Based on Seamoon Fuzz (...and Black Cat OD-1). An op amp clipping fuzzy overdrive with an active tonec ontrol tacked at the end. Note that the schematic have a few typos; the 470nF caps is actually 47nF according to some gutshots but 470nF might work for the bass players out there...
The modern version of EHX Frequency Analyzer. The ICL8083 IC is obsolete but there is still some vendors that have it in stock. Came out taller than expected since I wanted the bipolar voltage doubler circuit on the same board as the main circuit. But it will fit sideways in a BB enclosure...
Schematic is avaiable HERE.
Per request. Included the "Rate mod", a switch that toggles between two speed settings..
Schematic and info HERE.
Here is a cool one. It is essentally two separate circuits in one box, a fuzz with a switchable octave up and a tweaked Small Stone phaser. Original had separate boards as well and if you wish you can house them in separate enclosures. If you decide to house them in one enclosure, the fuzz is the first circuit follwed by the phaser.
Schematic is avaiable at Dead End Fx
Update 2 210514
Both schematic and layout is now corrected. A big thank you to Vince who traced the later 125b version which revealed how the active Mid control really works.
Update 1 210514
Caution! There was a mistake in the trace. The Mid control have a different setup than the schematic and layout below indicates. Do not proceed if you want a Mid control that is 100% identical to the stock ODB. I will update the the schematic and layout as soon as I can. Lesson learned, hesistant to trace from gutshots from now on...
Intended for bass but works really good for guitar as well. Based on OCD but tuned for more low end, headroom and gain. Treble and Bass controls is a passive James tonestack and Mid control is an active Bridged-T feedback control. Cut switch is Shelving filter for the first gain stage and Clip switch selects between assymetric MOSFET/Silicon, LED and none clipping. Traced by AlexS and fuzzhead and the layout is verified.
Two things, though. We couldn't figure out the value of the Treble cap in the James tonestack but values between 330pF and 1nF sounds good.
Also, the LTC1144 charge pump is only needed if if you want to run it on 18v to get a 36v swing within the circuit. They are pretty expensive and not that common. MAX1044 and ICL7660S can be used as well but the cut between pin 1 and 8 of IC2 must be omitted. Those charge pumps can only handle a maximum input voltage at 10v and 12v respectively so a 9v power supply/battery is higly recommended...
A slightly modified Tubescreamer with the input buffer replaced by a SHO MOSFET booster. The Calibre control can be noisy but I guess "Crackle is OK"....
Schematic is avaiable HERE.
Traced by AlexS and Fuzzhead, this is a quite tweakable and heavily modified HM2 variant with more gain on tap, more volume, two on/off/on diode switches and a very flexible four band eq.
It is a quite noisy beast when Gain and all eq controls is maxed out though but a buffer up front helps a lot. Or you can increase 1K resistor connecting to Gain 3 to calms things down. Stock HM2 value is 47k so there is a pretty wide margin to experiment within.
Layout is verified.
It is Pie Day so here is a layout of an old Ram's Head variant. Rarely cloned and some cap values is not found in any of the other vintage EHX variants. 220pF/680pF caps replaces the standard 470pF/500pF values and the tonestack has less mid scoop. Still added a Mid switch for some sligtly boosted mids.
Note that the FS36999 was house numbered 2N5133s. These varied in Hfe a lot, ranging between 100-800. So socketing may be a wise decision for the transistors.
Per request. Note that there is an option to choose between internal trim pot (as in original) or external potoentiometer for the Freq control. Freq switch is external and the MPQ3904 transistor array is replaced with ordinary 2N3904s.
Schematic is avaiable HERE.
An interesting high gain overdrive three cascaded mu amp stages with a poweful and flexible eq section
Schematic is avaiable HERE.
Came out a bit big with eight transistors and an IC so mounted sideways in a BB enclosure might be the best option when housing it...
Another Dunwich trace by evilarsen, AlexS and fuzzhead.
I believe this one was made on custom order and/or was a on/off product. However, compoent values varied over time but we added some notes at the bottom of the layout and schematic for the most significant changes that is worth experimenting with:
Input capacitors connecting to the input cap blend control (Depth) varied quite a bit. I ended up with a 15nF for C2 and an 1uF for C1 with a 100kC Depth control.
The other thing is one of the clipping diodes at Q4. Most units had a germanium diode but a few had a silicon transistor in TO-18 casing wired as a diode. Both layouts bellow have slots for both components but remember to use one of them, NOT both.
Two layouts, one normal and one with 1.5W carbon comp resistors. Both is verified.
Dunwich released a small run of DIY PCBs a few years ago of a modified HM2. There is a few changes from a stock HM2 most noticable the on/off switches for both soft clipping and hard clipping diodes. You may want to experiment with the cap values at one of the gyrators for a more effective separate Mid control. AMZ and Griffin Effects have very useful bandpass filter/gyrator calculators.
Some says this is a HM2 killer. I don't know about that but it differs enough circuit wise to deserve its own layout. Note that "Hard/Soft" switch is omitted as well as "Output 2" op amp circuit.
There is several versions of this one but the 4-knob version seem to be the most common version.
Initially, it was a custom fuzz for doom band Conan but it was later slightly modified and morphed into Dunwich/Magic Pedals lineup of pedals. Traced by evilarsen and fuzzhead who both dig the sounds coming out of this doom circuit...
Couldn't resist to draw a schematic and a layout for this interesting mutant of a circuit that just got traced.
First two gain stages is almost identical to a Jumbo Tonebender (except for one cap and one resistor value), the third gain stage is almost identical to the saturation stage in a Tonebender Mk. 3. Transistor bias is quite different with the zener diode, though. Tonestack is Big Muff style followed by a Volume control.
Note that earlier versions had 100nF or 470nF instead of 10nF so it might be worth socketing that cap.
