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Audio Technica AT4033a

Studio Condenser Microphone By Paul White
Published November 1996

A well‑respected studio favourite for several years, Audio Technica's cardioid AT4033 has now been slightly updated. Paul White reassures himself that the warm 4033 sound remains unchanged...

Audio Technica's original 4033 cardioid condenser has been around for some years now (check out the review in the April 1992 issue of SOS) and has become something of a modern studio classic, but now the company has updated this mic by redesigning the internal electronics and changing the capsule suspension system to reduce handling and stand‑borne noise still further. To indicate the differences, the redesigned 4033 has now gained a letter 'a' on the end of its name.

Part of the key to the original 4033's success was its affordability, and that in turn was made possible by using a fixed‑pattern, cardioid back‑electret capsule rather than a multi‑pattern, dual‑element capacitor capsule. In terms of performance, the back‑electret capsule seems every bit as capable as a conventional capacitor capsule, and certainly hasn't adversely affected the mic's success — over the years, the 4033's silky, detailed, warm sound has won it a lot of users.

Appearance & Features

Packaged in a similar way to other large‑diaphragm mics, the AT4033a is transformerless and features a capsule built around a two‑micron, gold‑deposited diaphragm that has been processed to artificially age it, the idea being to ensure long‑term performance stability. Even without the use of the 10db pad (see below), the capsule and preamp circuitry can handle levels up to a punishing 145dB without incurring more than 1% Total Harmonic Distortion (THD), and the new low‑noise circuitry is fully symmetrical, providing very low distortion figures and a fast transient response. Not only does the circuitry have a low noise figure, it also provides a high output, making this a very sensitive microphone within its class: at just over 25mV/Pa, the mic is up to twice as sensitive as some ostensibly similar models, and the 17dB noise performance is creditable.

A high‑pass, 80Hz, 12dB/octave filter can be activated with a recessed switch on the mic body, and there's also a 10dB pad which may be required to prevent console overload when operating at very high SPLs. The entire casework is finished in non‑reflective black and the capsule is protected by a dual‑layer grille. A thin layer of acoustic foam is positioned between the grille and the capsule.

It's nice to see a company making genuine improvements to a best‑seller without changing what made it so successful in the first place.

Because of the large, open‑basket construction, the off‑axis response of this microphone is particularly impressive — at 90 degrees off‑axis, the frequency response is almost identical to that on‑axis, but 6dB lower in level. The provided response plot shows the mic to be nominally flat from 30Hz to 20kHz, and though there are some slight undulations in the curve, there's no more than a couple of dBs of lift above 10kHz.

Two versions of the mic are available, but the only difference is in the mounting hardware provided — the AT4033a/SC includes a basic stand clip, while the more costly AT4033a/SM comes with a heavy‑duty shockmount system. The package comes in a practical, rigid vinyl carry case with foam lining.


Though the technical improvements to the original design may make a slight difference in marginal operating conditions, I don't think existing AT4033 owners need worry about selling their mics and trading up. Comparing the two models side by side, the mixer mic amp noise swamped any differences that might have been audible in the background noise level. I feel it's more important to confirm that in redesigning the electronics, Audio Technica haven't compromised the mellifluous tonality of the original — so many so‑called improvements seem to throw out the baby with the bath water. Fortunately, I couldn't detect any tonal change at all in a side‑by‑side comparison.

For those who haven't heard a 4033, both it and the newer 4033a produce a warm, flattering sound which somehow combines the solidarity of a really good dynamic mic with the transparency and detail of a top‑end capacitor model. There's a flattering fullness to the sound, which goes some way towards emulating the sound of a tube mic, although it falls just short of the real thing — tube mics often sound a little compressed, for some reason. However, if you make use of a tube mic preamp, or pass the signal through a channel with a tube processor in circuit, you can get very close indeed to vintage perfection.

All large‑diaphragm mics have their own character, and the AT4033a is certainly no exception. Put it next to an accurate reference mic such as the Earthworks OM1 (reviewed elsewhere in this issue) or one of the Sennheiser MKH‑series mics, and there's an obvious difference. It's always hard to describe mic characteristics in mere words, but the 4033a sounds both warm and intimate, yet there's plenty of space and air around the sound. It doesn't quite have the throatiness of a tube mic, but it certainly leans in that direction. Even though there are cheaper large‑diaphragm cardioid condenser and back‑electret mics, the 4033, and now the 4033a, remain my favourites within their price range. It's nice to see a company making genuine improvements to a best‑seller without changing the fundamental character that made it so successful in the first place.


  • Flattering on vocals and many acoustic instruments.
  • Sensibly priced.
  • Good technical spec including low noise, high sensitivity and tolerance to high SPLs.


  • The shockmount is rather expensive.


Audio Technica have made genuine technical improvements to this well‑loved microphone without disturbing its fundamental tonal character.