Moog Grandmother no modulation output

[Arpangel]

I’ve been on this for ages, and can’t see a way out, I’m controlling my BARP2600 from my Grandmother, very successfully, up until now, I like the simplicity of the sequencer/arp, and being able to inout notes via keys, not knobs
But now I’m trying to play melodies using the 2600 LFO to ad vibrato, controlled via the Moog's mod-wheel, and it’s not happening, and I think it never will, as the Grandmother doesn’t have a CV Modulation output, all you’ve got is the "Wave Output" but that’s fixed to the LFO, not the keyboard mod wheel.
I’m trying to think of ways around this, to no avail.

[Eddy Deegan]

Would it not work if you use MIDI instead of CV?

[Arpangel]

Would it not work if you use MIDI instead of CV?

Thanks Eddy, I’m using Midi!
The Mod wheel doesn’t seem to transmit anything, and even if it did, where do you take it from? there’s an external CV "Vibrato In" on the 2600, but I don’t have any CV source apart from CV/Gate on the GM.
PS, just checked, the manual states that mod-wheel data is sent via Midi, but I don’t know how I’m supposed to access it on the 2600.

[Wonks]

Hardware MIDI CC to CV module/box? A few Eurorack units around, and Kenton do a stand-alone box.

[The Elf]

Some of the Kenton boxes did (still do?) have an LFO on board, which can be set to respond to incoming mod wheel messages and apply to the CV output. It would be worth having a chat with John at Kenton to see which ones still do this. It makes for a much simpler set up.

[Arpangel]

Some of the Kenton boxes did (still do?) have an LFO on board, which can be set to respond to incoming mod wheel messages and apply to the CV output. It would be worth having a chat with John at Kenton to see which ones still do this. It makes for a much simpler set up.

Thanks Elf, that’s one solution, but I’ve been thinking about getting a Midi module for my modular, the cheap Doepfer one, it has a Mod CV out, I could use that with 2600 I suppose.

[BigRedX]

Is there a more comprehensive manual for the Behringer 2600 than the scant information contained in the quick-start guide? Or a proper MIDI implementation chart?

AFAICS unless there are other functions available through software settings via USB MIDI, the only MIDI functions available are note values and note on/off commands.

Even if you were to do it the traditional way with a CV mod wheel, you need a second VCA to patch the LFO through in order to use the mod wheel to control vibrato depth.

The keyboard that came with the original ARP 2600 has a second LFO along with a depth slider which could be used as a crude modulation controller.

[The Elf]

Some of the Kenton boxes did (still do?) have an LFO on board, which can be set to respond to incoming mod wheel messages and apply to the CV output. It would be worth having a chat with John at Kenton to see which ones still do this. It makes for a much simpler set up.

Thanks Elf, that’s one solution, but I’ve been thinking about getting a Midi module for my modular, the cheap Doepfer one, it has a Mod CV out, I could use that with 2600 I suppose.

I doubt it. I bet it just sends out a static Voltage based on the position of the mod wheel. You would need some other processor to apply that to an LFO depth. I'm not a 2600 expert, but I'm not aware of an input that does that - unless it's EXT VIB IN? More modular minds than mine may be able to offer a solution.

[The Elf]

Is there a more comprehensive manual for the Behringer 2600 than the scant information contained in the quick-start guide? Or a proper MIDI implementation chart?

Behringer seem to feel that a 'Quick Start Guide' is all the documentation we will ever need for their gear.

[Wonks]

They've done it the wrong way round. Back in the days when you were returning Behringer stuff shortly after you opened it, a quick start guide was all that was needed, instead of the comprehensive manuals they provided. Now it has become reliable kit, you really want the full manuals rather than the sole quick start guide.

[BigRedX]

I doubt it. I bet it just sends out a static Voltage based on the position of the mod wheel. You would need some other processor to apply that to an LFO depth. I'm not a 2600 expert, but I'm not aware of an input that does that - unless it's EXT VIB IN? More modular minds than mine may be able to offer a solution.

The device in question needs to send out a variable voltage dependant upon the position of the mod wheel within the range that the 2600 is expecting (min to max voltage). You then patch that into one of the VCO modulation inputs. The slider for that input sets the modulation amount for when the wheel is at its maximum. However unless the jack socket modulation inputs are ganged for all 3 VCOs you'll also need a voltage splitter for each VCO you want to respond to the mod wheel.

