When I sit down to make a new pedal circuit I spend time with the original and play it and scope it in very different ways to when I'm just "playing" a pedal. Even pedals I've owned and loved for years somehow take on a new way of listening (and looking) when I start to get all nerdy about making one with my name on it.
The DeArmond Square Wave Distortion Generator is another MXR Distortion + based circuit like so many of my favourite preamp/overdrive/distortion units 'cause, well, it's just a great little circuit.
You all know how much I love this circuit and I've written about them SO many times before in the forms of the Dist+ and the DOD250 which I make clones of in standard and modified forms as my Tymexar and ODP series and several signature versions for some of my biggest guitar heroes. This little circuit has been the inspiration for so many pedals over the years starting with the MXR Distortion + in the very early 70's with some of the inspired being direct copies and others being slightly modified versions. The DeArmond Square Wave is the latter.
Heavily influenced versions of this circuit are basically the same circuit with some slightly different component values and a different IC. In this circuit, like most effects IC driven circuits the IC itself makes very little, or no difference to the tone of the effect, and in some cases the limitations of the older ICs are indeed part of the "magic", and this circuit has had MANY different ICs used all based on the original MXR version using an LM741.
My original has a 941M IC which is just an "improved" 741 but after making a couple of circuits I tried all the usual suspects that are drop in replacements for 941's and could not hear or see a difference. I do have some old 941s here but not enough to keep making these if people want them and I hate making stuff I can't keep reliably replicating so it was either 741s or TLs which I have a very good supply of.
My original DeArmond has a nice slanted enclosure with a folded aluminium top and steel base pained in wrinkle finish black. The 4 foot screws hold it together which need to be removed to access the battery. Mine is all original and the pots date 24th week 1978 although I have seen these with pots dated 1980. I'm really not sure about all the details of these and this is the only one I have ever held, so I can't comment on whether the circuits changed slightly over the production which I'm assuming was only a few years, however mine is slightly different to a schematic floating around the www.
The rest of the components (7 resistors, 7 caps and 2 germanium diodes) are all common components and I tried several germanium diodes to match the original level on my scope and then listened intently. I settled on some nice 1N34A diodes that I have plenty of and BAM, there it was.
This version has more output than the original Ge Dist+ which just gets over unity when maxed out. The sound is ... similar but it's quieter and has slightly more punch but not the levels of the Si Dist+ or DOD. It keeps a nice bottom end but not as much as the Guyatone PS-102 (also a Dist+ circuit) which has a really nicely rounded bottom end you just don't get from the MXR/DOD versions. I might have to venture into the Guyatone version next (25th anniversary next year ....)?
Tone did some new artwork for my portrait style custom made stainless steel enclosure and I got some printed and populated some Tym PCBs ready for assembly.
Sitting down with the finished versions it reminds me why I love this circuit so much. The Dist+ was my first real distortion love and I played one into a solid state amp live for years influenced by Bob Mould. It's such a great overdrive/distortion with rich harmonics that gets a little bit "fuzzy" at maximum settings, which is where I usually inhabit. One of the things I always loved about this circuit is how crisp and tight it keeps even at maximum and string damping doesn't get "flubby" which I'm a big fan of.
So, the first batch of these new Tym Square Sound Non-Sinusoidal periodic waveform distortion sound generators (that's a mouthful ...) will be available on the site SOON, and, like all my pedals, if they go quickly there will be more coming when I get time.
