questions about using CV/Gate on sid

[chinard]

Helloooo

I'm just getting started building my first generation of midibox/sid and i have a question in regards to using voltage control with external devices.

My setup in my studio is starting to accumulate alot of analog machines including some moog stuff and a korg MS-20.

I've been looking through the archives and i've seen alot of promising talk about people that built their own moog LP filter and have it working off the envelope control from the sid.  Amazing project, but i've already got a moog filter (moogerfooger) so i'd like to figure out how to use that.

From what i can see, it appears that alot of the DIN and DOUT modules use the +/- 5v standard which looks like it can control an external aparatus like a moogerfooger LP filter, or even a set of korg MS-20 HP/LP filters.  This could even work for external modulation like with using the MS-20's freq~v converter and envelope follower.

I've also seen that there is a midibox project for creating a CV gate so it looks like alot of the groundwork is already done here.

I'm curious how one would go about wiring the CV inputs and outputs for something like this, and most importantly doing it in a way that would not impede the existing design.

Another thing i'm wondering is since one of my external CV sources/destinations would be an MS-20 which is Hz/V instead of V/Octave, how i would be able to bridge between the two standards.  (I believe the midibox is V/Octave much like the rest of the planet)

[kokoon]

MS-20 is V/Hz?!?!?! or is it V/kHz?

[illogik]

Hi;

From what i can see, it appears that alot of the DIN and DOUT modules use the +/- 5v standard which looks like it can control an external aparatus "

din/dout modules don't work on +/-5V just +5V, they are not suitable for generating control voltages (the dout module can be used for putting out (drum) triggers though); BUT the aout module (and the upcoming low cost aout module) are perfect for cv's and gates;

The thing with the SID you were talking about is that you can include a AOUT module in the sid-synth which can forward the application's envelopes and lfo's to cv outputs

cheers

[chinard]

Yes there are 2 standards for pitch tracking with voltage control.

There is the widely adopted V/Octave that was developed by R.A. Moog, and there was the lesser used V/Hz standard (korg, yamaha).  The differnece is linear vs logarithmic tracking.

The idea is that V/Hz provides better pitch tracking and is less suceptable to offset as components warm up.

theres a pretty good wiki on the subject. http://en.wikipedia.org/wiki/Control_voltage

Of course if you are just using volatge control to modulate something like a filter then pitch tracking means nothing and should work fine.

So what you are saying is that i can make an AOUT board to send the applications envelopes and lfos to an external output like the ms-20 or moog filters i have?

If so, how would i connect and configure it?

[kokoon]

i know about V/oct and V/Hz but i always wondered how the V/Hz works - it would directly translate that you need 4.000 volts for 4kHz ... and that looks a bit funny (dangerous?) - then i also read somewhere about the V/kHz (still linear) - i think it was the WASP synth - so i imagined that the actual V/Hz was used only by the "bass" synths... where the pitches aren't that high.

but now more that i'm thinking about it - there has to be some constant - V/C*Hz - so it still remains linear but the actual voltages still remain in normal limits :)

:)

i should think more.

[chinard]

well, i'm a bit sketchy on the details but i can explain the jist of it..

I may be totally wrong on the numbers here, but the basic idea should be correct.

the way octaves work on a frequecy scale, each octave increment is a DOUBLING of the hz.

for instance 440hz=note A4, 880hz=note A5, 1760hz =note A6, etc

Hz/V is a linear pitch tracking where every time you double the voltage you double the hz.

as you can see below the hz/v is a linear curve and the oct/v is a log curve

hz/v

0-0.25 first octave (A=55hz)

0.25-0.75 second octave (A=110hz)

0.75-1.5 third octave (A=220hz)

1.5-3.0 fourth octave (A=440hz)

3.0-6.0 5th octave (A=880hz)

oct/v

1v first octave (A=55hz)

2v second octave (A=110hz)

3v  third octave (A=220hz)

4v  fourth octave (A=440hz)

5v 5ht octave (A=880hz)

[kokoon]

that's all perfectly clear to me - apparently the constant for linear mode (V/Hz) i was speaking about is well below 0.01

all i'm saying is that V/Hz would mean "one volt per one herz" which would logically result in "880 volts (ouch) for 880 herz (A-5)"

instead it's apparently "X volts per one herz" where X is < 0.01 (roughly from your numbers)

but all that doesn't have anything to do with your initial post. i was just expressing my dissapointment about the MS-20 (which i always thought a synth to have once) being V/Hz - meaning it's incompatible (CV-wise) with the great majority of the modulars out there :)

[chinard]

i was just expressing my dissapointment about the MS-20 (which i always thought a synth to have once) being V/Hz - meaning it's incompatible (CV-wise) with the great majority of the modulars out there :)

Yeah, i hear ya, but what you gonna do right? its not like they make them anymore, and korg DID switch to v/octave later on which just shows the irony of this decision.

