Model D Filter EG as oscillator modulation source behaviour

[Quatschmacher]

I wondered if anyone who owns a Moog D could clarify something.

I recently acquired a Behringer D. When routing the filter EG via the mod section to the pitch of the oscillators the tuning goes sharp by about a semitone. I had it set with a short attack and short decay (under 10ms) and the sustain set to 0. Even with the modulation depth set to zero, there is a detectable rise in pitch when switching the “oscillator modulation” switch on. When I then turn the modulation depth knob up, the pitch rises, even if before doing so I have held the note long enough for the filter EG to have run its course.

I was trying to create a short pitch attack transient. As far as I understand it, if the sustain of the filter EG is set to zero, the oscillators should return to their original pitch once the attack and decay phases have completed. This is how it works on the iOS Model D app and on my Subsequent 37.

Do I have a duff unit? Or is this how it is on the reissue Ds too?

[noddyspuncture]

I don't believe the original Minimoog model D has the option to route the filter EG to pitch. I tried on four different Minimoog's and I couldn't manage it.

As this behringer module is supposedly and by all accounts an exact indistinguishable copy I'm surprised you managed it...!?

[ummagumma]

do you mean like this? check 24min 50 sec

https://youtu.be/qa4wo2Yv1DQ?t=24m50s

[Quatschmacher]

do you mean like this? check 24min 50 sec

https://youtu.be/qa4wo2Yv1DQ?t=24m50s

Yes, that is what’s happening.

[till]

I don't believe the original Minimoog model D has the option to route the filter EG to pitch. ...

Right. On the original /vintage) Minimoogs, you could only route VCO3 or Noise as modulation source via the modwheel. The only modulations available were the keyboard tracking of the filter via the ⅔ and ⅓ switches. And cutting the VCO3 off the keyboard voltage control.

[Quatschmacher]

I don't believe the original Minimoog model D has the option to route the filter EG to pitch. ...

Right. On the original /vintage) Minimoogs, you could only route VCO3 or Noise as modulation source via the modwheel. The only modulations available were the keyboard tracking of the filter via the ⅔ and ⅓ switches. And cutting the VCO3 off the keyboard voltage control.

What is the behaviour of the vintage Model D if you set oscillator 3 to modulate the pitch of oscillator 1? Mute oscillator 3 in the mixer and set it at a square wave, decoupled from the keyboard and set as slow as it will go. When the pulse is in its off phase, is the pitch of oscillator 1 the same as when the “oscillator modulation” switch is set to the “off” position. Try this with the mod wheel at zero and at maximum. Thanks in advance for your help.

[till]

What is the behaviour of the vintage Model D if you set oscillator 3 to modulate the pitch of oscillator 1? Mute oscillator 3 in the mixer and set it at a square wave, decoupled from the keyboard and set as slow as it will go. When the pulse is in its off phase, is the pitch of oscillator 1 the same as when the “oscillator modulation” switch is set to the “off” position. Try this with the mod wheel at zero and at maximum. Thanks in advance for your help.

Hi Quatschmacher (nice german nick name),
I just tested it:
When the Modwheel is at it zero position, there is no change in the pitch of OSC 1 when switching the Oscillator Modulation on or off.
At max modwheel position, the pitch goes a bit sharp when the Oscillator Modulation is switched on. With the modwheel at ⅓ position, the change is not real a real problem.
But solid pitch at off position or the above zero modwheel test.

[Quatschmacher]

What is the behaviour of the vintage Model D if you set oscillator 3 to modulate the pitch of oscillator 1? Mute oscillator 3 in the mixer and set it at a square wave, decoupled from the keyboard and set as slow as it will go. When the pulse is in its off phase, is the pitch of oscillator 1 the same as when the “oscillator modulation” switch is set to the “off” position. Try this with the mod wheel at zero and at maximum. Thanks in advance for your help.

Hi Quatschmacher (nice german nick name),
I just tested it:
When the Modwheel is at it zero position, there is no change in the pitch of OSC 1 when switching the Oscillator Modulation on or off.
At max modwheel position, the pitch goes a bit sharp when the Oscillator Modulation is switched on. With the modwheel at ⅓ position, the change is not real a real problem.
But solid pitch at off position or the above zero modwheel test.

Thanks, Till. How sharp is “a bit”? I’m guessing ideally it shouldn’t go sharp at all.

[till]

Thanks, Till. How sharp is “a bit”? I’m guessing ideally it shouldn’t go sharp at all.

It was less then a quarter tone. I have not measured it with a tuner. And I am sure it would vary from Minimoog to Minimoog a bit.
Welcome to the analog world of errors and design flows. And maybe a bit of decalibrating over the years.