twin phono to mono XLR

[RichM]

Can anyone suggest what the cheapest way would be to take a stereo signal on twin phono sockets (output of a DJ mixer), sum it to mono, then send it as a balanced XLR output (long run to another part of the venue)?

 

There's the PXB from Interspace Industries, but it's over £100, and for this job cheap and cheerfull is the order of the day :blink:

[Sound Man]

Twin phono to jack lead and a DI box. :blink:

[SPTTRIAL]

Hi Rich, I have just the thing for you, I have a phonic micro 1 mixer that you can have, couple of unbalaced inputs to a mono balanced output, give me call and you can have it. I dont think you can get any cheaper than that!

[RichM]

Hi Rich, I have just the thing for you, I have a phonic micro 1 mixer that you can have, couple of unbalaced inputs to a mono balanced output, give me call and you can have it. I dont think you can get any cheaper than that!

 

Check PM's :blink:

[john-sp]

Twin phono to jack lead and a DI box. :blink:

 

Not quite that simple, you need to combine a stereo signal to a mono signal before sending it via a DI box. You can't just use a Y-lead. There is an excellent Rane note on the subject. http://www.rane.com/note109.html It makes useful reading.

 

John

[Shez]

Not quite that simple, you need to combine a stereo signal to a mono signal before sending it via a DI box. You can't just use a Y-lead.

 

Whilst I personally wouldn't recommend it, plenty of people do. The output stages generally have current limiting resistors which can also help sum them when connected together. Or you can just make up a Y lead with a couple of resistors.

[Bobbsy]

The Y lead through a DI generally works okay but be warned that occasionally on certain programme material you can get funny (or not so funny) phase issues in the summing. It's not often, but when it happens your tracks can sound very strange.

 

Bob

[john-sp]

Or you can just make up a Y lead with a couple of resistors.

 

Indeed I have one sitting in my tool box for such occasions. They are described in the Rane note I linked, are very easy to make up, and cost very little. They save any phasing problems Bobbsy mentioned. I've used similar leads on installations when combining a signal feed into mono for feeding delay speakers in venues where stereo is not appropriate.

 

Just because plenty of people do it and generally get away with it doesn't mean it's right every time, one day it could bite you in the bum! I know I can be anal about such things (pun intended), but I prefer to try and do things the correct way when I can, especially on installations. I hate having to go back to a job because it "doesn't sound right"!

 

John

[KevinE]

I think we've had this conversation before; but I sometimes have to repair the output stages of mixers that have been 'summed' by joining the outputs together...it can stressthe fusible supply resistors to the output opamps (where fitted) and they can fail; not to mention the chips themselves. Certain Soundcraft desks are an example.

 

Not using summing resistors can lead to the weird phasing or volume-cancelling effects especially on heavily 'reverbed' tracks or where there's intentional phase shifts on the track for spacial widening purposes or other engineering techniques; using resistors of the correct value wont, as it just mixes the two channels properly like a stereo/mono switch. This is because the output of one channel can upset the output of the other by messing with the op-amp negative feedback on opposite channels; I know it's an esoteric point but it happens.

[mackerr]

Not using summing resistors can lead to the weird phasing or volume-cancelling effects especially on heavily 'reverbed' tracks or where there's intentional phase shifts on the track for spacial widening purposes or other engineering techniques; using resistors of the correct value wont, as it just mixes the two channels properly like a stereo/mono switch. This is because the output of one channel can upset the output of the other by messing with the op-amp negative feedback on opposite channels; I know it's an esoteric point but it happens.

 

Using resistors doesn't change the the phase. Any phase artifacts from a stereo mix that is not mono compatible will happen whether you use a resistor summing network, a DI, or a mixing console. A long time ago it was important when mixing recordings to check for mono compatibility, since most broadcast was mono. Today it is rarely even thought of. If the stereo signal is not mono compatible it may be better to lower th´ level of one of the channels to alleviate some of the artifacts. Or keep everything stereo.

 

Mac

[mervaka]

I'd say checking for mono compatibility in recordings is still just as important. how often do you listen to youtube etc in stereo? mono media will always exist somewhere.

[mackerr]

I'd say checking for mono compatibility in recordings is still just as important.

Just as important, yes. As rigorously checked and corrected, not in my experience.

how often do you listen to youtube etc in stereo?

Every time I watch YouTube. Every time I listen to my iPod. AM radio is about the only mono source I listen to regularly except mono PA feeds, where the compatibility issue raises its ugly head.

mono media will always exist somewhere.

It will, but in my life it is mostly in mono PA feeds, although I make the main PA stereo if at all possible.

 

Mac

[KevinE]

The difference is that mixing the two channels will add to the signal, but joining them can result in cancellation, loss of vocal or a 'tinny' or 'echoey' effect which is much more objectionable.

[mackerr]

The difference is that mixing the two channels will add to the signal, but joining them can result in cancellation, loss of vocal or a 'tinny' or 'echoey' effect which is much more objectionable.

 

Loss of vocal, or echoey sound is due to either inverted polarity on one channel, which can be in the original recording, or induced at some point where the audio was dubbed, or to a lack of mono compatibility, which is in the original recording. Neither one will be fixed by changing the method of combining the channels.

 

Directly wiring the 2 channels together certainly presents way too low of a load impedance to each output, which may cause some frequency response errors, but it will not cancel vocals nor cause echo.

 

Mac

[Andrew C]

Ah, there may be some confusion creeping in between combining L&R on pin 2, and putting L on pin 2, and right on pin 3, with ground on pin 1.

 

Not the same!