#1
Hello all,

This is my first post but I am familar with guitar building and have done a few builds to date. However this will be my first build of anything external to the guitar.

Basically I'm looking to build a device to set my volume remotely to the guitar.

I need this as my Hughes and Kettner Switchblade cause crazy bad microphonic feedback on the two Hi Gain channels it I turn any of my guitars to 10 regardless of pickup height etc.

With the guitar volume at 9 or even 9.5 it's fine. So the plan is to remotely set the volume to 9 or 9.5 and then no danger of feedback occuring even with the guitar up to 10

I've tried this last night using a behringer A/B box with two level controls (ie. 2 guitars to one amp or 1 guitar to 2 amps). Using this I was able to remove the feedback and running this set up into my MXR smartgate even with the gate fully open pretty much made things silent when not playing even without holding strings etc.

So I'm convinced this is the way to go but I don't want to use the behringer as I don't need to switching option or the inconvenience or accidentally losing sound by catching the switch (and invoking output to an empty jacksocket) or dead batteries causing the same switching problem.

For the project I've bought 2x Mono Jack Sockets, A Metal Pedal Sized Case, A 500k Audio Taper Potentiometer & A Knob.

I have a few quick questions:

1) Am I correct in thinking that a guitars 500k volume pot is actually 0k when fully turned and 500k when off. I this is the case would I be better off with a lower resistance pot (perhaps 100k) as the plan is to have more contol over the last part of the volume control rather than replicate the guitars knob (although that would work too).

2) I plan to wire the potentiometer using the centre connector and outside lug as in put and output from the jacks will this work or do I also have to solder the third lug to the rear of the pot?

3) Do I need to solder the earths from the jack to the back of the pot or can I simply put a wire between then in effect making the cable in and out as one long cable?

Any help would be appreciated


Dave
#2
A potentiometer, as used in a volume control, is comparable to two resistors in a voltage divider, where one is often connected to ground. As you turn the volume up, the "resistor" that connects to ground becomes smaller, and the resistor connected to the output larger.

So you will need to solder one lug of the pot to a ground source, be it the pot or chassis. There probably won't be much difference between a 500k and 100k pot due to the fact that both of the "resistors" mutually depend on each other.
Last edited by XgamerGt04 at Mar 20, 2009,
#3
I'd read :

"If only two terminals are used (one side and the wiper), it acts as a variable resistor or Rheostat. "

Hence the original queston.

If I need to earth the third pin do I also have to connect the two jacks to this earth too?

I'm becoming a little confused as if you think of the the guitar lead as in effect simply two wires (the shield and the signal) and you simply cut the signal wire and added a resistor in line then it would wouldn't need earthing would it?

This seemed such an easy project before I started. Although since posting I've at least managed to drill the box and add the knob and jacks so the hardware is ready to go and theres just the wiring to do now.


Dave
#4
I'd earth it all to the same place. Just connect the ground connection of the two jacks. Then connect one of the jacks, and the third lug of the pot, to a ground.
#5
Sounds like a plan ..that way it's the same as a guitar wiring and we all know that works so it seems to be a safe plan ..I'll be getting jiggy with the soldering iron shortly so I will post back for completeness.

Many thanks.
#6
All done ..usual outer earth lug plus the two shields soldered to back of pot ..input side tip to remaining outer lug and output side tip to centre lug ..all works a treat

Full guitar sound at reduced level and no more pushing the front of my amp into squealy feedback even with guitar volume fully up

Total cost just under £8
Last edited by dave_5150 at Mar 21, 2009,