David Kronemyer

Transformer-Based Processing Array

January 9th, 2009 by David Kronemyer · 3 Comments

DAVID KRONEMYER: I keep getting asked questions about the transformer-based processing arrays I designed in the mid-1990s, so here’s the information. The line output of most synthesizer modules sounds pretty lame. It might be characterized as “thin” or “weak.” It lacks spatiality and dynamics. In the case of IC or chip-based samplers and romplers (ROM-based player devices) this often is due to lack of integrity in the underlying sample (poor recording technique). Use of inadequate or inexpensive components in the output stage also is a culprit. The first can’t be fixed and the second requires internal modifications. These become increasingly elaborate with the complexity of the device and frequently aren’t worth the effort.

Another problem though is concealed by the nature of line output itself. While it varies with frequency for most synth modules it is around 1K Ω at A = 440 kHz. This level of impedance inhibits the blossoming and florescence of the sound. The outputs also are unbalanced, which is problematic under the best of circumstances. So I speculated what would happen if the impedance was stepped down to around 50 Ω, which is about the output impedance of a typical microphone. It then would be possible to use a mic pre to bring the sound back up to line level for injection into whatever recording media one was using.

Jensen Transformers makes a transformer that does just this, which is the JT-DB-E. Many eschew transformers on the grounds they undesirably interfere with the sound. They must be listening to inferior makes and models because the Jensen Transformers flawlessly accomplish their assigned tasks and additionally enhance the overall sonic presentation. I hypothesized it would be possible to design a simple circuit and array the transformers in a way that would facilitate the accomplishment of this objective.

The studio where I did most of the records I produced acquired a large quantity of the JT-DB-E transformer – approximately 96 channels if I recall correctly. I then went to work on interconnections and here is the result:

By way of explanation the inputs and outputs both are on ELCO/EDAC 90-pin connectors. The sound comes out of the modules on ¼” unbalanced connectors, which then go to an ELCO on the back of the rack where they are situated. Those outputs are cabled over to the transformer inputs; processed through the transformers; then routed to the inputs of a separate rack of mic preamps. From the mic preamps the sound then goes directly to the tape inputs (by-passing the console, which was used only for monitoring and mixing).

This particular studio conveniently had a large quantity of outboard mic preamps, facilitating this outcome. It would of course be possible to route the output of the transformers into the console’s mic pres or (more contemporarily) into the inputs of an A/D converter for routing to one’s preferred digital media. In such event the results would depend significantly on the circuit and component quality of each of those electronic intermediaries. With Apogee converters into Logic the outcome is as good as one would get to 2” Ampex 456 tape at 30 i/p/s with Dolby SR, which was my preferred recording combination.

We discovered these steps significantly improved the quality of the overall sound. In fact it improved it so much that we became somewhat known throughout the industry for the superb sound we were able to extract from otherwise poorly-performing samplers and other ROM-based devices. People constantly were asking what kind of secret devices we were deploying to achieve these results.

In addition to the mundane step of balancing the line output this technique also enabled one to pick up the mellifluous tonality and sonorous timbre of whatever mic pre one was utilizing. We experimented with a wide variety of mic pre combinations with various modules. Neve 1272s and GMLs typically emphasized higher frequencies and had a lot more “sizzle” around 10 kHz. API 512s typically supplied mid-range boost around 2.5 kHz. Others such as the John Hardy M-1 excelled across the entire frequency range. I could go on and on about these and similar nuances, which needless to say were dependent on a variety of other factors including monitor positioning and room acoustics. We did the best we could (and if I say so, succeeded) in controlling for these variables.

Thanks to Jensen Transformers, Bill Whitlock and Dave Hill for these amazing devices.