Amplifier volume knob noise

Status
Not open for further replies.
Jump to Latest
S

SatinMill

Member
Joined 2010
#1
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?
 
#4
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 !).
 
#6
4pyros said:
Clean the volume pot. This is a common problem. Thay make sprays for this.
Click to expand...
In most cases this is a sufficient step.
ashok said:
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 !).
Click to expand...

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:
#9
^^ 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.
 
#10

Attachments

  • AR A06.jpg
    AR A06.jpg
    860.4 KB · Views: 362
#11
#12
Remove pot and C A R E F U L L Y unbend tabs holding it together. Buy only Deoxid/Cramolin Red contact cleaner. Gently swab both resistive elements and contact fingers with quetip wetted with Deoxid/Cramolin. Reassemble and C A R E F U L L Y rebend tabs in place. Reinstall. Noise gone.

(Cramolin -now Deoxid- is the only substance I ever found that will successfully clean up an analog oscilloscope position pot. I was reffered to it in the 80's by John Fluke Company while looking for a replacement for the old Rycon they used to use in their voltage calibrator controls. Amazing stuff! Used to be manufactured by Caig industries, but Caig and Deoxid merged. What used to be called Deoxid went away and Cramolin got rebranded to Deoxid.)
Doc
 
#13
After a third attempt at cleaning with spray and a look at the tracks they don't look dirty, I'm starting to suspect this is something else as the right channel is perfect yet the left is so very wrong, the solder joints looked ok and taking the pot completely apart looked like it'd be quite a bother.

This problem also seemed to happen suddenly, there was no gradual creep in just suddenly it started doing it. As I mentioned earlier the noise makes the bass cones throw themselves out in a frankly scary way that I never see when listening to music within sane volume ranges, it makes me think that somehow higher voltage is getting in there somehow, definitely something way out of the range of line level audio.
 
#14
Put back the pot or put an equivalent resistor in place ( with slider and top of pot connected together ) and see if there is a dc voltage on it when the amp is powered up and if so does it drop with time.
Compare both channels. If there is nothing, then probably the pot is just bad !

Try using external wires to wire the pot terminals to the pcb so that left and right channel sections are reversed. If the problem goes to the other channel the pot is surely gone. If not ,look elsewhere ......like above ....
 
#15
Spray cleaners applied from the outside aren't always very effective. That's why I recomended taking the pot out and apart to clean it. Dust and even carbon from the pot element itself get stuck between the wipers and the elements creating variable resistance noise. Pots are usually held together three different ways; small bent metal tabs, sledged rivets and (the best) tiny screws. (A fourth method is epoxy encapsulation, but if that is so you are SOL). Most used in audio applications are bent tab types. The tabs can be unbent if done very slowly and gently to avoid even more metal fatigue (some of which exists from the initial crimp).
I've successfully taken apart, cleaned-lubed and reassembled literally hundreds at this point. The system I recomended works... nothing else ever did. Like I said it has worked with noisy oscilloscope position pots, which give instant visual feedback as to the success of cleaning the pots.
Doc
 
#16
I've unbent and cleaned quite a few myself, but I always thought, why am I doing this, can't they just stop trying to save pennies and make equipment that LASTS. Unfortunately, consumers are so greedy it blinds them of subtle differences they don't understand. Literally, $10 could make a huge difference in long term viability of products, but all the consumer sees is "it costs more and I see no reason why".
 
#17
Per my spec, all Racal Dana IEC 845 fully progamable .01Hz-15Mhz function generators now have pricey Spectrol calibration pots as standard issue. Why? To save on multiple service calls to Germany.

As to why I would repair a cheap style bent tab pot on commercial test equipment; because it was much quicker than putting a unit HFP (hold for parts) and got the equipment back to the person that needed it to ship product.

Doc
 
#18
it uses small bent metal tabs, I sprayed directly onto them and have inspected the tracks and can't really see anything. I've taken it apart a few times now and am trying everything that I can that's not potentially destructive first, if it comes to it I'll take the thing apart as best I can.
 
#20
thaumaturge said:
Spray cleaners applied from the outside aren't always very effective. That's why I recomended taking the pot out and apart to clean it. Dust and even carbon from the pot element itself get stuck between the wipers and the elements creating variable resistance noise. Pots are usually held together three different ways; small bent metal tabs, sledged rivets and (the best) tiny screws. (A fourth method is epoxy encapsulation, but if that is so you are SOL). Most used in audio applications are bent tab types. The tabs can be unbent if done very slowly and gently to avoid even more metal fatigue (some of which exists from the initial crimp).
I've successfully taken apart, cleaned-lubed and reassembled literally hundreds at this point. The system I recomended works... nothing else ever did. Like I said it has worked with noisy oscilloscope position pots, which give instant visual feedback as to the success of cleaning the pots.
Doc
Click to expand...
I am looking arround to manufacturers from variable resistors (pots), that I can completly disa'ssy into its all individual parts (as usually only possible by rotary switches like ELMA).
Do you know such brands with economy price class?

here an overview of various brands:
http://www.diyaudio.com/forums/soli...nny-giles-tkd-vishay-more-whats-your-fav.html
 
Status
Not open for further replies.
Top Bottom