Diaphragm-pickup from the old ampeg baby bass

[mafguitars]

Hi, everybody,
I,m working to build a "Salsa-bass", half-size/ full-scale like Ramirez build them.
I have allready wound some guitar and bass-pups, with fine results, but i never heard of a 'diaphragm-pick-up' wich are used on those perticular basses...
Does anyone know something about these pups ?
For as far i know they are placed under a pair of metal discs under the two feet of the bridge and the sound should be "sloppy" (wanted for salsa)
Any body who can tell me more about these pups should be very helpfull .
regards to all, Marcel

[jonson]

ampeg pickup patent

I think you will find that 3244791 is the patent of the one you are looking for but if you just want to browse other diaphragm pickups try these and there are still plenty of others in the same vein.
4061934
3538232
3725561
3600496
4450744
5461193
5925839.
Good hunting.

[David King]

I have a diaphragm pickup sitting in a plastic bag, I have no idea what it came off of but I think it was a bass pickup at some point in it's past. I'll dig it out and post some pics.

[David Schwab]

Didn't they use one of those on the Ampeg Scroll bass also?

[bbsailor]

David,

As teenager, tinkering with electronics, magnets, coils and guitar pickups, I met up with a custom guitar maker in Newark, NJ (Down Neck Section, Esther St) named Steve Blozen who initially made Yugoslovian stringed folk instruments in about the 1960s. He expanded to making guitars as the market for his folk instruments was rather limited once everyone in the performing folk group had one.

I was building my first laptop guitar when I met his son, who was looking for electronic paths for his father's first electric guitars, at Lafayette Electronics on Central Ave (I believe?). There was also a near by auto paint store where he purchased all the auto paint lacquer that were used to spray all his guitar bodies. Candle apple red with a black trim was a favorite and that was also used on the Ampeg Devil Bass.

I met Mike Roman, the inventor of the Devil Bass, at Steve's house/shop when I first saw the Devil Bass prototype. It was neck heavy with the long neck, scrolled head with heavy bass machine heads. I suggested to Mike that the horns may need to be extended to keep the beast balanced once you let go of the neck. I even showed him that if he extended the top horn by about 6", the bass would balance better. I recall being blown off by my balance observation as if he was saying, "What the hell does this kid know".

The Ampeg Baby Bass was introduced and popular with jazz/standards players as being something that is more portable and with a clean-sounding Ampeg amp, could get a respectable sound even using non-metalic gut strings. Here is where the hidden disk pickup comes into play.

Mike incorporated Jess Oliver's (Ampeg's then Vice President, real name Oliver Jessup) patent of the Baby Bass pickup into his Devil Bass design. I was too young to recognize the politics of all of this at that time. The prototype Baby Bass emerged as a candy apple red version with black hand sprayed overlay accents that was different from instrument to instrument, some with more or less black overlay, depending on the mood of the spray operator.

One summer, soon after obtaining my driving license, so I must have been about 17, I met Jess Oliver through Steve and Mike Roman who offered me a job at Ampeg in the Lindon, NJ factory. I worked the amp final assembly line which was near a factory entrance door to the Ampeg offices and could easily hear Everett Hull, the Ampeg President, and Jess Oliver jamming with visitors in their offices with Everett playing his popular Baby Bass. Mike Roman was working on his prototypes trying to get people to try using his new Devil Bass. Eventually I saw a Devil Bass prototype sitting next to a Baby Bass in Everett's office.

The big thing they were pushing about the Devil Bass was that it did not need to use metal strings, just like the Baby Bass, as the bridge was sitting on two metal disks. The authentic, amplified sound of an acoustic bass was still their priority. Each disk was mounted over a coil of 12,000 turns each of AWG 42 wire wound in series opposing with a N and S .25" diameter X 1" long magnet, wired like a series-connected humbucking pickup. These 12,000-turn coils were very good hum detectors if not set up as humbuckers.

Steve was building a metal string bass guitar and wanted some pickups for it. I took 4 Baby Bass coils, put them in custom made plastic pickup housing with two rows of two coils, staggered to fit under the strings and wired two series sets in parallel to keep the hum bucking effect. Later, I added miniature volume controls right in the pickup housing to adjust the volume of each pickup. The output was high enough that using series resistors to mix the individual string outputs worked pretty well.

I was very happy doing the final assembly on the amps that one Summer. I got to play with different models and see how the whole amp was constructed; assembly line chassis soldering, the wood shop to make the cabinets, the Tolex covering room, and then me, putting the final touches on a completed amplifier.

One day, while looking into the open chassis of a reverb and tremo-equipped amplifier, I was fasinated by a flashing light that I later found out, by looking at the schematic, was the low-frequency oscillator that works with a photocell creating the pulsating volume effect known as tremolo. I took an allegator test lead and placed it from the photocell output and attached it to the reverb output and suddenly now the reverb was pulsating. I walked into Jess Oliver's office after work and said: "I have something to show you". He walked with me back to my assembly station near the offices, and I showed him how the tremolo is now on the reverb sound. He was impressed and that is how the reverb repeat feature was added to later Ampegs amplifier models. As a kid, it was a nice feeling being listened to! What did I know about Patents?


