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[rudyrednose]

Hi,
I am about to purchase a Steinberg UR824, to drive directly my amps, currently driven from the pre-out of a receiver acting as pre-pro.
The balanced TRS line out of the UR824 will have to drive 8 unbalanced (RCA) amplifiers inputs.

As I do not want risking damage to the ur824 line outputs (by improperly shorting the cold terminal or Ring), what is the recommended circuit for the cable ?
My reference on cabling is this: http://www.rane.com/pdf/ranenotes/Sound_System_Interconnection.pdf

However, nowhere in the ur824 manual nor their forums I can see clearly a recommendation on how to drive unbalanced loads or what exactly is their output stage.

As there are several users here doing exactly what I want to achieve (using a UR824 as multichannel DAC straight to the amps) I thought a fellow here already has the answer.

Thank you

[mwillems]

I have a UR824, but it's been a while since I tried connecting the balanced outs to an unbalanced input (my current amps have balanced ins). When I did briefly run the Steinberg balanced to unbalanced, I used a conventional TRS to RCA adapter cable like you can purchase from any music supply store. When I took one apart, the ones I had seemed to be wired as shown in number 12 in the Rane paper. In any event, the UR824 operating manual suggests that the outputs are fine for unbalanced output (they're listed as "balanced/unbalanced outputs"), so you should hopefully have no problems on that front.

The bigger concern I would have would be the input sensitivity of your power amps; most power amps with unbalanced inputs are fully driven with 1 or 2 volts of input (i.e. "consumer" line level), but the Steinberg can put out 16 or 18 6 volts (i.e. "pro audio" line level) [edited: got my numbers jumbled, thanks mojave]. That kind of voltage could easily overload the inputs of some power amps leading to distortion or worse.  If your amp isn't expecting a "pro audio" line level signal (which, if it has unbalanced ins, it probably isn't), you have a couple options there, but the safest/best (in my view) is an inline passive line-level attenuator, which has the added advantage of lowering the idle noisefloor of the system.

[rudyrednose]

Thank you mwillems.  I have read with lots of interest several of your posts and mojave's.  You were instrumental in my interest toward a preamp-free world 
From those readings I am already aware about the advantages of in-line 10dB or 6dB attenuators.

It is the lack of precision of the manual that worries me.  And better be safe than sorry. 
Any additional input is welcome !

[mattkhan]

Thank you mwillems.  I have read with lots of interest several of your posts and mojave's.  You were instrumental in my interest toward a preamp-free world 
From those readings I am already aware about the advantages of in-line 10dB or 6dB attenuators.

It is the lack of precision of the manual that worries me.  And better be safe than sorry. 
Any additional input is welcome !

A digital multimeter is the way forward for putting your mind at ease on that score

[mwillems]

A digital multimeter is the way forward for putting your mind at ease on that score

+1

Direct measurements and/or making your own cables (or dissecting a sacrificial cable from a commercial batch) are really the only ways to be 100% sure. 

I personally had no problems with my brief foray into balanced to unbalanced connections using off the shelf cables, but measurements are the only way to true peace of mind.

[mojave]

The Steinberg UR824 puts out a maximum of 6.15 volts RMS (+18 dBu). You can use the Steinberg volume control to essentially limit the maximum output voltage and can also do it within the drivers or even within JRiver. What amps are you using?

I recommend 1/4" TS to RCA cables. I really like the MarkerTek TecNec cables and have used them without any problems with the UR824.

RudyRedNose - I sent you a PM.

[mwillems]

The Steinberg UR824 puts out a maximum of 6.15 volts RMS (+18 dBu).

Good catch, I just realized I got that snarled up (+18dBU, not +18 volts!).  6 volts is still more than enough to overload many inputs, so the bulk of my point still makes sense  .  Thanks mojave for keeping me honest!

You can use the Steinberg volume control to essentially limit the maximum output voltage and can also do it within the drivers or even within JRiver.

That is generally a good solution, but initially made me a little anxious as there was no way to set the Steinberg's volume in a way that couldn't be overridden from software (i.e. the hardware knob on the front can be overriden in the Steinberg software). That opened up the theoretical risk of full volume output in a PC failure state.  I'd experienced that outcome a few times years ago with other software and other sound devices, so I was a little worried about leaving it all up to software volume.

That said, I've never experienced a fault state that blew through JRiver's volume protection or the Steinberg's software volume settings (both have been rock solid even in blue screens or power faults), so the inline attenuators may just be "belt and suspenders."  That and they completely eliminate the soft hiss I used to get from the system when nothing was playing, which is a bonus.

[rudyrednose]

One very good advice I have seen here is that when the connection is direct between the DAC and the power amps, configure windows so the default output is anything but the DAC and specify the DAC as output device only in JR.

As my theater HTPC is dedicated to JR (and I have not played with JR loopback feature yet), I certainly intend to follow this great advice !