DX-style Operator (Thru-Zero FM/PM oscillator - FM Ogre)

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LektroiD
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Post by LektroiD » Fri Feb 05, 2016 11:07 am

Is this available now? I've been waiting ages for this one...

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Post by jt4tb303 » Fri Feb 05, 2016 11:53 pm

Very cool!! :sb:
I would love to get my hands one or possibly more of these if they become available! :guinness:

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Post by wsy » Sat Feb 06, 2016 7:59 am

Well, yes it is, and no it isn't.

There are at least three commercial companies that have signed up to produce it under license. Unfortunately, none have started
delivering. There are also a couple of individuals who *are* buidling them, and Ive encouraged them to make more and sell them,
but they have't. not yet at least.

There's been only one "failed to work" board among all of the builds; ther was a clock problem that as far as I know wasn't solved, which
may just be a defective board from the board house, since other boards from that run have been built out and work just fine.

The board Gerbers (known to produce good boards at both Sunstone and OSHPark) and the schematics and the BoM and the
whole Fritzing proejct are available for free.

So I don't know what's holding up the works. Yes, it's annoying me too.

- Bill
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Post by Jarno » Sat Feb 06, 2016 12:02 pm

Every DIY-er has a backlog of at least a couple of years :D

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Post by mxmxmx » Sat Feb 06, 2016 12:07 pm

Joonatin wrote:Has someone made too many pcbs and would be willing to sell me one or two? PM plz.
fwiw, i never meant to sell anything, but i have a few of the 6HP sets left, which i don't need. ie this one

Image

NB: these aren't an exact copy (in that i was using MCP6002s for the input buffers, the pin mapping is different, and there's just two non-latching illuminated buttons on the control pcb, so the regular code won't work out of the box.) it seems to work fine. the main pcb (pictured above) is pretty much self-contained, in case someone wanted to add attenuators or use a different panel layout.

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Post by wsy » Sat Feb 06, 2016 2:10 pm

mxmxmx wrote:
Joonatin wrote:Has someone made too many pcbs and would be willing to sell me one or two? PM plz.
fwiw, i never meant to sell anything, but i have a few of the 6HP sets left, which i don't need. ie this one

Image

NB: these aren't an exact copy (in that i was using MCP6002s for the input buffers, the pin mapping is different, and there's just two non-latching illuminated buttons on the control pcb, so the regular code won't work out of the box.) it seems to work fine. the main pcb (pictured above) is pretty much self-contained, in case someone wanted to add attenuators or use a different panel layout.
On the other hand, your design is maybe a third the size of mine. Mine is like three inches wide and over four tall, you've got it
way, way slim and tiny. I'd actually like to see the schematic you used; half of my board is just the input protection circuits.

- Bill
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Post by mxmxmx » Sat Feb 06, 2016 5:28 pm

wsy wrote: I'd actually like to see the schematic you used; half of my board is just the input protection circuits.
i'd have to clean up the schematic first, it's a mess (fritzing); or i can send you the .fzz file, if you wanted to take a look. but it's basically following yours, except:

- four MCP6002s > no clamping diodes. (4 buffers for the pots + 4 inverting mixers for CV)
- negative offsets via LM4040
- just one trim pot (for V/oct)
- only two LEDs/switches
- sync output: transistor switch, no comparator.
- sync input: must be done off-board (i've used another transistor switch on the control pcb; not ideal, but it seems to work for most practical purposes)

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Post by wsy » Sat Feb 06, 2016 5:54 pm

mxmxmx wrote:
wsy wrote: I'd actually like to see the schematic you used; half of my board is just the input protection circuits.
i'd have to clean up the schematic first, it's a mess (fritzing); or i can send you the .fzz file, if you wanted to take a look. but it's basically following yours, except:

- four MCP6002s > no clamping diodes. (4 buffers for the pots + 4 inverting mixers for CV)
- negative offsets via LM4040
- just one trim pot (for V/oct)
- only two LEDs/switches
- sync output: transistor switch, no comparator.
- sync input: must be done off-board (i've used another transistor switch on the control pcb; not ideal, but it seems to work for most practical purposes)
Without clamping diodes, how do you keep CV inputs outside of +-5V from blowing out the inputs on the PIC chip? The manual is very
specific on that - overvolting or undervolting the ADC inputs will blow them out, especially since you need to drive them at
100 ohms or lower impedance to get the sample and hold cap to charge fast enough. So be careful.with your boards unless you have
some other clamping magic to keep the ADC inputs on the DSP in the safe zone.

