Lollar Charlie Christian

[Greg Holmberg]

Hi everyone--


I'm new here, but I've been trying to understand pickups for a while.  A few months ago I bought a pickup tester from Ken Willmott.  I believe he is "stratotarts" on here.

I noticed some folks were asking if anyone has tested a Charlie Christian pickup.  I happen to have a Lollar CC, so I tested it. This pickup fits in a larger route (size of a humbucker).  You can see it has a metal frame around it (may induce eddy currents).

My meter read a DC resistance of 3.28 kOhms.  Lollar says 2.9.

I use a MOTU M2 audio interface connected to a Mac, and the Room EQ Wizard software. Here's my set-up:




Here are the graphs from the software (no smoothing):



I see these peaks:
Minimum load (11 MOhms 10 pF): 5.08 kHz at 84.2 dB (2.35 above baseline).
Load (200 kOhms 470 pF): 2.45 kHz at 82.4 dB (0.6 above baseline).
Inductance test: 1.106 kHz at 90.29 dB (8.44 above baseline).
Baseline level: 81.85 dB.

I entered these values into Ken's spreadsheet, which calculated some things:




I'm not sure what all these numbers mean, but I hope it helps someone here.

Let me know if you have any questions.


Greg

[aquin43]

Hello, thanks for those measurements. I have long been curious about the CC pickup which has such a grand reputation in the jazz guitar world.

Interesting to see the large amount of eddy current loss starting at quite a low frequency - 1k2 to 1k4 Hz, I would guess. This is probably due to losses in the rail, though the surround may also contribute. How is the pole piece magnetised in this version? The original, of course, had long flat magnets so the distribution of the string magnetising flux would be different.

[stratotarts]

Yes, you got the tester from me. Everything looks fairly normal there, but I see some small issues. The test leads are backwards - green lead is ground and should go to the pickup shield, gray is hot and goes to the pickup wire center conductor. That may introduce more interference, and skew the capacitance reading. I'm not sure if you moved the shield for the photo, but it should be underneath the integrator, the test wires and the device under test. I use the same foil, between sheets of thin cardboard to prevent shorting. You can definitely see some mains hum in the plots - present at 60 Hz and 180 Hz, the second harmonic. Some of that might also be the normal magnetic hum common to single coil pickups. But it looks quite strong. The results look quite believable for a CC style, the eddy current losses are visible in the "droop" and the numbers, the result of a lot of steel parts in the string field.

The spreadsheet is nominally colour coded - yellow are input numbers, pink are intermediate calculations or constants, and green are output values. You can ignore and omit the last 5 columns, they are just sanity checks or numbers used in some special studies.

Generally, my first thought would be to compare it with a P-90.

[Greg Holmberg]

May 23, 2021 8:17:57 GMT -5 stratotarts said:

Yes, you got the tester from me. Everything looks fairly normal there, but I see some small issues. The test leads are backwards - green lead is ground and should go to the pickup shield, gray is hot and goes to the pickup wire center conductor. That may introduce more interference, and skew the capacitance reading. I'm not sure if you moved the shield for the photo, but it should be underneath the integrator, the test wires and the device under test. I use the same foil, between sheets of thin cardboard to prevent shorting. You can definitely see some mains hum in the plots - present at 60 Hz and 180 Hz, the second harmonic. Some of that might also be the normal magnetic hum common to single coil pickups. But it looks quite strong. The results look quite believable for a CC style, the eddy current losses are visible in the "droop" and the numbers, the result of a lot of steel parts in the string field.

The spreadsheet is nominally colour coded - yellow are input numbers, pink are intermediate calculations or constants, and green are output values. You can ignore and omit the last 5 columns, they are just sanity checks or numbers used in some special studies.

Generally, my first thought would be to compare it with a P-90.

Great. Thank you for the help. I'll try it with the leads the other way.

For the shielding, I put the pickup in the plastic bag and then insert that into the aluminum foil pocket.  So completely wrapped in foil, which is connected to the tester's ground.  I guess the integrator should be inside too?

As far as the internal construction, I don't know.  And I don't know how Lollar magnetizes the pole piece. Maybe I'll un-solder the ring and take a look inside.  And try the test without the ring.

What surprised me about the pickup is that with a load the peak is only 0.6 dB and then it has practically no output above 3kHz.  You could call it pretty much flat with a 3k cut-off. I use it in a guitar (an archtop) with 500k pots, so I'm sure it's cutting off even lower there.  I use it with a guitar amp with Jensen C10Q speaker, which emphasizes the 2k - 5k range, and puts out little above 6k.  It seems that this pickup barely uses the best part of the speaker! The 3k to 5k harmonics are just gone.

It's funny that Lollar's chart for this pickup says treble and mid-range are about the same, and bass is lower.  It seems to me that it's the treble that is lower!  

