Fixing a microphonic pickup

[kurth83]

So I have two eastwood airline mandolas, which came with what I learned are called 'microphonic' pickups. This is a new term for me, never knew what it was until I got one by accident. Basically, if I hit the pickup with a pick, a fairly loud click comes out the amp, because the cover is conductive and acts like a string that vibrates when you hit it. By comparison, the rail pickup on the mandostang is quiet no matter how hard I hit it.

So... lowering the pickup is one option.

But I found this video, which suggests taking off the pickup cover, and adding wax, thus 'potting' the pickup (named for the early practice of dipping pickups in a pot of hot wax).

https://www.youtube.com/watch?v=FM68RMYOTME

I was thinking about using blu-tac putty instead, as I can find several electric guitar players who did that with good results.

Another option is to leave the cover off, but I'm worried about damage since the pick hits it a lot. If the putty doesn't fix the click, then I'll have to find another way to protect the pickup.

I'll post with the results in a few days.

[kurth83]

Tried to fix it today, my 100w soldering gun couldn't touch it, so I just lowered the pickup, seems fine, I think I like it better like this. :-)

But I ordered a 300w gun too, I will try again at some point.

[Soundfarmer Pete]

If it`s one of those covered mini humbuckers with no screw holes, you could dip the thing in shellac (French Polishing stuff), let it soak for a while and then clean the excess off the cover with alcohol when it`s drained and dried out.
It`s movement in a loose coil that causes the microphonic effect so binding the coil together is the solution.
I always use shellac for my pickups....safer than wax potting on very fine wire.

[mandroid]

[terminology unclear] Are you asking about a contact mic for sensing soundboard vibrations?
acoustic-electric..

Those are frequently discussed in the Equipment section of the upper sections of this page..

that's different than magnetic pickups sensing string motion in its magnetic field..









'/,

[kurth83]

This is a soapbar electric guitar humbucker pickup, see the Eastwood Airline Mandola if you want more details.

The 300W soldering gun got it apart no problem, and it was filled with wax, so adding putty was pointless, I put it back together and left it low, that's as good as it will get for now. Set low like that I don't hit it with the pick, but the signal is a bit weaker.

I didn't try to dig the pickup out of the wax, it was a solid bar of wax with a pickup embedded in it. Eastwood does a nice job with touches like that.

So living with it or replacing the pickup are the best options at this point.

[Tom Wright]

If the metal case is ferrous, i.e. steel, you’re out of luck. I have one made that way, potted properly but any tap on the case is really loud. Gibson and similar are chrome-plated brass housings, so not magnetic.

[Soundfarmer Pete]

Good point Tom....those pickups are cheap Chinese things so maybe the cover is part of the problem..... Since you`ve already had it apart, for the price, you could try one of these .....Nickel covers are better than brass (or so they would have us believe)!!! https://www.philadelphialuthiertools...lver-no-holes/

[kurth83]

Wow, those covers are a perfect fit, I'll give them a try.

I am pretty certain the OEM covers are ferrous, which is the root of the problem. Replacing the covers is the best solution.

[kurth83]

Replaced the cover today, no difference, old cover was not magnetic after all.

Not sure what it is now, pickup is set low so I don't hit it often, maybe that's enough.

How is a fully potted pickup microphonic? I don't know.

At least what I found in there was a pretty standard looking dual rail mini humbucker.

Seems like a lot of guitar pickups are available in this size, like this one, from a random internet search:

https://www.cbgitty.com/guitar-instr...-foundry-tone/

[BoxCarJoe]

I potted an electric bass pickup years ago.
It worked and was pretty easy to do.
As I recall you could speak into that pickup and record your voice! Now that's microphonic.

My Airline mandola does the tap thing also, but so far not a problem for me.

[kurth83]

Here is the end of the story: bought a new pickup, put it on, clicked the same, sounded worse, put the OEM pickup back on, in lowered position it is ok, the end. :-)

[Wrnchbndr]

I would suggest repotting the pickup. I use a cheap electric water kettle that typically sells for about $20 -- $10 at a thrift shop. It has an adjustable heat setting. I put about 1" of water in it. I have an aluminum insert that fits just about perfect in the kettle and sits just touching the water. I forget the exact ratio but I use a mixture of parafin and bees wax. I've been using the same wax for twenty years. The mixture ration I got from Jason Lollars pickup book which I don't have anymore but I don't see it being a problem if you use 50:50. The temp of the wax needs to be 140F much more hot and you risk degrading the insulation of the pickup coil. You must monitor this with a meat thermometer. You need the wax to be deep enough to fully submerge the pickup and you leave the pickup in the wax until the bubbles totally stop -- like you don't see a single bubble for two or three minutes. You don't need to remove the pickup cover. This is a very cheap setup but it works. I'd resist submerging the pickup into anything solvent based because there are a lot of different types of coil wire used and I have heard of shellac based coil wire insulation that would be compromised in a shellac solution.
When the bubbles stop, you just pull the pickup out and let it cool for an hour. I've never had a complication with any pickup doing this. Or, you could just mail the pickup off to any custom pickup maker and I'm sure repotting would be dirt cheap.