Moog why? (CV tracking)

[diddi_jo]

Does anyone know or understand why Voyagers (some, most, all?) do not track CV input at 1V per octave? They seem to track at slightly less, creating obvious problems. The factory mod is mostly useless for overseas peeps like myself.

Happy new year!

Sid

dadareykjavik.bandcamp.com
https://soundcloud.com/sigtryggurj-hannsson

[stiiiiiiive]

0,97V/Oct, if I remember correct.
The mod is feasible by any Moog tech I guess. Maybe even by yourself provided you get the right procedure and you have a little electronics background.

Hopefully someone will chime in and detail the procedure

[EMwhite]

The only answer to "why" that I have is a guess ...

My guess is that (I've said this before in other threads) Moog meant to have the CV input used for continuous voltage controllers such as Theremin, Pitch bend, Exp pedals, and yes, an analog sequencer (non-quantized) will work perfectly also.

I also think that the .97 is rumor or happenstance, or dumb luck... it's just the product of all of the tolerances within the components in that part of the circuit.. but again, I'm guessing. I've used a MP-201 quantized to a custom voltage and it's worked perfectly for me. The MP is an amazing device.

Fact is that R47 on the analog board is 100K and if you replace it with a 90K resistor and put a 25K trim pot in there, you can tune it to perfection.

Have a look at the first two photos on my Flickr... and read the captions. Don't pay too much attention to the colors of the resistors or caps, etc; this is from two diff Voyagers (both owned by me at diff times):

https://flic.kr/ps/2QTK3D

[MC]

The weird v/oct is a product of the DAC IC they selected which made the internal design easier.

[EMwhite]

But easily compensated by addition of a $0.52 trim pot? Would seem to be an oversight or maybe just a design consideration/opportunity missed.

I guess in 'those days', there wasn't much mind paid to 'other' CV gear. This was early 2000s and Analog was [still] dead post Andromeda.

Sort of makes one wonder what type of scheme was used in scanning the keyboard circuit and subsequently turning a depressed key into a precise voltage that WAS dead on.

Reminds me of the SSL 1200 OSC (in MU Modular); I had two of them, purchased at the same time and found that the 2nd CV input was NOT regulated so when I bent pitch with an analog controller, each of the OSCs bent differently; it was driving me up the wall. I asked the module designer WTF and was told "I could have done it so that it bent perfectly but that would have requited additional circuitry". wha?

In Moog's defense, I really don't think they were counting on a resurgence of analog controllers regardless of the fact that they lead it. Things have changed and we are all swimming in it.

[LivePsy]

My voyager is perfect. Outputs exactly 1V/Oct and is in great tune with other gear. I'd be cautious of suggesting many or most are not perfect without actual head counting.

B

[EMwhite]

My voyager is perfect. Outputs exactly 1V/Oct and is in great tune with other gear. I'd be cautious of suggesting many or most are not perfect without actual head counting.

B

"OUT" or in?

I could be wrong (ask my wife) but I think the subject of this thread is CV Pitch Input. My Voyager Old School (which incidentally has Pitch CV out withOUT the requirement of a VX-351) tracked perfectly OUT also but in was a nightmare.

My Select doesn't have a Pitch CV out onboard so yes, it's the CV-351 in action and luckily, they have a pot built in which can be tuned to be precisely 1V/oct. That's handy.

But for CV in? It's certainly possible that some are perfect but I think that many are not. Hence the mod which is discussed above.

Feel free to strike me down if I've got this incorrect, It's lack of attention to detail and my ADD more than anything internal or dismissive. Again, ask my wife... she rarely believes anything I say... I mean

[LivePsy]

My voyager is perfect. Outputs exactly 1V/Oct and is in great tune with other gear. I'd be cautious of suggesting many or most are not perfect without actual head counting.

B

"OUT" or in?

You're absolutely right. I'm handing in my Moog membership for not noticing that. Output from the VX-351 is exactly 1v each octave and the Voyager is perfectly in tune. But turn off local and feed the keyboard out to the pitch in is flat and only lasts a couple of octaves before it is out of tune.

The CP-251 four input mixer seems to correct for this, but then it fixes everything

B

[diddi_jo]

Thanks for that. I'll dive in with some assistance and get this under control.
Regards, sid