Trouble using CV tools

Questions and discussion about building and using Max for Live devices
Post Reply
invisibledan
Posts: 17
Joined: Mon Feb 23, 2015 8:23 pm

Trouble using CV tools

Post by invisibledan » Fri Jun 26, 2020 5:43 am

Hello.
Recently upgrade to Live 10. Woo!
Can't seem to get the CV lfo to work.(or any other cv tool)

I'm trying to get it to output from my Motu 828 mk2 which according to this https://www.expert-sleepers.co.uk/siwac ... ility.html should output cv as it's DC coupled.
I've just tried sending the lfo to sweep the filter on my neutron. Something obvious that you'd hear working but no luck.

Anyone shed any light?

Many thanks

eta....I've got all the right outputs assigned etc. Everything is working ok with the interface with audio.
Just feel I'm missing one little box to tick or something.

Oh, and I do have floating ring cables.

invisibledan
Posts: 17
Joined: Mon Feb 23, 2015 8:23 pm

Re: Trouble using CV tools

Post by invisibledan » Sat Jun 27, 2020 3:27 pm

Ok, so got multimeter.

The 'action' as it were is correct; the voltage sweeps to follow the chosen waves shape with correct phase, offset and depth and when triggered the CV instrument I get a voltage all the time the key is held down. Great.

Not so great, the voltage is 100 times too small. I'm getting around +-50mV on an lfo sweep and +50mV for a note on/gate.

Well, I suppose I've proven ableton to be working, I guess it's down to my interface.

Tone Deft
Posts: 24155
Joined: Mon Oct 02, 2006 5:19 pm

Re: Trouble using CV tools

Post by Tone Deft » Sat Jun 27, 2020 10:01 pm

invisibledan wrote:
Sat Jun 27, 2020 3:27 pm
Ok, so got multimeter.

the voltage sweeps to follow the chosen waves shape with correct offset

Not so great, the voltage is 100 times too small. I'm getting around +-50mV on an lfo sweep and +50mV for a note on/gate.
I followed up that your interface is DC coupled, cool.

I believe it's outputting the correct signal, it's the OFFSET that's wrong. that +/- 50mV signal IS a 100mV (that will trigger @ +50mV perfectly), it's just moved down to be centered around 0 (ground) somehow.

you either have an AC offset applied somewhere or a DC offset of -50mV applied set somewhere.


I have no experience with this kind of gear, I'm an electrical engineer with a music habit.
In my life
Why do I smile
At people who I'd much rather kick in the eye?
-Moz

invisibledan
Posts: 17
Joined: Mon Feb 23, 2015 8:23 pm

Re: Trouble using CV tools

Post by invisibledan » Sun Jun 28, 2020 8:13 am

Tone Deft wrote:
Sat Jun 27, 2020 10:01 pm
invisibledan wrote:
Sat Jun 27, 2020 3:27 pm
Ok, so got multimeter.

the voltage sweeps to follow the chosen waves shape with correct offset

Not so great, the voltage is 100 times too small. I'm getting around +-50mV on an lfo sweep and +50mV for a note on/gate.
I followed up that your interface is DC coupled, cool.

I believe it's outputting the correct signal, it's the OFFSET that's wrong. that +/- 50mV signal IS a 100mV (that will trigger @ +50mV perfectly), it's just moved down to be centered around 0 (ground) somehow.

you either have an AC offset applied somewhere or a DC offset of -50mV applied set somewhere.


I have no experience with this kind of gear, I'm an electrical engineer with a music habit.
Many thanks for the reply.
As it turn out, it was (slightly justified) user error :oops: :oops:

When first testing I wanted to use the highest outputs to keep them out of the way of any audio outputs I might use. Sensible.
So in the drop down selector I chose the highest number channel and tried that.
No luck, so moved down one socket and one channel in the selector.
No luck, so moved down one socket and one channel in the selector.

After that I thought sod it, I'll try at the other end, so after remembering that despite being numbered output 1 on the MOTU, it's shown as output 3 on Ableton.
No luck, so moved up one socket and one channel in the selector.
No luck, so moved up one socket and one channel in the selector.

This is when I swore a lot then bought a multimeter.

When I started checking with meter I started at output 1 (3 ffs!) I got what I described, in that correct stuff was happening but on too small a scale.
So I methodically moved up a few channels and they were all the same.

Then for some reason I had a funny feeling that I may have been doing something wrong.
I counted up from 3 on the back panel up to the last output which made 10.
The highest number input on the Ableton drop down was 14!!

Feel stupid? Check.

Anyway, it turns out after all this that only the last two outputs give me the correct voltage and work great. I'll look into the other channels now I know what I 'm looking for.

tl;dr I'm a bit of a bumbling fool but got there in the end :D

chapelier fou
Posts: 5223
Joined: Mon May 15, 2006 12:15 pm

Re: Trouble using CV tools

Post by chapelier fou » Sun Jun 28, 2020 9:47 am

:D output counts can be very messy indeed...
MacBook Pro 13" Retina i7 2.8 GHz OS 10.13, L10.0.1, M4L.
iMac 27" Retina i5 3,2 GHz OS 10.11.3 L10.0.1 M4L.

Tone Deft
Posts: 24155
Joined: Mon Oct 02, 2006 5:19 pm

Re: Trouble using CV tools

Post by Tone Deft » Sun Jun 28, 2020 9:20 pm

invisibledan wrote:
Sun Jun 28, 2020 8:13 am
Tone Deft wrote:
Sat Jun 27, 2020 10:01 pm
you either have an AC offset applied somewhere or a DC offset of -50mV applied set somewhere.
This is when I swore a lot then bought a multimeter.
AC offset - I was wrong on this, it's AC coupled. :oops:

very cool that you found the problem, you're earning your stripes in the CV world. 8)

FIWI I found a handheld oscilloscope for $100, I've longed for something like this for DECADES!!
www.amazon.com/SainSmart-Portable-Handh ... B074QBQNB7

Image
In my life
Why do I smile
At people who I'd much rather kick in the eye?
-Moz

invisibledan
Posts: 17
Joined: Mon Feb 23, 2015 8:23 pm

Re: Trouble using CV tools

Post by invisibledan » Sun Jun 28, 2020 9:40 pm

Tone Deft wrote:
Sun Jun 28, 2020 9:20 pm
invisibledan wrote:
Sun Jun 28, 2020 8:13 am
Tone Deft wrote:
Sat Jun 27, 2020 10:01 pm
you either have an AC offset applied somewhere or a DC offset of -50mV applied set somewhere.
This is when I swore a lot then bought a multimeter.
AC offset - I was wrong on this, it's AC coupled. :oops:

very cool that you found the problem, you're earning your stripes in the CV world. 8)

FIWI I found a handheld oscilloscope for $100, I've longed for something like this for DECADES!!
www.amazon.com/SainSmart-Portable-Handh ... B074QBQNB7

Image
That’s a sexy little device there. Hmmm, rather tempted....

Post Reply