Alesis/GT Electronics AM52 and AM62, July 1999

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Alesis has successfully made its mark in signal processors, drum
machines, sequencers, synthesizers, tape recorders (and what a mark
that is) and studio monitors, as well as introduced several mixers. It
was inevitable that the company would some day tackle microphones. In
1998, Alesis acquired the Groove Tubes line of electronics, securing
the talents of its designer, Aspen Pittman, and founding a new
division, GT Electronics.

The first offering from GT, the AM Series of microphones, comprises
four models of large-diaphragm condensers situated right in the middle
of one of the hottest and most competitive regions of the microphone
market: the mid-priced condenser. The AM61 ($999) and 62 ($1,299) are
built around a mil-spec Groove Tubes GT5840M tube, a subminiature
pentode wired as a triode to yield softer overload characteristics. The
GT5840M was also chosen for its suitability in implementing a circuit
with low microphonics. The AM61 and AM62 employ a nickel-core output
transformer from Cinemag, a small manufacturer of high-quality
transformers. The AM51 ($549) and AM52 ($699) are a Class-A FET design
and use more standard ferrite-core transformers.

Each design features a flagship multipattern model (the AM52 and 62)
and a less-expensive cardioid-only model (the AM51 and 61). The 52 and
62 have two-sided diaphragms to allow multiple patterns (cardioid,
bi-directional, omni and, on the 62, supercardioid), while the
single-pattern 51 and 61 employ single-sided diaphragms.

All of the AM Series models feature a brass capsule with a diameter
of more than an inch, a 3-micron gold-evaporated-on-mylar diaphragm and
a gold-plated center element, which works like the old "whizzer cone"
speaker designs to enhance high frequency and transient response by
creating a very small acoustical resonance circuit. Each mic also
offers a 10dB pad and 75Hz highpass filter with a 12dB/octave slope. It is
nice to find the pad and filter even on the 51/61; many competitive
mics do not include those. The 52 and 62 also have pattern selector
switches, and the 62 has an additional cardioid/supercardioid

The FET mics require 48V phantom power to operate, while the tube models
come with a power supply and special cable. (The cable runs from the
mic to the power supply; a standard XLR connector on the power supply connects to the
rest of the world.)

The AM Series mics come in heavy-duty, hard cases and include
slipcover "socks" to protect the bodies when not in use or when left
set up on stands overnight. The tube mic cases are particularly nice,
including spots for carrying the power supply and cable, along with a
shock-mount. (Swivel mounts are standard with all AM models.) The
mounts have a full range of motion, which is very useful in obtaining
proper placement with large microphones. All in all, the accessories
are luxurious for microphones in this price range.

For my review, GT supplied a pair of AM62s and a pair of 52s. The AM
Series is heavily touted for vocal applications, but I did try them on
instruments, too.

I first tested the AM Series on a touring singing group of 10
Tibetan nuns. The group was recorded at two San Francisco studios:
Outpost and D'Cuckoo Soundware Farms, home of producer Candice Pacheco.
At the first session, at Outpost, the nuns were sitting on the floor in
two rows facing each other. A number of mics were used, including the
AM52s and 62s, AKG 414, Neumann U67 and AKG 3000. The mics were placed
between the rows of nuns, faced alternately such that each nun had a
mic facing her.

Outpost engineer David Nelson said his first impression of the AM52
was that it was "crispy," which he feared would make the tracks sound
"artificial." However, as he soloed the various mics to adjust for the
best blend, he looked up several times when he liked the sound of a
soloed mic and found it was the 52. Over the course of the session,
Nelson became increasingly enamored of both the 52 and the 62, also
citing their off-axis rejection, which was vital in such a setup.

Pacheco, too, liked the GT mics, using them again at the session in
her studio, which she also engineered. To allow the greatest
flexibility in mixing, she wanted the nuns miked individually. That
session started with the same mic setup as at Outpost, but a series of
solo and duo prayers were also recorded with the 52 set to the
bi-directional pattern, a nun on either side of it.

"The nuns voices were really a challenge," Pacheco said. "They all
had a very pronounced resonance at 4 kHz, since they barely move their
mouths and mostly sing through their noses. Another challenge in the
recording is that they not only chanted but played instruments, which
bled through on their vocal tracks.

"Both the GT mics handled these problems better than the other
microphones we used. There was noticeably less bleedthrough, especially
on AM62s, than the other microphones. The AM62 handled the 4kHz
resonance much better and had a more warm sound while still retaining
the crispness. The AM52 also had very nice response, and for the price,
I think they are good microphones if you are on a budget. I was really
impressed with the AM62 and am planning on purchasing one."

I set up my own comparison test for vocal recording, pitting the 52
and 62 against an AKG 414B/ULS, which is in roughly the same price
class, and a Neumann TLM103, which costs three to four times as much.
The mics were fed through an Earthworks Lab102 mic preamp, converted to
48kHz/24-bit digital by a Panasonic DA7 mixer, and recorded at the full
24-bit resolution by a Mark of the Unicorn 2408 running AudioDesk
software. Playback was monitored through Genelec 1031A

I recorded myself and singer Dian Langlois so that I had both male
and female voices to compare. The most important performance aspect of
vocal microphones is not usually accurate, transparent pickup, but a
good match between the character of the mic and the sound of the
particular voice. Thus, it is no slight to say that the frequency
responses of the AM52 and 62 are not flat.

