Turntable mute footswitch

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chingon

Well-known member
Joined
Mar 21, 2007
Messages
49
Location
california
I have a DJ buddy of mine who asked me if there was a way to make a footswitch that would be placed in the signal path between the turntable and mixer that would allow him to mute the signal from either turntable that would allow him to to free up his hands a little more while he's mixing and playing along to the beat while playing keys. This would allow him to drop the beat, but instead of doing it on the DJ mixer he could do it via Footswitch.
I told him that there has to be a way, problem is I wouldn't know were to start.
Anybody have any ideas?
 
Hi,
I would implemet it in the mixer itselve. The signal coming from the turntable is very small and your friends turntable is maybe not able to drive long cables. You could break the conection going to the Phono/Line switch. Or if you want it clickless you could, depending on the mixer, find a solution somewere around the X-fader. Sometimes they control opto elements.
What mixer does your friend have?
 
I agree that the best place for the mod is in the mixer, but if you don't want to get into taking the mixer apart, you could put a relay between the turntable and mixer. That way you can keep the signal connection short, and still run a decent length cable to the footswitch (which controls the relay). There's a decent amount of gain on a phono preamp, so you may get some clicks or pops. Also, you'll want the relay to switch the preamp input to ground through a resistor when you are switching the channel off, instead of just leaving it floating to avoid noise pickup. The shorter the cable is, the less of a problem this will be. I'm not sure what resistor value is best, because I'm not too familiar with phono preamp impedances.
 
Standard phono preamp input termination is 47K so switching in a resistance shouldn't be necesary.

Source impedance of phone cart is probably on the order of 1.5-2k with some inductance, if you feel compelled to simulate source.

JR
 
I recommended the resistor based on speaker switching boxes I've built (between console outputs and speaker amplifier inputs). I've noticed that if I left a long cable input to an amp floating, it was much more susceptible to hum/buzz than if I grounded the signal conductor(s) at the switcher. Adding some resistance seemed to make it less likely to pop when switched. It seemed to make intuitive sense, but now that I think about it, I'm not sure I understand why it helps. A lower impedance path to ground for any crap that makes its way past the cable shield? (BTW, the ground reference would be from the amp (the cable shield), and kept seperate from the shields from the other amps and console outputs).
 
how about a little voltage divider; like signal>2 resistors in series>signal out

with a optocoupler (led-ldr, vactrol etc.) shunting to ground at the node 'tween the 2 Rs

then you are only switching the led with a footswitch and battery/voltage, so signal wiring can be minimal...and the optical switching would minimize click/pop that may result from switching contacts

I would think this best after the phono preamp as it would not present a constant termination to the cartridge
 
It would be good to know, what Mixer it is, as many pro-DJ-mixers allready use an Opto for the crossfader. This would make things very very easy.
 

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