Space Heater™ Development

Every once in a while you plug into a device and you are stunned with a jaw-dropping experience. The first time we plugged into the Space Heater™, we were rewarded with one of those rare occasions. This page describes the development and how we came to select the feature set.

Several years ago we began looking at the various summing mixers that were on the market, trying to figure out what was special and what these devices brought to the 'recording table'. Back then there was a lot of discussion on the various chat sites where some engineers preferred to mix in-the-box, while others preferred the out-of-box experience. Although one could certainly argue for one camp or the other, the difference between the two mix methods seemed to be incremental. In other words, they both worked and could get the job done. In our minds these analog alternatives merely brought some version of a resistive network in line with the signal path. None seemed to deliver excitement.

Back in 2009 we developed a prototype for a preamp that cleverly utilized a 12AX7 in stereo. During product development sessions, the concept was resurrected as a summing mixer. Radial president Peter Janis explains: "We had the idea of applying the same trick we use in our Tonebone pedals of reducing the voltage to starve the tube so that more harmonic overtones could be generated. We also felt the Space Heater should offer plenty of headroom to enable ultra-clean summing with just a touch of tube character. To this end, we employed the same type of high-voltage power supply that is in our highly acclaimed 500 series PowerTube™ preamp and we got to work. Once the basic circuit was developed, four variations were produced so that we could listen and compare."

The decision was made to offer three voltage settings: A low 37 volt setting starves the tube to create more distortion while the higher 150 volt setting cleans it up. By adding an input drive and a variable output level control on each channel, the user can set the degree of distortion to suit. A variety of input and output connections were then added so that the Space Heater could be inserted in series to warm tracks, used as a summing mixer, or maybe add more to the creative process by enabling the engineer to insert EQs and dynamics after the tube and transformer when summing.

Peter Janis continues: "We then went through the process of deciding what kind of transformer should be used in the signal path. Smaller output transformers saturate more quickly while larger ones deliver more bass and headroom. To test, we incorporated two footprints on the prototypes and then did a bunch of listening. In the end, we felt that since the Space Heater will likely be used on both drums and bass, having a bigger more robust bottom end would be best. So when you look inside, you will see eight oversized transformers just waiting to be beat up!"

Today's studios and live touring racks need to be compact and mobile. To fit the footprint, the decision was made early on to make the Space Heater a compact, single-space device. With limited front and rear panel space, selecting the feature set comes down to compromise. For instance, combining the stereo Mix Bus output with the headphone out provides sufficient monitoring facilities while eliminating a bunch of redundant switches.

Peter Janis goes deeper: "During a festival concert last summer, we had the pleasure of discussing the use of distortion for in-ear monitors with Joe Nichols' monitor engineer and how distortion can act just like a compressor without some of the unpleasant artifacts. The primary complaint was a lack of natural sustain, particularly with bass guitar. If you think about it, distortion in communication systems has been around for some time; most commonly heard with CB radios when the input exceeds the available amplitude which causes the diode to distort like a fuzz box. We then contacted a number of artists and engineers and discovered that many had been experimenting with distortion, yet no one had come up with a practical solution. We thought that we could actually use this studio distortion unit 'live' for this very unique application. Finally, we had a discussion with Tape Op's Review Editor Andy Hong about the Space Heater and he mentioned the importance of having extra high-pass filters. So we jammed some of these in for good measure, added a bunch of connectors and ended up with one of the most sought after products we have ever announced.