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Those skinny hex synth pickups

5/4/2006 9:50 AM
Mark Hammer	Those skinny hex synth pickups I realize most folks are interested in the sound pickups provide as pickups, but once in a while pickups are just "note sensing devices". Like with synths. Looking over the schematics for the onboard electronics of a variety of 80's guitar synths this morning (Ibanez, Roland, Korg, etc.), I realized those little skinny hex pickups by the bridge likely had some unusual characteristics. First, virtually all these pickup sections were fed directly to non-inverting op-amp stages with input resistors from the inverting input to ground that never exceeded 4.7k. Second, many units permitted the gain of those input stages to be set as high as x681. Naturally, for the inquisitive type like myself, I find that intriguing. Does anyone have any info on the specs/parameters of these hex pickups? Not the bigger ones like those from Bartolini that are intended to be used AS pickups, but the skinny ones you install between your bridge pickup and bridge. Based on the accompanying electronics, it would seem that: a) those individual sections are very low impedance, and b) string to string variation in output level can be huge (a gain adjustment range of 146-681, or 6.8-34 suggests that to be the case).

5/4/2006 9:50 AM

Mark Hammer

Those skinny hex synth pickups

I realize most folks are interested in the sound pickups provide as pickups, but once in a while pickups are just "note sensing devices". Like with synths.

Looking over the schematics for the onboard electronics of a variety of 80's guitar synths this morning (Ibanez, Roland, Korg, etc.), I realized those little skinny hex pickups by the bridge likely had some unusual characteristics. First, virtually all these pickup sections were fed directly to non-inverting op-amp stages with input resistors from the inverting input to ground that never exceeded 4.7k. Second, many units permitted the gain of those input stages to be set as high as x681.

Naturally, for the inquisitive type like myself, I find that intriguing. Does anyone have any info on the specs/parameters of these hex pickups? Not the bigger ones like those from Bartolini that are intended to be used AS pickups, but the skinny ones you install between your bridge pickup and bridge.

Based on the accompanying electronics, it would seem that: a) those individual sections are very low impedance, and b) string to string variation in output level can be huge (a gain adjustment range of 146-681, or 6.8-34 suggests that to be the case).

5/5/2006 2:10 AM
Andrew C	If anyone knows all the answers to Mark's questions, I am in contact with a major Asian musical instrument maker who would like to introduce midi trigger systems to their gutiars. They would like to hear from you. Contact me. EE's only. Regards, Andrew

5/5/2006 7:38 AM
Mark Hammer	Just to maybe save you some labour, Andrew, note that it is cheap and easy to purchase/make individual piezo saddles for Strat-type bridges (and their cousins) these days. I still haven't installed the ones I bought last year so I can't talk from personal experience, but my hunch is that they provide better string-to-string separation than polepieces might. It is the prevention of "leakage" from adjacent strings that has been one of the chief problems in making guitars MIDI-compatible. The low-output "skinny" pickups that snuggle up against the bridge are relatively insensitive to string signal from next door and are situated where the strings are least likely to wiggle enough to be sensed by the next coil/polepiece over. However, separate piezo sensors per string present another way of keeping a 6-string signal as reliably divided as possible.

5/5/2006 7:38 AM

Mark Hammer

Just to maybe save you some labour, Andrew, note that it is cheap and easy to purchase/make individual piezo saddles for Strat-type bridges (and their cousins) these days. I still haven't installed the ones I bought last year so I can't talk from personal experience, but my hunch is that they provide better string-to-string separation than polepieces might.

It is the prevention of "leakage" from adjacent strings that has been one of the chief problems in making guitars MIDI-compatible. The low-output "skinny" pickups that snuggle up against the bridge are relatively insensitive to string signal from next door and are situated where the strings are least likely to wiggle enough to be sensed by the next coil/polepiece over. However, separate piezo sensors per string present another way of keeping a 6-string signal as reliably divided as possible.

