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Radial Space Heater 500  From Radial

500-series version of the Radial Space Heater tube drive.

Radial Engineering


Retail:  $800.00

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Manufacturer's Description from Radial

  • Studio grade 12AX7 tube overdrive
  • 35, 70 & 140 volt Heat switch to set plate B+ voltage
  • Transformer coupled output for vintage tone
  • Variable HPF & LPF filters to focus distortion

The Radial Space Heater 500™ is a studio-grade tube distortion for the 500 series format. Built to provide anything from subtle warmth to thick and heavy harmonic distortion, the Space Heater 500 is both useful and fun!

Designed for use in the Radial Workhorse or any other 500 series rack, the Space Heater is built around a 12AX7 tube. First, a drive control lets you determine the amount of signal passing through the tube. Next, a 3-position heat switch allows you to apply 35, 70 or 140 volts at the plate to change how the tube reacts to the signal. At the low 35V setting the tube is starved for voltage which causes the tube to break up at a very low volume. The middle 70V setting is a great starting point and allows the tube to handle more level before breaking up to a moderate distortion. At 140 volts, maximum voltage is applied to the tube producing slight saturation and warmth. Sweepable high-pass and low-pass filters can be assigned 'pre or post' tube, allowing you to focus the tube effect on a particular frequency band or cause the tube to react in a different way. Finally, an output level control provides attenuation or boost through an oversized Jensen transformer specially selected for its big bottom end and vintage character.

Enhancing a snare with a touch of distortion can increase presence without losing dynamic range. Blending in some overdrive to a bass track can add clarity without overpowering. Adding distortion to a vocal track can add character and sizzle to cut through the mix without over-compression. The Space Heater 500's amazing 'adjustability' allows it to be used as a subtle effect or as a high gain monster. And no matter your approach, it is sure to find its way on nearly everything you record!

The Space Heater 500… to infinity and beyond!

Radial Engineering

About Manufacturer

Radial Engineering is a manufacturer and distributor of professional audio equipment, building tools for the working audio and audio-video professional. Radial is located on the Fraser River, just outside Vancouver, British Columbia in the municipality of Port Coquitlam. The company began operations in the fall of 1991 as the Canadian distributor of Mogami cable and Jensen Audio Transformers. In 1992, it became a limited corporation under the JP Cabletek Electronics Ltd. banner. The Radial name was first used on house branded cables and snake systems. The Radial name and logo represents a cross section of quad cable; Radial being round. In 1996 the Radial JDI direct box was launched. This led the way to the Radial JDV and today, over 50 electronic products are now being produced under the Radial, Tonebone and Forest Audio brands. In 2001, the Primacoustic brand was launched to address the growing demand for acoustic products for the burgeoning home recording market and in 2006, the company officially changed its name to Radial Engineering Ltd.



  • Circuit type:   Thermionic Gain stage with solid state input and output buffers
  • Frequency response:   20Hz - 20KHz ± 1dB
  • Total harmonic distortion:   Varies with Drive and Level settings
  • Dynamic range:   92dB
  • Input impedance – bypassed:   50K
  • Input impedance – active:   1M
  • Maximum input:   +20dBu
  • Maximum gain:   32dB@140V, 27dB @70V, 13dB @35V
  • Clip level - output:   +22dBu 
  • Output impedance:   100Ω 
  • Equivalent input noise:   -102dBu 
  • Noise floor:   -70dBu 
  • Intermodulation distortion:   Varies with drive and level settings 
  • Common mode rejection ratio:   -60dB
  • Unity gain control position:   Drive & level at about 11 o'clock



  • Controls:   Drive, Level, Hi-Cut filter, Lo-Cut filter
  • Switches: "Heat", EQ Pre/Post, IN 
  • Switches - rear panel:   Heater polarity selection
  • Filter slopes:   12dB/Octave 
  • Omniport function:   Unbalanced instrument input



  • Construction:   500 Series module
  • Finish:   Durable powder coat
  • Size:    (W x H x L) 5.3" x 1.6" x 6.7" (134mm x 40mm x 170mm)
  • Weight:   1.55lb
  • Shipping size:    (W x H x L) 6.7" x 1.9" x 9.1" ( 170mm x 48mm x 231mm)
  • Shipping weight:   2lb





Space Heater 500 User Manual

User Manual