convert cv out from 1v/oct to hz/v

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stevesavage
 
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Joined: Thu Dec 02, 2010 12:55 pm

convert cv out from 1v/oct to hz/v

Post by stevesavage »

Hi,

Been looking at a way of controlling a korg CS-5 from the x0x via the cv outs, but as far as I'm aware, its the wrong type of cv coming out from the x0x to go into the korg.

Does anybody on here have any info regarding converting said cv into korgs not so standard cv input.

I've found a schematic to convert from the cv output from hz/v to v/oct,

(TOP RIGHT)
Image

but typically I need it the other way round :wink:

Any help would be great!

Thanks

Steve
Last edited by stevesavage on Fri Dec 03, 2010 9:21 am, edited 1 time in total.

xlarge
 
Posts: 151
Joined: Wed Jul 11, 2007 2:02 pm

Re: convert cv out from 1v/oct to hz/v

Post by xlarge »

The korg is hz/v and the moog/roland stuff is v/oct so you DO need v/oct to hz/v converter.

stevesavage
 
Posts: 8
Joined: Thu Dec 02, 2010 12:55 pm

Re: convert cv out from 1v/oct to hz/v

Post by stevesavage »

xlarge wrote:The korg is hz/v and the moog/roland stuff is v/oct so you DO need v/oct to hz/v converter.
Yeah my mistake, my posted image is converting from hz/v to v/oct, not the way I want it.

So if you have any ideas please help :wink:

xlarge
 
Posts: 151
Joined: Wed Jul 11, 2007 2:02 pm

Re: convert cv out from 1v/oct to hz/v

Post by xlarge »

The "Antilog amp" on your schematic?

stevesavage
 
Posts: 8
Joined: Thu Dec 02, 2010 12:55 pm

Re: convert cv out from 1v/oct to hz/v

Post by stevesavage »

xlarge wrote:The "Antilog amp" on your schematic?
No way, I didn't even seen that :oops:

What a f#*king fool I am!

Thank you

Steve

xlarge
 
Posts: 151
Joined: Wed Jul 11, 2007 2:02 pm

Re: convert cv out from 1v/oct to hz/v

Post by xlarge »

No problem, please come back when you've built it and let me know how it works. :)
I've got an ms-10 but haven't tried it yet.

Btw:
http://www.cykong.com/Synths/Korg%20MS- ... loured.gif

Brassteacher
 
Posts: 248
Joined: Fri Oct 08, 2010 4:49 am

Re: convert cv out from 1v/oct to hz/v

Post by Brassteacher »

Do the gate voltages match up? On your schematic, the trigger processor shows and output voltage from 0 to 15V. If the CS-5 has a 15V gate, you'll need another converter, but at least it will be easier to build. I'll need to do the same for just about any midi-CV converter that will drive my Roland SH-09. Atypical of most Roland stuff, the SH-09 has a 14V gate.

A couple suggestions if you build the anti-log amp:
1. If at all possible, do not substitute another opamp for the CA3140 (the output opamp). It's a "BiMOS" opamp, meaning it has MOSFET input transistors and bipolar output transistors. It also has offset null inputs, so if you need to sub, make sure the opamp is MOSFET in-bipolar out, with offset null inputs, which brings me to...
2. VR-2 in the schematic adjusts the DC offset in this circuit. I would use a decent multi-turn trimpot here if nowhere else in the circuit. The whole circuit is DC-coupled, and since you're going from 1V/Oct to Hz/V, any DC offset coming in will be greatly magnified coming out.
3. If you have trouble finding yet ANOTHER 2SC1583, you can use a 2SC2259, which may be easier to find. The NTE sub is NTE44, but again, it's a matter of finding one.
4. An LM4558 or NE4558 will be easy to find, but feel free to sub with your favorite dual opamp. 4558 tends to be noisy and slow (which makes them very popular for guitar distortion pedals, no kidding :mrgreen: )

I'd like to know how well it works myself. I'd breadboard one here, but since there are 69,975 other projects going on at the moment...

If you decide not to build one, a lot of modular synth makers build a similar item as a module. Once you see the prices though, you may be very glad you have a schematic and can build one yourself! :D

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