Matching transformer for Mac headphones output

[daniel.sneed]

Klaus, Usb-pro is intended to work both with amp and mic inputs.
So with mic inputs, it delivers huge levels, but with amp inputs it's just right.

IMOE, I had to push somewhat my computer daw track outputs to feed the amps. No more -6dB on each amp channel...
Till now, it has been 100% ok, level wise, with my Nexo processors and Digam amps. I never had to insert a limiter to push the levels upwards.

[musicman691]

I can't resist to suggest this one:
http://www.radialeng.com/usbpro.php

It's computer powered and, IMHO, high class sounding.
I use one on several dramatic shows, to feed the PA amp and am glad with it.

BTW, the transformers are to be disengaged unless needed (hum or 48V), for they lower somewhat high frequencies.

I hadn't included that one because the op wanted to go from the headphone output of his computer and didn't mention looking for a dac.

[bayswater]

I had a different take on "what are you trying to accomplish". E.g., does the sound actually have to come out of the headphone jack, or is the purpose to just get audio out of the Mac properly. Can the signal be routed (by sound prefs or Soundflower) to come out of another port). E.g. my iMac has 1/8" audio ports that can be configured as 24/48 digital that can be connected to my interface via TOSLINK.

[Klaus]

Yes, just a Mac mini and audio cables ( and needed upwards transformer ) in between the DJ and the processor / amp...
Cheap and simple...
I had a test Mac mini running and it did the job ( just level wise not fully compatible , had to crank the processor up ). The Mini boots ( no video monitor ) with an AULab file and auto creates an ad hoc network with a script at boot, and I controlled it via VNC from the venue. The DJ could literally throw 'everything' to the Mini and it leveled out and a multi band compressor did the rest. AULab showed 6 % CPU used with 'some' latency though.
Thanks for contributing
and
best regards
Klaus

[daniel.sneed]

I'd like to warn you, Klaus: small size headphone jack is not a reliable connection.

I was in an audience one day, when such connection did ruin an entire show. Not one of my own projects, but I got the warning, though.

[Klaus]

Yeah, some 1/8" plugs don't work reliably - with Apple stuff, I've seen it too...
I usually make my own cables
Best

Klaus

[musicman691]

Yeah, some 1/8" plugs don't work reliably - with Apple stuff, I've seen it too...
I usually make my own cables
Best

Klaus

It's not the cable but the actual connector that's the issue. Way too small for a reliable connection. In your case it's better you go the Dac route Radial box mentioned earlier.

[mikehalloran]

Ok, you've answered one of my questions and told us what you are going into but not what you're coming out of. Is this your Mini 1.1 or something newer?

Yes, it makes a difference.

[Klaus]

Yes, Mini 1,1 and 2,1

Klaus

[EMRR]

I haven't found Mac->power amp interfacing to be a problem, but it reads like you have.

Consider a used Aphex 124A. Frequently can be had in the $25-50 range.

Transformer step up will probably still require a bridging load on the power amp side, and the 50 ohm rated output probably can not actually drive anything near a matched 50 ohm load without a large increase in distortion. Then add transformer artifacts. To do this right requires the best possible very expensive transformer set. I wouldn't consider them for this job.

[Klaus]

Thanks a lot Doug, glad you mention the distortion part ...
Best

Klaus