Not surprisingly, there was greater clarity and evenness in the
TLM103 than any of the other three, but the differences between the 414
and the GT mics were mostly in their character. The sound of the AM62
had some high-end roll-off and low-end boost, which is typical of
many tube microphones I've heard. This tended to nicely soften my
voice, which has a somewhat harsh nasal quality that is exacerbated by
most vocal mics. Dian's voice sounded great through the 62 when she was
belting it out, though I did detect a bit of splatter in the high-mids
when she hit strong notes.

In contrast, the AM52 has a prominent rising response, which sounded
wonderful and breathy when Dian sang a soft ballad but produced a good
deal of sibilance on my voice. In fact, I found that I had to sing
off-axis to the 52 to avoid the headphone feed singeing my ears. By way
of comparison, the 414 landed squarely between the 52 and 62, with a
flatter high and low end, but a bit of boxiness in the mids. My little
test served mostly to reinforce the notion that few vocal mics are
suited to every need; the 52 and 62 worked great with the right voice
match and poorly when the strongest characteristics of the voice played
into a weakness of the mic. The 414 came out as the best all-around,
but the trade-off was that it was never able to attain the pristine
cleanliness of the TLM103, the rich warmth of the AM62, or the airiness
of the AM52.After doing the bulk of the comparison with all of the mics
set to cardioid, I tried some of the other patterns, starting with supercardioid. The 52 does not have hypercardioid or supercardioid patterns, but the
62 offers a supercardioid pattern. The off-axis response of the 62 in
this pattern fell off more smoothly than some hyper- or supercardioids
I've tried. This means that there was less tonal change when Dian or I
moved around while we sang, but the rejection was not as tight as some
other mics.

When I experimented with the bidirectional setting, I was surprised
to find that the rear pickup of both the 52 and 62 sounded noticeably
different than the front, with less low frequencies and a bit more
high-mids. I did not find anything as noticeable between the front and
rear of the 414 or TLM103 when set to bidirectional pickup. Although
this could be beneficial if you are using the pattern to pick up
ambience from the rear, it would be problematic if you were using it to
record two vocalists singing together while standing on opposite sides
of the mic.

I also tried the GT mics for speech, reading from a little-known
book by Robert Louis Stevenson. In this application, the 62 was the
clear winner, as the 52 created a sibilance problem. Again, a different
voice could produce another result. The 62, however, produced a rich,
articulate sound that was quite satisfying.

Having put the mics through their vocal paces, I set them to work on
instruments. The results were exactly what I predicted from the outcome
of the vocal tests. For drum overheads, the 62s worked well with jazz
playing and yielded a sort of rolled-off, British sound for rock. The
52s were a little too aggressive for me as drum overheads; both they
and the 62 presented some distortion on the cymbals (which I hear from
almost all mics I use for drum overheads except DPA/B&K and
Earthworks). However, that same bite proved advantageous when I put the
52 on snare. I also liked the 52 quite a bit on dumbek, as I like to
hear the sound of my hands on the head very clearly
articulated—the 52's rising high end accomplished that

At composer/keyboardist Peter Drescher's Twittering Machine studio,
I tried both GT mics on his 1927 Steinway baby grand piano, feeding the
mics through a Studio Technologies preamp into a Panasonic SV-3800 DAT.
The 52's high end was too strident for Drescher's mellow piano, but the
62 was lush and full, producing the most pleasing sound Drescher has
gotten recording that instrument. In this trial, the mics were placed
inside the piano, but the same brightness that made the 52 unsuitable
in this situation could make it ideal for a mid- to far-field miking
approach, providing compensation for the air absorption of high

The 52 proved to be a better performer when we recorded some of
Drescher's bells and ethnic percussion; however, close-miking loud
instruments like agogos sometimes resulted in a bit of "splatter"
(sounding like slight high-mid- to high-frequency distortion) in the
high end.

The most interesting instrumental test, however, was when I put the
GT mics on my vibraphone and compared them to a pair of Earthworks ZX30
small-diaphragm condensers, which are squarely in the same price
class. Although I have yet to find anything that tops the ZX30 for this
sort of acoustic recording, the AM52 did better than I expected in
producing a sound that was bright but did not overly accentuate the
transient of the mallet hitting the bar. The 62, predictably, produced
a softer, mellower tone, which would be great for ballads. However,
neither produced the pristine clarity and pinpoint imaging of the

The GT Electronics AM Series microphones are solid all-around
performers and a very good value. As with most Alesis products, they
are excellent for their intended applications and serviceable for a
number of others. The AM52 is quite bright and seemed to work best when
not very tight on the source, while the AM62 had exceptional warmth but
less "air" in the very high frequencies.

It is important to have a variety of microphones in one's cabinet,
even if only for voices, but that quickly becomes an expensive
proposition. The GT AM Series mics provide a means of broadening the
mic selection to match a given vocalist or ensemble without breaking
the bank. At these prices, one could easily end up buying one of

Alesis Studio Electronics,