Groove Tubes has been in the MI market for 25 years, initially manufacturing what were probably the first premium matched-set guitar tubes available for guitar and bass amplifiers, and then, component amplifiers, microphones, preamps and compressors. Highly sought after by guitarists and studio technicians in the quest for Holy Grail tone, Groove Tube products are known for quality, innovative design, and attention to detail. But the underlying foundation for most all of their product line is tube electronics, and so I was intrigued by the introduction of the low-cost ($149) FET condenser microphone dubbed “The Convertible.”
Studio, live sound
Hypercardioid pattern; condenser element; gold-covered Mylar diaphragm; switchable address angles; removable ball screen
www.groovetubes.com The Convertible, as claimed, has the unique ability to switch from a ball screen vocal-style microphone (a la Shure SM58) to a top-firing instrument mic (a la Shure SM57) by unscrewing and removing the windscreen, which reveals a black metal mesh capsule enclosure. The Convertible thus has the versatility to adapt to several miking situations in a pinch, making it desirable to both sound reinforcement and recording engineers. But while the similarity of the Convertible to the Shure designs are described for illustrative purposes, it is a different animal, being a powered condenser microphone in lieu of a standard dynamic design.
The Convertible has a mid-sized (21mm) true condenser capsule, as opposed to small capsule electret designs that are popular on the market in this price range. The capsule has a 6-micron gold-coated Mylar diaphragm and is rubber isolated to help cope with handling noise and other induced vibration phenomena. The unit’s polar response is hypercardioid, and it obviously requires phantom power to operate. Its output impedance is 200 ohms looking for a matching load of over 500 ohms. This makes it a good overall impedance match for most microphone preamps and mixing console channel strips on the market.
My first opportunity to use the Convertible was in my project studio, where I currently have a selection of condenser offerings from Marshall, AKG and Shure. I inserted the mic through a Focusrite Platinum mic preamp and into my TASCAM 2488 DAW to test the signal quality of a close-miked 1958 Martin D18 dreadnought acoustic guitar (with ball windscreen removed). I monitored the results with a pair of AKG K240 headphones. In a flat EQ setting, I was immediately impressed with the airy immediacy of the G, B and high E strings, indicating very good impulse response and high sensitivity, with a well-tempered evenness in the low midrange where this Martin can be “boomy” in use with other condensers. The microphone’s preamp section was ghostly quiet, indicating a considerable dynamic range capability. With the ball windscreen reinserted, vocals seemed well balanced; plosives were controlled, with a slight bump around 3 kHz, lending a nice high-midrange punch.
In a live environment, the Convertible offered immediate dividends. Utilizing the microphone through a Mackie 1620, dbx DriveRack, QSC PLX power amps and a set of Yamaha Club Series V speakers within a typical club backline of 60W Fender combo amps (Pro Reverb, Vibrolux, Bandmaster), the mic sans the ball screen jumped out of the mix compared to my standard lineup of dynamics. Substituting the Convertible for an SM57 on a zealous Ludwig chrome snare drum displayed the mic’s ability to handle high sound pressure levels without folding (its claimed maximum SPL capability is 146 dB). With a quick addition of the ball screen, and after replacing one of my favorite condenser microphones (name withheld) at lead vocal, I was digging the fat midrange and detailed highs the unit yielded along with very low handling noise that the band, the audience, and I, enjoyed.
At the end of the day, I was very impressed by the Groove Tubes Convertible microphone. Not mentioned earlier is a very detailed fit and finish: a solid well-balanced black powder-coat handle with laser etched nomenclature as well as a rugged, removable ball screen and stainless steel capsule housing. The unit is handsome and will easily fit in appearance-wise with any other mic on the floor. But the real beauty is in its flexibility and performance; I would match the Convertible up sonically against any other condenser microphone in its price range (and quite a few costlier models), notwithstanding its ability to handle many differing situations. Kudos to the engineers at Groove Tubes; they have a winner here. Let’s hope more ideas like this one come our way.