Regardless. that only covers pitch tracking anyways and has no bearing on the envelope control or lfo that i can (apparently) use just fine with an AOUT board.

The only thing i'm not clear on is where to connect the AOUT in a 1 sid configuration with the full control surface (1xcore, 1xsid, 2xDOUT, and 3xDIN) and how to get it to send filter control voltages when desired to my external sources. (moogerfooger MF101 and afforementioned ms-20)

I cant see this working to smoothly in a multiple sid configuration without some pretty creative mixer features and multple external filters.

[raphael]

The only thing i'm not clear on is where to connect the AOUT in a 1 sid configuration with the full control surface

http://www.midibox.org/forum/index.php?topic=5266.msg32418#msg32418

[moebius]

http://www.midibox.org/forum/index.php?topic=5266.msg32418#msg32418

And as always, AOUT page at the uCApps.de: http://www.ucapps.de/mbhp_aout.html

MS-20s VCO in is exponential. (http://www.korganalogue.net/korgms/mstt.html) and +5VDC is easily converted to S-trig. (at least it worked with micromoog I had, one NPN transistor and one resistor)

Bye, Moebius

[Davo]

FWIW, the Paia Fatman is a V/Hz machine and is still manufactured.  In the manual this is justified by saying that V/Hz is cheaper to implement because you don't have to worry about temperature compensation.  The math involved in V/Hz, however, seems hairier than in V/Oct and doesn't sound as nice.

[kokoon]

yeah i know about Fatman - actually right now i'm considering buying it... seems a nice and cheap monosynth.

[Davo]

yeah i know about Fatman - actually right now i'm considering buying it... seems a nice and cheap monosynth.

Not only is it cheap, but it's quite hackable.  I'll have to take a pic of mine sometime.  I cut out the front panel jack area and put in a piece of aluminum painted black (boy, that was an experience).  On that panel I mounted five toggle switches and a pot.  The pot is a 5k-ohm unit wired in series with the offset pot to allow fine control over the VCOs offset.  I've applied Lee's diode mod and the CMOS 555 swap.  Both combined seems worse than using just the Lee mod.  The toggles are for "bandpass enable", "filter boost", "ring modulator", "hard sync", and something else.  I replaced the AR/ASR with a center-off DPDT to cause the VCF to repeat itself.  The output jack now has an "input level" pot in its place.  All jacks were moved to the back of the optional chassis.

I need to get some more parts to finish the mods, but other things have taken precedence.  My only complaints about the Fatman are that the silk screening on the rack panel has a tendency to flake off and I wish that pitch-bend would do more than just one semitone.

The sounds it makes are very nice.  It's pretty easy for me to remember and come back to settings I like.  I probably spoke to soon when I said V/Hz sounds worse. 

[kokoon]

hmm sounds good... and i've heard the samples on paia.com. do you find it useful for stuff other than basslines? cause... i'm thinking - maybe it's worth shelling out another 300$ and get the 9700... that thing KICKS ASS! i'll probably end up getting both.

BUT WHY IS FATMAN V/HZ!? you can't even drive it from tb-303!

[Davo]

I can't seem to dig up a quote from Paia on their reason for using V/Hz.  As it is now, the synth sounds rather flat if used for lead stuff.  Adding a subharmonic generator and an LFO or two may help.  I'm not sure about the 9700.  I don't like its design of do-everything modules; and there are only four modules available.  I've had my eye on modular synths for quite a while and Arrick (aka Synthesizers.com) looks like the best combination of price and performance.  I'd like one of those with a couple modules from Blacet and/or Wiard.  Wiard's Wogglebug seems especially interesting.

[kokoon]

well the 9700 is just perfect IMO - the 4 modules actually contain like 15 modules. 2x VCO, 2x VCF, 2x VCA, 2x EG (AR), 1x EG (ADSR), 1x SLEW LIMITER, 1x NOISE, LFOs, ... and even more. and for only 450$. the synthesizers.com 100$/month scheme is also interesting but in the end after paying the 1200$ you only have a handful of modules. much less than the paia. then maybe the doepfer modules. they're pretty cheap too.

that's what i'm looking at - at the moment :)