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CAD Equitek

Back-electret Condenser Microphones By Hugh Robjohns
Published June 1997

Hugh Robjohns checks out a range of keenly‑priced condenser mics from over there that look set to do rather well over here...

With most kinds of sound recording equipment, you get what you pay for. Quality costs money, and in terms of microphones, the established front‑runners are going to set you back typically a thousand pounds or more. That is not to dismiss less costly designs, of course; there are some extremely competent designs costing a fraction of the big names, and all engineers have their own preferences in microphones at any price.

The Australian company Rode re‑established the cost/performance relationship recently with their NT2 studio condenser microphone (see review in SOS June '95), but the trend is continuing with the new Equitek range of studio microphones from American company Conneaut Audio Devices, better known as CAD.

The Equitek Range

The CAD Equitek range currently comprises three microphones, all of which are side‑addressed studio‑quality condenser mics. The basic model is the E100, a back‑electret hypercardioid. The second mic, the E200, uses a pair of the same back‑electret capsules arranged to provide selectable polar patterns (omni, cardioid and figure‑of‑eight). Lastly, the top‑of‑the‑range E300 is a large‑diaphragm (1.1‑inch) true condenser mic, very much along the lines of an AKG C414 or Neumann U87, with switchable patterns and other facilities in common with the E200. Both the E200 and E300 have large cylindrical bodies, while the E100 is a very slim rectangular design.

The E100 uses a single electret and a head amp based around an OPA2107 integrated amplifier. The E200's head amp is necessarily a little more elaborate (although it still uses the same basic configuration). Finally, the E300 uses a high‑quality twin‑condenser capsule, but retains the same head amp as the E200 (with slight modifications to generate the necessary capsule polarising voltage).

All of the Equitek microphones are powered by a combination of standard 48V phantom power in concert with a pair of internal 9‑volt PP3‑style NiCd (Nickel/Cadmium) batteries. A number of condenser microphones have facilities for internal battery power, but I am not aware of any professional studio mics that actively rely on batteries in the way these do. Basically, CAD claim that by using very high‑quality Operational Amplifiers (integrated circuits) in the head amplifier, they can achieve far better distortion and non‑linearity performance than with conventional FET designs. However, the inherent disadvantage is that a lot more current is needed from the power source, especially under high signal level conditions. Normally, phantom power cannot supply large amounts of current, so the Equitek microphones use the NiCd batteries as a power reservoir system, and the phantom supply serves as an automatic trickle charger for the batteries whenever a phantom power source is connected. To charge the batteries from new, the mics need to be connected to a phantom power source for around 14 hours. If necessary, the microphones can be powered for a few hours from the batteries alone, although a link must be re‑positioned inside the microphone to disable the automatic power‑down system (this turns the microphone off when phantom power is removed, to prevent accidental flattening of the batteries if the user forgets to switch the mic off).

Equitek E100

This is the baby of the range, and is the odd one out in terms of its shape. The E100 is a slim rectangular unit measuring 62 x 153 x 55mm (whd), weighing about half a kilogram, and is supplied in a hard plastic carrying case with protective foam lining. The active side of the grille is a fairly garish gold colour, while the back is a more sombre black. Three miniature toggle switches just below the grille provide for Power on/off, high‑pass filtering (a ‑10dB shelf from 80Hz) and a 20dB attenuator. The bottom section of the microphone case can be removed by releasing one cross‑point screw to access the battery compartment.

The rear of the microphone houses the XLR connector, and a blind 5/8‑inch threaded hole, which could be used to mount the microphone onto a boom‑arm stand directly — I can think of a number of applications in small voiceover booths where this would be very useful. The mic is also fitted with an elbow bracket (also machined with a 5/8‑inch hole) which affords a more conventional mounting arrangement, as well as adjustment of the microphone's angle. I was disappointed to find that 3/8‑inch thread adaptors were not supplied with any of the review microphones, because it seems you can never find one on a mic stand when you want one! The microphone serial number is engraved on the rear panel below the XLR socket, and the final nice touch is the rubber bump stop below the mounting bracket.

These microphones look and sound a lot more expensive than they really are...

