Les Paul Lo-Z pickups

[R.G.]

These are different ways to say the same thing. If the magnetic field is uniform, the total flux is simply the field strength times the area of the loop.

I'm good with that - and, as I said, if the other variables are kept constant, if you change the number of turns, you directly change the size of the output voltage. Otherwise transformers, which may be considered to be a special case of a guitar pickup plus a driver coil, would not work as they do.

Because low-Z pickups have fewer turns, the voltage they produce is lower, but is this the real issue? Probably not. We know we can use a transformer to increase the voltage.

Probably the real issue is how much power does the pickup produce? When the impedance of the pickup is the same as the amp, the pickup transfers the most power to the amp and drives the amp hard. This is usually desirable. If not, we turn the volume pot down on the guitar.

Actually I think the real issue is not the power produced, it is the voltage. It is rare to need maximum power transfer in audio, with the exception of driving speakers, long lines, or distribution networks. A triode grid is a very high impedance load, much higher at low frequencies than the 1M grid leak resistor which is almost universally used. And a triode is a voltage-to-current converter, best described by its transconductance. You want maximum signal voltage to get the signal up out of the noise.

The noise issue is one where you may need impedance matching. There is an optimal set of input impedances for a given source impedance to keep noise lowest. In audio, this is usually a lot smaller than the nominal 1M input impedance of the nominal guitar pickup. I believe that the low-Z pickups and the "recording" nomination put to the guitar was to get down into low noise impedances for recording.

The low-Z pickup probably does not produce quite as much power as a high-Z pickup. Is this bad? Not with all the high gain amps and foot pedals available today. Was this bad back in the day when the Les Paul Recording was made. Probably.

For a given coil area, path permeability, and flux density/flux change, the number of turns in a coil volume have no effect on the available power. You can pull as much power out of X flux change with one turn or many, within reason (assuming that only the turns change and you can ignore the coil resistance change) if you rearrange the load to have the maximum power transfer impedance for each number of turns

[Mark Hammer]

But none of you have gotten to the most important question, and that is what gauge I should buy from the bin of surplus magnet wire spools near my home? They've got just about everything from the high 20's up to the mid 40's, for a mere $4/lb. They're going to be moving to a new location in a month and since they consider this "merely" scrap copper, I doubt that the person working the forklift will take ANY precautions to prevent damage to the the spools and their contents. I have to act fast.

[tbryanh]

Yeah, it doesn't appear to be a power issue.

It appears to be strictly a voltage issue.

It appears that the transformer didn't increase the voltage enough to distort the amp as much as other guitars.

True, the Recording was made for direct plug in to line level, and that is what Les Paul loved. The Recording was his invention and his favorite guitar. He bragged that his guitar did not require any EQ by the recording engineers. But he was a jazz player, not a rock and roller.

Plugging your guitart directly in to line is not a popular idea, and the transformer does not provide a hot output.

I think low Z pickups might be a hard sell to the public for the same reasons the Recording didn't fly. Thats not an issue for me because I do not sell pickups. Maybe in the future, but not now.

In spite of this, I plan to wind low Z pickups for my use.

[R.G.]

I actually think you might want to look into the Low-Z-plus-onboard-preamp.

The LM387 is discontinued, but still available, and there are other chips that will do a similar job.

These chips can get your total input noise down around 1uV in a 10kHz bandwidth, and will drive capacitive cables with no treble loss. If you do the source-impedance-versus-impedance dance right with one of these, you can probably come up with a pickup that is humbucking, low thermal noise, and has a usable output to a standard amp.

[David Schwab]

But none of you have gotten to the most important question, and that is what gauge I should buy from the bin of surplus magnet wire spools near my home? They've got just about everything from the high 20's up to the mid 40's, for a mere $4/lb. They're going to be moving to a new location in a month and since they consider this "merely" scrap copper, I doubt that the person working the forklift will take ANY precautions to prevent damage to the the spools and their contents. I have to act fast.

Well... Alembic uses 40 gauge. I think we established that the LP recording pickups used 28. Old CC pickups used 36 I think. They weren't low Z per se, but you could use that gauge to wind a Low Z coil.

I wind what is probably medium impedance pickups (as are Alembic's) and I use 42 and 43, because that's what I had available, and they sound great.

