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  #1  
Old 12-11-2002, 09:51 AM
apetrocelli apetrocelli is offline
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Default Monitor Output, is there a risk of a short?

Hello, guys. In page 34 of "Getting Started with Digi 001", it says that to connect the Digi to a home stereo you should use the monitor output.
This output is balanced, while most home stereos are unbalanced. It also says to use a 1/4" cable, and to use a special adaptor for to convert to the common RCA inputs on the stereo.

The instructions doesn't say if you should use a TRS connector or a TS connector, it just says a 1/4" cable. I am currently using an RCA cable with two 1/4" TS (mono) adapters on the output of the Digi. Is this dangerous, could it cause a short in the output? What's the proper way of connecting them? even using individual cables for left and right, there's still the doubt between TRS and TS.

Can you help me? Thanks in advance, Andrés
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Old 12-13-2002, 03:41 AM
mr means mr means is offline
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Default Re: Monitor Output, is there a risk of a short?

You should be fine.
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Old 12-13-2002, 03:01 PM
DONNY WRIGHT DONNY WRIGHT is offline
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Default Re: Monitor Output, is there a risk of a short?

See if this de-mystifies TRS and TS:

TRS=balanced. It stands for Tip Ring Sleeve (the parts of the physical 1/4 inch connector.
The signal has three parts: hot, out of phase (sometimes called cold), and ground. Important to be balanced when running long cables.

TS= un-balanced. It stands for Tip Ring
The signal has two parts: hot, and ground.
Not good to run much over 50 feet (gets noisy).

When going FROM balanced TO UN-balanced use Un-balanced cable.
It is ok to run an Un-balanced signal into a Balanced input, no harm done.
The rule is to UNBALANCE at the source.

Happy cabling.
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Old 12-13-2002, 08:44 PM
Doc Doc is offline
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Default Re: Monitor Output, is there a risk of a short?

apetrocelli,

I understand where you are coming from. If you plug a TS connector into a balanced TRS output socket, you are effectively shorting to ground the out of phase signal with the sleeve of the plug.
However, there is usually (but not always) short circuit current limiting included in the output stages to protect against damage when doing this.
Just to be sure, I usually use a TRS connector with the ring connection left open (or grounded via a 1K Ohm resistor) and the unbalanced signal connected to the tip and sleeve.
In a pinch, you can use a TS connector pushed half way in so it connects to the ring and sleeve of the socket. Keep in mind that doing this results in an out of phase signal.
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Old 12-13-2002, 08:55 PM
where02190 where02190 is offline
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Default Re: Monitor Output, is there a risk of a short?

Quote:
Originally posted by DONNY WRIGHT:

Not good to run much over 50 feet (gets noisy).
<font size="2" face="Verdana, Arial">The max recommended length is 20 feet.

there is no danger, however if you are connecting the monitor outs to a home stero, you have a sensitivity mismatch, as the monitor outs are +4 pro level ant eh home stereo is -10 consumer level. Best ot use outs 3-8 which are both unbalanced and -10.

Hope this is helpful.
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Old 12-16-2002, 12:03 AM
Doc Doc is offline
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Default Re: Monitor Output, is there a risk of a short?

Quote:
Originally posted by where02190:
...the monitor outs are +4 pro level ant eh home stereo is -10 consumer level. Best ot use outs 3-8 which are both unbalanced and -10.

Hope this is helpful.
<font size="2" face="Verdana, Arial">Good point [img]images/icons/smile.gif[/img]
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Old 12-16-2002, 05:34 AM
apetrocelli apetrocelli is offline
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Default Re: Monitor Output, is there a risk of a short?

thanks to all for the answers. Doc: I wish there was some place where it says that the Digi has no problems with this kind of shorting.

I have one more question: does anybody know what kind of balancing scheme does the Digi use?
Suppose you're using unbalanced cable, then you're summing R+S, that is out of phase + ground. So do you have a varying ground signal? Also, Brent said that if you measure the ouput with a voltmeter you'll read 1/2 the voltage? Is this so, and why? Doesn't the system compensate for it?

Cheers, Andrés
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Old 12-16-2002, 06:12 AM
Doug Ring Doug Ring is offline
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Default Re: Monitor Output, is there a risk of a short?

You don't need to worry about shorts in this situation. They're only a problem with high-current situations. The currents involved here are milliamps or less, so there'll be no sparks and nothing will get hot! Shorting will simply convert the output to unbalanced and because you're now only using one half of the signal, you only get half the power. Cannae change the laws of physics, Captain!

If you use outs 3&4 you won't have control over the volume with the pot on the 001, which clinches it for me. I use the monitor outs into an unbalanced Quad 405 power amp (which has no volume control) with no problems whatsoever.
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Old 12-16-2002, 06:25 AM
apetrocelli apetrocelli is offline
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Default Re: Monitor Output, is there a risk of a short?

hey Doug. I understand what you're saying, but also keep in mind that maybe there's some highly sensitive component that can be damaged, I guess it's all a problem of scale and no absolute currents. I was reading some papers at the Rane site, where they say that the short practice is plain wrong. Also in Brent's post it says that too, and he recommends an adapter that terminates the line correctly for doing measures.
And in the FMR Audio site - makers of the Real Nice Compressor and Pre - they say that if you're using a transformer balanced connection, the transformer will compensate the loss of voltage. It also says that the Electronically Balanced (E-BAL) connection won't compensate, and the Electronic-Servo Balanced (S-BAL) will do.

So you see why I am after some official answer, cause I am getting different answers on the same subject.

Cheers, Andrés
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Old 12-16-2002, 05:16 PM
Doc Doc is offline
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Default Re: Monitor Output, is there a risk of a short?

From a tech point of view, I agree with Rane and Brent. Even though there is probably a current limiting resistor in series with the outputs, I personally don't like having the op amps (output stages) driven that hard (ie, shorting the ring and sleeve).
Quote:
...I guess it's all a problem of scale and no absolute currents
<font size="2" face="Verdana, Arial">That is correct. A component can easily be damaged with any current (or voltage) that exceeds its ratings.
It is simple enough to use TRS connectors as I mentioned above for peace of mind.
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