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Stereo Volume pot wiring issue

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Billschillin

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I am attempting to add a volume pot in line for some remote speakers. I have a 100K Dual-Ganged Stereo Volume Control Model: 271-1732 from Radio Shack. I understand that the center lug is the wiper and outpit should go there and that the other two lugs are for the input and a ground. However this pot has a fourth lug on each of the two gangs. I do not know for sure what this is for and I am baffled because no matter which way I attach the wires I only have sound when the shaft is fully rotated one direction. In the event that the pot may be bad, I have tried a second one with the same results. Can anyone provide a concise diagram for the correct way to wire this particular pot?

Thank you
 

kpatz

New Member
Are you using the pot on speaker-level signals? (You said you're using it in-line for remote speakers). You'll need a special volume control pot for this application (check out russound.com for the ones I've used). The pot you're using is for small-signal applications (e.g. in a pre-amp or amplifier's preamp stage, or for line-level rather than speaker-level signals).

The 4th lug is a 40% loudness contour tap. AFAIK it's used for low-volume bass boost circuits, so you can leave that pin unconnected.
 
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Billschillin

New Member
I am not highly technical in electronics so please bear with my ignorance. I have a 600 watt Pyle amp feeding a bank of Niles distribution boxes. They feed an assortment of speaker pairs around the property. I have two pair of speakers on the deck which I want to be able to control from the deck without going in to the master control. I would assume from your response that my choice of pots is incorrect. Based on the above additional information, is this still the case?
I was going to just add a dual Niles control but figured I could save some money by buying a couple of pots and mounting them in a handy box since it seemed pretty simple initially.

By the way, what is AFAIK ? ( I'll guess" And For All I Know" )

Also, if I wanted to use this 40% bass boost, how is that connected? or is it not an option on the recommended pot?

Please use laymans terms in your response, although I consider my self relatively smart, I am not familiar with the all jargon of electronics.

Thanks so much for any feed back you can provide.

Bill
 

audioguru

Well-Known Member
Most Helpful Member
The little pot has a very low power rating. It can be used at the input of an amplifier. If it is connected to a speaker then it will instantly burn out at certain levels.

Stereo stores sell speaker volume controls that are a tapped transformer and a stepped switch. They don't waste power by getting hot.
 

PatM

Member
I am attempting to add a volume pot in line for some remote speakers. I have a 100K Dual-Ganged Stereo Volume Control Model: 271-1732 from Radio Shack. I understand that the center lug is the wiper and outpit should go there and that the other two lugs are for the input and a ground. However this pot has a fourth lug on each of the two gangs. I do not know for sure what this is for and I am baffled because no matter which way I attach the wires I only have sound when the shaft is fully rotated one direction. In the event that the pot may be bad, I have tried a second one with the same results. Can anyone provide a concise diagram for the correct way to wire this particular pot?

Thank you
The control you list from Radio Shack is intended for use in a circuit and not for connection between the amplifier and a speaker.
What you should look for is a L-pad.
L-pads are used to control the output level of a speaker while maintaining the same impedance.
You should try to match your speakers to the output of the amplifier.
Just adding speakers in series or parallel to the output without determining the correct load, isn't the correct way to go.
The total load should match the output of the amplifier.
PatM
 
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Billschillin

New Member
The control you list from Radio Shack is intended for use in a circuit and not for connection between the amplifier and a speaker.
What you should look for is a L-pad.
L-pads are used to control the output level of a speaker while maintaining the same impedance.
You should try to match your speakers to the output of the amplifier.
Just adding speakers in series or parallel to the output without determining the correct load, isn't the correct way to go.
The total load should match the output of the amplifier.

PatM
The speakers and amp are matched ( actually the Niles units are impedence matching units) . I just want to be able to have a secondary volume control at the speakers on the deck. It sounds like the L-Pad may be just the ticket. Glad the Radio Shack pots were only 3-4 dollars ea. No great loss there.
 

audioguru

Well-Known Member
Most Helpful Member
An old L-pad gets hot and wastes power by making heat. A transformer volume control stays cool.
 

crutschow

Well-Known Member
Most Helpful Member
Yes, use a transformer volume control (or impedance matching volume control as they are also known) as audioguru suggested.

The pots you bought are 100k ohms, the speakers are likely 8 ohms, giving a large mismatch in impedances. You don't get much sound until the pots were near 8 ohms, which only occurs when the pots are near or at the limit of their rotation, as you observed.
 

Billschillin

New Member
Thanks for the advice everyone. I have ordered two volume controls that are ' Impedance Matching Stereo Dial Volume Control w/100 Watts RMS Per Channel and a frequency response 20-20 kHz +/- 1dB'. Considering my system is NOT audiofile quality this should be more than adequate.
 
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