Radial Engineering’s Space Heater 500 tube overdrive module for its Workhorse and other 500-Series processor racks.

The design uses a single 500 series module steel enclosure. This not only protects the electronics but also helps prevent outside radiation from causing noise, or from the Space Heater 500 creating buzz, due to the high voltage required by its 12AX7 tube.

A three-position Heat switch enables 35V, 70V or 140V operation to be selected for the desired level of tube distortion. Distortion is further adjusted using the combination of a drive control plus a level for make-up gain. The plate voltage is generated by an internal charge pump while the Workhorse or 500 series 16V supply provides the 12AX7 tube the 12V needed for the heater. A Jensen transformer is employed at the output to bring a more vintage character to the signal path while benefiting from galvanic isolation to reduce hum and buzz caused by ground loops.

To further refine the sonic response, the Space Heater 500 is equipped with both high-pass and low-pass filters. These allow the engineer to focus the tube effect on a particular frequency band or spread it out as needed. The EQ can also be applied to the signal path either pre or post tube for even greater tonal flexibility.

As the Space Heater 500 employs a high-voltage tube circuit with a current draw of 235mA, a special power allocation switch adjacent to the card edge connector is available to balance the draw for use with most 500-Series racks.

‘When we launched the eight channel Space Heater, it became immediately apparent that we had to make a module for our 500 series customer base,’ says Radial’s Jay Porter. ‘The Space Heater sounds huge and brings so much excitement to production it will likely become one of those tools that you use each and every time you lay down a track.’

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