Arpangel can you post a link for the MIDI module you are talking about?

[Arpangel]

Arpangel can you post a link for the MIDI module you are talking about?

Yes, thanks, it’s this one,

https://www.signalsounds.com/doepfer-a ... ack-module

I had the first version of this many years ago, and the ctrl output worked fine providing a variable voltage to say a VCA for controlling the level of an LFO for vibrato, I’m just wondering, if it does work, how I’m going to plumb it in to the 2600?

[BigRedX]

Thanks,

There doesn't appear to be an actual block diagram of the 2600 signal and voltage paths, so I've had to try on work out what does what from the front panel controls and labels, which without an actual 2600 in front of my to play with isn't always obvious.

My first concern is that the LFO appears to only be directly patched into VCO1. Is that correct? If you want to apply LFO modulation to the other two VCOs do you need to make manual connections? Or does that mod input also control VCO2 and 3?

However the biggest stumbling block AFAICS is that you need to second VCA to allow the Mod Wheel to control the output of the LFO before it is patched into the FM input of the VCOs. This second VCA doesn't appear to be present, unless one of the other modules can be repurposed for this task.

If I'm right you are also going to need a basic VCA module such as this one as well as the MIDI one. So you patch the triangle wave output from the 2600 to the signal input of your VCA module, and the signal output of that to the one of the FM inputs on each VCO that you need to apply vibrato to. If there isn't an internal way of linking the FM inputs of all three VCOs you'll need to patch this via the "Mult" sockets on the 2600 first so the LFO can be applied to each VCO. You then connect the CV Control output of the MIDI module to a CV input of the VCA module.

IMO this is all getting a bit too complicated for simply being able to add vibrato via a mod wheel control. Hopefully someone who actually knows the 2600 has come up with a better way.

[Arpangel]

Thanks,

There doesn't appear to be an actual block diagram of the 2600 signal and voltage paths, so I've had to try on work out what does what from the front panel controls and labels, which without an actual 2600 in front of my to play with isn't always obvious.

My first concern is that the LFO appears to only be directly patched into VCO1. Is that correct? If you want to apply LFO modulation to the other two VCOs do you need to make manual connections? Or does that mod input also control VCO2 and 3?

You’re correct, only VCO1, you have to take the output of the LFO section to modulate OSC2/3

Thanks,

However the biggest stumbling block AFAICS is that you need to second VCA to allow the Mod Wheel to control the output of the LFO before it is patched into the FM input of the VCOs. This second VCA doesn't appear to be present, unless one of the other modules can be repurposed for this task.

If I'm right you are also going to need a basic VCA module such as this one as well as the MIDI one. So you patch the triangle wave output from the 2600 to the signal input of your VCA module, and the signal output of that to the one of the FM inputs on each VCO that you need to apply vibrato to. If there isn't an internal way of linking the FM inputs of all three VCOs you'll need to patch this via the "Mult" sockets on the 2600 first so the LFO can be applied to each VCO. You then connect the CV Control output of the MIDI module to a CV input of the VCA module.

IMO this is all getting a bit too complicated for simply being able to add vibrato via a mod wheel control. Hopefully someone who actually knows the 2600 has come up with a better way.

You’re right, it’s not worth it, I think, the original 2600 was able to do this from the supplied keyboard.
I’m going to connect another Midi keyboard today, and see if that does anything.

[BigRedX]

The 2600 keyboard had a second LFO on it whose depth could be controlled by slider in a crude emulation of a mod wheel. AFAICS it didn't have a conventional pitch bend control either.

I suspect the problem lies with the MIDI implementation of the Behringer 2600 in that it only responds to MIDI note on and off commands, so trying a different controlling keyboard won't make any difference. It would be nice if manufacturers supplied MIDI implementation charts with their equipment, like they did in the early days. Then you'd be able to see exactly what MIDI commands the 2600 responded to.

[The Elf]

I can confirm that the Behringer 2600 responds to pitchbend commands, and sends these from it's own resulting keyboard Voltage output. But I can't see any way at all of accessing incoming MIDI mod wheel messages as a Voltage output, and it seems to have no hard-wired response to mod wheel.

I fiddled around with the 2600's Voltage mixer to see if I could come up with anything, but no combo I could think of.