(and yes, the ohter stuff is perfectly reasonable - I thought about dropping the output trimpots and putting in fixed resistors there
instead myself. It'd definitely save some cost and space.

- Bill
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Post by mxmxmx » Sat Feb 06, 2016 6:01 pm

wsy wrote: Without clamping diodes, how do you keep CV inputs outside of +-5V from blowing out the inputs on the PIC chip? The manual is very
specific on that - overvolting or undervolting the ADC inputs will blow them out, especially since you need to drive them at
100 ohms or lower impedance to get the sample and hold cap to charge fast enough
oh, but they run off 3.3v ...

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Post by synchromesh » Sat Feb 06, 2016 6:27 pm

For everyone's information, a nice chap on Facebook is doing a (UK-centric) group buy of open source PCBs - initially the expected Mutable Instruments layouts for the most part, but also mxmxmx's Terminal Tedium. And the prices are extremely reasonable, particularly compared to previous efforts.

But the second round includes other boards, including the FM Ogre (if there's enough interest).

As much as I hate to do anything to encourage people to divert their attention from this forum to bloody Facebook, I feel obliged to point this out, if only so that the good wsy is kept aware of his design's progress... :cloud:

(disclaimer: I am investing heavily in the aforementioned MI & TT PCBs, and have put my name down for an FM Ogre PCB. Vive la open source!)

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Post by wsy » Sat Feb 06, 2016 9:05 pm

mxmxmx wrote:
wsy wrote: Without clamping diodes, how do you keep CV inputs outside of +-5V from blowing out the inputs on the PIC chip? The manual is very
specific on that - overvolting or undervolting the ADC inputs will blow them out, especially since you need to drive them at
100 ohms or lower impedance to get the sample and hold cap to charge fast enough
oh, but they run off 3.3v ...
AHhhhhhh... coool trick! With 100K on the inputs, the internal clamp diodes of the rail-to-rails keep everything within bounds.

Nice trick.... saves a lot of components.

I almost think this warrants a Version 2. Can I steal your methods? :hyper:

- Bill
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Post by mxmxmx » Sun Feb 07, 2016 4:08 am

wsy wrote:
AHhhhhhh... coool trick! With 100K on the inputs, the internal clamp diodes of the rail-to-rails keep everything within bounds.

Nice trick.... saves a lot of components.

I almost think this warrants a Version 2. Can I steal your methods?
go ahead, it's not my trick, of course. i stole it from olivier gillet.

it's odd the single/same supply scheme didn't seem to get much use around here until mutable instruments came around; when you go look for it, it's often mentioned though, e.g. here Figure 3-46 A

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Post by wsy » Sun Feb 07, 2016 7:20 pm

mxmxmx wrote:
wsy wrote:
AHhhhhhh... coool trick! With 100K on the inputs, the internal clamp diodes of the rail-to-rails keep everything within bounds.

Nice trick.... saves a lot of components.

I almost think this warrants a Version 2. Can I steal your methods?
go ahead, it's not my trick, of course. i stole it from olivier gillet.

it's odd the single/same supply scheme didn't seem to get much use around here until mutable instruments came around; when you go look for it, it's often mentioned though, e.g. here Figure 3-46 A
OK, check me on this then: The following circuit fragment takes in a +/- 5 volt bipolar signal, maps it to the range 0 to 3V3, and
because it's only driven with 3.3 volts and has 300K input impedance, effectively clips the signal into the 0-3V3 range (plus or minus a diode drop)

Image

If so... great! :guinness: it will save me a whole lot of parts (only R1, R2, and one op amp stage per channel, everything else is 1-per-card.)

