Downside to tapped single

[Mick Bailey]

Is there any downside to tapped (dual impedance or dual coil) single coils compared with regular pickups? I'm referring to Tele pickups of 7.3k/11k for the neck position, 7.5k/16.1k bridge.

[Helmholtz]

In tapped mode effective PU self-capacitance can become quite high.
Reason is that the tapped PU acts as an autotransformer regarding capacitance.

E.g. if full coil capacitance is 200p and the coil is tapped in the middle, the reflected capacitance at the tap will 800p.
Means that the unloaded resonant frequencies of full and tapped coil are the same.

[Antigua]

Is there any downside to tapped (dual impedance or dual coil) single coils compared with regular pickups? I'm referring to Tele pickups of 7.3k/11k for the neck position, 7.5k/16.1k bridge.

Because of the capacitance issue, you might expect one thing and get another in tapped mode. If you go at it with the idea that the full mode is the sound you would use most often, and the lower impedance tapped mode is like a bonus, then you'll probably like the option. 11k and 16k sound like "hotter" coils, as if the idea is to get a boost out of the full coil, and a good clean from the tap, but I've personally only been happy with taps when the full coil is a only little hotter than average, and the tap a little cooler than average, not attempting to go for extremes in functionality, treating it more is a slight tone variation.

[Mick Bailey]

They're commercial pickups that someone is selling locally, but it seems the idea is maybe too compromised (at least for me).
http://www.irongear.co.uk/irongear_pickups_015.htm

[SoulFetish]

Because of the capacitance issue, you might expect one thing and get another in tapped mode. If you go at it with the idea that the full mode is the sound you would use most often, and the lower impedance tapped mode is like a bonus, then you'll probably like the option. 11k and 16k sound like "hotter" coils, as if the idea is to get a boost out of the full coil, and a good clean from the tap, but I've personally only been happy with taps when the full coil is a only little hotter than average, and the tap a little cooler than average, not attempting to go for extremes in functionality, treating it more is a slight tone variation.

This is relevant to something I've been thinking about lately. I recently built a tele using two single coil pickups. It's my first tele; I've traditionally been a strat/les paul player.
Arguably, choice of pickups has the biggest influence on how the guitar sounds, but I kind of settled on using traditional style single coils in this guitar. Ultimately, I decided on a Lollar Royal T neck pickup, which I absolutely love, and Lollar Vintage T for the bridge pickup. The choice for what to use in the bridge position was the challenge for me because I didn't have much experience playing Teles.
Personally, I don't love this bridge pickup for this guitar. It has a bit too heavy on treble freq. and is overly microphonic for my taste. It's not a great pairing with the neck IMO. Now, I want to say that I don't think there's anything wrong with this pickup. I think it probably does exactly what it's designed to do, and would be a great pickup for someone else's taste. It's on me, I just didn't make a great call on this one.
So, what does that have to do with this topic? This:
I was going to just replace it altogether, but a friend suggested the possibility of using the existing coil output as a tap, and increasing the winding to solve the output and tonal complaints I was having.
There is plenty of room for this on the bobbin, and would appear to be a relatively simple modification. If executed correctly, it would probably result in a coil you described above - a little hotter at the full coil and a little cooler at the tap.
If I were to attempt this, how would you folks recommend going about this? Would you use the same wire gauge, or a slightly larger one? Also, would you pot it after?

[Helmholtz]

Wire diameter itself doesn't influence tone - only resistance.
Lower diameter allows for more additional turns.
The sheer existance of additional turns is likely to make even the original winding sound darker because of increased effective capacitance.

You could test the effect of increased capacitance by wiring a cap of some hundred pFs across the bridge PU.

[Antigua]

This is relevant to something I've been thinking about lately. I recently built a tele using two single coil pickups. It's my first tele; I've traditionally been a strat/les paul player.
Arguably, choice of pickups has the biggest influence on how the guitar sounds, but I kind of settled on using traditional style single coils in this guitar. Ultimately, I decided on a Lollar Royal T neck pickup, which I absolutely love, and Lollar Vintage T for the bridge pickup. The choice for what to use in the bridge position was the challenge for me because I didn't have much experience playing Teles.
Personally, I don't love this bridge pickup for this guitar. It has a bit too heavy on treble freq. and is overly microphonic for my taste. It's not a great pairing with the neck IMO. Now, I want to say that I don't think there's anything wrong with this pickup. I think it probably does exactly what it's designed to do, and would be a great pickup for someone else's taste. It's on me, I just didn't make a great call on this one.
So, what does that have to do with this topic? This:
I was going to just replace it altogether, but a friend suggested the possibility of using the existing coil output as a tap, and increasing the winding to solve the output and tonal complaints I was having.
There is plenty of room for this on the bobbin, and would appear to be a relatively simple modification. If executed correctly, it would probably result in a coil you described above - a little hotter at the full coil and a little cooler at the tap.
If I were to attempt this, how would you folks recommend going about this? Would you use the same wire gauge, or a slightly larger one? Also, would you pot it after?

