DOD 250 "original spec" worth a try

[lars]

A while back I built a "grey spec" version DOD 250. I was surprised to find out there was actually an earlier grey spec version than the one commonly used. The easiest way to identify the very first 250s is that they don't have a DC power jack. Now that I know what to look for, this version appears to be extremely rare. The PCB is the same, but has some different/missing components compared to other grey specs. JHS did mention the different components used on DIYs, but I don't think these constitute what they change in their typical 250 "JHS mod". It doesn't appear many clones or mods have been done according to these very early specs.
I went ahead and made the changes to my 250 clone, and I have to say it sounds really good. It gives the pedal a little more smoothness and warmth, and sounds more like an overdriven tube amp IMHO. In fact, with the level at about 3/4, and the drive about 1/2, I would swear this thing emulates tube rectifier sag. It would make sense that later grey 250 versions would modify this sound out, since most 70's tube amp designs had changed to solid-state rectifiers to get rid of sag. Whatever it's doing exactly, I think it sounds great; very musical.
I would recommend trying out this version. It's such a simple circuit, it's easy to change back if you don't like the tone. Here are a couple pictures I found (the only ones I could find actually) that show the insides of the very first versions. People familiar with the DOD 250 will instantly recognize the differences, and it makes it easy to see what has to be changed. At first I thought these two pictures were just the same pedal that somebody had modded. But a close examination shows that a couple of the resistors are orientated differently, and the input caps are different, so DOD did send out the first 250s with these components.

From these pics it appears the main changes are:
1) The 4.7uf cap is a much larger 22uf
2) The clipping diodes are a 1N400x type, most likely 1N4001s
3) There is no 10uf cap (holes still present)
4) The usually missing cap from the input to ground is present. Not sure what the value of this is, I used a .001uf "102" cap. Since it's the same size/type as the output cap, it's probably a .02uf.
5) The output cap is .02uf instead of .001uf
These don't seem like huge differences, but the tone is definitely different than any 250 I've heard.

[Scruffie]

No idea if you've seen it but this guy was obsessed with the 250 a few years ago and here's his research https://sites.google.com/site/snmavronis/NeoClassicFX/741overdrive/research

Thought it might be of interest.

[lars]

That is a great site, thanks. His Neo-Classic 741 looks very professional. Still, there's not much info on what is referred to as the "'76 gray 250". A lot of "?'s" for the part values. Obviously people know these earliest versions exist, and efforts have been made to demystify them, yet not as much effort has been put into cloning them as the later 1979-80 grey versions. The above pictures shed a lot of light, and it's a great sounding version. Maybe not as well-suited for lightning-fast arpeggios though...

[Scruffie]

If you search through his posts on DIYstompboxes (Steve Mavorinis was his user) you should find all the photos that he was using as reference, probably the same photos you have there hence the question marks.

Without the 10uF stabilizing cap on the V.Ref, I guess there might be more sag going on which could account for your comment about it not being so suited to fast arpeggios.

Personally regards diodes, I can't really hear a difference between 1N4148 & 1N400X, both have about 0.6fV, sure some can hear or feel they hear something though.

The 2n2 to ground input cap probably makes a decent difference to the feel, even if it just knocks out a bit of hiss, i've found hiss while it may be above where your guitar frequency range sits, can actually be a part of the overall sound of a pedal.

Interesting anyway.

[lars]

An odd-ball popped up recently on ebay. Interesting variations to the components, somewhere between the very early greys, and not quite the common "grey spec".
http://www.ebay.com/itm/DOD-Overdrive-Preamp-250-3-D-LOGO-Green-Circuit-Board-VERY-EARLY-yngwie-/301335660031?pt=Guitar_Accessories&hash=item46290145ff
For only $640 it could be yours!