CV scale problem - what will fix it?

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poladark
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CV scale problem - what will fix it?

Post by poladark » Thu Jun 17, 2010 11:31 am

I know that there are a couple of threads involving this subject already but i haven't seen any clear answers, so i'm creating a new thread and hoping that this question will be answered once and for all for everyone's benefit.

I have trouble with the CV input on my Moog LP Stage II. The CV doesn't track properly across octaves. In fact, it seems to detune around a quarternote per octave when controlled by equipment providing a standard 1v/octave control signal. This is not a problem when playing with MIDI or the keyboard, so clearly this is part of the LP design.

Will getting a Moog CP-251 module fix this? (Alternatively, is there some other product that fixes this, or can i recalibrate the instrument myself somehow?)

To be perfectly honest I feel misled by Moog not informing about this CV problem. Prospective buyers should be informed about things like this. One of the reasons i bought the LP was to be able to interface with my existing analogue cv equipment. When this doesn't work i feel like i've been cheated.

Also, i have a problem with the Gate input. It doesn't work, most of the time with my eurorack gear. According to the manual it will trigger on +5v or when an on/off switch is connected. Is there some way to disable the on/off switch part (since i'm suspecting that this could be causing a problem)?

theglyph
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Re: CV scale problem - what will fix it?

Post by theglyph » Thu Jun 17, 2010 2:30 pm

The LP Stage I & II's CV input can be made V/Oct with the addition of several trim pots and some tuning. The Voyager's CV input is not V/Oct as well but can be modded like the LP (Note: the VX-352 is set to V/Oct when used with the RME). Both the Voyager and the LP are V/Oct from the KB, and as such MIDI, so Moog isn't leaving anything from the customers. The CV inputs were designed for use with expression pedals hence the 5V on the ring of the TRS input.

As for the gate input, I've have various levels of success with my Euro modular triggering both the LP and the Voyager. I've traced most of the problems back to the Euro modules. There are a ton of standards and grounding issues within that system. For example there isn't a consistent Doepfer standard for Gate voltage levels. They can range from 4V to as much as 12V.

poladark
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Re: CV scale problem - what will fix it?

Post by poladark » Thu Jun 17, 2010 6:54 pm

Thanks for a quick answer theglyph!
theglyph wrote:The LP Stage I & II's CV input can be made V/Oct with the addition of several trim pots and some tuning.

Cool. Where are these trim pots located? Will input from the MIDI port and keyboard still be properly scaled if this is adjusted?
theglyph wrote:As for the gate input, I've have various levels of success with my Euro modular triggering both the LP and the Voyager. I've traced most of the problems back to the Euro modules. There are a ton of standards and grounding issues within that system. For example there isn't a consistent Doepfer standard for Gate voltage levels. They can range from 4V to as much as 12V.
I never had any problems with the gate signal before between individual eurorack modules or when connecting to my Novation Bass Station Rack. This is why i assumed that the LP was to blame.

What can be done to bring gate signals to a format that the LP can accept?

theglyph
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Re: CV scale problem - what will fix it?

Post by theglyph » Fri Jun 18, 2010 12:31 am

poladark wrote:Cool. Where are these trim pots located? Will input from the MIDI port and keyboard still be properly scaled if this is adjusted?
The trimmers are surface mount so they should be installed by Moog technicians whom can also properly tune it. I believe they'll do it for a reasonable fee. The MIDI and KB scaling will only benefit from this mod. You'll just need to rerun the software tuning routine.
poladark wrote:I never had any problems with the gate signal before between individual eurorack modules or when connecting to my Novation Bass Station Rack. This is why i assumed that the LP was to blame. What can be done to bring gate signals to a format that the LP can accept?
Which Eurorack modules are you using? Unfortunately there are different standards being used between the many Eurorack module manufacturers. Here's a funny one about Buchla if you're interested: http://buchlatech.blogspot.com/2008/10/ ... ny-to.html

poladark
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Re: CV scale problem - what will fix it?

Post by poladark » Fri Jun 18, 2010 3:34 am

Thanks again theglyph.
theglyph wrote:The trimmers are surface mount so they should be installed by Moog technicians whom can also properly tune it.
Do new trimmer pots need to be installed??
I won't solder on surface mount trim pots, but adjusting existing ones would be a different matter for me. Sending my LP to an authorized Moog tech will cost a bit and shipping is just as likely to break something.

Is there a recommended external solution for this?

I found the following schematic (in the written hand of mr Moog himself apparently) for fixing the scaling problem of the 0.95v/oct micromoog synthesizer:
http://machines.hyperreal.org/manufactu ... oogfix.jpg
theglyph wrote:Which Eurorack modules are you using? Unfortunately there are different standards being used between the many Eurorack module manufacturers. Here's a funny one about Buchla if you're interested: http://buchlatech.blogspot.com/2008/10/ ... ny-to.html
Currently i'm most interested in using the MFB SEQ-02 module (gate signal is +9v) and the Doepfer A-198 Trautonium Controller module (gate signal is +5v). As long as i can get the gate issue working, the Trautonium controller scale doesn't matter as much as it does for the MFB sequencer.

A bit of googling turned up this little article on the doepfer web site, for creating an s-trigger cable (specifically mentioned as useful for Moog synthesizers). I successfully used this previously for making a gate input for my Chimera Synthesis bC8:
http://www.doepfer.de/faq/gen_faq.htm#S-Trig

This doesn't explain why the voltage detection on the gate input (as described in the user manual) doesn't work right. For everyone's benefit i think some light needs to be shed on what the problem is here. :shock:

Mangos
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Re: CV scale problem - what will fix it?

Post by Mangos » Thu Jun 24, 2010 1:46 pm

all i know is that when using the FLame CLockwork. i can only trigger the gate on the LP with my CV out from each time bank.. The designated gate on the module does not retrigger the kb gate.

:(
french press

proturboplus
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Re: CV scale problem - what will fix it?

Post by proturboplus » Fri Sep 23, 2011 11:55 am

Hi there, I just found this thread by googling.
I want to go modular with my RME and want to confirm if connecting the VX-352 will fix the 1v/oct scale problem. So is the fix "built-in into the VX-352?

Thanks

OHES
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Joined: Mon May 14, 2012 12:55 pm

Re: CV scale problem - what will fix it?

Post by OHES » Sun Apr 27, 2014 6:49 pm

Up! :D
Does the vx352 is 1v/oct?

OHES
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Joined: Mon May 14, 2012 12:55 pm

Re: CV scale problem - what will fix it?

Post by OHES » Tue Jun 16, 2015 1:33 pm

UP :mrgreen:

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