So I think you have a lot of latitude! From what I have read, you will get more highs with larger gauge wire, and more mids with smaller gauges.

I'd love to find a place that sold surplus like that. I want to give different gauges a try, but don't want to buy big spools....

[Louie Seven]

wow...this thread just kept on going......like the energizer bunny.

ANYWAY, back to MY original inquiry - about the compostion of the Gibson Lo-Z pickups in the Les Paul Recording guitars.....

I THINK, I have fit another piece in the puzzle.

Those pickups utilized BLADE magnets.

I don't recall if anyone mentioned that in this thread. I know there was specUlation about the composition of the magnets...cobalt and such...

But they are definately BLADE magnets. I located a rather large picture of Les Pauls LOG guitar with some 'red' substituted Lo-Z pups in which you can see the blades quite clearly because they don't have covers on them.

As I recall, the Charlie Christian pups had blade magnets too. And I've seen several picture of Les playing hollow-bodied guitars with Charlie Christian pups installed. I think he used them just prior to developing his own Lo-Z's...

Comments ?

Louie Seven

[David Schwab]

I located a rather large picture of Les Pauls LOG guitar with some 'red' substituted Lo-Z pups in which you can see the blades quite clearly because they don't have covers on them.

Are those the "clock" pickups I wonder? I always remembered it with the red pickups.

[Louie Seven]

Thanks..... well, I guess only the 'man' his own self knows for shure. They probably don't even make that particular clock any more. *heh*

So..... this whole blade thing is something I've ignored for years. Yes, my '66 Country Gentleman has a Supertron 'Blade' pup on it, but I'll be darned if I've given it even the slightest bit of attention.

I've never been given a blade pup to rewind either...... so, I've done some research. From what I gather, the idea is to allow more even reproduction, specially when bending strings - freedom from dead spots, etc.

Despite the heavy guage strings of yesteryear, Les Paul WAS known to do a lot of string bending....in addition to all the other tricks up his sleeve. So I can understand why he's gravitate toward 'blades' rather than 'poles'.

I'm toying with the idea of crafting a Lo-Z pup for my own use, since the Gibson LP Recording Guitar pups don't really show up on eBay and such.

Since the Gibson Lo-z's are encapulated in epoxy, I suppose my 'model' or 'example' will end up based on pictures and descriptions of hand-made Lo-Z's, such as the red ones that Les has on his LOG.

One main issue that I'm grappling with is the fact that my guitar body is routed for normal HUMBUCKERS, not narrow stacked coils normally associated with the Les Paul Lo-Z pups. I don't want to remove any wood from the guitar in the eventuality that I put conventional pups back in someday.

Therefore, the idea of an UN-stacked Lo-Z pickup (coils sided by side as per normal humbuckers) seems like the way to go.

If I do this evil deed, I'll probably try to go with 'blades'.

The first layout in my mind is a blade sitting on top of a regular aLnIcO V bar magnet with about a thousand turns of 29awg, times two of course, for the humbucking effect.

Obviously, I'm going to have to do some math. Regular wound coils in conventional humbuckers are usually about half the desired ohms, so that when you wire them together, you get the total. That's fine when you're dealing with 7K pickups and thousands of windings of 42awg. But if you half the already Lo-Z coils, that's not much windings per coil. Half of very little is very very little !

IDEAS ? COMMENTS ?

Louie Seven

[David Schwab]

Therefore, the idea of an UN-stacked Lo-Z pickup (coils sided by side as per normal humbuckers) seems like the way to go.

If I do this evil deed, I'll probably try to go with 'blades'.

The first layout in my mind is a blade sitting on top of a regular aLnIcO V bar magnet with about a thousand turns of 29awg, times two of course, for the humbucking effect.

That's what I do. I'm not sure you will get 1000 turns of 29 on a humbucker bobbin though. I filled a bobbin from a bass humbucker up with about 300 turns of 30 AWG. Of course it was hard to get enough tension on it with my winder, which isn't made to use such heavy gauges, so it was a bit loose. It came out to about 30 ohms!

Just wind 500 to 1000 turns of 40 (or even 42) on a regular humbucker bobbin. Wire the two in series, and then choose how you want to boost the levels up.

