CV inputs

at0m · Post by **at0m** » Tue Sep 10, 2002 10:25 pm

Hi,

A Pc1600x has 2 analog inputs, a CV and one switcheable CV/footswitch. What can I connect to them?

I know the switch, it's a pedal that acts as on/off. Can I connect analog outputs from synths or Luna2496 to a CV input and use them to mudulate stuff? Or will it burn the outputs from the synth or Luna2496?
Before I try, I'd like to read some suggestions...

Cheers!

davo · Post by **davo** » Wed Sep 11, 2002 4:20 am

Boldly going where no man has gone

I dunno At0mic, Control voltage is a lot more than Audio signal. Correct me if I'm wrong but isn't CV around 5volt, I doubt an audio signal would do anything unless you crank the s#t out of it and that may open a whole set of other problems.

Davo

ernest@303.nu · Post by **ernest@303.nu** » Wed Sep 11, 2002 4:39 am

I have both the PC-1600 (2) and Doepfer Drehbank (8 CV-inputs) and currently I use those inputs to convert things like my analogue sequencer output, analogue synth LFO's etc to MIDI controller or note data.
In the past I've connected audio-sources to the inputs and there *did* appear some modulation of the MIDI-controller although the result wasn't exactly like an envelope follower (which would be cool!:) )

I think 2 things are to be considered:
- an audio signal is AC, thus passing the 0-V axis every now and then (negative voltage causes a sampling of value "zero")
- the sampling rate of the Peavey or Doepfer is very low compared to the frequency of the audio signal.

Don't know much about electronics (yet), but I thought about making a simple diode bridge rectifier to have the wave rectified (stay above 0V). But first I have to amplify the audio signal to a 5 V range (a cheap radio amplifier will do, I guess) to use the full sampling depth of the Peavey and get beyond the 0,6V minimal voltage for the diodes. (Right?? Any electronicians here?

)

And then maybe add a small RC filter to even out the frequency contents a bit for easier sampling by the Peavey.

I hope this will me an envelope follower, but I'm hardly sure.....

at0m · Post by **at0m** » Wed Sep 11, 2002 1:50 pm

Okay, thanks guys!

The rectified signal should be no problem, I think it can be done in Modular. And DC can be sent from the analog outs on CW cards. I'm sure rectification can be done w electronics too, but Modular makes it more simple. (for example using an ADSR)

Guess I'll need that pre-amp though, to get from .5 to 5V. Anyone knows how I can fix one? Or knows a page that explains how to make a mini analog amp? Sound quality is obviously not important, and it'll convert .5V DC to 5V DC.
But 5V, isn't that S/P-DIF operating range? Anyone been so experimental to output via S/P-DIF out? What resistance is to be on the CV? This may be interesting!

Btw, yesterday I experimented with this. It is getting more and more fun this Pc1600x! Probably this Doepfer-type sequencer can be emulated on other remote devices too!

More CV fun w Pc1600x may be a fun read too. Ernest, is this yours?

ernest@303.nu · Post by **ernest@303.nu** » Wed Sep 11, 2002 4:04 pm

I think it's possible to have the modular throw out some interesting waveforms for the Peavey to sample... but it depends on the D/A and amplification used whether the signal will be rectified in the end.
I've taken the low-fi shortcut and threw some brute-force audio into the PC1600 in the past (taken from the speaker-out connector on a 2 x 12W ghetto blaster, which is a nice sources for noises anyway) and tweaked the volume and EQ until I somehow got full CV-range modulation. No rectification or other electronic wizardry, but the results turned out to be almost random modulation (wich was interesting enough, of course

) And the good thing: the PC-1600 survived the torture!!! Also some of my analogue stuff throws out +/-10V and still no smoke from the Peavey... your mileage may vary of course

I don't think the s/pdif-out will be give much pleasure for this purpose... the specs state 0.5-1.0V for s/pdif (although some CD-ROM-drives and soundcards give a whoppy 5Vpp) and 3-10V for AES/EBU.... But more important: the frequency of this 2-state signal is over 2 Megaherz! Peavey nor Doepfer will be able to sample it

This document gives a pretty good description of s/pdif and AES/EBU standards.

And thanks for pointing me to the More CV fun w Pc1600x-link.... Potverdriedubbeltjes, that asshole stole my name!!!

Those dutchmen have no respect......

Neutron · Post by **Neutron** » Tue Sep 17, 2002 3:41 pm

If you are going to rectify the input signal you will need to boost it and then attenuate it aftewards, or else use a precision rectifier chip. if you just use diodes it will not be very good because they do not work below 0.6 volts.

ernest@303.nu · Post by **ernest@303.nu** » Thu Sep 19, 2002 2:24 pm

I know it won't sound hifi.... nevertheless it will sound, errr, interesting

I know a person who made such a crude diode-based amplified rectifier-device and it sounded like a frequency-doubler with a ringmodulator-kind-of vibe...