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Old 5th September 2011, 01:28 PM   #1
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Default Amplifier volume knob noise

I have an acoustic research A-06 amplifier, when I change the volume there is quite a bit of noise on the left channel as I move the knob, it's motorised however I do not use the motor as I lack the optional remote control.

This noise also seems to throw my 12" woofer cones in and out in a way that is slightly concerning, though once it's left the amplifier functions perfectly, the noise is only produced by the act of altering the volume.

I was pondering just taking it apart as best I can and cleaning everything I could, is there anything else you could suggest that could remedy this issue?
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Old 5th September 2011, 01:40 PM   #2
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Clean the volume pot. This is a common problem. Thay make sprays for this.
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Old 5th September 2011, 03:25 PM   #3
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Thanks, I think I have a can of servisol switch cleaner kicking about the place, should this suffice?
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Old 5th September 2011, 03:41 PM   #4
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This can also happen if there is dc flow through the pot. Like if it's a dc coupled amp , a slight dc offset in the source can cause a very noisy pot till things settle down. Sometimes it might not settle down. For this problem you need to use a decoupling cap which is another major issue. What value and what type/brand and how many dollars !
It could also be dc from the stage following it ! Try to look at the circuit diagram and see how the stage is designed.
Then of course it could be just particles from the track or dust which needs to be blown off by air or a non condensing spray.
Obviously the first try will be the last one.

I've had this problem with some pots which became OK after a spray clean. But after some time it appeared again and had to be cleaned again. Guess it was just particles coming off the tracks or just dust settling in. ( Alps blue pot !).
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Old 5th September 2011, 03:46 PM   #5
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Quote:
Thanks, I think I have a can of servisol switch cleaner kicking about the place, should this suffice?
As long as its safe for plastics.
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Old 5th September 2011, 09:18 PM   #6
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Quote:
Originally Posted by 4pyros View Post
Clean the volume pot. This is a common problem. Thay make sprays for this.
In most cases this is a sufficient step.
Quote:
Originally Posted by ashok View Post
This can also happen if there is dc flow through the pot. Like if it's a dc coupled amp , a slight dc offset in the source can cause a very noisy pot till things settle down. Sometimes it might not settle down. For this problem you need to use a decoupling cap which is another major issue. What value and what type/brand and how many dollars !
It could also be dc from the stage following it ! Try to look at the circuit diagram and see how the stage is designed.
Then of course it could be just particles from the track or dust which needs to be blown off by air or a non condensing spray.
Obviously the first try will be the last one.
I've had this problem with some pots which became OK after a spray clean. But after some time it appeared again and had to be cleaned again. Guess it was just particles coming off the tracks or just dust settling in. ( Alps blue pot !).
Exactly. In cases with dc coupling or by electrolytic caps with internal residual transition resistance cleaning of the attenuator is not enough. In case of used electrolytics in front of the pot and behind of the pot replace this parts through foil caps. By dc coupling pots cut the wires and introduce foil caps (consequently dc coupling in amplifier set-ups from the source to the loudspeakers I hate in general).
Then the shoot-noise during rotation goes away.
An example for this effect is the integrated Linn amp "INTEK" (probably even the "PRETEK")

Last edited by tiefbassuebertr; 5th September 2011 at 09:26 PM.
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Old 6th September 2011, 02:53 AM   #7
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I had noise from my volume pot. After desoldering it from the PCB to get to the part number (ALPS blue velvet thingy) then resoldering - all noise was gone. Dunno what it was ; maybe a dodgy joint; but worth a go!!

J
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Old 6th September 2011, 04:49 PM   #8
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Cleaning with spray hasn't worked, I guess I'll have to take it apart further or buy a replacement :/
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Old 6th September 2011, 07:35 PM   #9
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^^ Sometimes there's grease in it that'll harden and heat melts it away (or cleaner dissolves it), though especially on any mechanical part with repeated stress from use, cracked solder joints are possible.
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Old 6th September 2011, 08:12 PM   #10
Xoc1 is offline Xoc1  United Kingdom
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Download a service manual from
ElektroTanya | Service manuals and repair tips for electronics experts
C501 and 502 after the volume pot are probably worth replacing with new parts.
Hope I found the right schematic!
Regards
Martin
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