Regarding the P-90, I see another test here of an Epiphone P-90 with a plastic cover, in which the neck pickup has a loaded resonance at 1.92 kHz of 1.2 dB, cutting off a little below 3k.  So, not so different from the Lollar CC.

[Greg Holmberg]

OK, this time with the ring removed.  You can see the magnets now.








Tested this time with the leads reversed.  I also tried better shielding (put the tester inside the aluminum), but there's still 60-cycle hum:




Minimum load (11 MOhms 10 pF): 5.55 kHz at 4.54 dB (91.59-87.05)
Load (200 kOhms 470 pF): 2.66 kHz at 1.59 dB (88.50-86.91)
Inductance test: 1.125


Calculations:



What changed?

Both resonance peaks rose a little in frequency.  5.08 -> 5.55 and 2.45 -> 2.66 kHz.

The level of the peaks rose significantly: 2.35 -> 4.54 and 0.55 -> 1.59 dB.

I still see the dips above 200 Hz though.  I thought that without the metal ring, these might disappear.

The inductance test changed slightly: 1.106 -> 1.125 kHz.

Inductance dropped slightly: 4.41 -> 4.26 H.

You can see the differences more easily in this graph:



I think, when I re-install it in my guitar, I will use it without the metal ring.  I may even bypass the volume and tone pots, to get more of the high frequencies in the 3k to 7k range.  Of course, then it might not sound like a Charlie Christian pickup!

It would be interesting to see tests on a CC pickup built like the original, to see if this Lollar captured it accurately.


Greg

[stratotarts]

Thanks for the test and teardown. I don't get much chance to do it any more, time constraints and no theories to test at the moment. The more people publish tests, the more robust the entire process becomes.

It's not necessary to fully surround the pickup with shielding material while testing. Of course, if it works for you, it's harmless. I've found that a sufficiently wide ground plane under the entire test area provides more than adequate shielding. It's possible that some environments have strong RF fields, that's the only thing that might be an exception, but I've never encountered any problem like that myself. In the early stages of development, I thought I would need a fully closed box and drove myself crazy with parts from the hardware store. It was a relief to find that in practice I didn't really need it. Interestingly, I just ran across a commercial product for ham radio equipment, that functions exactly the same way. It's a half desk sized copper sheet that you ground, and place all your radio equipment on - said to reduce interference from stray electrostatic fields around the wires. So, working exactly the same way. Any sufficiently large conductor creates an electrostatic "shelter" around it, the closer to it your equipment, and the wider it is, the better. My ground sheets are about 12" (40cm) square.

Magnetic hum can not be stopped by any normal kind of metal shielding, it's possible but uses esoteric materials like mu-metal. The best thing you can do, is rotate the pickup around and try to null it out. Usually the interference is directional.

Apart from the blade instead of pole screws, the other difference from a P-90 is that the coil is tall and thin, where the P-90 is famously wide and short. I think a genuine Charlie Christian pickup is on every tester's wish list.

[antigua]

Thanks a lot for doing this, with and without the cover, too. That's a surprisingly high inductance, given the low DC resistance. Even if it's using a larger gauge of wire, 5 henries is a non-trivial inductance. 

It would be interesting to see how Lollar's compares to the real deal, but the real deal costs ~$500 and doesn't really fit into any contemporary guitar, so I don't think I'm likely to see one in person. 

The steel bar in the Lollar looks somewhat thicker than the steel bar in the original CC pickups, and someone on another post claimed the CC's inductance was closer to 2.5 henries, which is completely unsubstantiated hearsay, but I'm most curious if the originals had a lower resonant peak and a higher inductance. The high inductance Lollars are suitable for modern rock'n'roll, no doubt. 

[gckelloch]

I think the originals used 38AWG wire, so the 5H measurement at the low DCR with the Steel blade makes sense. ~10% higher than the Lollar stated DCR could be partially from the temperature at which it was measured. I think the CC pickup thing is more about fashion and hype than anything tonally desirable about the pickup, but I appreciate the work done here. There are other SC pickups I'd use for jazz b4 a CC -- a Wilde Nd-Microcoil probably being my first choice, if not a maybe a low inductance L609 or L610. Whyddaya need a blade pickup for jazz anyway? Bending notes is sacrilege. A properly configured Q-filter will sweeten the midrange of any pickup -- the mid-dip starting from 600Hz~1.6kHz (depending on preference). A mid-dip centered in the 3-3.5kHz range strikes me as essentially jazzy.

[aquin43]

Actually, thinking further about this Lollar CC pickup, it seems to have very little connection with the true Charlie Christian pickup. Every parameter is radically different, including the shape of the field distribution about the pole.

A rail pickup is one sort of field plot that 2D FEMM can do quite well.

[antigua]

I found a couple picks below that show what is said to be an original CC, and a Lollar, and seeing the pic of the original reminds me that they never had a shielding ring of any sort. The Lollar appears to use a blade that is nearly twice as thick as the original. 

