Why does no one make a floating DeArmond copy?

[Mike Sulzer]

I would use a three piece bobbin, top, bottom and middle, all made from the same material, and use the glue designed for that type of plastic. You drill six holes in the middle for the magnets to go in before you glue it together. I would use slightly smaller magnets. It will be low impedance/ low voltage output so you put a preamp at the amp end. You can resonate it with a C (much larger than normal) if that is the kind of sound you want. Another option is to use one of those small recording interfaces as a preamp (mic. input or other input as required) and then adjust for any sound you want on your computer and then back out through the interface to the amp.

Kent makes a decent pickup. Unfortunately, I have maybe 3/8" between the string and body, Some of that space would need to be between the surface of the pickup and the string, leaving 1/4 or less (likely less) for the actual pickup itself. The neodymiums I'm using are 1/10" thick and 1/4" in diameter. The total height of the magnet, flatwork, and glue was (and will need to be) somewhere in the vicinity of 3/16", if that much. Apart from getting the right adhesive, another big challenge is winding a coil that slender/short without precision equipment.

[rjb]

Arriving after the party has ended.

I have a 1937 Kalamazoo KG-21 that, unfortunately does not have sufficient space between strings and body to mount any commercially available pickup in (it's about 1/4-3/8" clearance). I've attempted to wind my own, using some very small neodymiums, but I used the wrong adhesive and the structure cracked.

Before it self-destructed, how did you like the pickup? I'm guessing it had a clear, open "hi-fi" sound.

One alternative to DIY might be to find and modify a "less desirable" DeArmond pickup.
From what I've read, many models are basically the same, all about 1/4" high.

I have a Harmony Patrician with about the same clearance as your Kalamazoo, that I've outfitted with a DeArmond Model 40.
Model 40s, designed to be installed on round-hole acoustic guitars, occasionally show up on eBay.
They had 2 mounting tabs that screwed into the guitar face , and an attached cable to a control box with volume and tone controls.

I got mine for free- and, since the control box was missing and the shielded lead cut to a 1" stub, I had no qualms about potting it in beeswax/paraffin, hacking it up and mounting it to a repro pickguard.

My particular Model 40 seems to have been wound "hot". (Rdc=11.3K; all others I've found online range from 7.2K to 9.9K).
I'm not sure if that's the cause of its overwhelming bass output (highs are still clear)- but I had to install 4.7nF in series to prevent it from feeding back on the archtop guitar.

The bobbin was two pieces of credit-card thin PCB board, with the flatwork and magnets held in place (well...for a little while) with cyanoacrylate.

FWIW, the Model 40's coil is wound around a bar magnet (North up) which is glued directly to the enamel-painted steel baseplate. The top flatwork is two pieces of thin black plastic (like that used for flat-top acoustic guitar pickguards) laminated and glued to the magnet.

[Mark Hammer]

Sadly, never got to install it so I don't know how it sounded. Wound another one recently, or at least got most of the way done winding, following some useful advice from David Schwab, only to have to partially unwind to recover a free starting end. I need to get back to it. I had been truly "handwinding" - i.e., ONLY hands and wire involved with no intermediary - this one, a couple hundred turns a night....for as long as my patience could stand. I've managed to live without a pickup on the thing since 1985, I figured I could live without it a few more weeks.

I like your bi-directional tone control. I'm very partial to that arrangement myself, and have it installed in a couple of solid-bodies. I wish I had a center-detente for those pots to make life a little easier, but even without it they work fine.

[David Schwab]

My particular Model 40 seems to have been wound "hot". (Rdc=11.3K; all others I've found online range from 7.2K to 9.9K).
I'm not sure if that's the cause of its overwhelming bass output (highs are still clear)- but I had to install 4.7nF in series to prevent it from feeding back on the archtop guitar.

It's probably just thiner wire. You can't fit much wire on those bobbins.

I'm curious why you have the 1nF cap in parallel with the pickup.

[rjb]

It's probably just thiner wire. You can't fit much wire on those bobbins.

Yea, but I would think DeArmond would use the same thin wire on the same model pickup.

I'm curious why you have the 1nF cap in parallel with the pickup.

Me too. I copied from a G&L S-500 wiring diagram you provided in another thread. It shows a .001uF cap across a "normal" tone circuit.
I figured it was either for RFI or to provide a minimum C load (equivalent to 20ft of old-school 50pF/ft cable) with the tone knob maxed.
Anyways, I convinced myself it made the difference between "ice picky" and "bright".

