@cybercow
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18 months later, I found my Dual Chorus in a box with several other builds and thought to pull it out and play with it. Wow! I am just amazed at how flexible this thing is. Seeing as it was plugged into my PC’s DI box, I thought to go ahead make a quick (about 6+ minutes) demo.
Here is the link for the Stereophonic Gizmotronic Symphonic Harmonic Perambulator Dual Chorus
Just for re-refernce, here is the pedal description:
Based on a pair of GuitarPCB “Mini-Me” chorus circuit boards (basically a modified Small Clone circuit), this unit uses Wilkie’s “Depth Mod” on each circuit, (and some fancy switching to link both chorus circuits to either of the LFO’s – or not), for some extreme chorusing ranges. And with two of them in one box, configurable for mono and/or stereo, it is a chorus monster.
The “Sync” switch determines which LFO is charge. When one LFO (Left or Right) each chorus can be set to different Depth settings and a nice psycho-acoustic effect ensues. It will connect as Mono (from “IN 1” to “OUT 2”), can be used as two separate chorus pedals (using “IN 1” to “OUT 1” and/or “IN 2” to “OUT 2”) or Mono in and Stereo out (using “IN 1” and both “OUT 1” & “OUT 2”)
Each circuit has its own Rate, Depth and ‘Depth Range’ controls. In any configuration, the ‘Depth’ and ‘Depth Range’ controls remain independent. When the “LFO SYNC” toggle is in the middle, the LFO’s are independent and the ‘Rate” control of each side works independently.
(9v @ ~15mA, neg. center)
Based on the photo of the solder-side, I would definitely reflow several of those solder joints – several of them look “dry” or incomplete.
Ollie – as Billy points out, BJTs and FETs and even JFETs do not have the same pin identifiers. BJT pinouts are typically all over the map – there is no “standard” pinout ordering. Same pretty much goes for FETs.
What a lot of builders don’t know about JFETs is that the Drain and Source are interchangeable. JFETs are symmetrical devices. Simple FETs are not and all three legs need to be properly identified as per their respective datasheets. (BJTs certainly are not.) For JFETs, identifying the Gate is vital. The other two legs can go where they most readily fit. And it’s OK to cross legs (if need be) when substituting parts – just be sure to use a bit of insulation on the crossed legs so they do not short together.
99.99% of any BJT, FET or JFET of the same part ID (J201, BC549, or what have you) will have the the same pinout as other parts of that same type – even across manufacturers.
Using sockets is always a good idea during initial builds to easily swap or re-orient a part if need be.
And as Billy points out for your J201 JFETs, just match the shape of the silkscreen to the shape of the J201 – if that build calls for J201 JFETs.
e_man – yup! It’s definitely a game of “Operation”. No avoiding that. Smaller soldering wands help. But it’s still like playing “Operation” and takes a steady hand and even then, practice helps. I know of no special tricks.
ACTUALLY . . . . . C1 is a 100nF, 120nF or 1µF cap – depending on which variant is being built. I’ve built a number of Muff’Ns and used the 100nF without issue on all of them. The “RAM” variant calls for a 1µF at C1and can be an MLCC, a box film or a non-polarized electrolytic.
Andy – IMO, adding an extra toggle to switch between the default value and the Roto-Tone Depth Mod won’t hurt anything; but the difference will be subtle and there will be some overlap when adjusting the Depth pot. The values you posted (330pf, 194pf, 103pf and 32pf) are the results one gets from the 330pf, 470pf, 220pf & 47pf being wired in series when switching thru the four options.
And for the MN3207 & MN3007 – there is zero sonic difference between them. I’ve done several Mini-Me builds and used both the MN3207 and MN3007 BBDs. I cannot tell the sonic difference between them. Just be sure to follow the correct jumper orientation for each of those two BBDs.
I used headers and jumper sleeves in one of my builds just to be able to easily go back and forth between the MN3207 & MN3007 for testing purposes.
Also, from the build notes beneath the BOM page:
“You can use the higher gain 2N5088, but you must put a ~33K resistor in R25.”
Craig – Dbl-check that there is +4.5v at the junction of C21 (22µF), R18 (10K) & R19 (10K)
If there is not +4.5v at that junction, dbl-check the values of R18 & R19 and ensure C21 is not shorted or open.
Are the JFETs J113s? (Cannot see from the photos.)
For socketed BJTs I always “wrinkle” the ends of the legs a bit so they will fit snuggly into the sockets.
Another point worth noting is that the exposed backs of the pots can easily short out the solder points beneath them.
The Industrial Fuzz is one of the easiest builds to go thru only to find that it doesn’t sound right. There is a LOT of knob fiddling to do to get really good, or really bad, sounding fuzz from this circuit. Double-check the build guide at the bottom of page 2 to see how to set things for different sounds.
That being said . . . . looking at your build photos, several of the solder joints look dry and may not be complete. Try reflowing the solder joints and add a touch a fresh solder to those joints that are not completely filled. Let us know how that goes.
Oh, and for further clarification, two diodes of the same type (back-to-back) form a symmetrical clipping configuration. By datasheet definition, they will have closely matched Fvd to start.
For asymmetrical clipping configurations, one wants to intentionally mis-match the Fvd of the diodes. Say one is silicon and the other is germanium. Or one side of the clipping configuration can be doubled up. (See attached image.)
These linked articles may also be of some benefit . . . .
Clipping diodes are going to generate additional harmonics to the audio signal. And with as much, there is no practical benefit to matching diodes in a clipping application. As long as they are the same ID & type, there is nothing to be gained with further efforts to achieve clipping symmetry. (IMO)
