[LAU] XLR mixer -> TRS audio card connections

Ricardus Vincente wizardofgosz at gmail.com
Sat Aug 15 16:11:13 EDT 2009

On Sat, 2009-08-15 at 14:04 -0500, Brent Busby wrote:

 It's fine.  All pro audio balanced connections are low impedance outs
to high impedance ins.  This is done so that you can mult outputs (make
copies) and the inputs won't mind a lower dB input signal.


> Is it wrong to use a regular cable (no transformer) to connect the XLR 
> main and submix group outputs of a console to the TRS (balanced) inputs 
> of an audio card, or should impedance matching be done in that case? 
> It is quite common in music stores these days to find cables that are 
> XLR male on one end and TRS male on the other.  (I'm currently using 
> those on my mixer outputs.)  The cables *are* balanced, but they do not 
> contain a transformer at all.
> The impedance of my console's main/submix outputs is rated as less than 
> 75 ohms, but the input impedance of my audio card is 10k ohm.  This 
> would seem to almost answer the question by itself, it weren't for the 
> near impossibility of actually finding a matching transformer that's TRS 
> and not TS on its 1/4" end.  I looked at a lot of them.  They're all 
> made for hooking up guitars, amps, and mics, and they all seem to have 
> an unbalanced plug opposite from the XLR end.
> If there is indeed a need transformers on each XLR mixer output in this 
> instance, where can I get one that won't unbalance the connection in the 
> process?  Or is it fine to just use these common XLR->TRS cables that 
> don't have any?  The reason I started to investigate this is because I'm 
> not sure I'm not getting some of the "tone suck" you might associate 
> with a badly matched connection, and this seems a likely cause.
> Addendum:  On the realtime end of things, I'm now achievable a solid, 
> unbreakable 2ms.  I can't seem to do anything that causes an xrun. 
> That's good at least!

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