[David Schwab]

Yea, but I would think DeArmond would use the same thin wire on the same model pickup.

They are notorious for using different gauge wire on the same pickup model.

Me too. I copied from a G&L S-500 wiring diagram you provided in another thread. It shows a .001uF cap across a "normal" tone circuit.
I figured it was either for RFI or to provide a minimum C load (equivalent to 20ft of old-school 50pF/ft cable) with the tone knob maxed.
Anyways, I convinced myself it made the difference between "ice picky" and "bright".

I believe that was a treble bleed cap on the volume control. But if you swapped the volume control position and left the cap on the wrong side of the circuit, that's what you might get. I'd have to go back and look. Most of the control boxes I have seen only had two caps. This was the first one I saw with that 3rd cap.

It would shape the tone of the pickup, but I was wondering if that's why you said the pickup had too much low end. Because you are removing some highs, and then later removing some lows.

[rjb]

I believe that was a treble bleed cap on the volume control. But if you swapped the volume control position and left the cap on the wrong side of the circuit, that's what you might get. I'd have to go back and look. Most of the control boxes I have seen only had two caps. This was the first one I saw with that 3rd cap.

The G&L has a treble bleed (which I don't have), but it also has a .001uF cap (C3) across the tone circuit.
I used what Mark calls a "bi-directional" tone control, but also have .001uF across the tone circuit.

It would shape the tone of the pickup, but I was wondering if that's why you said the pickup had too much low end. Because you are removing some highs, and then later removing some lows.

I've tried the tone control in middle position both with & without the 1nF cap; the difference is noticeable but not huge. With the cap, the high end is a bit less piercing.

For low end rolloff, I originally had a 1.5nF cap across the "rhythm switch", with no other series cap.

With the switch closed ("normal" or "lead" position), I got farty distortion when playing in the bottom octave of the guitar through three different (solid state) amps with clean settings. Also, the guitar was prone to howling feedback, which would die away and cease when I switched to "rhythm" position.

I then tried running through an ART Tube MP Studio preamp into a powered PA speaker. Watching the VU meter while flipping from "rhythm" to "normal", the "normal" position sounded WAY louder than the "rhythm" position, and the needle leapt from ~0% (but audible) to "pegged".

Through trial & error, I found that 4.7nF in series rolls off the bass enough so the pickup sounds well-balanced to my ear, while preventing farts and feedback. Also, the volume difference between the "lead" and the thinner "rhythm" tones is now much more reasonable.

For reference, here are DeArmond Rhythm Chief control box and G&L S-500 wiring diagrams.

[David Schwab]

The G&L has a treble bleed (which I don't have), but it also has a .001uF cap (C3) across the tone circuit.

That's a bass control. I mean one of these:

[David Schwab]

Here's the wiring of the Rhythm Chief control box I had here recently (excuse the sloppy hand writing!):

[rjb]

That's a bass control. I mean one of these:

On the G&L wiring diagram, C1 is the bass control cap; C2 is a treble bleed, and C3 is the "WTF" cap in question.
I think.

[David Schwab]

On the G&L wiring diagram, C1 is the bass control cap; isn't C2 a treble bleed?
C3 is the "what is that for?" cap.

Oh I thought you meant the bass control. OK I found the S-500 schematic. Yes, C2 is the treble bleed cap. C3 appears to be removing some high end from those very bright MFD pickups.

[rjb]

Here's the wiring of the Rhythm Chief control box I had here recently (excuse the sloppy hand writing!):

That's similar, but slightly different from photos I've seen on this board. I've never seen one with a treble bleed cap before.
Would you say this schematic matches your sketch?

BTW, I started out with the R.C. wiring shown in post 22, but experimentally found it worked better wired "backwards" - which turns out to be the G&L configuration (more or less).

[rjb]

Oh I thought you meant the bass control. OK I found the S-500 schematic. Yes, C2 is the treble bleed cap. C3 appears to be removing some high end from those very bright MFD pickups.

Now we're on the same page. Same reason for my 1nF cap. Not that the DeArmond pickup is unbearably bright- but I want an archtop to sound like an archtop (not a screaming Strat or something).

Anyways, I'd like to hear from Mark when he gets his "truly hand wound" pickup up and running.

[rjb]

Would you say this schematic matches your sketch?

I noticed a minor, functionally irrelevant mistake (tone pot connections).
Here's an updated schematic.
OK, I think I'm done with hijacking the thread now.

[David Schwab]

Looks good.