Does the Grandmother's own LFO 'WAVE OUT' connector vary its amplitude with the mod wheel position? That might provide a compromise solution by connecting it to the 2600's 'EXT VIB IN'. You would lose independent control of the Grandmother's internal LFO, but you could then use the 2600's LFO to add PWM, or filter modulation to the Grandmother.

[BigRedX]

I can understand the 2600 responding to pitch bend information - after all it is essentially hardwired to the note values. Does it have a preset range? ±1 octave?

However the mod wheel tends to be more flexible in its function. And even if there was a voltage output for it on the 2600, you'd still need a second VCA for it to modulate the LFO depth.

Seems like a weird omission on the 2600 - even the Korg MS20 which is a lot less flexible in its routing has a second VCA for exactly this purpose.

[The Elf]

I can understand the 2600 responding to pitch bend information - after all it is essentially hardwired to the note values. Does it have a preset range? ±1 octave?

It can be set by the SynthTribe application. Mine, for instance, is set to 2 semitones.

Pitchbend is essentially a 14-bit controller message, not related to MIDI note values.

[BigRedX]

It can be set by the SynthTribe application. Mine, for instance, is set to 2 semitones.

Thanks! Are there any other adjustable parameters for the 2600 in the SynthTribe application?

[The Elf]

It can be set by the SynthTribe application. Mine, for instance, is set to 2 semitones.

Thanks! Are there any other adjustable parameters for the 2600 in the SynthTribe application?

Low/High/Last note priority. Apart from calibration steps, that's it.

[BigRedX]

Pitchbend is essentially a 14-bit controller message, not related to MIDI note values.

But since you are doing a MIDI > CV conversion you might as well also add the pitch bend CV value to this because most of the time on a normal synth it would be hardwired to note pitch.

However on anything but the most basic of synths the mod wheel can have multiple functions and is not just for adding vibrato.

Unless someone with more modular synth knowledge than me has a clever idea, I can't see anyway of adding vibrato from the mod wheel without having additional MIDI and VCA modules.

[Arpangel]

I can confirm that the Behringer 2600 responds to pitchbend commands, and sends these from it's own resulting keyboard Voltage output. But I can't see any way at all of accessing incoming MIDI mod wheel messages as a Voltage output, and it seems to have no hard-wired response to mod wheel.

I fiddled around with the 2600's Voltage mixer to see if I could come up with anything, but no combo I could think of.

Does the Grandmother's own LFO 'WAVE OUT' connector vary its amplitude with the mod wheel position? That might provide a compromise solution by connecting it to the 2600's 'EXT VIB IN'. You would lose independent control of the Grandmother's internal LFO, but you could then use the 2600's LFO to add PWM, or filter modulation to the Grandmother.

Elf, yes, pitch bend works fine!
That wave out thing, tried that, it’s a direct out from the mod osc on the Grandmother, and it’s not connected to the mod wheel.
This is one of "those situations" a simple thing, I’m not asking for the earth!
But that’s it, it’s a shame, I’ve tried getting the same sort of sound on another synth, and the Grandmother, but it’s not possible, the 2600, in these situations, you realise it is very unique, and has a definite sound.

[The Elf]

t'was ever thus - you're dealing with recreations of ancient technology, and that involves compromises.

It seems 'a simple thing', but how many CV-based synths would be capable of doing what you ask? We once tried to connect two Korg Sigmas together, so both would react as one from a single keyboard and set of performance controls. You would think this straightforward, given their connection options; an obvious requirement - nope.

Simple using MIDI (which is what we've become used to), yes, but with CV cables?... Not really.

The 2600 (a 'semi-modular' it must be noted) is a recreation from an older world, where dinosaurs ruled, keyboards were full sized and power supplies were internal. Its MIDI capabilities, basic though they are, are simply a bonus.

[BigRedX]

In order to do what you want with CV cables you really need both synths to be fully modular and have the correct complement of modules. From a modulation control PoV any MIDI synth with assignable CCs will offer far more control than most modular synths.

[Arpangel]

In order to do what you want with CV cables you really need both synths to be fully modular and have the correct complement of modules. From a modulation control PoV any MIDI synth with assignable CCs will offer far more control than most modular synths.

Trouble is at the 2600 end, the Midi isn’t good, as Elf said, it’s a bonus.