To see that the Lollar 


Supposedly an original:




Lollar:





This is a replica of original CC base, with two large "cobalt steel" magnets. It looks like magnets were a lot farther away from the coil and strings than is the case with a P-90. 




The coil of the supposed originals is also rather bulky, as would be expected given the bobbin size, but the Lollar version uses very little volume of wire by contrast. 




I understand that given the large size of the original, that a P-90 footprint is the only way to fit something like this in a Gibson route, but it doesn't look like much care was probably given to copying the electrical values and geometries of the original. A lot of Chinese manufactures are doing the same sort of thing, using a PAF or P-90 footprint to cheaply and superficially replicate the facade of vintage pickup designs, which would otherwise be expensive to produce. 

[Greg Holmberg]

May 25, 2021 5:19:09 GMT -5 gckelloch said:

I think the originals used 38AWG wire, so the 5H measurement at the low DCR with the Steel blade makes sense. ~10% higher than the Lollar stated DCR could be partially from the temperature at which it was measured. I think the CC pickup thing is more about fashion and hype than anything tonally desirable about the pickup, but I appreciate the work done here. There are other SC pickups I'd use for jazz b4 a CC -- a Wilde Nd-Microcoil probably being my first choice, if not a maybe a low inductance L609 or L610. Whyddaya need a blade pickup for jazz anyway? Bending notes is sacrilege. A properly configured Q-filter will sweeten the midrange of any pickup -- the mid-dip starting from 600Hz~1.6kHz (depending on preference). A mid-dip centered in the 3-3.5kHz range strikes me as essentially jazzy.

Yes, the temperature in my shop was fairly cool--around 67°F  = 19.4°C.

Unfortunately, I don't have an LCR meter.  I'm thinking about getting this Hantek one, $183.

Is this the line of pickups you're referring to?  Micro-Coil T  I couldn't find any products on their website mentioning Neodymium.  Also couldn't find any products there called L609 or L610.

Greg

[gckelloch]

May 25, 2021 12:59:17 GMT -5 Greg Holmberg said:

May 25, 2021 5:19:09 GMT -5 gckelloch said:

I think the originals used 38AWG wire, so the 5H measurement at the low DCR with the Steel blade makes sense. ~10% higher than the Lollar stated DCR could be partially from the temperature at which it was measured. I think the CC pickup thing is more about fashion and hype than anything tonally desirable about the pickup, but I appreciate the work done here. There are other SC pickups I'd use for jazz b4 a CC -- a Wilde Nd-Microcoil probably being my first choice, if not a maybe a low inductance L609 or L610. Whyddaya need a blade pickup for jazz anyway? Bending notes is sacrilege. A properly configured Q-filter will sweeten the midrange of any pickup -- the mid-dip starting from 600Hz~1.6kHz (depending on preference). A mid-dip centered in the 3-3.5kHz range strikes me as essentially jazzy.

Yes, the temperature in my shop was fairly cool--around 67°F  = 19.4°C.

Unfortunately, I don't have an LCR meter.  I'm thinking about getting this Hantek one, $183.

Is this the line of pickups you're referring to?  Micro-Coil T  I couldn't find any products on their website mentioning Neodymium.  Also couldn't find any products there called L609 or L610.

Greg

The L609 and L61o are no longer being made at present, but Becky or Shanon might accept a special request in the future if you really know what you want. They were ~$60 each, and are a hum-canceling magnetically phase-aligned design like the NF series. The wider coil does reduce upper harmonics a little, making them like a more clear P90, also offered in lower instance levels. I think the L609 has AlNiCO or Permalloy poles. The L610 may have a "soft" Fe core and screws. I wonder if they could use the same core as the Microcoils?

The Microcoils with the screw poles are Nd-powered with what I think are Permalloy inserts & pole screws and "moderator bar", which increases the efficiency and coil inductance without rolling off the high end as does a "soft" Fe core. I think the inductance is N = 1.8H & B = 2.8H, but they are relatively high output with low string pull. The coils are of 0.044mm (~46AWG gauge) wire and are very small, so the S/N is much higher than typical 42AWG AlNiCO pole SC's by what I estimate at ~1odB. The only issue I found with my older S-type set is that I had to put something sticky in the screw holes for the pole screws to stay snug where I set them. I used slivers of electrical tape, but you could place a thin plastic grocery bag over the holes b4 screwing the screws back in or apply some liquid electrical tape on the screws. They are very punchy and warm with a smooth and extended high end. Raising pole screws increases the upper to lower harmonic ratio for a brighter note timbre, so you can tune them per string and position. I think I know the best way to do that. Let me know if you are interested. Using a Q-Filter with low inductance pickups isn't all that useful because the inductance goes so low that the high-end peak is often above the guitar speaker range, but you can still get some upper mid-dip with the right cap value, and acoustic guitaresk tones if your speaker can deliver 8kHz+. They actually sound really nice into the Hi-Z input of an A/I unit with no processing. Les Paul would have loved them.