Universal Audio 175, 176, and 177

Shipping your UA to us for servicing



Universal Audio’s Compression Obsession page explains that the 175 evolved from the 108 tube preamp, which was used in Bill Putnam’s console at Universal Recording in Chicago. The 175, introduced in 1961, was one of UA’s very first products. Interestingly, The UA badge on our 175-B shows the address as 6000 Sunset Blvd. in Hollywood. This was the location of Western Studios, the larger of the two United/Western buildings. Studio 1 and Studio 3, where countless hit records recorded, were part of the Western facility. UA’s manufacturing facilities were no doubt located upstairs, above the studios. (By the time I started at United/Western in the 70’s, UA had become UREI and moved to Sun Valley. The upstairs offices were then occupied by The Crusaders, Paul Stookey of Peter, Paul, and Mary, voice over personality comedian Joe Nixon.)

Like the Fairchild, Gates, and other classic tube compressors, the 175 uses a variable-mu tube as the gain change element. It uses 5 other tubes and of course, input and output transformers. The 175’s have a gain reduction ratio of 12:1 and are known for their somewhat slow but extremely smooth attack and release characteristic. While the famous Fairchild limiters are more valuable, many audio engineers feel that the 175 is the best sounding limiter ever made.

These early UA units were released in several configurations. Here’s a quick rundown:


The 175-A had stepped input and output attenuators, along with vernier controls for fine adjustment of In/Out levels. The hinged front panel dropped down to reveal Attack and Release time controls and calibration pots for GR Zero, Cathode Balance, and Plate Balance.

THE 175-B moved the Attack and Release controls out to the front panel. With the inside control panel removed, a slightly shallower chassis was used. The unit we’re restoring has Langevin balanced pots on the input and output, instead of the stepped attenuators.

UA175-B_Fs (1)

THE UA 176 added a gain reduction selector switch, with 2:1, 4:1, 8:1, and 12:1 settings. A custom output transformer with balanced taps allowed the different ratios.

THE UA 177 was just like the 176, but included no meter on the front panel. The rear terminal strip has connections for an external VU meter.

**** Special thanks to Will Shanks and Universal Audio for the great 175 info on their site. ****