[OT] MOTU 828mkII Output Impedance

Nov 19, 2008 at 10:53pm

[OT] MOTU 828mkII Output Impedance

I am trying to do some spectral analysis of analogue ring modulation to compare it with my attempts to set up an analogue sounding ring modulator in Max.

One step in my experiment I was not ready to try was going to involve sending a pair of sine waves out of Max via a MOTU 828mkII into a Buchla 170 Dual Mic Preamp module and use the Buchla ring modulator on the resulting two signals. After some quick searching I was unable to find what the impedance of the balanced TRS output from the MOTU would be and since I need a new fuse for my ampere meter I can’t test it myself.

Does anyone know what the balanced output impedance on the MOTU 828mkII is? or is there anyone with a volt and ampere meter who could test it for me?

Thanks! more on the results of these experiments to come.

#40938
Nov 19, 2008 at 10:58pm

I’m sure it can’t be as hot as a modular signal. I would think it’s fine, I send audio signals out my motu828mk2 into my euro modular all the time. Unless Buchla has some odd way of dealing with audio, maybe they do, the 1.2volts/octave for CVs is certainly not the norm.

#145316
Nov 19, 2008 at 11:04pm

The thing is, there is a setting on the Buchla170 (preamp) to select the output impedance, so I’m sure one option is acceptable, but I am not sure which. I can’t just go experimenting since it is not my Buchla–especially since the preamp is one of the few modules I haven’t used before.

I should be able to get enough info to analyze from the other tests I as going to run, but if anyone has some specific info that would be great!

#145317
Nov 20, 2008 at 9:01am

motu.com should be able to supply the desired info.

jrp

#145318
Nov 20, 2008 at 9:37am

actually i checked motu.com for you now, there’s no info available on the output impedance of it’s line outs. there’s not even manual downloads, which is very weird. the only way to obtain a manual from them is to buy a printed one for 20 $.

you should check your own manual, if you have one, or try to to get it from whomever the owner of the 828 mkII is.
as i have a motu user id i send tech support a mail there, but honestly i don’t expect them to be of much help.

in case i get an answer i’d post it in here.

jrp

#145319
Nov 20, 2008 at 9:49am

Yeah, I already checked both the site and the manual and no luck.

Since I’m not in the studio anymore I’m going to give them a call when the office is open to find out. If they can’t help, I guess I’ll just need to find someone else with an ampere meter that is ready for action.

Thanks for looking though!

#145320
Nov 20, 2008 at 8:23pm

Incase anyone else was interested, here is what I found:

So after lots of calls and getting a busy signal, I found out the impedance is <100Ω. Not an exact figure, but close enough for what I need to know for now.

At some point when my test equipment is ready for action again I may try to calculate a more specific value later to satisfy my curiosity.

#145321
Nov 20, 2008 at 11:03pm

Quote: Roth wrote on Thu, 20 November 2008 13:23
—————————————————-
> Incase anyone else was interested, here is what I found:
>
> So after lots of calls and getting a busy signal, I found out the impedance is <100Ω. Not an exact figure, but close enough for what I need to know for now.
>
> At some point when my test equipment is ready for action again I may try to calculate a more specific value later to satisfy my curiosity.
—————————————————-

i have a motu 828 mkii and a voltmeter, but im not very handy with electronics.. i could do it for you, but you would literally have to tell me /exactly/ what you want me to do (e.g. what settings and what to plug in where)

#145322
Nov 21, 2008 at 5:37pm

got this reply from motu support, confirms what you’ve found:

“…

Line level outputs on all MOTU interfaces is under 100 ohms.

Dave Roberts – MOTU”

greets, jrp

#145323

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