Actual effect of volume/tone pots on acoustic tone

[Brian Evans]

I kind of know the theory, less is more, anything stuck to the top will affect tone, etc. But has anyone actually done a test? A/B, before and after on the same instrument kind of test? I want to add a pickup to one of my archtops. I've long favoured a neck mounted pickup, so either a D'Armond re-issue or a Johnny Smith style. I don't use pick guards so mounting controls there is out of the question. I have two viable options - thumb wheels inside an F-hole or the classic two in a row knobs on top mounted pots. Visually I favor the latter on a traditionally styled instrument. I can stick modelling putty on the top, of the same mass and location, but I can't tell the difference. Any thoughts?

TA, Brian

[John Clifford]

I haven't done this to an acoustic archtop, so I can't speak from experience. But I would worry more about vibrations from the pots and wiring connected to the top than about the small 3/8" holes and minimal added mass. In theory you could connect everything tightly enough to prevent vibration, but in practice things get loose and vibrate.

[Mike Conner]

I have tested this on my archtops with magnetic pickups. Every build also has piezo transducers superglued to the inside of the top plate. All of my builds have been X-braced. I always test in the white, and after finishing, prior to completing the installation and wiring for the pickups.

Neck mounted humbuckers float on the end of the fretboard, so no affect that I could detect.

I have one build with a full size StewMac Golden Age humbucker mounted on the top, and I did this by removing the usual metal mounting tabs and then attaching the pickup to the top with heavy duty mounting tape. A small ebony "mounting ring" is attached to dress up the pickup. The location is at the end of the fretboard, the typical spot for a neck pickup (about 6" from the bridge). This location is also above the upper arms of the X braces, and I expected this location to be acoustically neutral since the neck block and braces constrain the top there. No affect on volume or tone that I could detect, so the mass of the pickup did not seem to matter.


I use thumbwheels in the bass side f-hole. These are low mass and minimal cross-section affect the f hole. The wires are also attached to the underside of the front plate with very small adhesive cable clips. No affect on acoustic tone.

In a future build I will likely test regular volume and tone pots mounted in the usual 3/8" holes, but on the rim side of the treble f-hole to hopefully minimize any acoustic affects.

Kind of long winded response, and maybe more than you wanted to know, but at least I did try to test the acoustic affects.

[Alan Carruth]

Do you have actual objective measurements, or is this subjective?

[David King]

It seems like small thumb wheels attached right to the end of the pickup might be your best bet if there's room. It would be cool if the thumbwheels could be mounted in the pickup ring. Or just use a volume pedal like everybody else.

[John Clifford]

Thumb wheels, even if mounted inside the f-holes, are a safer option than pots because they attach with removable adhesive, they're very low mass, and are less prone to vibrate than pots with their mechanical connection involving nuts and washers. But you have fewer options for resistance, taper, treble bleed circuits, etc. And knobs. Don't forget knobs. Knobs are cool.

[Mike Conner]

Alan - totally subjective on my part

… and, I haven't built enough instruments to be considered "expert". I just liked that to my players ears it didn't seem to matter.
//mike