Moog Music Forum

I have a voyager and CP251. I'd like to use the CP251 mixer to combine some control voltages to use with my Waldorf Pulses and the Voyager. I can't find in the the manual sufficiently reassuring confirmation that the mixer output limits potentially damaging summed voltages, apart from - ' the maximum nominal output voltage range is +/- 5 volts' . I suspect that this means I'm ok but is it safe to send say four voltage sources to one output? Or, do I have to juggle the inputs 1 & 2 using the attenuation to maintain safe voltage?

thanks - anxious user

Hi,
first, welcome on the forum.
I hope the "veterans" will show up with better explanations. I think that if you mix 4 CVs, the resultant CV might be
over 5V (- or +). On page 10 of the CP-251 manual it is said that the OFFSET knob raises or lowers the voltage of the mix.
It looks like to me that it is "pushing" the mix on the + side or on the - side if you plot the mix on a graphic. That's why
if you turn the OFFSET knob full - or +, it will add voltage. On page 26 of the CP-251 manual it is said that the OFFSET knob
can be considered as a 5th. input with a range of -5 to +5V.
I will manage to stay within -5 to +5V at the Master output. I will check that with a voltmeter, black probe on sleeve
and red probe on tip of a TRS cable plugged in the Master out (- or +). I think that "maximum nominal output voltage range"
means that the device is "intended" to be use in that -5 to +5V range. Thanks for posting that question, it is a good "lesson"
for me. Anybody correct me !
I will post graphics of a single square wave at the #1 input to show you what is happening when you turn the knobs...

hoping it helps you, others and me too !

Hi,
here it is...
there should be symmetrical results from positive jack (+) compare to negative jack(-). The OFFSET knob
was not perfectly "electricaly centered" when I took the negative jack (-) readings.

hope it helps you, others and me too !

Hi again,
there is a "useful performance or programming tip" on page 105 of the Voyager's manual, the bottom paragraph...

Hi to all,
sorry, I was wrong in the first post, it was the OFFSET knob and not the ATTENUATOR's knob I was
talking about. I corrected the text.

Hi JnGd - thanks for that investigation - I think I'm going to need to be careful using that mixer,

zeb

Hello!
I am wondering if I could use the CP 251 mixer to boost 10V Gate signals from a sequencer CV Out to 10+5=15V
I would do that to trigger S/H Gate on ARP 2600.

I must admit so far the documentation and posts above are not clear wrt the Offset in the mixer.
If that offset can add + 5V, then the Max Out of the mixer should be 10V if the Input signal is 5V.
But the manual only mentions “nominal max out”...
The manual also does not say whether or not it is safe to input more than 5V in the mixer Ins...
Also: not clear if the mixer is summing the 4 inputs (in which case you might go up to 4x5=20V +5V Offset= 25V?) or if the sum gets limited at +5V anyway...

Thank you!
Cheers

Hmm I have been experimenting with a MIDI sync'd Voyager feeding gates to a dotcom Q960 sequencer & Q107 envelope generators, and found I need to boost the LFO square wave to +5 on the attenuator to get it to work decently. This must be related.

I will measure the voltage outputs & post here, if it's useful

Here are some results from the Voyager XL patch panel attenuator, which should be the same circuitry

based on internal LFO's:

LFO1:
square wave, base voltage range: 0v to +3v
amount ranges:
+5: 0.34 v to 3.2 v
0: 0.27 v to 0.34 v
-5: -0.34 to -2.54 v

offset range:
max: 5.41 v to 8.26 v
min: -2.08 v to -4.94 v

LFO2:
square wave, base voltage range: -4.90 v to 4.96 v
amount ranges:
xxx

offset range:
max: 0.43v to 10.25 v
min: 0.1 v to -9.51 v


one of the probes on my cheap multimeter just broke, so I couldn't finish

the "amount" appears to be more or less a pad that lets the full signal through, zero's it, or reverses it? although it looks like it added something...and I needed to crank it up to get the envelope generators firing. hmm