Weird clicking on pan pot using wireless

[georgesdayout]

I swear I've run into this before on this forum or another similar, but I can't get the search engine to give it too me this time...
 
I've had this behavior with a couple different wireless units on my Essence 4-string: When I rotate the pan pot for the pickup selector fully to either extreme (all bridge or all neck) I get a little click or pop. I know I called Alembic on this back in '94-95 shortly after I got my first wireless and got a little bit of (polite) brush off, but perhaps, now that 13 years have gone by, more experts either in or out of Alembic have seen this behavior first hand and have a suggestion or two? For reference, the Serial # is 94K8231.
 
Thanks!
 
(Message edited by georgesdayout on October 08, 2007)

[terryc]

I am not an expert but your wireless system might be picking up the centre detent on the pan pot, although the wipers in the pots are well engineered the lock poistion in the pot might produce the tiniest of sparks that produce a very small RF signal which has passed through the pre amp to the transmitter unit. Like I say I am not an expert but you never know..Maybe Mr Fung could chime in on this.... David???

[georgesdayout]

Thanks for the response Terry. I don't think what you suggest is the situation since it happens, not going past the detent, but even moving the slightest distance away from the extreme to max or min.
 
I have a similar theory though. Not knowing the interior of these pots, I may be way off base, but here goes: there is some sort of discontinuity in the resistance curve at the end, almost as if a wiper is going past the end of the film before it hits the blocks.
 
This does boggle my mind, but there must be something different electrically when going to the extreme with this pot that is audible with a floating (or relative) ground (like the wireless) but not with a true ground such as plugged into an amp or board.
 
Thanks again for the response.

[811952]

My filters click and pop and sometimes let out a bit of a squeal when I roll them back from the full-clockwise position, but then they're almost 26 years old and have seen MUCH use.  It is possible that you simply have a pot that has developed either a slightly dead or slightly microphonic spot along the coil or wiper.
 
I would suggest getting a second opinion from someone who knows electronics a bit and can listen to it with and without the wireless system in the signal chain.
 
John

[terryc]

Mica has said that the pots are self cleaning and don't be tempted to use Servisol or any other switch cleaner and as I said they are very well engineered, in the ten years I have owned my MK they controls have worked perfectly with no crackles or silent spots. Surely if you were going off the end of the resistor film it would go dead, I guess it doesn't happen with the good old cable into amp then??

[dfung60]

When you have clicky or scratchy electronics behavior with wireless systems, it's often due to grounding weirdnesses, particularly if the transmitter you use has the antenna integrated into the audio cable.  
 
Everything to do with radio is mysterious, but I think the problem tends to be that the length and shape of the antenna is pretty important for proper performance.  To prevent having extra wires dangling around, some manufacturers use the shield of the audio cable as the antenna as it's about the right length for the common frequencies.  The problem with doing this is that that shield is in contact with the shielding in the body of the instrument, which means the antenna is now untuned.  Things generally work with regular guitars which have minimal internal shielding, but on a highly shielded instrument like an Alembic, this can have a significant and unpredictable effect.  
 
Often the effect on a shielded guitar is that it sounds scratchy or clicky when you're turning the pot, but sounds completely normal when it's sitting still or when you're plugged in with a cable.  
 
I've never been told exactly what is happening here, but the solutions are sort of wacky.  If you have a wireless unit where the transmitter doesn't have an independent antenna, you probably want to switch systems or contact the manufacturer to see if there's a mod where you can add a separate antenna.  If you have a thin separate wire that appears to just be hanging out of the transmitter, that is the antenna, but it may also be wire or foil inside the transmitter case.  
 
The other thing you might try is wrapping the battery with tape.  Sometimes, the metal case of a 9V battery can act like an antenna when it comes into contact with the grounding paint in the instrument.  Wrap it with tape (masking tape is fine, you probably don't want to use electrical tape because of the mess) and see if that doesn't make the problem go away.  It's a bit of a shot in the dark, but as you isolate away pieces of metal from the ground, you are re-tuning the antenna!
 
After that, the next thing you would look at is modifying the lengths of the leads in the electronics cavity, but again, it's sort of random - it would be hard to know which wire is the problem and what the critical lengths to get to would be.  If you have a shielded 1/4 extension cable (this would be a very odd thing to have lying around), you could plug it in between the tranmitter and bass.  That changes the antenna length, again retuning the antenna and possibly getting rid of the problem.    
 
At least this is something to try.  I hope something will make a difference here for you,
 
David Fung

[georgesdayout]

David,
 
Thanks, that's the most promising lead yet on this issue. I've stopped using that wireless, but if I recall it was a Nady that did not have an external antenna. If it really was using the ground as an antenna, then there could have been minor impacts to that antenna when the pickup pan control was at the extremes where one of the pots would have been at 0 ohms (assuming that the pan control is really two volume controls with inverse tapers ganged together and not just a change in a gain control on an op amp).
 
In any case, the next time I go wireless, I will look for a unit with a separate antenna (even if it is internal).
 
Thanks,
 
George