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Retro Instruments 176 review: One-of-a-kind piece of gear

The UA 176 is perhaps one of, if not the most highly sought-after compressors of all time. Simply finding one is an extremely difficult task on its own, and even then, trying to buy one for any less than $20,000 is just about next to impossible.

Enter the Retro Instruments 176, which is an attempt to not only bring this coveted tech to the masses, but to expound upon and heighten its capabilities.

Retro Instruments 176 tube limiting amplifier review
176 limiting amplifier | Image: Higher Hz

Final verdict on the Retro 176 5.0

The Retro 176 is a beast in terms of sound quality, design, and versatility. Most other compressors in line with this one are extremely expensive and you’ll be hard pressed to find anything that sounds as good as the 176 for under $4,000, much less under $5,000.

This is a true one-of-a-kind piece of gear that I would highly recommend to anybody looking for an affordable vari-mu unit.

What I like

  • Sonically rich and full of character.
  • Versatile.
  • Excellent design and quality of build.
  • Amazing cost-to-value ratio.

What I don’t like

  • Nothing to note.
Buy Retro Instruments 176 at: SweetwaterVintage King

Why you should trust me

Brandon Schock, writer at Higher Hz

I’m a producer, composer, and audio engineer with a decade’s worth of experience with a wide range of gear and recording techniques. I’ve worked with a myriad of different equipment, from Neve, Neumann, Universal Audio, and more.


Use these jump links to navigate to the desired section of the review.

Functionality and controls 5.0

In spirit of the iconic UA 176, the Retro Instruments 176 boasts a variable-mu design not unlike the original UA unit.

While I wouldn’t consider the Retro 176 to be a clone by any means, it does retain much of what made the UA 176 so special, and in fact, has a bit more in common with the 1176LN. For instance, it has a fixed threshold and input/output controls, and four ratio settings (2:1, 4:1, 8:1, 12:1) for versatile compression.

In terms of its design, the 176 flaunts some exceptional speed, having attack times spanning 0.1-2 ms and release from 27-572 ms. These settings, coined as “single mode” by Retro Instruments, resemble those on the original unit.

Depressing the Attack dial, however, will help you to achieve “double mode,” in which the release becomes more program-dependent, allowing for compression to be applied more slowly and smoothly.

The Retro 176 also showcases a sidechain hi-pass filter with a fairly broad range, going up to a little over 2 kHz (-3 dB) at its highest setting. This can be deactivated by a switch when at its minimum setting.

Lastly, the unit has a few more interesting features for even more variety in sound. Firstly, the interstage transformer can be switched in and out of the signal path, and there is an asymmetry function which can be toggled either to “+”, “-“, or off.

Retro 176 interstage and asymmetry settings
Interstage, Asymmetry, and Amplifier switches | Image: Higher Hz

Essentially, some waveforms are more or less symmetrical than others, and this switch decides whether the detector is reacting to the full waveform or one side of it.

The effect of this is that it can allow the compression to open up on tracks that might feature this natural imbalance, such as vocals, horns, or strings.

Sound quality 5.0

The unit’s sonic character is plenty versatile and can go from extremely subtlety in its application to some serious squashing.

It boasts 20 dB of available gain reduction, a SNR over 76 dB, and a relatively flat frequency response of 20 Hz – 20 kHz, allowing it to reproduce audio accurately while still delivering the distinct character of tube circuitry. Harmonic distortion barely reaches the one percent mark even when set to higher levels of gain reduction.

It truly works great on just about anything you throw at it. One thing I’ve personally enjoyed immensely about the unit is that I can track through it at a low ratio (say 2:1), and when it comes time to mix, setting it to a 4:1 ratio in post isn’t too much. So you can really take some liberties with your tracking without having to worry so much.

In the manual, Retro Instruments has written that the 176 “adjusts tone in a way that equalization cannot,” which is completely true. There’s something particularly mystical about units like this, because it’s not just that it makes the tone brighter in the way that high-end shelving filter does.

It’s usually a bit of saturation, coupled with the compression you’re already applying, as well as the relationship amongst all the separate components within the unit that give tracks a particular flavor when running through it.

Build quality 5.0

This thing is built like a tank, and can make you feel like you’re working for NASA when manning it. Mounting can be a bit nerve racking since the unit is rather heavy and the valves are exposed, but once it’s in, it’s phenomenal.

Retro 176 limiting amp rear view
Rear panel view | Image: Higher Hz

The look is sharp, the dials and switches feel great and the flow of its layout is very intuitive. I don’t think there’s anything about the build that I’d want to be different.

Who is the Retro 176 limiting amplifier best suited for?

This unit is best suited for professional engineers, musicians, and recording artists who are looking for a compressor that delivers character, versatility, and exceptional performance.

Buy Retro Instruments 176 at: SweetwaterVintage King

Video demo

You can also watch this video by my colleague Fabio, where he puts the Retro Instruments 176 tube limiting amplifier to the test.

Recent updates

  • April 9, 2024: I’ve added quick jump links for faster navigation and updated the text for accuracy.
  • December 14, 2023: I published the original review based on my experience with the unit.