Bassman bias balance pot dilemma

[M Fowler]

I've had a situation where the noise was coming from my picking hand touching the pup adjusting screw head while playing causing a popping sound due to poor grounding.

[bluesguitar]

re: static buildup on plastic pick-guards

I usually put adhesive copper-foil beneath the pick-guard (I source it from Stew-Mac), making sure it contacts the copper-foil I line the pick-up and control cavities with. The copper-foil is then grounded. That pretty much eliminates the problem.

HTH = Hope this helps

Thanks for the suggestion. I was seriously thinking of doing something like this to my Eric Johnson strat, which is much more sensative to static and hum than my other strats. I gave up on the idea for fear of the dynamics possibly changing the true sound of the pups. What do you think of this?

[NickC]

re: static buildup on plastic pick-guards

I usually put adhesive copper-foil beneath the pick-guard (I source it from Stew-Mac), making sure it contacts the copper-foil I line the pick-up and control cavities with. The copper-foil is then grounded. That pretty much eliminates the problem.

HTH = Hope this helps

Thanks for the suggestion. I was seriously thinking of doing something like this to my Eric Johnson strat, which is much more sensative to static and hum than my other strats. I gave up on the idea for fear of the dynamics possibly changing the true sound of the pups. What do you think of this?

As long as the copper-foil is carefully applied and not contacting the pups directly (grounding any wiring), there should be no detrimental side-effects at all. Some Fenders have the control cavities coated in a conductive paint that can also block stray electro-magnetic interference.

The copper-foil tape is expensive. You can achieve the same result using heavy gauge aluminum foil applied to the underside of the pick-guard using spray adhesive (3M makes it). If you do that, be careful to mask about 1/4" of the underside along the outer edges, and the pup cutouts, so that the spray adhesive will not contact the guitar surface when installed.

Step by step:

Mask

Spray

Remove masking tape

Apply aluminum foil (all the way to the edge)

Remove the unstuck surplus foil along the edges with a razor knife

The copper-foil tape is easier and faster; and you can do it without removing the pups. That might warrant the additional expense.

[bluesguitar]

Thanks. I don't mind the extra cost to get the best result.

[Structo]

I've used the Stew Mac copper foil with adhesive on a few guitars.

The adhesive is supposed to be conductive and it is but when I metered the conductivity there was a bit of resistance.
So I carefully added a small bit of solder where the tape overlaps in several different places to avoid any ground loops.

[NickC]

I've used the Stew Mac copper foil with adhesive on a few guitars.

The adhesive is supposed to be conductive and it is but when I metered the conductivity there was a bit of resistance.
So I carefully added a small bit of solder where the tape overlaps in several different places to avoid any ground loops.

Yes, I forgot to mention soldering the overlaps to maintain continuity of the ground. Good call!

[Firestorm]

I just did a MIJ "not for export" Strat using copper foil from Home Depot (they sell it for flashing and termite barriers). 8" x 20' for around $25; enough for many guitars. It's not really adhesive so you have to use rubber cement or contact cement and it's pretty heavy gauge so kind hard to cut, but the end result was great.

[jubal81]

Anyone have a link to a really clear guide/tutorial on converting cathode-bias to adjustable fixed bias?

I've been eyeballing the analog panel meters at Mojo and would really like to incorporate those as well.

[ic-racer]

Anyone have a link to a really clear guide/tutorial on converting cathode-bias to adjustable fixed bias?

I've been eyeballing the analog panel meters at Mojo and would really like to incorporate those as well.

Some info here: http://www.londonpower.com/cath-fix.htm

[Bear]

Back on the strat shielding, anybody used an aluminum under-guard like this one? http://www.guitarfetish.com/Aluminum-St ... _p_90.html Seems relatively cheap and easy as can be.

[Structo]

Yes, those came on some strats if I recall.

The pots will ground to the shield so your ground plane covers the top.

But in reality, shielding or star grounding does little to alleviate the 60Hz hum that most single coil pickups are plagued with.
We are surrounded by 60Hz noise from the home wiring and the EMI from the amp.

[loicdulux]

Not sure if this aa371 is your Bassman, but here's how you can add a variable bias to the balance circuit. The red jumper from the diode to the cap is already there. A 10mm round Piher trimmer would be a likely candidate for this.

Hi Martin,

Does this look to the right candidate to you? (I live in Germany so I need to find something onshore..). Not sure how this has to be mounted on the board, to be sure it is tighten..

http://www.tube-town.net/ttstore/produc ... -Poti.html

or

http://www.tubeampdoctor.com/en/shop_Po ... TS_USA_913
(much more expensive!)

Edit: may I ask you something.. I'm not sure to clearly see the three pons of the trim on your schematic, nothing is going to the middle connection?

[martin manning]

A trimmer like part number PT15D-5K on this page is what I am suggesting: http://www.mouser.com/catalog/catalogusd/646/873.pdf

There are actually 4 pins, so you'd have to add a couple of eyelets to the bias/rectifier board. There are two wiper pins, one on each side instead of just one at the top as shown in my drawing.

[Baxtercat]

Yes, those came on some strats if I recall.

The pots will ground to the shield so your ground plane covers the top.

But in reality, shielding or star grounding does little to alleviate the 60Hz hum that most single coil pickups are plagued with.
We are surrounded by 60Hz noise from the home wiring and the EMI from the amp.

My experience too. Lots of trouble wrapping & soldering copper tape around the routes and p/ups for little effect.

[Baxtercat]

[duplicate]