[Louie Seven]

Hmmm... that's interesting

Yeah..... that's the ticket.

Actually, I just threw 1000 turns out there for the sake of discussion....as a nominal figure, so I could keep typing. *heh*

I'm not too concerned about boosting the level, (although I'm open to any suggestions and/or tips)........

My primary objective is to get the impedance down so I can go straight into the console. Naturally, the wider freq response of the Lo-Z is of primary importance too.

In case I didn't mention - BASICALLY, I'm seeking to approximate the 'tone' that Les was getting for his recordings back in the 50's.

He's forgotten more about sound and recording than I'll ever know. But I've picked up a few pointers here and there. His criteria was the same as I outlined.... higher fidelity and direct to the board. Plus he wanted the ability to use very LONG audio cables on stage. That's something interesting, but of no real concern to me. I'm just looking to record a certain sound.

I suppose IF a known manufacturer offered a real passive Lo-Z pickup similar to Les Paul Recording guitars, I'd just skip this effort and buy a couple.

On the otherhand, I do a limited amount of pickup repair and rewinding in my business, so it's not a HUGE undertaking for me to do this. It just seems that way because I'm spending a lot of time studying UP on this topic.

I have most of the materials together. I just want to make sure I have all my ducks in a row, before I sit down with the tools.

Do YOU think chromed steel would make a good 'blade' ?

Louie

[David Schwab]

I use plain steel, but my blades are covered. Certain types of stainless would work also... I always thought stainless wasn't magnetic, because most of the samples I tried weren't... such as rulers and stuff. But magnets stick real well on kitchen knives!

You need a really low impedance pickup to work with a mixer. The pickups I wind do work without a buffer, but you really have to crank the mic pre up, and they don't have as much top end as with the buffer.

But a lower impedance pickup should work right into a mixer.

[Louie Seven]

I see..

no, I just thought that chromed-steel might wear (and look) better.
plus, I happen to have some that's about the right size.

L7

[jmiked]

Interesting thread......

I have a Les Paul low-z pickup I got from eBay. The mounting ears were broken off, so I haven't yet used it for anything, but I did take DC resistance measurements from it. Mine is coil-tapped, and I can dig the measurements from my notes of the time if anyone is interested,

I built two low-z pickups from that info... I used 1100 turns of 34 gauge wire to produced two coils of 150 ohms each, on a stacked frame. I liked the Agile Les Paul copy I had, so I bought another one, spent two days (mostly setup time) on a friend's milling machine routing out larger holes for the pickups and ended up with a very nice sounding instrument. One of the hardest things about the construction was finding the proper value pots. I ended up using linear pots instead of audio taper, because that was all I could find after 3 months of research.

It sound very, very close to the sound on the Les Paul and Mary Ford albums.

If anyone is still interested, I can furnish more info on the process (I took photos during the project), and on info I found out by talking to the fellow that does the sound board for Les at his Monday night gigs and has known him for 25 years.

Mike

[David Schwab]

Mike, that sounds cool.

I'd love to see the photos and hear more about the pickups.

[clementc3]

Cross-post: 'Les Paul Recording pickups - how low is "low-impedance"'

I posted this in the "Stacked humbucker bobbins/Les Paul Recording pickups thread" also:

I recently acquired a 1970's Les Paul Recording guitar with the low-impedance pickups and I want to take advantage of the low-impedance output without using the transformer that is built into the guitar.

There are several low-to-high impedance transformers that I can put at the amp end of my cable but I wondering how low the "low-impedance" output from the guitar is. For example, Shure has their A95U which can accept low-impedance input in the 75-300 ohm range or 19-75 ohm (if you re-solder a lead), while Electro-Voice has their E-V 502CP at 150 ohms. Radio Shack has one at 900 ohms (I think).

Reading this and other threads I see people say the Les Paul Recording pickups have values of 10 to 150 to several hundred ohms.

Which impedance matching transformer is most appropriate, and does it matter?

(Note that my electrical knowledge is from one physics class that I took in 1975 - about the same time that my guitar was being marketed by Gibson - AND my electrical knowledge has not been updated since, so it's pretty rusty!)

Thanks for your collective knowledge!