Ampeg got their reputation for making guitar and bass amps that were extensions of high fidelity amplifiers with a clean sound. They catered to the traditional players still using gut bass strings. I do not recall any players other than Jazz or standards players making music out of the front offices when I was there one Summer. It took a while for Ampeg management to recognize that some people liked loud amplifiers with even-harmonic-distortion that amplifiers like Fender etc. add to the sound.

It was at Ampeg, with their Burns Guitars, that I got introduced to low impedance guitar pickups and the wide variety of sounds they can produce.

Joseph Rogowski

[David Schwab]

Thanks for the bit of history Joseph. I actually worked in the same "industrial park" that Ampeg used to be located in Linden. I remembered that from reading the address on my 60's B-15N Portaflex amp's schematic.

Yeah rock guitarist never liked Ampegs because they were so clean, since Hull disliked loud rock music. I'm always amused reading the tube amp section here where people are fixing old Ampeg guitar amps!

I had an Oliver bass head once. That had a nice tone.

[bbsailor]

Thanks for the bit of history Joseph. I actually worked in the same "industrial park" that Ampeg used to be located in Linden. I remembered that from reading the address on my 60's B-15N Portaflex amp's schematic.

Yeah rock guitarist never liked Ampegs because they were so clean, since Hull disliked loud rock music. I'm always amused reading the tube amp section here where people are fixing old Ampeg guitar amps!

I had an Oliver bass head once. That had a nice tone.

David,

I think it was Blankie Street in that industrial park.

When Jess Oliver left Ampeg, he went into his own sound manufacturing business. He designed Oliver Sound Projectors that were actually elevated (on a tripod) using high efficiency 8" cone speakers in a fancy horn load enclosure mounted high to be more efficient.

The Oliver amp was a real excersion into unnecessary but interesting engineering. He used the retractable AC cord reel from a vacuum cleaner to retract the power cord. He also had a version of the Ampeg Portaflex but the Oliver amp had a motor to automatically raise the amp up out of the cabinet. The spacing of the power transformer and output transformer has to be wide enough apart to allow the speaker magnet to fit between them when the amp was lowered into the speaker cabinet. The tubes fit on the chassis in the space between the back of the speaker magnet and the rear of the enclosure.

The Oliver Amps were still of the high fidelity vintage.

Here is one edited additional thought. If people want to push the Ampeg clean amps onto musical distortion, all they need to do is to push the front end tube gain up inside the amp or outside the amp by using a preamp to overdrive the front end. Clean amps can sound musically dirty when pushed harder!

Joseph Rogowski

[David Schwab]

Yes, Blancke Street! I couldn't remember the name. It was one of the Edward Cantor industrial parks, right off of Stiles St.

My wife and I actually drove through that area a couple of weeks ago. It's been 20+ years so it was all very fuzzy.

I remember that Oliver amp with the motorized lift.

[mafguitars]

Thank a lot . this is real information, you wrote; The big thing they were pushing about the Devil Bass was that it did not need to use metal strings, just like the Baby Bass, as the bridge was sitting on two metal disks. The authentic, amplified sound of an acoustic bass was still their priority. Each disk was mounted over a coil of 12,000 turns each of AWG 42 wire wound in series opposing with a N and S .25" diameter X 1" long magnet, wired like a series-connected humbucking pickup. These 12,000-turn coils were very good hum detectors if not set up as humbuckers.

this is information i needed, i intended to try a cheap precision pup wit metal plates upon, but now i changed mind, but i wonder, does it need a foam layer between the coil and the disc ? for the movement or the FAT-tone ?
thanks anyway, this information is very welcome !
regards, Marcel

[Dave Kerr]

Here is one edited additional thought. If people want to push the Ampeg clean amps onto musical distortion, all they need to do is to push the front end tube gain up inside the amp or outside the amp by using a preamp to overdrive the front end. Clean amps can sound musically dirty when pushed harder!

Joseph Rogowski

A few years ago a relative gifted my son an Ampeg M-15 that he found curbside with a blown power transformer. Fliptops farmed it out for a custom rewind for around $125 and it's now his primary amp used for recording - he loves it with a Tubescreamer driving it.

[bbsailor]

A few years ago a relative gifted my son an Ampeg M-15 that he found curbside with a blown power transformer. Fliptops farmed it out for a custom rewind for around $125 and it's now his primary amp used for recording - he loves it with a Tubescreamer driving it.

Dave,

I picked up an old Gemini GV-22 with a single 15" speaker and 2 6L6 output tubes, reverb and tremolo for about $25 about 20 years ago. When I took off the back to check out the circuit and wiring, it was a simple fix. It was sort of like a flashback to my teen years working on the final amp assembly line at Ampeg.

I loaned it out to someone and one of the pot shafts was broken even with the end of the pot mounting threads. Those pots are very hard to replace and even find a circuit board mount style, so I am thinking I may just drill a small hole in the center and epoxy a shaft extension and secure it with a #2 self tapping screw.

This amp is a great sounding amp for playing jazz and standards.

