Relab 176

Name: Relab 176
Price: 149 USD
Author: Relab Development

by Relab Development · Compressor · Variable-mu tube compressor/limiter

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A circuit-level model of a vintage 1960s 176-style variable-gain tube compressor/limiter, with every tube, transformer, timing network and power-supply interaction solved in real time.

Beyond the four hardware ratios it adds sidechain polarity selection, switchable transformer or resistor stage coupling and hidden bias trims, so tone and transient response can be tuned like the hardware's internals.

Best for: Vocals, Drums, Bass, Mix Bus, Mastering. Genres: all genres.

Keywords: tube, vari-mu, vocals, sidechain input, transformer, utility, 60s, bass, bus processing, circuit-modelled, drums, mix bus, vintage, component-modelled, full mix, glue, CPU-heavy, gentle, kick, mastering, mixing, reference & monitoring, single-band.

What it does

Relab 176 is Relab's recreation of a 1960s American 176-style variable-gain tube compressor, pitched as "Hardware-Accurate Tube Compression In Software Form." Instead of fitting curves, it runs the whole audio circuit through a real-time circuit solver so timing and harmonics come from the modeled components.

Four hardware ratios: 2:1, 4:1, 8:1 and 12:1 on a fixed-threshold design, with knee position and slope changing per ratio, from gentle leveling to firm limiting.
Program-dependent timing: attack and release come from RC networks coupled to the tube stage rather than fixed millisecond values, with a Fixed/Auto release toggle.
Sidechain polarity: the detector can respond to the positive, negative or both halves of the waveform, for targeting specific transient edges such as kick attack or vocal plosives.
Stage coupling: a transformer path gives faster (sub-millisecond possible) attack and a slight smile curve; a resistor path gives slower attack and a more vintage low-end thump.
Calibration and trims: one Calibration control shifts tube bias, threshold and harmonic mix together; clicking the logo opens trims for 6BC8 bias, 6BC8 anode balance, 12AX7 bias and a Reference Level.

Source: Relab Development product page

When to use it

Relab 176 models the same family of hardware as Universal Audio's UA 175B & 176 Tube Compressor Collection, while the Manley Variable Mu Limiter Compressor and Fairchild Tube Limiter Collection cover other vari-mu designs. Relab 176 is the pick when you want the circuit-solved response and extra internal controls (sidechain polarity, coupling, bias trims) and have the CPU to spare; the UA version is lighter.

Best for: vocals, bass, drums and mix bus glue where you want tube color and program-dependent movement rather than clinical control.
Genres: works across styles; users mention it on mix buses and masters as well as single tracks.
Look elsewhere if: your computer is older or you run many instances on Intel/AMD machines; users report very high CPU use.
Standout: the Stage Coupling switch and bias trims, which change attack speed, tone and harmonics in ways most 176-style plugins don't expose.

What producers say

Early users on KVR praised the sound and the component-level modeling, with CPU load the main complaint.

KVR users (2025) one wrote "It sounds really good. Like REALLY good." and another, who owns hardware, said "this sounds absolutely amazing."
Modeling approach: a KVR user welcomed "actual component modeling which is rare" and preferred high CPU to compromised quality.
Gripe: several KVR users called it very CPU hungry; one said it is "currently super demanding of processor time", and others found it runs better on Apple M-series chips than on Intel/AMD.

KVR Audio forum: Coming Soon: The Relab 176 (Retro 175) Tube Compressor/ Limiter

Where to buy

Plugin Boutique: $149 (regular $199)
Relab Development: $199
PluginFox: $199

Tutorials and reviews

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