V/Oct Problem.....i think.

[notinachos]

hello all,

i have a question regarding the V/Oct output on the voyager control voltage expander.

in the voyager manual, it says the V/Oct jack is actually like 1.3 something volts per octave.........why?

i tried using my v/oct out jack to track pitch on my synthesizers.com modular, but the oscillators would be out of tune on only the second key. they do not actually "pitch drift" per say but the voltage difference is signifigant enough to provide a discernable pitch difference from the moog. so the only thing i use my v/oct jack for is modulation (filter cutoff, res, lfo freq, etc.)

the only way i can control both synth's pitch using the same keypress is MIDI out from the voyager into a MIDI/CV interface on the dotcom. i kinda wanted to use my dotcom interface with my other keyboard for a total of 3 voices.... 2 layered, controlled by the moog, and one seperate left hand sound on the dotcom using the other interface.

i know full well WHY they don't track properly. moog spells it out in the manual clearly enough. my question i guess is why would moog do that with the voltage scaling? it makes no sense to me not to have the jack available as a pitch controller to other equipment. to me, it seems they are trying to make a "propriatory" moog pitch voltage. or mabye there is something i am not understanding.

anyway, that's my frustration.
thoughts? concerns? other frustrated folks out there?
or am i just missing something silly here....

[bunnyman]

Do you have the breakout box? If so, have you tried attenuating the pitch CV? Not sure if that would work or not...

-a bunny

[notinachos]

yeah i have the breakout box.

i would think that any attenuation would be not as effective as having a dedicated TRUE 1.00 v/oct output. i mean to get really accurate you would need to break out a volt-ohm-meter......(sp???? you know what i mean )

shouldn't really be necassary. a v/oct jack should be just tthat.
why would they do this?

[latigid on]

I remeber reading on the "Lord of the Ring Modulator" article, found on Moogspace, that one needs to iteratively tune the oscillators. So, patch the Pitch CV to an attenuator, then to a Pitch input. Play a low note, and adjust the attenuator until the pitch matches on both sources. Play a high note, and attenuate again. Then the low note and so forth until you are in tune.

Isn't it 0.935 V/Oct?

[GregAE]

in the voyager manual, it says the V/Oct jack is actually like 1.3 something volts per octave.

Actually, my manual (from a 2003 Voyager Performer) says the VX-351's Kybd Pitch jack provides 0.935 V/Oct. In fact, Moog later changed the VX-351 to provide 1 V/oct at this jack, which is what I observe on my '351 using a Multimeter. The 0.935 V/oct spec is the Voyager's internal pitch CV.

i tried using my v/oct out jack to track pitch on my synthesizers.com modular, but the oscillators would be out of tune on only the second key. they do not actually "pitch drift" per say but the voltage difference is signifigant enough to provide a discernable pitch difference from the moog. so the only thing i use my v/oct jack for is modulation (filter cutoff, res, lfo freq, etc.)

Try this experiment to troubleshoot: Connect the '351 kybd pitch out to one of your dotcom oscillators. Adjust the Voyager and dotcom oscillators to a unison pitch using the Voyager's middle 'C' key. Now go up an octave on the keyboard. If the dotcom oscillator is flat relative to the Voyager, then your '351 is probably putting out 0.935 V/oct instead of 1v/oct. If the dotcom oscillator is sharp relative to the Voyager, then the '351 is putting out more than 1v/oct (assuming your dotcom oscillators are calibrated). Now you know what's going on, but in either case, you'll need to contact Moog about it to get it fixed/adjusted.

I remember reading on the "Lord of the Ring Modulator" article, found on Moogspace, that one needs to iteratively tune the oscillators. So, patch the Pitch CV to an attenuator, then to a Pitch input. Play a low note, and adjust the attenuator until the pitch matches on both sources. Play a high note, and attenuate again. Then the low note and so forth until you are in tune.

Actually, this iterative process is unique to the RM: you start by adjusting the RM's FREQUENCY control for unison tuning with the Voyager's low 'F'. Then play the Voyager's high 'C' and adjust the '351 attenuator for unison tuning. Then return to the low 'F' and readjust the RM Frequency control for unison, then high 'C' and adjust the '351 attentuator. A few iterations of this will get the pitch scaling right, then you can set the RM Frequency for any pitch you desire and it will track the Voyager. However, this procedure should not be necessary if you are connecting to other 1v/oct equipment.

FWIW, my RM's carrier oscillator tracks at 0.737 V/oct (others may be different). This is a strange scaling value, but then Moog probably never intended to use the RM carrier as a stand-alone oscillator.

