MOTM

What happens when you run a CV (trigger, gate, modulation, etc.) through a
regular audio mixer such as a Mackie?

I am a little afraid to try it, so I thought asking first would be better.

Thanks!
Shemp

Audio mixers are designed to NOT pass any constant DC signal.  When you
initially applied the CV, you would hear a click and another when you
removed it.

You probably would not damage anything EXCEPT if you had some speakers
attached.  The 5-10 volts of the CV is many many times larger than the usual
low-level audio signal and the initial transient passed through the mixer
( your "click" ) could be of sufficient amplitude to blow the tweeter in
your speaker or damage the amplifier.

It would be otherwise OK to try - just keep the levels down really low.
Mixers usually cut off around 10-20 Hz so anything higher than this ( a fast
LFO ) should go through OK.



-> -----Original Message-----
-> From: Tentochi [mailto:tentochi@...]
-> Sent: Sunday, May 06, 2001 12:37 PM
-> To: MOTM Mailing List
-> Subject: [motm] Mixers and CV
->
->
-> What happens when you run a CV (trigger, gate, modulation,
-> etc.) through a
-> regular audio mixer such as a Mackie?
->
-> I am a little afraid to try it, so I thought asking first
-> would be better.
->
-> Thanks!
-> Shemp
->
->
->
->
-> Your use of Yahoo! Groups is subject to
-> http://docs.yahoo.com/info/terms/
->
->

Thanks for the info!
--Shemp

> -----Original Message-----
> From: David Halliday [mailto:dh@...]
> Sent: Sunday, May 06, 2001 3:49 PM
> 
> Audio mixers are designed to NOT pass any constant DC signal.  When you
> initially applied the CV, you would hear a click and another when you
> removed it.
> 
> You probably would not damage anything EXCEPT if you had some speakers
> attached.  The 5-10 volts of the CV is many many times larger 
> than the usual
> low-level audio signal and the initial transient passed through the mixer
> ( your "click" ) could be of sufficient amplitude to blow the tweeter in
> your speaker or damage the amplifier.
> 
> It would be otherwise OK to try - just keep the levels down really low.
> Mixers usually cut off around 10-20 Hz so anything higher than 
> this ( a fast
> LFO ) should go through OK.
> 
> -> What happens when you run a CV (trigger, gate, modulation,
> -> etc.) through a
> -> regular audio mixer such as a Mackie?
> ->
> -> I am a little afraid to try it, so I thought asking first
> -> would be better.

>Audio mixers are designed to NOT pass any constant DC signal.  When you
>initially applied the CV, you would hear a click and another when you
>removed it.

Right.  Audio mixers are "AC coupled" -- they have capacitors at their
inputs.

>You probably would not damage anything EXCEPT if you had some speakers
>attached.  The 5-10 volts of the CV is many many times larger than the
>>usual low-level audio signal

I'm not sure what you mean by low level. 10.96Vpk (or 21.92Vp-p) is only
20dBU.  The MIL of most Mackie line inputs is 24dBU, which is over 34V
peak-peak -- less than the MOTM PS.  Just do not use the mic inputs.

>It would be otherwise OK to try - just keep the levels down really low.
>Mixers usually cut off around 10-20 Hz so anything higher than this ( a
>>fast LFO ) should go through OK.

I've run the output of the 320 directly into my Mackie with no problems --
even a _slow_ pulse (about 9Vpp) wave merely clicks at each transition
point.  I've also come up with some interesting sounds using the UEG
(approximately 0-5V) as an oscillator with no problems.

The only danger is using signals that are beyond the audible range.  The
mixer can pass subsonics that can damage your woofers.  If you use
nearfields I strongly suggest fusing the bass drivers, even if you are not
using synthesizers.

-> >You probably would not damage anything EXCEPT if you had
-> some speakers
-> >attached.  The 5-10 volts of the CV is many many times
-> larger than the
-> >>usual low-level audio signal
->
-> I'm not sure what you mean by low level. 10.96Vpk (or
-> 21.92Vp-p) is only
-> 20dBU.  The MIL of most Mackie line inputs is 24dBU, which
-> is over 34V
-> peak-peak -- less than the MOTM PS.  Just do not use the mic inputs.

Right - the mixer can be adjusted to accept the 20dBU input with zero
problem.

My concern was that since the person was asking a question like this in the
first place, I didn't want them to plug the CV into a mic level input.  It
probably would not hurt the mixer but it would sure increase the possibility
of frying a speaker.


->
-> The only danger is using signals that are beyond the audible
-> range.  The
-> mixer can pass subsonics that can damage your woofers.  If you use
-> nearfields I strongly suggest fusing the bass drivers, even
-> if you are not
-> using synthesizers.
->

Excellent point too - I was concerned about the high-frequency content of
the transient causing problems with the tweeters but an LFO running into a
decent powered amp could cause heating problems with the woofer - our ears
aren't that sensitive at those frequencies so the temptation would be to
crank it up...

Thanks for the comments!

I normally use a Mackie 3204, so there is no way to "accidentally" plug
something into a mic level input.  For those of you not familiar with the
3204, it provides 2 mic pre-amps with XLR ins and 1/4" outs.  And then you
have to patch the outs into the mixer itself.  Actually a very cool setup
because the preamps do not have to go directly into the mixer at all.

This was actually just a thought.  I got into a debate with a friend a
couple of days ago.  Good info!

Anxiously waiting for my MOTM one-size-fits-all mixer.

Cheers!
Todd

> -> >You probably would not damage anything EXCEPT if you had
> -> some speakers
> -> >attached.  The 5-10 volts of the CV is many many times
> -> larger than the
> -> >>usual low-level audio signal
> ->
> -> I'm not sure what you mean by low level. 10.96Vpk (or
> -> 21.92Vp-p) is only
> -> 20dBU.  The MIL of most Mackie line inputs is 24dBU, which
> -> is over 34V
> -> peak-peak -- less than the MOTM PS.  Just do not use the mic inputs.
>
> Right - the mixer can be adjusted to accept the 20dBU input with zero
> problem.
>
> My concern was that since the person was asking a question like
> this in the
> first place, I didn't want them to plug the CV into a mic level input.  It
> probably would not hurt the mixer but it would sure increase the
> possibility
> of frying a speaker.
>
> -> The only danger is using signals that are beyond the audible
> -> range.  The
> -> mixer can pass subsonics that can damage your woofers.  If you use
> -> nearfields I strongly suggest fusing the bass drivers, even
> -> if you are not
> -> using synthesizers.

>
> Excellent point too - I was concerned about the high-frequency content of
> the transient causing problems with the tweeters but an LFO running into a
> decent powered amp could cause heating problems with the woofer - our ears
> aren't that sensitive at those frequencies so the temptation would be to
> crank it up...