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Ridge Farm Gas Cooker

2-Channel Tube DI Box By Paul White
Published June 1995

Despite the preponderance of digital technology in the modern recording world, many independent manufacturers continue to produce valve‑based processors for the subjective warmth they add to recordings. Paul White looks at one of the latest, Ridge Farm's new valve DI box.

The charmingly‑titled Gas Gooker is a very ruggedly‑built, dual‑channel valve DI box, employing three 12AX7 tubes in the circuitry. The unit features both unbalanced jack and transformer‑balanced XLR outputs, as well as a buffered amplifier output. This last output carries a buffered version of the input signal, allowing the unit to be patched into an existing signal path to deliver a split feed, but without the need to disrupt the original signal feed. The unbalanced jack input (which is situated on the rear panel) is high‑impedance, which makes the unit suitable for use with electric guitars and basses, as well as many piezo pickup systems.

The physical presentation of the aptly‑named Gas Cooker is suitably retro while still being practical. Both channels have independent Ground Lift and Pad switches, and the only rotary controls are the large bakelite Gain dials, with unity gain marked around one third of the way up the scale.

In order to furnish the user with some degree of control over the amount of tube coloration, the Gain control comes after the input buffer, but before the output stages, which means that it is possible to drive the valves into audible distortion by switching out the Pad and turning up the Gain. This can be useful for creating obviously dirty keyboard sounds, but the Gas Cooker is at its most musical when used in its ostensibly clean mode. Because of the Gain arrangement, even when the valves are operating in reasonably linear fashion, the Gain control may still be used to adjust the amount of coloration. I tested the Cooker with various music CDs, and the subjective result was to create an illusion of increased transparency. I found little audible change at the low end of the audio spectrum — any detail within bass sounds was just slightly enhanced — but at the top end, the sound definitely 'opens up', allowing the listener to seemingly get further inside the mix. With the Pad switched in and the Gain set to unity, I patched the Gas Cooker into my console insert points, and found that this setting produced a subtle but significant degree of 'sparkle'. The over‑used term 'musical' springs directly to mind, but you don't get that bass end thump associated with valve guitar amps.


Having established that the Gas Cooker has a flattering sound, where might you use it in a typical studio? Firstly, it may be used as a conventional DI box for recording guitar and bass. Although it's very nice with bass guitar, most electric guitar sounds will need further tonal control, so it may be that a guitar preamp combined with the Gas Cooker would give the best results. Keyboards may also be DI'd, and the Gas Cooker's valve sound can help to impart a little warmth and spaciousness to otherwise sterile‑sounding digital synth patches. Furthermore, because both channels are completely independent, you aren't limited to processing stereo signals — you can treat the unit as two separate mono DI boxes.

Using the jack connectors, the Gas Cooker can also be patched into any of the insert points of a typical console, and it's here that things start to get really interesting. For example, you could patch the Cooker into a mic channel to create a tube mic sound (either when recording or while mixing), or patch it into the console's main stereo insert points to add a pinch of valve flavouring to an entire mix. You could treat sub‑groups in the same way if you don't wish to process the whole mix.

The more you play around with a box like this, the more uses you find for it. You have all the benefits of a conventional DI box, including transformer isolation, plus a controllable degree of valve 'flavouring', and though the effect might not be as pronounced as you'd get from something like an exciter, it's arguably a lot more natural. Definitely worth a close listen, especially if you're a valve freak!


  • Solid, retro‑style construction.
  • Flattering sound.
  • Transformer isolation.


  • Relatively expensive compared to solid‑state DI boxes.


A professional, well‑designed DI box that combines genuine valve coloration with transformer isolation.