Measuring ohms on pickups, help please

[Busker]

Opinions please. Several days ago I posted about a Squier P bass I found that had Alembic P/J pups installed (no one replied to that thread, but no matter). I went ahead and bought the Squier with the idea of selling the pups out of it. I believe these are the "Activator" pups, but the previous owner installed them without any preamp, and the pups were not very loud, compared to my stock P bass.

The Alembic P pup measures 14 ohms resistance. That doesn't sound too far out of normal, especially if that means 7 ohms per coil.

The J pup however, measures about 35 ohms. Is the J pup shot? And if so, why? Its an expensive pup, encapsulated in epoxy. It looks OK from the outside.

 

[bongomania]

I'm not an expert, but maybe the Alembic pups were designed and wound specifically to match their preamp? In which case it would not be surprising for them to perform poorly passive, and have an unusual measurement.

 

[Passinwind]

Opinions please. Several days ago I posted about a Squier P bass I found that had Alembic P/J pups installed (no one replied to that thread, but no matter). I went ahead and bought the Squier with the idea of selling the pups out of it. I believe these are the "Activator" pups, but the previous owner installed them without any preamp, and the pups were not very loud, compared to my stock P bass.

Does your bass have a fresh battery in it? Those are active pickups and will not work correctly without being powered. Check this out: [Invalid or Expired Link Removed] .

As far as the pickup DC resistances, I hope you mean K ohms, not what you posted.

 

[Busker]

Yes yes, K ohms, sorry. Thanks for the link. I saw that.

 

[Passinwind]

Anyhow, the Activators I had in my old guitar (not a bass) were pretty low in output even when they were correctly powered. I hated the preamp that went with 'em, FWIW, but it worked a lot better than nothing. And yes, one of the three died at some point before they came into my possession, so it can happen.

You might ping A9X, he knows a fair bit about Alembic electronics.

 

[A9X]

To the best of my understanding all the Alembic pickups are passive, ie they have no built in pre inside the casing like an EMG. 14R is way too low for a pickup, and based upon my experience with the AXR and S1, 14K is too high. From memory they were 6k (but half of that is the passive bucking coil) and a bit under 3k, respectively.

Busker, without knowing what meter you're using, I can only guess that there is a range switch with a multiplier for the resistance scales, eg x10, x100 etc. Someimes the multiplier is an unusual value like x32, x320 etc. 14 and 35 if x100 are OK, but 14k and 35k are too high. There is every chance the P is connected in parallel intenally.

Ron worked on the idea of low impedance (and I think layered sectioned windings a la good output transformers to keep stray capacitance low) to keep the resonant peak up high, above the useful bass range, so that the filters would work optimally. This is part of the reason for the low output. They also need to work into a defined load and I'm not sure what that would be for the J pickups; I'd need to measure them myself and calc the value required to optimally damp the resonance.

Busker, email Alembic and ask. They're usually quite responsive (within a couple of days) and very helpful and nice people.

Edit: the Alembic page says nothing about the pickups themselves being active, and the pic below shows the normal (for Alembic) two wire pickup connector, so definitely not active pickups.

 

[Busker]

To the best of my understanding all the Alembic pickups are passive, ie they have no built in pre inside the casing like an EMG. 14R is way too low for a pickup, and based upon my experience with the AXR and S1, 14K is too high. From memory they were 6k (but half of that is the passive bucking coil) and a bit under 3k, respectively.

Busker, without knowing what meter you're using, I can only guess that there is a range switch with a multiplier for the resistance scales, eg x10, x100 etc. Someimes the multiplier is an unusual value like x32, x320 etc. 14 and 35 if x100 are OK, but 14k and 35k are too high. There is every chance the P is connected in parallel intenally.

Ron worked on the idea of low impedance (and I think layered sectioned windings a la good output transformers to keep stray capacitance low) to keep the resonant peak up high, above the useful bass range, so that the filters would work optimally. This is part of the reason for the low output. They also need to work into a defined load and I'm not sure what that would be for the J pickups; I'd need to measure them myself and calc the value required to optimally damp the resonance.

Busker, email Alembic and ask. They're usually quite responsive (within a couple of days) and very helpful and nice people.

Edit: the Alembic page says nothing about the pickups themselves being active, and the pic below shows the normal (for Alembic) two wire pickup connector, so definitely not active pickups.

Wow. So these are passive pickups. But I assume they were still designed to go with the special Alembic pre-amp system pictured above, because they are not as loud as a stock MIA P bass pickup. They seem to be low output on their own.

To be honest, I just bought the Squier so I could pull them out and sell them, and maybe get an extra cheap or even free Squier out of the deal when all said and done (sans pickups however).

Anyway, thank you all for your responses.

A9X,

I have an old RCA Tech VOM WV-547A hand held job. It probably belonged to a TV repairman years ago. It has the RX1, RX10, RX100 settings. I'm probably using it wrong. Can't figure out how it works really, no instruction manual. The other day I was trying to measure the impedance of a speaker cab, and it just kept going to zero, like a simple continuity test.

 

[A9X]

Wow. So these are passive pickups. But I assume they were still designed to go with the special Alembic pre-amp system pictured above, because they are not as loud as a stock MIA P bass pickup. They seem to be low output on their own.

All of the above is correct.

I have an old RCA Tech VOM WV-547A hand held job. It probably belonged to a TV repairman years ago. It has the RX1, RX10, RX100 settings. I'm probably using it wrong. Can't figure out how it works really, no instruction manual. The other day I was trying to measure the impedance of a speaker cab, and it just kept going to zero, like a simple continuity test.

When you measured them, what range were you on? If it was x100, then whatever you read off the scale you multiply x100 etc. Make sure it has a fresh battery when you make the measurements too.

 

[Passinwind]

Wow. So these are passive pickups. But I assume they were still designed to go with the special Alembic pre-amp system pictured above, because they are not as loud as a stock MIA P bass pickup. They seem to be low output on their own.

Thanks to A9X for the clarification. Many people (incorrectly) call anything that works best with a preamp "active", and calling the pickups "Activators" is a nice red herring, eh? As a practical matter though, you still need a battery and a preamp to get decent results from those pickups.

I hope the bass version sounds better than the guitar one!