John Sayers' Recording Studio Design Forum Archive

Hi Folks,
I am converting small bedroom into studio and just ran electric behind baseboard to iso booth and want to know before I close it up permanently if I can run the following allong with it (touching, but insulated of course)

2 XLR Cables
2 1/4" Guitar cables
2 1/4" Headphone cables

That would be 6 cables along with the electrical Romex (14/2)

Also, do I need special wire, or can I simply cut the ends of of some existing Mic, and guitar cables and then solder them to there apropriate jacks in there wall plate.

I guess I am wondering if this will lead to terrible hum or buzz because they are so close and parellel?

Anyway, Thanks for your time and I appreciate any advice you could give.

Thanks,
Al

Al, that would definitely give you major hum problems - you don't want ANY audio lines within about a foot of AC power lines, more is better - if power and audio wires must cross, they need to do so as close to a right angle as you can get. It's also better if you can keep high level audio (like headphone or line level) at least a couple inches away from low level audio (like mic cables) - it's possible to get crosstalk otherwise, especially if you're in a recording situation and want things as quiet as you can get them.

In an industrial plant I once traced a wire that was hanging loose at one end of a bundle of wires - with a meter, the wire measured 60 volts AC - I traced the wire through about 15 feet of bundled wires, and found that the OTHER end wasn't connected to anything EITHER - point being, with only a high impedance load on a wire that's running next to other AC wires, you can get several TIMES as much hum as your line level audio puts out.

As to your other question, you can just cut the ends and resolder to jack plates as you said - no problem... Steve

Thanks Steve,
I guess it's back to the drawing board for me.

Thanks again for replying.

Al

Steve,
This brings up another question on how studios do there wiring, I mean they obviously don't spread them out to make sure there are inches between each line? (24)(36) etc.
And what about audio snakes? I would think these would be a disaster by design.

Thanks,
Al

I mean they obviously don't spread them out to make sure there are inches between each line?

That is exactly what they do between power and signal lines.

Live audio gets dicier. that is why ofen live audio ssystems will use audio transformners due to their high immunity to common mode interference.

Andre

Al, Andre's right - however, between same-level signals there is less need for isolation. Reason being, they are all at the same nominal level, and each twisted pair is shielded separately to minimise cross-talk.

When two signals are the same strength, they both will be amplified about the same amount overall; this means that one stronger one (like line level vs. mic level, which can be around 60 dB different) can interfere with a weaker signal from a mic, which WILL be amplified 60 dB more to bring it to line level.

If you amplify a mic signal by 60 dB, and it's been contaminated by a much stronger signal from a line feed, you'll also amplify the CROSSTALK by 60 dB, making it a fair chance that the crosstalk might be stronger than the original signal. Obviously this wouldn't be a good thing.

Now, if a line level audio signal can induce crosstalk into a mic level signal wnen the level difference is about 1 volt, imagine putting a wire carrying 120 volts next to your mic level wires... Steve

Sorry for the delay in posting. Been busy w/ work lately.

Looks like Andre and Steve have covered this pretty well. You don't want to run power & low voltage (mic) cables parrallel to each other unless you have some distance between them.

I mean they obviously don't spread them out to make sure there are inches between each line? (24)(36) etc.

Al, in wiring a studio, you do need to spread them out and take the time to separate audio from electrical. Attached is a picture of the floating floor that I built earlier this year. As you can see, the PVC pipes are for low voltage (mic lines, etc) and the metal conduits are for electrical.