[latigid on]

Thanks Greg, you always seem to clear things up!

What does the VX-351 output adaptor for old Voyagers do? Perhaps it re-scales the Pitch CV output to 1V/Oct?

[GregAE]

What does the VX-351 output adaptor for old Voyagers do? Perhaps it re-scales the Pitch CV output to 1V/Oct?

I'm fairly certain the Output Adapter is just a kind of buffer/termination device for the Voyager's CVs, and nothing else.

[till]

The output adapter is adding only some capacitors for decoupling.
it is a kind of a hardware upgrade for a hardware bug in the original Voyager's hardware design.

[notinachos]

ok.....i made some headway. kind of.

gregAE, you were right about the output voltage...wow i really misquoted that one!! (i knew it was something other than 1.0 though )

ok so i plugged the pitch output straight into a dotcom v/oct jack and presto......perfect tracking across the keyboard. from the clickiest lows to the brassiest highs it was all in tune. very cool.

enter multiple module

problem!

if i plug the pitch out to the dotcom mult i get immediate pitch problems after the second note away from my calibration key. please note that one osc is all that is plugged into the mult so i am not even really sending the signal anywhere else. (i know that can occasionally happen when you send a single analog signal to many destinations) it drifts worse as i play up the keyboard too.

at this point i thought it was just my dotcom mult, but..........

if i use the 351's built in mult instead of my dotcom, the problem is the same. the 351 seems to handle it's own pitch signal better staying accurate for about 3 keys in either direction before bad drifting.

i am using all mono cables. should i be using TRS out of the moog gear?? (the dotcom still only takes TS) that's all i could really think of

thanks for the help guys!!!

[notinachos]

oh yeah and i should also add that if anyone is unfamiliar with how multiples work they just take an input jack and wire the tip and sleeve pins to other jacks, essentially "multiplying" the input signal to give many outputs with the same voltage.

there's no circuit board or electrical wizardry that could be faulted for the pitch problems i am experiencing. i still have not tried TRS cables but i have swapped out the cables i was using for my testing a couple of times to ensure they were not the problem. the cheap cables i use for modulation signals have crapped out on me in the past.......i need to start making my own!!

anyway i'm still stumped. can anyone duplicate the problem on their own setup?

[GregAE]

Can anyone duplicate the problem on their own setup?

Duplicated and confirmed. I observed a voltage dip as additional connections were made from the VX-351 Keyboard Pitch jack through the Mult to various other inputs. Using the Ring Modulator as a stand-alone oscillator, I noticed an obvious change the change in keyboard scaling when the Pitch CV was routed to more than one destination. A slight adjustment to the Attenuator control (boosting the voltage a tiny bit) was all that was needed to bring the RM oscillator back in tune, however. (Note: The RM's carrier oscillator needs about 0.74 V/oct)

Obviously, this information doesn't help if you need a 1V/oct CV, since the voltage dips below 1V/oct when loaded down with multiple routings. If you have a CP-251, however, you can make the Pitch CV adjustable to 1V/oct. Here's how:

1. Connect the Keyboard Pitch CV to the VX-351 Mult
2. Run TWO cables from that Mult into the Mixer 1 & 3 inputs on the CP-251.
3. Set the Mixer 1 control to zero (fully CCW)
4. Set the Mixer OFFSET control to the 12 o'clock position
5. Set the MASTER control fully CW.
6. Connect the Mixer output to the CP-251 Mult
7. Make all '1V/oct' connections from the CP-251 Mult.

Using a Voyager oscillator as a reference, tweak to the correct voltage by comparing the reference to one of the Dotcom oscillators as you play octaves. Slowly adjust the Mixer 1 knob as you make the comparision. You should only have to raise the Mixer 1 level a little bit to boost the voltage. You might also need to adjust the Offset control to match the pitches.

It takes a bit of tweaking to get it right, but it does work. Once you get the controls adjusted properly, you can use the Mixer's Offset control as a master frequency offset for any connected oscillators (handy!).

Good luck!

- Greg

[notinachos]

excellent!

thanks for the speedy reply. i do not have a cp-251, but now i know that the v/oct dipping output is a limitation of the voyager rather than a specific problem with my voyager.

and that is a huge relief.

well that's just some added incentive to purchase the cp251. there's no sense in delaying the inevitable anyway!

although i am kind of suprised that nobody seemed to notice before. (or mabye i just missed the post) i guess that speaks to the credit of the moog's already ample oscillators and mod routings.

thanks again