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Volume pot values

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Volume pot values

Postby soundguy585 » Fri Jun 07, 2019 3:51 pm

Hello, I am looking to build a remote volume control for a stage monitor. It will be line level from the mixer. I know I need an audio taper-A type logarithmic pot. The question is what value pot it needs to be. Any help is appreciated. Thank You.
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Re: Volume pot values

Postby Hugh Robjohns » Fri Jun 07, 2019 4:27 pm

If you're talking about an unbalanced line level feed from a mixer to an active speaker or power amp, it's not that critical. Anything between 10k-50k would be fine.

However, if you're talking about a balanced line level feed things get a little more complicated. Same general value range applies, but you'll need a ganged pair and the way you wire it up gets slightly more complicated...

Here's a simple solution for you. Not the most elegant, but it will get the job done: http://www.audiotechnology.com/on-the-bench-diy-monitor-controller/

H
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Re: Volume pot values

Postby soundguy585 » Fri Jun 07, 2019 8:58 pm

Thank you Hugh, for your quick reply. The situation is, I have a 60-70 foot run from the soundbooth to a powered stage monitor. It's for a Church's installed sound system, where I plan on having a volume control on the podium so the soloist can adjust the background level themselves. It is coming from the mixer's monitor output which would be unbalanced. If I need to, I have a DI box to use if it would help with preserving the signal.So I need to find out the value of the pot that is needed. :headbang:
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Re: Volume pot values

Postby Hugh Robjohns » Fri Jun 07, 2019 9:12 pm

Hmmm. 70 foot of unbalanced cable isn't a great idea, either from the point of view of potential interference pickup, or potential ground-loop hums. It would be less problematic if you could run balanced between a balanced console output and balanced active monitor input.

But if you're absolutely sure the unbalanced thing is what you want to do, then use a 10k audio taper or log pot wired such that the resistor ends are connected to the unbalanced signal and ground/screen from the console, with the wiper and ground/screen feeding the active monitor.
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Re: Volume pot values

Postby soundguy585 » Fri Jun 07, 2019 9:58 pm

I know that it's not a great idea for such a long run. The cable has already been run for a unpowered monitor and I would like to use that cable. It's 14/2 jacketed. The output from the board is 1/4" ts. I thought I would try to use it and if any problems occur I'll come up with something else.
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Re: Volume pot values

Postby ef37a » Sat Jun 08, 2019 12:10 am

soundguy585 wrote:I know that it's not a great idea for such a long run. The cable has already been run for a unpowered monitor and I would like to use that cable. It's 14/2 jacketed. The output from the board is 1/4" ts. I thought I would try to use it and if any problems occur I'll come up with something else.

Are you saying that is an UNSCREENED speaker cable? If so you will almost certainly drown in hum and RF crap. Solutions in order of cost and complexity...

1) You must get the power driving the cable higher. I suggest a headphone amplifier and I hate to say it but the Behringer HA400 is pretty good at about 20 quid. Put Hugh's 10k pot at the far end if you can. If not put it pre the HA400 although you could use one of the pots on the amp if the signal does not overdrive it.
2) H/P amp driving a 1:1 line transformer, second traff remote end to unbalance and feed the pot.
3) use two, identical, passive DI boxes, again pot at remote end. Will need XLRs on the unbal cable. Don't HAVE to be identical but better if they are.

Even with any of these measures, RF interference is still a possibility and a screened cable the only likely solution.

Dave.
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Re: Volume pot values

Postby soundguy585 » Sat Jun 08, 2019 2:04 am

Thank you guys for your help. I will try the headphone amp route first. Hopefully It will not be amplifying too much noise . Last resort is to run a balanced cable (very difficult in our situation). Then go from there. If anyone has other ideas I will consider them as well.
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Re: Volume pot values

Postby ef37a » Sat Jun 08, 2019 6:00 am

soundguy585 wrote:Thank you guys for your help. I will try the headphone amp route first. Hopefully It will not be amplifying too much noise . Last resort is to run a balanced cable (very difficult in our situation). Then go from there. If anyone has other ideas I will consider them as well.

My HA400 is a very quiet device indeed so, provided you don't introduce any gain in the system it should not affect the noise level. What it CANNOT do is prevent noise pickup on the cable itself but the low output resistance of the amplifier, around 100 Ohms should help.

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