- Bill
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Post by mxmxmx » Mon Feb 08, 2016 2:34 am

wsy wrote:
OK, check me on this then: The following circuit fragment takes in a +/- 5 volt bipolar signal, maps it to the range 0 to 3V3, and
because it's only driven with 3.3 volts and has 300K input impedance, effectively clips the signal into the 0-3V3 range (plus or minus a diode drop)
yeah, biasing the + terminal would work, too, though (i think) the bias voltage would have to be 1.2375v in this case: V_out = - (100/300)*V_in + (100/300+1)*V_bias ; if you use, say, R3 = 82k and R4 = 49k9, the output should swing around ~ 1.65v.

since we actually have dual supplies, i find it much easier to mix in a negative reference voltage (LM4040, they're tiny). this is what i did:


Image

i kept the series resistor, just in case the PIC doesn't like to be driven from the op amp output directly; i don't know, i had never used one (ie dsPICs). it's probably not needed. the low pass is ~18kHz, IIRC the ADCs are sampled quite a bit faster though.

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Post by wsy » Mon Feb 08, 2016 5:53 am

mxmxmx wrote: yeah, biasing the + terminal would work, too, though (i think) the bias voltage would have to be 1.2375v in this case: V_out = - (100/300)*V_in + (100/300+1)*V_bias ; if you use, say, R3 = 82k and R4 = 49k9, the output should swing around ~ 1.65v.

since we actually have dual supplies, i find it much easier to mix in a negative reference voltage (LM4040, they're tiny). this is what i did:


Image

i kept the series resistor, just in case the PIC doesn't like to be driven from the op amp output directly; i don't know, i had never used one (ie dsPICs). it's probably not needed. the low pass is ~18kHz, IIRC the ADCs are sampled quite a bit faster though.
AHA! Forgot the +1 in the Vbias term. That's why (and how) the 1.235 volts kept showing up on older board revs, not 1.65 volts.

The justification to bias the V+ input is that I can share the voltage bias network among all of the inputs (it's only feeding the high-Z
op-amp inputs). If I use an add-in current on the V- node, then I can't share the resistor across all of the inputs, I would need a 100K
resistor for _each_ protected input (eight or more of them).

As to the 33ohm resistor (I used 100 ohms) is that the PIC analog input is a capacitive load and some op-amps don't like driving such
things without oscillation. MicroChip recommends a 100 ohm resistance there unless you know the circuit will be stable without it. That's
why I put a 100 ohm resistor there; it probably would be fine without it but I am not good enough to prove it to myself.

Thank you!!!

- Bill
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Post by wsy » Mon Feb 15, 2016 8:55 am

mxmxmx wrote:
Joonatin wrote:Has someone made too many pcbs and would be willing to sell me one or two? PM plz.
fwiw, i never meant to sell anything, but i have a few of the 6HP sets left, which i don't need. ie this one

Image

NB: these aren't an exact copy (in that i was using MCP6002s for the input buffers, the pin mapping is different, and there's just two non-latching illuminated buttons on the control pcb, so the regular code won't work out of the box.) it seems to work fine. the main pcb (pictured above) is pretty much self-contained, in case someone wanted to add attenuators or use a different panel layout.
Encouraged by your PCB above, I am trying to do the same thing - put it into a 6HP sized card and DAMN, that's hard to do.

I'm using SOIC-8's for the op-amps, and tried (but failed) to do it with 0805 resistors. Are you using something
smaller, like TSOP-8 and 0603 resistors / caps / diodes?

Or maybe I should just realize I'm not that great at laying out a PCB.

- Bill
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Post by mxmxmx » Mon Feb 15, 2016 2:22 pm

wsy wrote:
Encouraged by your PCB above, I am trying to do the same thing - put it into a 6HP sized card and DAMN, that's hard to do.

I'm using SOIC-8's for the op-amps, and tried (but failed) to do it with 0805 resistors. Are you using something
smaller, like TSOP-8 and 0603 resistors / caps / diodes?
yes, the passives are 0603. the op amps are SOIC. if you want, i'll send you the .fzz, so you can take a better look?

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Post by wsy » Mon Feb 15, 2016 4:09 pm

mxmxmx wrote:
wsy wrote:
Encouraged by your PCB above, I am trying to do the same thing - put it into a 6HP sized card and DAMN, that's hard to do.

I'm using SOIC-8's for the op-amps, and tried (but failed) to do it with 0805 resistors. Are you using something
smaller, like TSOP-8 and 0603 resistors / caps / diodes?
yes, the passives are 0603. the op amps are SOIC. if you want, i'll send you the .fzz, so you can take a better look?
Let me give it a with 0603 and only two mounting holes instead of four before I give up and admit defeat.. 100 mm tall x 30mm wide, right?
Although if it was 8 HP wide (45 mm) that wouldn't be too bad, would it (especially if it had the full complement of switches and LEDs and
reversed-power protection..

