Jams Audio

615-383-JAMS ( 5267)

Office Hours
Monday - Friday
10:00 am-5:30 pm CST

Visa - Mastercard
Credit cards processed:


Payment Processing

In response to the outpouring of e-mails and phone calls we have received regarding the re-issue of the PDI-03, the original designer and manufacturer, Martin Schmitz, has graciously agreed to answer your questions.

Now you know everything we do!

Happy Reading!
JAMS Audio www.palmergear.com


Would you tell us a little about yourself?

It all started with a Christmas present - an electronic experiment kit. I was about 13 years old and from that time on I spent most of my pocket money for electronic components. It was the time when “The Beatles” fever broke out in Germany and my interest quickly focused on musical electronics.

During my time at the university I got a side job as a repairman in a music shop. This was the time when I received my “real” education in electronics.

When and where did you start Palmer?

It was in the summer of 1978 when I started a small production of tube amplifiers. January 1981 is when Palmer officially became my brand name. (In Germany, bureaucracy is a big lame duck which cannot be by-passed.)

Very soon after we had started the amplifier production I realized that only by making our own transformers could I get complete control over the sound.

It was a small step from tube transformers to quality microphone and line transformers. The growing public address (P.A.) market in the 80’s created a demand for audio tools we called the DI boxes, signal splitters, isolation boxes and so forth. I turned my focus on these products. In 1989 the amplifier production was ceased. After about 500 amps, the decreasing quality of available tubes at the time had crucified me.

What are you doing now?

I am in charge of the Palmer Products division of Adam Hall GmbH. Today many Palmer products are based on the transformers which we produce here in Germany. Additionally, to stay in touch with the current developments in live sound and recording studio technique, I give classes in electronics at an audio engineering school.


What year did you release the original 03?

I built my first simulator in the seventies to use in my tube amplifier workshop. We used a special unit which we called the “silent speaker” which eliminated the noise in the air when testing our amps fully cranked.

I did not like the load boxes made with resistors. As a repairman I had seen a good number of amps killed by the use of an Altair Power Attenuator (at that time a very popular item). Based on the literature of Thiele/Small I had built a circuit which simulated the impedance behavior of a guitar speaker in a box. This became the load part of the silent speaker. To have an acoustic control I included a filter to simulate the frequency response of the speaker as well and fed the signal into my old stereo. Everybody was happy with it, especially our neighbors.

Home recording had become popular. It was only logical to convert our in-house "silent speaker" into a commercial product. The term "silent speaker" was altered to Speaker Simulator. During the Musikmesse 1989 in Frankfurt (this is the equivalent show to the Winter NAMM in Anaheim) the Speaker Simulator was first displayed at a trade show. It was also in our product flyer 1989/90.

How many versions were there? What were the major differences?

The original unit was only labeled “Speaker Simulator”. Inside is one main pc-board. Potentiometers, sockets and switches are connected with leads to that board. The resistive part of the load comprises 3 aluminum cased resistors on a bent aluminum sheet metal. Though the resistors were rated at 150 watts, the unit got really hot. The sound could be varied with two switches, flat or deep for the low end and mellow, normal and bright for the treble end.

One of the first modifications was to replace the heat sink with an aluminum extrusion and to add one more resistor to make the unit run cooler.

In 1990 all Palmer products got stock numbers. Since we had a passive DI box (PDI-01), an active one (PDI-02), and the Speaker Simulator was a kind of Direct Box it became PDI-03. After October 1990 all units were issued with a serial number. In January 1994 the “battleship grey” housing was replaced with a metallic anthracite color and the silk screen printing was green. Also the metal knobs, a surplus from the amp production, were replaced with plastic types.

The last PDI-03 was made in July 1996. The other electric modifications were marginal. For easier production the potentiometers and sockets were put on auxiliary p-c boards. The switch for the low end response received a third position which is between Flat and Deep. The 1K log taper potentiometers were replaced with 10K linear types and a 1K resistor, because of the large tolerances. The potting boxes of some components have changed due to availability.

But I never ever have changed the filter circuit. It is the original filter design that was used for my workshop model. Since the beginning, we used 5% capacitors and 1% resistors in the filter network.

We've read reviews that say the PDI-09 and PDI-03 have the same filter circuit. Is that true?

Yes. The PDI-09 uses the same highcut-filter circuit as the PDI-03. The PDI-09 is nothing else than a PDI-03 without the load part and the signal splitter feature. The PDI-03 has an extra (switchable) bass boost.

Oh! In the mid 90’s the “Normal” position was made a bit softer, but this is the only sound modification the PDI-09 has ever gotten.

What is the difference between the PDI-03 and PGA-04 filter circuits?

The PGA-04 was my answer to customers asking for more versatility. Though you may read many different comments, the heart of the PGA-04 is the original filter circuit with the two switches replaced thru two potentiometers for a continuous control between the extreme positions of the switches.

The original 03 is surrounded by almost legendary status. We found one on E-Bay today that was selling for $1200. If you can, please explain the mystique surrounding the PDI-03.

I can only guess, but the fact that the PDI-03 was used and praised by some very popular artists and producers, the unavailability in the U.S. for the normal customer, and that Palmer is a small boutique-like company without publicity could be the reason.

We know you are excited about the re-issue of the PDI-03. What prompted you to re-issue it?

There existed a patent for a unit that claimed to do the same job as a PDI-03. Though I never had seen the unit before, this guy threatened me with legal action and defamed me as a thief having stolen his ideas. Ridiculous. Palmer did not infringe upon anyone else's patent--and now the patent has expired. It looks that there is still a demand for a more authentic speaker sound even after all the modeling amps with digital speaker simulation. E-Bay is the confirmation. Shall I wait until I see a knock-off copy from China?

How close to which original is it?

It will be a re-issue of the early 90’s model with the "battleship grey" housing, metal knobs, and of course the improved heat sink.

Is it the exact same technology as the older 03 or is it a new design? How much is it going to cost?

Fortunately we kept all the production paperwork and test charts. And hopefully the fact that the new housing is laser cut instead of punched will not influence the sound. The price will be the same as for the PGA-04.

When do you expect to have it ready for release? What are some of the problems you have had with trying to get it back in production?

Since we had all the production documents I was very optimistic to restart the production very fast. But it turns out that we have had some difficulties in getting our components. Especially the switches which used to be “off the shelf components”. We are now having to get them custom made for us.

Martin, thanks so much for taking this time out of your busy schedule for this interview. Are there any closing comments you would like to add?

Please allow one (very last) comment about the PGA-04 vs. PDI-03 discussion.

The PDI-03 was a very simple to use piece of equipment. You couldn’t go wrong. With the more versatile PGA-04 you can produce some really weird sounds. But this does not mean that -as some people say- the PGA-04 is rubbish.

In case someone is telling you that, please charge him with twice the price for his PDI-03.

Martin. Martin. Martin. You know we can't do that! (Can we???) Thanks so much for a great interview!


Contact Us    ||   Customer Service

Copyright © 2005. JAMS Audio. All Rights Reserved.