Urei / Universal Audio 1176 Compressor/Limiter - Vintage King (2024)

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Evolving A Classic Design

The design of the unit went through numerous changes, taking a while to hit its stride. The originals were somewhat noisy, prompting Brad Plunkett of Urei to design the Low Noise circuit that gave the unit its "LN" designation. Improvements continued to be made over the years, with the result that there are 9 major revisions of the vintage 1176, given the letters A, A/B, B, C, D, E, F, G, H . The substance of these revisions is detailed below, gleaned from notes by Barry Rudolph, the Universal Audio website, and research on units sold by Vintage King.

The original Bluestripes A, A/B and B
These are the edgiest versions, with plenty of noise and distortion to provide a distinct color to any signal.

The low-noise Blackfaces C, D, and E
These have the classic character and lower noise floor that is the heart of the 1176 sound. Modern versions hearken back to this era.

The push-pull, higher output Blackface F.
This version continued the classic sound, but changed the output transformer for considerably higher gain.

The op-amp input Blackface G and Silver-face H
The final refinement was to eliminate the input transformer in favor of an op-amp, giving a cleaner sound. One-third of all vintage 1176 units are of this type.

The original 1967 design by Bill Putnam used an input transformer at the industry standard 600 ohms resistance (Peerless, later UTC), a T-pad resistive attenuator to drop the input voltage, a FET acting as a voltage variable resistor to control gain, followed by a bipolar transistor as a preamp (the famous 1108 circuit with a Darlington pair). The output amp circuit was similar to the preamp, but followed by a 2N3053 bipolar transistor operating in Class A. The output matching transformer at 600 ohms was a UA-5002 (later improved to UA5002A) with a split secondary, a tertiary winding for negative feedback to the final line output circuit, and a separate emitter winding.

Covering up all this electronic wizardry was a brushed aluminum faceplate with blue paint around the Weston meter. The rest of the design features two black plastic control knobs with silver tops and clear plastic collars, two smaller black and silver knobs, eight black plastic pushbuttons and a red power indicator light. All the revisions to follow would maintain the same controls, but the red power light would disappear when the black faceplate was introduced.

In 1970, two major and two minor changes were implemented. Low Noise circuitry was added to the preamp stage in order to reduce the drain-to-source voltage of the gain reduction FET, keeping it within its linear range. This circuit was sealed in epoxy to keep it secret while a patent was pending. Also, a Q-bias pot was added to the feedback circuit of the audio FET, to minimize distortion. Both of these mods were mounted onto an otherwise normal Revision B circuit board.

The important addition of the Low Noise circuit changed the model designation from 1176 to 1176LN, which was prominently displayed on the new black anodized aluminum faceplate. The blue stripe disappeared and the UREI logo was placed over the meter, which was changed from a Weston to a Modutec with two overhead bulbs. This was a major facelift for the model that would become the basis of all future 1176 versions.

In 1973, some major changes were implemented. UA had developed a new preamplifier, the 1109 model, and this was the basis for changing the output amplifier from a Class A design (the 1108 model) to a Class A/B push-pull configuration (the 1109) providing more output current. In conjunction with this, the UA5002A output transformer was replaced by the B11148 transformer (used in the LA-3A), providing 12 dB of gain. The meter drive circuit was also changed, replacing the discrete circuit of balanced bridge transistors with an operational amplifier, to simplify meter calibration.

Around unit #6950, the Urei plant moved from North Hollywood to Sun Valley, California. Many units still bore the old serial number stickers with the former street address, as the chassis built in Hollywood were still being used until the move was finally complete.

The final revision made no changes to the circuitry, only the cosmetics and the layout. The faceplate was changed from black anodized to natural brushed aluminum. The Universal Audio silkscreened logo was removed and replaced with a blue Urei logo on a raised badge, (sometimes only a black printed Urei logo is used). The VU meter was changed to a Modutec "light box" type, using two internal lights, and the Off button for the meter was changed from black to red plastic.

On the rear panel were some key safety improvements: the fuse holder went from round to square and the voltage switch was moved to be above the new IEC cable input, replacing the attached power cord that had been a literal fixture of the device since the very first model.

At approximately serial number 10750, Harman Electronics took over Urei, and the familiar black and silver Urei sticker on the rear was changed to a Harman sticker. No changes were made to the circuitry, and another couple thousand units were manufactured before the brand folded.

Further Reading on the Universal Audio / Urei 1176

Comparing Universal Audio Plug-Ins To Their Hardware Counterparts

Vintage King's Inside Look At Universal Audio

Vintage King's Guide To Compressors And Using Them In The Studio