That's a cool idea, I wish I would have thought of it myself, but more so with Strat pickups, it could be tough with a Tele bridge. Also a Lollar pickup has rather high used value, I'd probably sell it off and buy something more modest to modify. Once you modify this pickup, the value would vanish even if you like the end result better.

The tricky part with a Tele bridge would just be added a third or forth hold to thread the new wire to, because it has a steel base plate.The new hole could be very tiny, just enough to thread through the magnet wire and the end of the lead wire so that they can be soldered together. I don't think you technically need a metal eyelet in the hole, so long as you're careful with it up until the point it's installed. I'd use a drill press to make the new holes, for the sake of precision. A hand drill could slip and destroy the pickup very easily. On top of that, a vintage correct Tele bridge will have the wax or lacquer potted string tied around the coil, or it might be taped over. Removal of either could break the existing coil.

Any gauge of wire can be used to add more turns. If there is a lot of room left, you can use more 42 AWG. Wax potting the new turns would be a good idea, because the outer layer of wire will be more microphonic than inner layers in any event. You could also look into using lacquer instead of wax to immobilize the coil wire, it might be less of a hassle.

[SoulFetish]

Wire diameter itself doesn't influence tone - only resistance.
Lower diameter allows for more additional turns.
The sheer existance of additional turns is likely to make even the original winding sound darker because of increased effective capacitance.

You could test the effect of increased capacitance by wiring a cap of some hundred pFs across the bridge PU.

Even though I would prefer more output, the added capacitance to the existing coil seems like it might be a beneficial effect of an additional winding.
It's a good idea though. i'll drop in a couple of caps across the coil and test them. 220pF and 390pF seem reasonable?

[Helmholtz]

220pF and 390pF seem reasonable?

Yes.

BTW, if your bridge PU is mounted to a traditional style Tele bridge steel plate this might be the reason for microphony.

[SoulFetish]

BTW, if your bridge PU is mounted to a traditional style Tele bridge steel plate this might be the reason for microphony.

it is mounted to a traditional steel plate. You come across any techniques to damp the microphony?

[Helmholtz]

it is mounted to a traditional steel plate. You come across any techniques to damp the microphony?

Sorry, no. It's a common Tele issue. Of course bridge to body contact matters.
Non- magnetic stainless steel would avoid the problem. Don't know if those exist.
Or a (chrome plated) brass plate. But that might change the sound somewhat.

[Mick Bailey]

I've been giving more thought to the tapped S/C pickups. I notice that the maker I linked to recommends 500k pots, and that may make quite a difference with their rather extreme windings. I did think myself of overwinding some existing pickups to get a slightly hotter sound, but the only ones to hand are a really nice neck pickup which I didn't want to play with, or a pair of bar-magnet MIM pickups, which don't sound that good anyhow and would perhaps be a waste of time.

One of my Teles has G&L MFD pickups and I've been unable to tame the microphonics with those. Regular Tele pickups are a lot better, though the Tele lends itself to microphony anyhow. I've tried the trick of silicone under the bridge plate etc and re-potting the pickups under vacuum (twice - the second time round with slightly more beeswax in the mix to give greater adhesive qualities). Nothing I've tried makes the slightest bit of difference with those.

[Helmholtz]

The problem left is that the PU as a whole (and thus its magnets) can move relative to the plate.
The ferrous plate gets magnetized like the strings by the field that returns at the sides of the magnets and thus any slightest movement of the PU or vibration of the plate induces a signal.

[SoulFetish]

Hmmm… perhaps a nonferrous stainless is the way to go, then.
The steel plates are stamped, so they wouldn’t seem to be a hardened form of steel. So you probably wouldn’t even perceive a difference in sustain or acoustic coupling with a Stainless.

[Mick Bailey]

The MFD bridge pickup is well known for the loose baseplate problem - It's not particularly well made and quite thin. Despite being well stuck with wax maybe there's still enough movement relative to the pole pieces. The thing is, the neck pickup is just as microphonic. Maybe the adjustment slugs move as well with vibration, even though they appear to be firm.