Purple 4

Name: Purple 4
Price: 237.32 USD
Author: Acustica Audio

by Acustica Audio · EQ · Passive EQ and tube preamp collection

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Purple 4 is a collection of eight plugins that emulate vintage passive equalizers and tube preamps, including the mastering-grade MT Ultra.

It uses Acustica's Hyper technology and costs €209 (about $237.32).

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

Keywords: tube, bass, mastering, hardware emulation, vintage, mid/side, vocals, classic, full mix, modern, airy, bus processing, drums, dual-mono, enhancement, fat, kick, mix bus, mixing, musical, resizable UI, silky, static, tight.

What it does

Purple 4 is Acustica Audio's suite of classic passive tube EQs and preamps, in eight separate plugins that cover both vintage units and modern reissues. This version runs on Acustica's Hyper technology, which the developer says lowers CPU use, and adds a new mastering EQ, MT Ultra.

P-1: the best-known design of this EQ style, aimed at big bass and silky air.
P-AA: a modern clone of the same design, with tighter bass and a different top end.
M-5 and M-5V: mono midrange EQs with two boost bands and one dip band between 200 Hz and 7 kHz; M-5V is the vintage variant with narrower bandwidth, boosts of roughly 8–10 dB and about 11 dB of cut.
H2: a passive tube EQ for boosting and cutting low frequencies to fatten bass.
HLF and Pre: HLF adds 12 dB/oct low-cut and high-cut filters with a preamp emulation; Pre offers five tube preamps for color on their own.
MT Ultra: a stereo mastering EQ with independent left and right controls, a Mid-Side mode, detailed bass and a clear top end.
Monitoring and workflow: Delta, Left/Right, Mid and Side listening modes, a resizable GUI and presets from sound engineers.

The sources do not list a demo.

Source: Acustica Audio product page

When to use it

Purple 4 covers the same family of units as Universal Audio's Pultec Passive EQ Collection and Waves PuigTec EQs, the standard passive tube EQ emulations, but in more variations: two takes on the main EQ, the midrange units, a bass-focused H2, separate filters and preamps, and a mastering version with Mid-Side. That makes it the better pick if you want to choose a slightly different flavor of the same classic for each source, or use the preamps alone for color. It is less of a quick fix than a single Pultec plugin, since you have to pick the right unit first.

Best for: broad, musical boosts on bass, kick, vocals and the master, and tube color from the preamps.
Genres: any.
Look elsewhere if: you need precise or dynamic EQ (Pro-Q 4 or F6), or one simple Pultec-style plugin (Pultec Passive EQ Collection or PuigTec EQs).

Where to buy

Acustica Audio: $237.32 (€209 (KVR listing price) converted to USD (ECB rate, 29 Sep 2026))

Tutorials and reviews

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