5/5/2006 9:32 AM
Lukas	piezo saddles works very good and you need not any visible guitar modifications you may use graphtech ghost saddles, many types, they can be used both piezo/midi, and they are string savers too

5/5/2006 7:49 AM

David Schwab

quote:
"Based on the accompanying electronics, it would seem that: a) those individual sections are very low impedance, and b) string to string variation in output level can be huge (a gain adjustment range of 146-681, or 6.8-34 suggests that to be the case)."

Well they are low impedance pickups. I'd imagine they maybe have a couple of hundred turns of wire on them.

I've made polyphonic pickups like this. I used very thin poles with a small magnet under them. Each coil had its own output and preamp stage. I had made it for a custom lucite guitar I made and to trigger an old ARP Avatar guitar synth I owned. It was a thin pickup similar to the Roland units.

It's not a difficult thing to do.

Bartolini did separate coils for a different reason. As an added bonus you could use his hex pickups to drive a synth, but that wasn't the main reason he did it.

5/5/2006 2:14 PM
Mark Hammer	"Bartolini did separate coils for a different reason. As an added bonus you could use his hex pickups to drive a synth, but that wasn't the main reason he did it." Understood, which was why I separated them. I gather the intent there was for things like every-other-string stereo outputs, similar to the Ripley. I have an old Guild unit from somewhere in the late 60's or early 70's that employed a proprietary hex pickup to drive 6 octave dividers. The footprint is about the same size as a P-90, with a height similar to those old goil foil Silvertone/Harmony pickups, and it looks to be epoxy potted. Terrible. Simply terrible. The large size obliges it to be too far out from the bridge. Unless you installed it on a guitar with no bridge pickup, you would be obliged to add it between neck and bridge pickup on most instruments, where there would be so much string-to-string bleedthrough that tracking was impossible unless you used heavy gauge flatwound, a thin pick and strummed lightly. Are the magnets on these things strogn for their size, or is the intent to have them be deliberately weak pickups?

5/5/2006 2:14 PM

Mark Hammer

"Bartolini did separate coils for a different reason. As an added bonus you could use his hex pickups to drive a synth, but that wasn't the main reason he did it."

Understood, which was why I separated them. I gather the intent there was for things like every-other-string stereo outputs, similar to the Ripley.

I have an old Guild unit from somewhere in the late 60's or early 70's that employed a proprietary hex pickup to drive 6 octave dividers. The footprint is about the same size as a P-90, with a height similar to those old goil foil Silvertone/Harmony pickups, and it looks to be epoxy potted. Terrible. Simply terrible. The large size obliges it to be too far out from the bridge. Unless you installed it on a guitar with no bridge pickup, you would be obliged to add it between neck and bridge pickup on most instruments, where there would be so much string-to-string bleedthrough that tracking was impossible unless you used heavy gauge flatwound, a thin pick and strummed lightly.

Are the magnets on these things strogn for their size, or is the intent to have them be deliberately weak pickups?

5/7/2006 8:18 AM
David Schwab	[QUOTE]"Bartolini did separate coils for a different reason. As an added bonus you could use his hex pickups to drive a synth, but that wasn't the main reason he did it." Understood, which was why I separated them. I gather the intent there was for things like every-other-string stereo outputs, similar to the Ripley.[/QUOTE] I forgot all about the Ripley! I had a Vox Phantom XII with three split pickups wired in stereo, so you could assign each half of the pickup to the L or R output. Actually from reading the patents, Bartolini used separate coils as part of his unique magnet circuit and because smaller coils have less inductance than one larger coil. It was mainly just to improve the sound. I never heard of the Guild unit. Sounds interesting.

5/7/2006 8:18 AM

David Schwab

[QUOTE]"Bartolini did separate coils for a different reason. As an added bonus you could use his hex pickups to drive a synth, but that wasn't the main reason he did it."

Understood, which was why I separated them. I gather the intent there was for things like every-other-string stereo outputs, similar to the Ripley.[/QUOTE]

I forgot all about the Ripley!

I had a Vox Phantom XII with three split pickups wired in stereo, so you could assign each half of the pickup to the L or R output.

Actually from reading the patents, Bartolini used separate coils as part of his unique magnet circuit and because smaller coils have less inductance than one larger coil.

It was mainly just to improve the sound.

I never heard of the Guild unit. Sounds interesting.

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