "raspy" break up. I'm using the now legendary LM741 chip, a primitive early single op amp IC thats "limitations" are what makes it sound like it does in these but to be honest the difference in these compared to some of the original LF351 chips is VERY (and I mean VERY) negligible, but I have a good supply of 741's and they're THE chip for this circuit, so why not ?

My Overdrive Preamp/666 has true bypass switching, an LED and a Boss style 9V input adaptor, none of which the original (or re-issue) DOD 250's had. These all just make life a little easier while keeping the true vintage tone and look intact.

Once I had several collected and ready to go the prototype was built. Usually from here I will fine tune the circuit to taste, like with my Big Mud clones. This one however was ............ spot on. I ran all the originals I had and the prototype side by side and there it was.

I sent the idea to Tone from GuitarNerd who does all my artwork and he sent back the file to be printed. It always makes me smile when he sends artwork as I never really know what it's going to be, but even "the obvious" like this is still a joy.

While I know that the look of my pedals is part of the reason people like to buy (and collect) my pedals, I also know that the time and effort, and quality of them, all of which I put my name on, is also a big (and important) part of it.




To my ears (and my scope) this sounds like a good DOD 250, which is now one of my favorite pedals. It's a very responsive and sensitive overdrive and while being VERY closely related to the MXR Distortion plus, it is a very different pedal indeed. This has more overall volume and clean headroom and more rounded bottom end all of which work well on all setting of volume and gain.

The MXR Distortion plus has been my favorite OD/dist pedal forever, until now. I think the DOD has surpassed it for flexibility and tone. At least until I start work on my new MXR clone ..........

DOD/250 shootout


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