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Groove Is In The Heart

Groove Tubes MD1 & MD2 Tube Microphones

They're Groovy, they're Tubey, they're born in the USA and they glow in the dark. Bring a little warmth into your life.

Paul White discovers that just as Californian wines are putting up a fight against the German brands, their microphones seem set to do the same.

The Groove Tubes MD1 valve microphone has been on the market for some time now, but the introduction of the brand new MD2 seems an ideal time to put both mics into context.

Perhaps Groove Tubes isn't normally a name you associate with microphones, but it's certainly a name you associate with valves — the company market selected valves under their own name for both the music and hi-fi markets, and in more recent years have gone on to build their own valve guitar amps, power amps, mic preamps and now microphones and DI boxes.

The MD1

The original MD1 is a fixed cardioid pattern microphone employing a large diameter, back-electret capsule which, I believe I'm correct in saying, is built by Primo. The housing is a chunky, stainless steel tube with side-entry grilles for the capsule; a threaded stand mount is integral with the bottom of the case. The top end of the case is also formed into a grille aperture, the grille itself being a dual layer structure with a robust, open-weave steel basket on the outside and a much finer steel mesh on the inside. There's no foam, which can often change the character of the sound.

Being a valve design, the MD1 requires a power supply, and Groove Tubes manufacture three different models (PS1, 2 or 4) which can feed one, two or four of their microphones or tube DI boxes. Unusually, the power supply connects to the mic via a 9-pin delta connector with locking clips. This is a tragically unlovely device, but I concede that for a mere fraction of the cost of a Neutrik connector, you get a functional locking connector with gold-plated pins that works perfectly well and, if a lead should get damaged or lost, replacement connectors can be picked up in any high street electronics component shop for pence rather than pounds. The mic signal emerges from the power supply in the form of a standard, balanced XLR connector, though there is no level control and no pad or rolloff switch.

Ventilation holes in the side of the case provide a glimpse of the single valve within, a 12AT7, and a screened Groove Tubes logo tells you that you're singing into the wrong side! The business side is the side with the ventilation holes.

The MD1: Warmth, depth and flattering tonality.

Groove Tubes MD1

  • Warm valve sound.
  • Relatively inexpensive compared to other tube mics.

  • Exorbitantly priced connecting cable


When I first tried an MD1 some two or three years ago, I was impressed not by it's honesty (because it isn't) but by its flattering tonality. The valve circuitry gave the capacitor capsule rather more warmth and depth than you'd expect from most solid-state designs, and those comments still hold today. Indeed, given the powerful, confident sound of this microphone, the RRP is very favourable, even when you remember that you have to budget for a power supply module to drive it. However, I do feel that the connecting lead should be included in the price; it is a very expensive item considering the low cost of the connectors and I would be inclined to make my own. As far as I can see, the connections are pin for pin, with pin 1 being the screen.

The MD2

Similar in outward appearance, the MD2 is distinguished from the MD1 by its black crackle paint finish. Furthermore, the Groove Tubes logo takes the form of a cutout, thus augmenting the existing cooling arrangements and allowing the valve to shine through in a rather endearing way.

Once again, a locking nine-pin delta connection handles the power supply link, but there is no stand adaptor — in its place is a rotary control which adjusts the microphone sensitivity by varying the polarising voltage on the capsule. Because there is no stand adaptor, the mic needs to be mounted in a shock mount, and Groove Tubes just happen to build a model that fits perfectly, called the Shock Therapy. This costs a little over £70, but alternative general-purpose clamps may be used. Some form of shock mount is desirable because the mics suffer quite badly from handling noise.

Groove Tubes MD2

PROS (both models)
  • Warm valve sound.
  • Relatively inexpensive compared to other tube mics.

  • Exorbitantly priced connecting cable


The main difference between this microphone and the MD1 is in the capsule. In conversation with Aspen Pitman, the man behind Groove Tubes, I was told that the same capsule was bought in as for the MD1, but that it was completely stripped down and rebuilt as a true capacitor element, using a gold-evaporated, mylar diaphragm. Apparently Aspen has solicited the services of a local craftsman who normally rebuilds top-name German microphones to do this job, and after much experimentation with diaphragm tension, they have a design that they are more than pleased with. Certainly, in comparison with other top-end capacitor mics, this one comes over very much larger than life, with immense warmth and intimacy. Compared directly with the MD1, the sound has more presence, though the overall sensitivity is slightly lower. Again this character is all down to electronic flattery — if you want a mic that tells you the truth, then don't go near this one with a barge pole — but if you want to listen to the world through a rose-coloured ear trumpet, then this is a model you should definitely check out. It won't suit everybody, but if you want to sound like a singing Brut commercial or an intimate late-night DJ, then make the MD2 your first stop.


Because these mics are not built by a traditional microphone company, the housings are a little more chunky and unsophisticated than you might expect from someone like Neumann or AKG, but they are distinctive and practical. Very little technical specification is available on the mics, but as they are normally purchased for their sound rather than their honestly, it could be argued that a frequency response plot is meaningless. Though valve equipment is usually a little more noisy than solid-state devices, the fact that these mics will spend most of their life acting as close vocal or instrument mics means that the little noise they produce is well below the level at which it might cause problems.

When I first tried the MD1, I was surprised at just how warm and powerful it sounded, but now, having tried the MD2, it seems the new model has taken yet another stride in the direction of out-and-out flattery. As I said earlier, different mics suit different people, but if you're after a warm, punchy sound with lots of detail and intimacy, at least try one of these mics before signing any cheques.

Further Information
MD1 £659.92; MD2 £1099.83; PS1 power supply £165; PS2 power supply £256.01; PS4 power supply £409.93; EC1 25-foot soft connecting cable £102.42; EC2 25-foot hard connecting cable £66.02.

Groove Tubes UK Ltd, (Contact Details).

Previous Article in this issue

A Brief History Of Live

Next article in this issue

Lexicon Of Love

Recording Musician - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Recording Musician - May 1993

Review by Paul White

Previous article in this issue:

> A Brief History Of Live

Next article in this issue:

> Lexicon Of Love

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