The E100 has a quoted frequency response of 10Hz to 18kHz, an equivalent noise level of 16dB SPL (A‑weighted), and is specified as having a supercardioid polar pattern. In use, it was commendably quiet, and certainly exhibited a well defined and tightly controlled polar response which remained stable across the full frequency range. As is normal with a back‑electret capsule of this type, the rear‑lobe sensitivity reduced slightly with increasing frequency, and the frontal pick‑up angle narrowed, but this should not cause any problems in practice. The wide dynamic range capabilities of the head amplifier allow the E100 to be used on all manner of instrumentation — even drums — and it is certainly neutral enough to work well in most applications, providing a pretty faithful rendition of the source.

Each microphone is issued with its own frequency response plot (made during final checking at the factory) and this showed the mic to be flat within a dB between 10Hz and about 7kHz. It fell to ‑6dB by about 15kHz and was roughly ‑8dB by 20kHz. The ambiguity in these figures is caused by the ludicrous plus/minus 40dB range of the frequency response plot! Why do manufacturers do that?

The chart also showed a slight presence bump of a dB or two centred on 4kHz: an intended characteristic of the design. The extreme HF rolloff was apparent during listening, as was the slight presence lift, but these contribute to the microphone's character, which was well suited to voices in particular — both spoken and singing. The microphone output level is quite high, and required roughly 50dB of gain to bring a speaking voice at 300mm up to normal line levels.

The microphone has an elaborate combination of outer metal weave grille plus a fine inner mesh, together with a reasonable air gap before the capsule's own integral pop shield. This comprehensive windshield arrangement gives the microphone very good pop rejection on plosives, even when used very close up. The back‑electret capsule is mounted on rubber suspension arms between a pair of metal pillars in a kind of 'H' arrangement, and this gives some mechanical isolation, but vibration on the microphone stand is readily picked up by the microphone unless the high‑pass filter is used.

Equitek E200

The E200 is a cylindrical microphone, designed to operate with the capsule towards the bottom. The mic (the front of which is again a rather gaudy gold colour) is 237mm long and 64mm in diameter, and weighs only 340 grammes (lighter than the E100, despite its larger size). A hard plastic carry case and swivelmount stand adaptor are supplied.

The E200 uses a pair of the same back‑electret capsules as the E100, and these are mounted in a similar way, on rubber cross arms between two vertical metal pillars. The capsules are arranged back‑to‑back, but with a space between them and a separation between front faces of 25mm or so. The capsules have their own integral pop shields, but these are supplemented by a fine wire mesh and the outer metal weave. The volume of the air‑gap between outer mesh and the capsules again plays an important part in the mic's remarkable resistance to popping.

The front of the microphone carries four miniature toggle switches. The first turns the unit on; the second selects a polar pattern (figure‑of‑eight, cardioid or omni‑directional); another introduces the high‑pass filter, and the last switches in a 20dB pad. The top of the cylinder can be removed by releasing three screws to gain access to the batteries, and as with the E100, there is a 5/8‑inch threaded mounting hole and XLR connector (on the top face of the E200) along with the engraved serial number.

The microphone is supplied with an SM1 swivelmount bracket which fits to the top of the mic and allows easy positioning from a boom stand. As with the E100, stand vibrations pass easily into the microphone through the swivelmount, although the high‑pass filter removes the worst effects if bass rolloff is acceptable on the sound source.

The microphone specifications are essentially the same as for the E100 in terms of frequency response, noise and dynamic range. Perhaps not surprisingly, I found the on‑axis frequency response changed slightly between the different polar patterns, but this was really in the form of a change of character rather than anything more serious. The frequency response given on the supplied plot was ruler‑flat up to 2kHz, where there was a slight ripple giving two presence lifts of a dB or so at 2.5kHz and 8kHz. The top end fell off more gently than the E100, being about 5dB down at 20kHz.

The polar responses were as expected considering the spacing between the two capsules. The cardioid is pretty loose around the back at low frequencies, tightening markedly with high frequencies and with the usual narrowing across the front. The figure of eight was actually much better than I expected, with very good side rejection indeed, although the off‑axis sensitivity falls off quickly at extreme high frequencies. The omni‑directional pattern is probably the most consistent with frequency, only showing significant sensitivity variations at the extreme top end.