The amps of this vintage are designed right out of the tube manuals, not pushing the voltages like Fender does to get more output.

Joseph Rogowski

[52 Bill]

...Those pots are very hard to replace and even find a circuit board mount style, so I am thinking I may just drill a small hole in the center and epoxy a shaft extension and secure it with a #2 self tapping screw.

Rebuild the original pot by replacing the entire broken plastic wiper element with one from another pot. I think those were CTS brand pots and shouldn't be hard to match up with another pot. Just open up the 4 tabs that hold on the cover, swap out the wiper element and replace the cover.

[bbsailor]

Rebuild the original pot by replacing the entire broken plastic wiper element with one from another pot. I think those were CTS brand pots and shouldn't be hard to match up with another pot. Just open up the 4 tabs that hold on the cover, swap out the wiper element and replace the cover.

52 Bill,

Thanks for the tip. I'll give that a try when I open the amp up again.

Joseph Rogowski

[David King]

Marcel,
I dug it out again, I'm really not sure if this is what you had in mind. It was made for upright bass and it's just a dynamic mic from the looks of it.
The Ampeg Scroll basses had pickups that used a fixed coil and a moving magnet that was built under the bridge (it might have been the other way around). The guy who knows as much as anyone is Bruce Johnson of Johnson's extremely strange instruments. He has recreated amore refined pickup in his shop and has some of pictures of the originals in his collection. I'll ask him if he's willing to share.
Meanwhile this is what I have, I can probably pop the front cover off it but I think it will look like any diaphragm mic inside... I'll have to try it out, I think it just bolts through the F-hole and you tilt it to get the best response. I'm curious.

[Bruce Johnson]

Hi guys;

David invited me to join in here since I have many years of experience working on Ampeg Scroll Basses.

It's good to hear your Ampeg memories again, Joseph! We talked about a year ago.

A little more technical info about the diaphragm pickups in Ampegs:

The basic operating principle is simple. The diaphragm is a thin spring steel plate which is mounted over a chamber in the wood structure of the body, sort of like a small drum head. The bridge, or the foot of the bridge, rests in the center of the diaphragm. When you pluck the strings, the diaphragm flexes, approximately along with the motion of the strings.

Under the diaphragm is one or more magnetic coils with magnets in the center, very much like a standard magnetic pickup. As the diaphragm flexes within the magnetic field, it creates the small alternating current in the coil, which goes out to the amp, etc. The diaphragm is just taking the place of what the metal strings themselves do in relation to a standard magnetic pickup.

On the Baby Bass, there were two complete assemblies, one under each foot of the bridge. Each assembly has its own small round diaphragm, a cylindrical coil, and a magnet in the middle. As Joseph said, the two coils are connected in humbucker fashion to reduce hum.

On the horizontal Scroll Basses, including the Devil Basses, it was one assembly. There is a single square diaphragm, about 5" square, that mounts down to a round chamber about 4 1/2" in diameter. Inside that chamber is a cast epoxy assembly with two coils side by side. Each coil is about 2" dia x 3/4" thick with a 5/8" diameter magnet in the center. I don't know the exact count on the factory coils, but it's around 12,000 to 15,000 turns of #42 wire.

As a historical note, this so-called "mystery" pickup on the horizontal Scroll Basses was invented and developed by Dennis Kager, who worked at Ampeg. He did this work from the summer of '65 through the summer of '66, when the AEB-1 and AUB-1 Scroll Basses were put into production and introduced. The Devil Basses were slightly later, introduced in early 1967. Although Mike Roman probably experimented with other variations of the pickup on his prototypes, the production Devil Basses had the exact same pickup system as the production AEB-1 and AUB-1 models.

Back to the original questions, sure, you can make up your own version of a diaphragm pickup. Just be prepared to do some trial and error to get the sound that you want. The important thing to understand about this type of pickup is that the final sound that you get out of it is almost entirely dependent on the mechanical stuff. The magnetic coils really don't have that much to do with it. The diaphragm is a spring, and how you tune that spring will change the tone significantly. The size of the diaphragm, the thickness, the material, the downloading from the bridge, and the clearance to the coils underneath, will be the big factors. The geometry of the coils, number of turns, wire gauge, etc., are relatively unimportant. They just have to be powerful enough to get a reasonable signal level over to the amp.

For example, I've done many, many restorations on Ampegs and quite few come to me missing the original mystery pickup coils. As experiments, I've substituted Seymour Duncan Quarter Pounder Jazz and P-Bass pickup coils down in the chamber in place of the original coil assembly. As long as the mechanics of the diaphragm were the same, I couldn't tell any difference in the sound between the different coils.

On my own Series IV Scroll Basses, I've taken the mystery pickup idea to another level. Instead of the simple steel diaphragm, I've worked out a framework of spring steel rods that controls the motion in three dimensions. I spent about two years messing around with it on a mule instrument to get it tuned out for this bass design. If I took these same components and put them into another design instrument, they'd have to be modified by trial and error to work with that instrument.

I hope this helps! My overall point is that these are mechanical pickups, not electro-magnetic pickups. If you want to make your own, that's where you'll have to do the experimenting.