Mono PA, but stereo playback feed and no open mic pres, what to do?

D

Daniel Postilnik

Junior
Jan 14, 2011
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San Francisco, CA
I mix at a small venue on an older Soundcraft Spirit FX8, and we will soon be upgrading to a Spirit M8. I just reconfigured the PA to run in mono (just using the left main output) in order to free up a return on the 8x4 snake for a second monitor mix on stage. With bands this is fine because all sources (mics) are mono by definition.

In between bands the venue plays music with a little internet radio box. Rca / headphone outputs routed to one of the stereo channels on the board. I need to sum this signal so we're not losing the right side of the audio signal. Whirlwind makes an ipod DI box, but I don't have a free mic pre for that. Basically I need to sum the signal but still have two cables, for a dual-mono signal. The spirit boards have a "mono sum" output but this is already being used to pipe audio to different zones.

Any tools out there that would help with this?
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

21RM85DFEML._SL500_AA300_.jpg


No need to reinvent the wheel.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Tim Weaver said:
21RM85DFEML._SL500_AA300_.jpg


No need to reinvent the wheel.
Click to expand...

It's not a good idea to do that, because the outputs will see their own impedance as the load, which might be too low for them to drive without distortion. Try it, if it sounds good, it is good, if it sounds like crap, you need to do it the right way (with a summing circuit, DI box, etc).
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

I was hoping the market had produced some kind of pre-fab summing box that can output to TRS. Instead it seems the invisble hand of the market is slapping me in the forehead.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Why would you need a TRS for a summing box? theres no reason to keep it balanced since it should be located at the board. Not to mention you don't want to use the stereo feature of the TRS. you should only need TS
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Silas Pradetto said:
It's not a good idea to do that, because the outputs will see their own impedance as the load, which might be too low for them to drive without distortion. Try it, if it sounds good, it is good, if it sounds like crap, you need to do it the right way (with a summing circuit, DI box, etc).
Click to expand...

I know that there are reasons not too, but I've yet to encounter an example where a simple wye cable made things unusable.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Chuck Simon said:
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/direct-boxes/pcdi
Click to expand...

Actually, that would work fine, as I don't believe it needs phantom power. He'd need an XLR to 1/4" adapter cable, and hopefully his 1/4" mixer inputs have some additional gain available since passive DI outputs are usually pretty low (or, are at least a lot lower than the input level). My preference is actually a Radial Pro AV1, which doesn't require phantom either.

Annoyingly, he could probably just buy this and be fine - it's less than half the price of either DI option.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Silas, you seem to have the right idea. Whirlwind makes a PodDI that sums to one xlr output, and then I would use an adapter. The 1/4" inputs have plenty of gain.

I don't see how the behringer would work - it doesn't have rca inputs.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Daniel Postilnik said:
I mix at a small venue on an older Soundcraft Spirit FX8, and we will soon be upgrading to a Spirit M8. I just reconfigured the PA to run in mono (just using the left main output) in order to free up a return on the 8x4 snake for a second monitor mix on stage. With bands this is fine because all sources (mics) are mono by definition.

In between bands the venue plays music with a little internet radio box. Rca / headphone outputs routed to one of the stereo channels on the board. I need to sum this signal so we're not losing the right side of the audio signal. Whirlwind makes an ipod DI box, but I don't have a free mic pre for that. Basically I need to sum the signal but still have two cables, for a dual-mono signal. The spirit boards have a "mono sum" output but this is already being used to pipe audio to different zones.

Any tools out there that would help with this?
Click to expand...

Check the pan routing for your board to be sure, but if typically if you pan a stereo input it will sum both channels to one. Just pan the stereo input to the channel that is still connected to your snake. That should negate the need for any external solution.

Edit:

Ugh, never mind. The FX8 doesn't do it that way. Nor do many mixers... I guess I was thinking about the aux buses.
 
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Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Tim Weaver said:
I know that there are reasons not too, but I've yet to encounter an example where a simple wye cable made things unusable.
Click to expand...

Blech. There are good solutions that do this right for not a lot of money... As usual there is an excellent Rane Note on the subject. http://www.rane.com/note109.html

http://www.radialeng.com/re-proav2.htm <- The Pro AV1 sums to mono, you can adapt to TRS out of it, and will drive a snake line no problem.
http://www.rapcohorizon.com/p-377-ltiblox.aspx <- Here is another way that should be cheap as hell.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Bennet saves the day. I ended up ordering the rolls unit earlier today that sums rca to mono xlr, but thanks a bunch for pointing out that ltiblox thing.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Silas Pradetto said:
Actually, that would work fine, as I don't believe it needs phantom power. He'd need an XLR to 1/4" adapter cable, and hopefully his 1/4" mixer inputs have some additional gain available since passive DI outputs are usually pretty low (or, are at least a lot lower than the input level). My preference is actually a Radial Pro AV1, which doesn't require phantom either.

Annoyingly, he could probably just buy this and be fine - it's less than half the price of either DI option.
Click to expand...

Yeah, I deleted my post because after posting I realized he did not have an XLR input available on his board, but if he is willing to use an XLR to 1/4" adaptor, the Whirlwind unit will work well.
 
Re: Mono PA, but stereo playback feed and no open mic pres, what to do?

Tim Weaver said:
I know that there are reasons not too, but I've yet to encounter an example where a simple wye cable made things unusable.
Click to expand...

I have had Sony DiscMan's distort badly with Y cables. Also, the 2nd generation iPod distorted horribly with a Y cable. (the one with the 4 buttons, if you remember that.)
 
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