potting

[SK66]

OK, I see the point here... but what about bondable magnet wire?

One example is Q-Tuner pickups. They have free standing air coils wound with bondable wire, which after it's been bonded into a free standing shape (in an oven) is molded into a pickup with epoxy.

I can see that wax, being soft, would have a damping quality. But if your coil is bonded as one solid mass, it's only going to vibrate along with the rest of the substrate, which in this case is the cured epoxy resin.

I think of potting as making sure you don't have loose windings. Along with wax, things like lacquer and vanish have been used, and those of course dry much harder than wax.

In my case I'm dipping the coils into polyurethane (and it's not a quick dip, I let them sit there for a few minutes) to glue the windings together. The epoxy is really for structural integrity, and to prevent casual noisy people from looking inside.

Some of my early pickups skipped the poly step, and I haven't had any problems with microphonics or feedback. I really started the poly step because I was concerned the epoxy might not get inside the coil, even though it flows freely. It is epoxy potting compound after all. I don't see a problem with having the coils cemented together.

I mean, why did Gibson and others epoxy pot their pickups, when they could have just done wax? I doubt those Super Hubuckers were wax potted first, and I know that Bill Lawrence pickups are not. I just followed these examples.

A Q-Tuner pickup, which isn't trying to hide anything!

Bondable wire is on par with shellac coating during winding. It's as close to a "complete potting" as you will get.
It's not surprising that you did some with no other potting besides epoxy with no negatives. I've wound pickups with no potting whatsoever without negative. Potting is more "consistent" in results making it better for "production". The characteristic changes can be adjusted for IMO. Generally very hard potted pickups are what I would call "sterile"....unless softly potted inside. (kinda like a coil with major scatter inside and several firm layers on top to clean it up and firm the coil.)

[NightWinder]

Hum..

Thats a great question....I've had some that were microphonic and wondered the same thing. Maybe perhaps just one thing is vibrating inside. I'd think maybe there could be a hole/Air pocket or tunnel type. Maybe a hot wax bath for a few?? Not really sure.
I have some Mini's that are epoxed for gibby too....I managed to get the pickup seperated really easy from the cover, but damned if its not hard as a brick and totally unable to take apart....Got the cover off though. Could It be safe to assume some scarring on the inside of the cover would help the epoxy grab a bit. On top of the bobbins, is a pool of shiny black epoxy. It never adherred to the cover??

[David Schwab]

Bondable wire is on par with shellac coating during winding. It's as close to a "complete potting" as you will get.
It's not surprising that you did some with no other potting besides epoxy with no negatives. I've wound pickups with no potting whatsoever without negative. Potting is more "consistent" in results making it better for "production". The characteristic changes can be adjusted for IMO. Generally very hard potted pickups are what I would call "sterile"....unless softly potted inside. (kinda like a coil with major scatter inside and several firm layers on top to clean it up and firm the coil.)

Interesting. I have to say that one set of pickups is what I used in my bass for about a year of regular playing. They weren't potted at all. I usually don't pot any of the pickups for my own use, and I haven't used wax at all. The only time I got any feedback was once when I went right up to the amp, and I was right by the tweeter.

Keep in mind these were low Z bass pickups... not a lot of wire on them.

I later potted them in poly and epoxy, and they sounded exactly the same. I then sold them to a guy in France who was happy with the tone.

I have yet to pot any of the high Z bass pickups I'm doing, but I have been recording them every step of the way, so I'm interested in any changes that they might incur from the potting.

I'll report back here when I do.

[SK66]

[QUOTE=SK66;63281]I don't make pickups this way so I shouldn't be considered "an authority" on the subject.[/QUOTE]

Just wanted to re-emphasise this from my first post.....

[David Schwab]

I don't make pickups this way so I shouldn't be considered "an authority" on the subject.

Just wanted to re-emphasise this from my first post.....

You have a valid point though. I hadn't even though of those things. I agonize over details, and wasn't sure how to go, so I just looked at a lot of other pickups. I had never epoxy potted a pickup before. I've avoided wax mostly because some people seem to think it changes the tone, and it was more mess than I wanted to handle in my kitchen pickup lab!

But I started thinking something more than the epoxy wound be a good thing, and after reading that Rick Tuner uses varnish on his horseshoe pickups I tried the poly because I had a can sitting here. Wasn't any more scientific than that!

Turner talked about how he liked the tone of the varnish potting, so I figured what the heck? I have some Fender pickups potted in what looks like lacquer, as well as my Ric bridge pickups. So I reasoned they must have used a varnish like substance for a reason, especially fender, who normally used wax.

It seemed to work well, didn't alter the tone as far as I can tell, and prevented any feedback when I was near the tweeter.

I'll try anything at least once though.

[Bruce Johnson]

Hi guys;

I realize that this is somewhat of an old thread, but I thought I'd add something that may be of interest to you, in regards to epoxy potting.

If you build instruments, you may already be familiar with the Smith's company, who make a great line of structural epoxies. They're the guys who made the Tropical Hardwood Epoxy about ten years ago, which has now been replaced by the even-better Oak & Teak Epoxy.

Anyway, Smith's also makes an interesting product called MultiPrime. It's a two part epoxy, but it has a viscosity somewhere between water and gasoline. Its intended use is as a coating for bare wood, to sink deep into the grain and provide a bonding layer for subsequent finish coats. It's neat stuff, and I've found a lot of uses for it.

For the last two years I've been using it for potting pickups. It's much thinner than any of the commercial epoxy potting compounds (that I've tried) and it absolutely soaks all the way into the core of the coil. It also doesn't dry into brittle-hard, like a superglue. It's more like a paint when it's cured. It also doesn't seem to build any noticeable heat as it cures. I haven't seen any change in resistance after potting with it. I suspend my coils horizontally over a drip pan and pour it on several times until it seems than no more is soaking in.

After the MultiPrime has cured overnight, I put the completed coil in a silicone mold and "overcast" it with West Systems epoxy, tinted black. This is a protective, decorative shell.

I obviously don't have 20 years' experience with this process, but I haven't had any coils fail, change tone, or become microphonic yet.

[madialex]

I read today from Frank at Seymour Duncan that Seymour wax pots his Actives first then Epoxies them...

[David Schwab]

EMG also wax pot their coils first.

I still use polyurethane. It's real easy... I sit them in a container until the bubbles stop, just like with wax. Except there's no heat involved. I let them dry two days and I'm ready to put them in the cases and fill them with epoxy.

I'm using MG Chemicals black potting epoxy, but it's not any different from regular slow curing epoxy, as far as I can tell.

I'll have to look into that MultiPrime Bruce. Sounds like interesting stuff.