What did you use for voltage regulators? I am putting the Thru-Hole resistor in there as you did, to take some of the heat load off of going from 15 V down to 3.3V.

- Bill (losing, but not yet lost)
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Post by mxmxmx » Mon Feb 15, 2016 4:56 pm

wsy wrote: Let me give it a with 0603 and only two mounting holes instead of four before I give up and admit defeat.. 100 mm tall x 30mm wide, right?
Although if it was 8 HP wide (45 mm) that wouldn't be too bad, would it (especially if it had the full complement of switches and LEDs and
reversed-power protection..
there's probably no reason to cram everything into 30mm; i had some 6HP panels left from a different project which happened to have roughly the same i/o, that was the only motivation.
wsy wrote: What did you use for voltage regulators? I am putting the Thru-Hole resistor in there as you did, to take some of the heat load off of going from 15 V down to 3.3V.
LM1117. it doesn't get too warm, but then i have a 12V supply. the through hole part is a 10uH inductor, it sits in between VDD and VDDA; though mostly it made things easier to route...

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Post by wsy » Wed Feb 17, 2016 10:28 am

mxmxmx wrote:
wsy wrote: Let me give it a with 0603 and only two mounting holes instead of four before I give up and admit defeat.. 100 mm tall x 30mm wide, right?
Although if it was 8 HP wide (45 mm) that wouldn't be too bad, would it (especially if it had the full complement of switches and LEDs and
reversed-power protection..
there's probably no reason to cram everything into 30mm; i had some 6HP panels left from a different project which happened to have roughly the same i/o, that was the only motivation.
wsy wrote: What did you use for voltage regulators? I am putting the Thru-Hole resistor in there as you did, to take some of the heat load off of going from 15 V down to 3.3V.
LM1117. it doesn't get too warm, but then i have a 12V supply. the through hole part is a 10uH inductor, it sits in between VDD and VDDA; though mostly it made things easier to route...
Got another question for you- what footprint did you use for the LM1117 and for your "little regulators"? I'm using the most recent
release of Fritzing (0.9.2b) and its got the usual quirks but it's pretty stable.

(Yes I managed t get the parts down in 100mm x 30mm (6HP); I'm in the process of routing it now. I'm going to add a few little tricks,
do a short run at least, and then put it up. I really like your trick of using a big-ohms resistor followed by a rail-to-rail opamp
as the input protection circuit. It saves like a third of the board area by itself!

- Bill
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Post by mxmxmx » Wed Feb 17, 2016 10:55 am

wsy wrote: Got another question for you- what footprint did you use for the LM1117 and for your "little regulators"? I'm using the most recent
release of Fritzing (0.9.2b) and its got the usual quirks but it's pretty stable.
the LM1117 should show up in the search bar; at least, it does here. it's in a/the sparkfun package (SOT-223) it looks like, can't remember though whether that was there by default; maybe you have to install it.

the "little regulators" -- you mean the LM4040? i just used some sot-23 part and re-labelled it in the parts editor. also from the sparkfun parts, IIRC. (there's two different sot-23 ones in that package (NPN transistors), one with slightly bigger pads, which is what i normally use for those)

(a nice "little" regulator i use a lot is the ADP150, but i didn't use it here.)

wsy wrote: (Yes I managed t get the parts down in 100mm x 30mm (6HP); I'm in the process of routing it now. I'm going to add a few little tricks,
do a short run at least, and then put it up.
cool, what's the tricks?

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Post by wsy » Wed Feb 17, 2016 11:28 am

mxmxmx wrote:
wsy wrote: (Yes I managed t get the parts down in 100mm x 30mm (6HP); I'm in the process of routing it now. I'm going to add a few little tricks,
do a short run at least, and then put it up.
cool, what's the tricks?
Purely gratuitous.... for reverse polarity protection, I put in a full bridge rectifier in the power input stage, so no matter which way the
Doepfer power connector is inserted, the module works.

So, I'm going to run a line from Doepfer+ *before* the bridge rectifirer thru a 1-megohm resistor to an otherwise-unused logic input. Then
the DSP can tell if it's been plugged in backwards or not.

