When the far east meets the west coast

Here is a short review of the amazing Model 158 with NOS transistors crafted by Tokyo Tape Music Center Tokyo Tape Music Center (TTMC) from Japan. I do not want to keep back that Buchla recently announced the official recreation of the Buchla 100 Series under the brand Red Panel.

Tokyo Tape Music Center Model 158

As far as I know the new Red Panel designs are based on SMD production and a very careful replacement of old transistor types. However, if you are hunting a hand build through-hole design with NOS parts, which is compatible to Eurorack, TTMC might be an interesting option.

Some very brief history about the Model 158

The TTMC module is a Buchla inspired Eurorack clone of the Model 158, the first voltage controlled oscillator made by Don Buchla back in the 60ties. Due to its age it is a discrete design based on transistors. The original design from the Buchla 100 Series is legendary and celebrates it debut in the famous early electronic composition Silver Apples of the Moon by the well-known American composer Morton Subotnick from the San Francisco Tape Music Center.

The Model 158 layout

The layout of the Model 158 itself is quite puristic from a today’s perspective. It’s quite simple a dual oscillator with frequency potentiometer at the bottom.  The switch chooses between the internal frequency (set by the big knob) and the1.2V/Oct control voltage input.  The shape potentiometer crossfades between sine and saw (no CV option here). Finally, there is an AC coupled modulation input with an attenuator (i.e. DC voltages slew to zero).

Front and back showing NOS parts

The Tokyo Tape Music Center design

The reviewed version is the Model 158 V2 with NOS transistors (IT122, 2N4339, 2N5020) and upgrade of capacitors. Some details regarding the transistors can be found on
https://ebolatone.blogspot.com/2012/12/buchla-158a-pcb-build.html
TTMC also adds a second internal/external switch, which is very helpful to save resources in a small system because enabling the external control requires mixing and offsets of CV, which is typically realized with the Voltage Processor (Model 156). TTMC was very helpful and now offers white panels. The panels are made from PCB material. The dark panel has a rough surface and the white one has a very plain structure.

Dark and white panels

Some further technical specifications

The frequency response goes approximately from 5Hz to 10kHz. The tracking is the Buchla typically 1.2v/Oct in contrast to 1V/Oct tracking in the Euroland.  Actually I didn’t test the calibration. I do not care about tonal tracking that much. The 100 system is based on frequency modulation and in exponential FM the principal tune depends on the modulator. The output level depends on the shape and frequency (3.2v to 3.8v Vpp). In contrast to the original design, the TTMC output is compatible to Eurorack levels. It also pairs very well with the Catalyst Audio recreation of the 100 System (with activated op-amp buffering) and probably to the new re-branded Red Panel versions.

How does is sound?

In short: lovely and amazing! It easily does the full picture from pure and raw to very complex overtones. Chaotic patterns are also possible with a twist of a knob.

Sine wave of the NOS version

Saw wave of the NOS version

The sine is clean and pure compared to the conventional version without the NOS replacement. The example shows the frequency range, cross-fading between sine and saw, FM modulation with 50% and 100% depth and bunch frequency cross-modulation. The latter ones show the unstable nature of the discrete core. The evolving patterns were recorded without touching the knobs at all!

 

Acknowledgment

Many thanks again to Kurosaki, who is the awesome person behind Tokyo Tape Music Center!