On the whole, the microphone worked well using each of the polar patterns in appropriate applications. Once again, this is a very neutral‑sounding mic which produced quality results with every source I tried. It can cope well with transient‑rich material, and the provision of selectable polar patterns makes it truly versatile.

Equitek E300

This is the undoubted star of the range, and I'm sure this accolade is entirely due to the classic condenser capsule design. Physically, the E300 is slightly shorter than its sibling at 227mm, and weighs significantly more at 845 grammes, but retains the same diameter. The microphone is supplied with a hard plastic carrying case, the SM1 swivelmount stand adaptor, and the ZM1 suspension shockmount.

The control switches are identical to those on the E200, as is the construction of the head amplifier and other mechanical arrangements, but the capsule is mounted rather differently. The 1.1‑inch double‑sided condenser capsule is supported on a rubber cone within a wire mesh and metal weave pop shield. This time, the front of the microphone is a much more tasteful silver colour, and the grille has been flattened on the front and back in a manner vaguely reminiscent of a Neumann U87 (the E200 grille is perfectly cylindrical).

As soon as I heard the E300, I knew it was going to produce classy results

The E300 capsule clearly performs rather better than the back‑electrets used in the other Equitek microphones, because the noise performance is a full 5dB better (the equivalent noise level is 11dB SPL A‑weighted) and the frequency response extends beyond 20kHz. Indeed, the plot is a flat line up to 2kHz, with that characteristic 1dB lift at 2.5kHz, and then a rather more pronounced 4dB peak at 10kHz, falling back to the nominal zero at 20kHz. The flattest response seems to be in the figure‑of‑eight mode, and the most pronounced HF peak appears in the omni‑directional mode (where it actually works very well to counteract the natural tendency for omni‑directional mics to sound a little flat in diffuse soundfields). The polar responses are good in all three modes, although they all show more severe high‑frequency narrowing than the E200, particularly in the case of the omni pattern.

Despite (or perhaps because of) the comments above, as soon as I heard this microphone I knew it was going to produce classy results — which it most certainly did. It was quite superb on spoken voice, particularly when used very close, and once again, it was very hard to make the thing pop or bump! On dynamic acoustic guitar recordings, it came up trumps, being very accurate and detailed, and coping extremely well with the complexities of 12‑string harmonics.

I used the E300 exclusively in the supplied ZM1 shockmount, and I found this to be excellent, completely isolating the microphone from even quite severe vibrations deliberately introduced into the mic stand. I would recommend buying the ZM1 for use with the E200 too; it really did make a big difference. The only frustration with the shockmount, and one I also had with the simple swivelmount, is the complete absence of any cable management to dress the XLR cable away from the mic body and reduce the strain on the connector. This would be fairly easy to put right, and would make an enormous difference to the operational elegance of the microphone.


I recommend the Equitek range; the three mics share some innovative technology to produce accurate, dynamic and attractive sounds. Broadly neutral, they are all sufficiently flexible to be useful on a very wide range of sources, and apart from the problems with cable dressing on the E200 and E300 models, they are very easy to use. The E100 and 200 sound very similar to each other, and do much for the credibility of the back‑electret concept, while the E300 could hold its head up high in the company of such stalwarts as the classic solid‑state Neumanns or AKGs. These microphones look and sound a lot more expensive than they really are, and the E300 in particular is a bargain when you consider what it's capable of.


  • Accurate and well controlled polar patterns.
  • Quiet electronics, wide dynamic range and smooth frequency responses.
  • Quality sound overall, but especially so in the E300.


  • Susceptible to stand vibration unless on the ZM1 shockmount.
  • No provision for cable dressing.


The Equitek range consists of very versatile and competent mics, essentially neutral in character but with a slight presence lift, and all work well with pretty much any source. The multi‑pattern E300 is the star of the range, but the E200 is no slouch, and the hyper‑cardioid E100 makes a good vocal microphone. All in all, these mics are an example of clever and innovative design.