One option: depending on the sense of the power polarity signal, switch the 1V/Octave and Pitch knobs to work _backwards_ - negative
voltage and turning counterclockwise makes the pitch go up. Laugh, laugh, laugh.....

Another option: if the module is plugged in backwards, play a .WAV of Madgel Barett saying "MALFUNCTION, MALFUNCTION",
or HAL singing "Daisy, Daisy...." or something like that.

Tricks like that... or maybe something grander. Not saying on that till I'm sure it will work.

- Bill
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Post by diablojoy » Fri Feb 19, 2016 3:29 am

hmm interesting
I don't think i could shrink my panel design down from 12HP without losing some functionality somewhere or making it too cramped to be user friendly but the circuit changes suggested would ease the board congestion considerably might even be able to make more of it through hole or at least 1206.
It probably wont happen today but if it does it definitely wont go smoothly.

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Post by mxmxmx » Fri Feb 19, 2016 4:00 am

diablojoy wrote:hmm interesting
I don't think i could shrink my panel design down from 12HP without losing some functionality somewhere or making it too cramped to be user friendly but the circuit changes suggested would ease the board congestion considerably might even be able to make more of it through hole or at least 1206.
sure .. matter of taste, i suppose. i'm long past the make-everything-4-HP thing, but in this case, with the song huei trimmers things aren't particularly cramped, and the reasoning (part of my reasoning) was that a three or four operator device would still check out at 18HP or 24HP. (and that would be just the oscillators):

Image


but it's true, some options will be lost, like attenuators, unless things get really cramped; but it's only the core board that's 30mm; the control board could always be larger/more fully featured.

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Post by wsy » Fri Feb 19, 2016 6:21 am

mxmxmx wrote: .... but it's true, some options will be lost, like attenuators, unless things get really cramped; but it's only the core board that's 30mm; the control board could always be larger/more fully featured.
That's actually the plan. The "brains" are 6 HP wide, so you can go that narrow if you want. But nothing forces you to go that
narrow; I lead out all the voltages you'd want for any front panel you might want, be it PCB-based or fly-wired (which actually is easy
given the bus-oriented design of the I/O - bus all grounds, bus all +5 and -5, then eight wires, one for each pot or jack.

In fact, the current board setup can plug right into a proto-board (one of those white plastic prototyping boards with a bazillion
rows of five contacts each? Yeah. THOSE boards.) It makes audio DSP a prototypeable "brick". (simple-actually.
All I/O is on two rows of 0.100 pins that are 1 inch apart. That leaves one hole exposed on each side for your prototyping pleasures.

As to a thru-hole version: ain't gonna happen unless MicroChip makes a 40- or 44-pin version of the DSP chip. The original used
the 28-pin DIP version which only has six usable analog-in pins (there are four more, but they use the same pins as the 16-bit analog _outputs_.

So you could do a thru-hole version if you did your attenuators off-chip in hardware; the first proto-board version did exactly that. But it
will cost you an extra op-amp per channel and it means that most of your inputs are now non-tracking (they've got analog attenuators on them
so alternate software can't "do the right thing" for 1V/octave there or anysuch. It also means that you can't make "attenuverters" by
trivial software changes.

The way it broke down for me on the 28-pin thru-hole was

AN0 - 1V/octave calibrated pitch
AN1 - Pitch potentiometer
AN2 - Feedback
AN3 - Frequency Modulation (thru-zero linear)
AN4 - Phase Modulation (thru-zero linear)
AN5 - Output VCA (less useful than anticipated)

That's not to say it's undoable... just that it's way less versatile than I have visions of.

And it's _still_ a 3.3 volt part, so you have to have voltage converter op-amps anyway and those are also going to be thru-hole parts
so you've now got this huge area (2.5 square inches) of board space doing nothing _useful_. But it may well end up bigger
than a Rubicon, maybe the size of a Zeroscillator (but not as complex; gawd that thing's a monstrosity)

Maybe someday if I'm bored I'll lay it out in DIP-28 thru-hole and see how bad it looks- but for now, I'm hot for making a 6HP fullfeatured module
that anyone can just buy and use as a building block anywhere... including a 4-op FM. :)

- Bill
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