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  1. #1
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    putting a vol control inline in balanced mic cable

    has anyone put a passive volume control in line in a balance instrument/mic cable?... I'm trying it with a 1meg audio taper potentiometer... The question I have is do I need to use a dual stacked pot so as to "pot' both hot and cold signals or can I just use a single pot and do it to one wire/signal (hot or cold)?

  2. #2
    Senior Member SC358's Avatar
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    I have never done that, nor have I heard of anyone doing it. What is the actual signal are you trying to pot down because from the what I've understood so far is the the signal hasn't even been amplified yet?

    The only time I've wired a poteniometer is for speaker control when the amp was in another room/floor from the speaker.

    Beware also, potentiometers are really variable attenuators, they bring signals down, they don't amplify - just want to make sure, we're on the same page.
    SC358
    Relationships are based on compromises - behavior accepted is behavior repeated.

  3. #3
    Why, exactly, would you want a potentiometer in a balanced signal chain, let alone a passive one? (variable attenuator is right on the money, SC358). It's balanced for a reason, and it seems to me that if you are using balanced equipment you would have enough control over the gain structure to begin with, but I'm just fishing.

    However, if you must have more control, I would buy an active preamp of some sort that is also balanced and will maintain the signal's integrity.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  4. #4
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    I have a good reason for an attenuator on a balanced signal...

    What if you have a distributed audio system and would like to put a simple knob in a wall box that would provide control to those listening? A full on active preamp is not practical because 1. too big 2. power is not available. We're still dealing with long cable runs, hence the need to keep it balanced.

    I think a 10K stereo pot would work, affecting both hot and cold, and that's probably what I'll try unless someone has a better suggestion...

  5. #5
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    to control volume use a 10k pot conected to a VCA (voltage controled amplifier) at the mixer output. Check out Radio Design Labs (RDL) products for simple audio devices such as VCA

  6. #6
    By a distributed system, I wonder if you mean a 25 volt or 70 volt system, such as what MUZAK is, or other background commercial systems are, in which case those wall attenuators are available from many distributors. In this case, the wall attenuators are made for the system (25 or 70 volt), and are interchangeable. The number of speakers doesn't matter as long as you don't go over the ratings of the amplifiers. The speakers in this case will have transformer taps ranging from 1/2 watt to up to 5 watts. Add them up to find what you need for an amp, watt-wise. Add 20% to it, to be on the safe side. TOA.com makes such equipment.

    These controls are passive, but they have electronic components that match the 25v or 70v system that, without taking them apart and bench testing, you won't know what they are, and just a pot won't work.

    If this is not the case, can you give me the layout of the equipment you have, including model #'s, etc.?
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

  7. #7
    And you have to use a stacked pot, 500k, and make shure the bottom of each pot is grounded to the metal case along with the cable shields for a balanced attenuator.
    'I think my intimate relationship with electronics started as a child when I was playing with a screwdriver and a wall plug, Doc, and...'

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