Universal Audio UAD A-Type Plug-in — A Mix Real-World Review

New York, NY (September 29, 2025)—UAD’s A-Type Multiband Dynamic Enhancer plug-in emulates the long-obsolete Dolby A-Type noise reduction system, which was invented to take care of the deficiencies and flaws of analog tape recording. In the 1960s, multitrack tape recorders came into wider use, and with it came a corresponding buildup of tape hiss, buzzes, hum, high-frequency noise, and layer-to-layer print-through.

The buildup of tape hiss became unacceptable, especially when recording and mixing large orchestras, with the many tape tracks each contributing to the tape hiss. The Dolby A-Type stereo A301 (1966) and single-channel A361 (1970) units achieved about 8 dB to 10 dB of noise reduction. UAD’s A-Type plug-in addresses the most egregious flaw: tape hiss.

HOW DOES IT WORK?

Dolby A-Type uses a multiband, two-part compression/expansion (companding) technique. Part One encodes input audio by splitting it into four overlapping frequency bands that were determined to be the most effective in reducing audible noise. These four bands are each inversely compressed with quiet, low-level sounds compressed more, and louder sounds less, or not at all.

Principally, the lower-level mid- and high-frequency bands are emphasized and recorded at a higher level on the tape. The same four filter bands are also used in Part Two to decode the recorded audio using an expander. If the system is carefully aligned, the original recording’s amplitudes, phase and spectral makeup are restored, but with less high-frequency noise.

In those days, studios had racks of Dolby A-Type units connected to and from the multitrack tape recorder and mixing/recording console. Studio techs aligned both the Dolby units and tape recorders before every session. Likely first discovered by accident, somebody played a Dolby-encoded tape without the decoder and a whole new studio effect was born.

In 1975, I tried this trick intentionally to chase the sound of a lead vocal I had heard on a hit album recorded in England. What I heard was amazing! On the lead vocal track, it sounded like a super-bright EQ but also had a unique, compressed clarity and crystalline quality. But I also heard subtle nuances and annoying pops and clicks and the extreme sibilance in the recording. The Dolby units were used as a send/return effect like reverb or delay, but not designed to be a special effect.

Eventually, hardware “hacks” were developed to customize the effect for particular sources. One was to remove low-frequency Band 1 and 2 cards from an A301 unit, leaving only a high-frequency “gloss.” The newer A361 units had all four bands on a single, removable Cat-22 cartridge in which certain parts were bypassed or removed to produce a desired effect. A few producers had collections of modified Cat-22 cartridges, each labeled for specific uses—vocals, drums, acoustic guitars etc.

The UAD-A Type plug-in provides control over many internal parameters not available in the original hardware units, transforming this vintage noise-reduction system into a fully adjustable, multichannel, dynamic effect. Included are presets that duplicate circuit modifications used by a “who’s who” of hitmaking record producers and engineers at the time.

A-TYPE FRONT PANEL

A-Type’s GUI starts with a center-mounted, edgewise VU meter for reading Gain reduction from 0 to -40 dB, also setting Input level from -60 dB to +12 dB. You will be surprised to see huge gain reductions with most of the presets.

The Side Chain Filter has flat, a 12 dB/octave 150 Hz highpass filter and Tilt positions. Tilt is a linear 3 dB/octave boost. The main controls on the GUI are the large Amount (threshold) and Wet/Dry knobs. Practically speaking, I was constantly tweaking these two controls and the three-position Sidechain switch.

Two of the five processor modes, Excite and Expand, produce the encode and decode functions of the original Dolby A-Type noise-reduction units. The other three are for special effects not possible with the vintage units.

Excite uses a variable, infinite:1 compression ratio and is the basis for the “A-Type EXCITE Stock HW Encode” preset. An Excite-based preset called “Acoustic Guitar Clarity and Detail” worked great for acoustic guitars, along with the Side Chain Filter. Expand is the decode mode analogous to the green “Play” button on the A361 units. Expand is used in the “A-Type EXPAND Stock Decode” preset for playing back encoded recordings correctly.

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Air mode sounds like how I remember playing back Dolby-stretched tapes. It adds a classic glassy, airy sound. In honor of the recently departed producer, I called up a preset called “Roy Thomas Royalty.” It sounded fantastic on backing vocals. The manual says that with Air mode, “a little goes a long way.” It will definitely reveal and make audible fast attacks, ticks and crackles just like un-decoded audio back in the day.

The Dolby A-Type hardware used a variable ratio from 4:1 to infinity:1 that provided the most transparent sound. Crush and Gated are single-band processors with a fixed 4:1 ratio that adds A-Type’s utility. The Crush-based “A-Type Multiband Enhancer 3” preset was killer for a flabby kick drum at 50% wet. The Amount control works like the input control on a UA 1176LN, making Crush a good-sounding, FET-based compressor. The Straight Gate preset (with some tweaks) chopped up an acoustic guitar track into techno hamburger. The Amount control now sets the threshold.

CIRCUIT MODS AND EFFECTS

Clicking on a small arrow under the GR/Input meter opens up the Circuit Mods window. Circuit Mods includes many of the hardware mods done on the original units with all the controls to modify processing. This window shows a small four-band parametric dynamic equalizer display with the active bands enabled for a particular Mode.

You may alter frequency centers, band crossovers and gain of each band. I got in the habit of leaving this window always open to check on these parameter changes when switching Modes. I also kept the Auto Cal switch disabled to lock in my customized parameters to retain them when switching through modes, but you can revert to the preset values. This is a great feature. Using a 4:1 ratio along with an adjustable soft/hard Knee control and slow/fast Release time settings opens up A-Type to be a dynamic compression processor adaptable for any source.

Attack time is nonlinear, with an initial fast attack that slows down as threshold is reached. A useful Output level fader and the adjustable HR Headroom control are for reducing or increasing dynamic range. Higher HR I for more subtle processing, and lower settings for extreme processing effects.

DECODING AND ENCODING DOLBY AUDIO

A noted mastering engineer sent me a stereo .wav (at 192 kHz) copy of a Dolby-encoded stereo master tape from the mid-1970s, including its 100 Hz, 1 kHz and 10 kHz alignment tones. He also sent the same master tape (.wav file) decoded using a Dolby A361 system. Both the encoding and decoding processes were carefully set up using the same alignment tones and tape recorder. On the encoded track, I inserted the A-Type plug-in with “A-Type EXPAND Stock HW Decode” preset.

I used Trident Audio’s TriMeter plug-in to measure the -18 dBfs, 1 kHz alignment tone split into two mono channels and fed to separate L/R faders going to the input of A-Type. It read -1.5 dB below 0 VU, and less than 0 dB on A-Type’s input meter. However, a second TriMeter placed on A-Type’s output read 0 dB. To set 0 dB on A-Type’s input meter required turning up the Amount control a little above the grease pencil mark—the output remained at 0 dB. The Wet/Dry Mix control was at maximum in this preset, and the Side Chain Filter was off. It all works! When played through A-Type, the encoded copy matched the decoded tape copy.

I think Universal Audio is on to something here with A-Type. What started as an emulation of a vintage noise reduction system has expanded the capabilities to become a new multiband effect—one that was discovered by accident a long time ago but has withstood the test of time.