Compress to Impress: The Top 10 Free and Cheap Audio Unit Compressors

Outside of EQ there isn’t an audio effect I reach for more often than the trusty compressor. Coming in all different flavours, shapes and sizes, no two compressors are the same and it’s one effect I find I can never have too many of.

At the heart of it, compressors work by reducing the dynamic range of an incoming signal. They can be transparent or add colour or audibly distort your signal. They can be used correctively or creatively and even radically change your sound.

However, while there’s a plethora of decent native compressors, excellent options by Waves, AD and Slate Digital, I want to take a look at some compressors that wont break the bank. Here’s the dry drum track I’ll be using throughout. Thanks to Stuart Pringle for the help recording these!

So, in no particular order…

01. Acustica Audio ACQUA Tan (FREE)

A nice simple VCA compressor from the nice people at Acustica. Perhaps better known for their plethora of vintage channel strip emulations, Acustica have a couple of freeware plugins available; this and their Homebrew EQ.

The headline feature of this compressor aside from it ease of use is the SHMOD – or shape modulation to you and I. This is fiddly to describe and isn’t detailed extensively in their manual but it allows fine tuning of the otherwise fixed position attack times.

I’m a new Tan user but I’ve been having fun plastering this on overhead mics using the dry/wet control for some fake parallel compression.

Download it from their site.

02. Klanghelm DC1A (FREE)

One of two Klanghelm entries on in this article, the DC1a is a slimmed-down version of the more comprehensive DC8C. While the DC8C is a hugely flexible compressor the DC1A is deliberately limited in its usage and that’s sort of why I love it.

I’m very much right tool for the right job and because this compressor does so little it has a highly particular sound – it’s colourful and brings up atmosphere in acoustic recordings but it’s too smashy and aggressive.

Despite it’s limited buttons and knobs set there are some other cool features such as the ability to unlink the stereo channels (DUAL MONO), a built in high-pass filter (DEEP).

Get it for free from their site.

03. Audio Damage Rough Rider (FREE)

Of course this was going to come up somewhere! One of my favourite tools for obliterating drums or transient information. The default preset it loads up sounds fantastic with minimal tweaking, but even with so few controls there’s a lot of mileage out of this beast.

The site claims it has a uniquely warm “vintage” without name-checking anything it models directly. Honestly it’s like nothing I’ve ever heard. I’ve been using it a lot recently on room microphones to get that huge pumping atmosphere heard in many classic breakbeats.

Perhaps more known for the eurorack modular, Audio Damage produce some awesome plugins, including all-destroying freeware Fuzz and an excellent cheap Mutron Bi-Phase clone.

Download Rough Rider for free.

04. ToneBoosters ReelBus (£27/$35)

While not technically a compressor I’ve been addicted to the ToneBooster range and in particular ReelBus. This is a tape emulation with all the added advantages (and disadvantages) of a real one (see what I did there?).

Tape saturation like other distortion can work very similarly to compression, and overdriving a good tape machine is almost interchangeable sonically. The Recording Level acts a little like an input gain and ratio all rolled into one, driving this harder will increase the effect.

And for some added vintage brownie points there’s controls for wow & flutter, hiss, asperity noise and a spectrum control, allowing for a duller or brighter sound. The different tape-model algorithms will change the makeup of your sound from hardly at-all to almost unsalvageable tape-deck.

While I’m not of the reel to reel generation I did grow up on cheap consumer tape cassette machines and this even has an option for that! ReelBus is on its fourth incarnation now these plugins are fully demo-able from their site, as if you need any more excuse to try them out.

Buy here.

All £ to $ conversion is correct at the time of posting.

05. Pensadia SOR8 (£22/$29)

What collection of compressors would be complete without at least one Distressor emulation? The Empirical Labs Distressor was a hugely popular hardware compressor that was introduced to the world in 1995.

Much like the original Distressor, the SOR8 doesn’t emulate one specific compression style. It has ratio switches that range from subtle 1:1 low harmonic distortion to 2:1, 4:1 compression right the way through to optical and what it called NK (a nod to the original’s Nuke brick-wall limiter setting).

Distressors sound great on snares, overheads, synth and electric bass I’ve even using them on distorted guitars busses. Similar to an 1176, the SOR8 doesn’t have a threshold control so all compression thresholds are determined by the input gain.

This is one of the few compressor that sounds really good at super short attack times and the built in distortion, dry/wet control and input filter are a nice added bonus.

At this price it’s hard to look past.

Buy from Cocell Productions.

06. Nomad Factory Bus Driver (£15/$19 Discounted)

I was introduced to this plugin as a limited demo but I’ve used it so much I had to purchase. Normally priced at $89 it seems to be listed as one of those eternally discounted plugins on Don’t Crack.

Bus Driver is an FET compressor with the standard 1176 limited controls. The fixed ratio 2:1, 4:1 and 8:1 are all present as well as a limit option (assuming that’s ∞:1) but what I’ve used this for more than anything else is the mild tube distortion.

Comparing it to my TLA Ivory Mir Pre it sounds remarkably similar without the sound breaking up or dulling too much in the higher frequencies. So while I don’t use this as a blatant compressor and more of a character/channel strip emulation, it makes my list.

Buy it now from Don’t Crack.

07. Klanghelm MJUC jr. (FREE)

If you’re after something simple, this couldn’t be easier to operate. With two dials, one for compression and the other makeup gain, this tube-styled Vari-Mu* compressor is the younger brother of their MJUC and is designed to sit on the master bus compressor.

Dialing in a small amount of compression will subtly soften the higher frequencies and transients. More extreme values give you instant vintage satisfaction. While it is great on the master channel I’ve found uses for it on drum busses, guitars and even vocals.

The kind of compressors that this models were normally used for radio broadcast before finding new life in musical applications. For that reason they’re smooth and transparent, perfect for mastering.

*The term Vari-Mu® is actually a registered trademark of Manley Labs, in reference to their stereo limiter (link), but while Klanghelm don’t directly reference it, the comparisons are clear.

Download it for free.

08. Xfer Records OTT (FREE)

While most compressors model the likes of levelling amplifiers, dbx 160s or SSL Bus Compressor, Steve Duda’s OTT is one of the only compressors that not only models a digital compressor, but really it just models a preset!

Any Ableton Live users might well be familiar with the Multiband Dynamics plugin that comes bundled with it. This performs upward and downwards compressor (a bit like an expander to you and me) over three bands. One of the presets was OTT (Over The Top) and this proved to be really popular with the dubstep and electro guys. So, Duda’s Xfer modelled it and gave it away for free!

Even at fairly subtle settings OTT will colour your sound quite a bit, which is part of the nature of multiband compressors. However just using the expander on the higher band can breathe life into dull breakbeats or overhead mics, allowing airey cymbals to breathe and pump in unnatural way.

While originally designed as a mastering plugin this is more often than not used as a sound design tool to amplify every last harmonic hiding in the audio spectrum. Not for the faint hearted.

Download it for free, as well as loads of other great Xfer plugins.

09. vladg/sound Molot (FREE)

This is another self-styled Vari-Mu compressor in the vein of the classic Fairchild bus compressors. With direct design head-nods to Soviet era broadcast equipment, the Molot could be confused for being a little complicated at first but all the usual suspects are here.

While Molot is advertised as a Vari-Mu I’ve found the response times really fast and sound great on picky disco guitar lines, percussion and close mic’d drums.

If your version is plastered in Cyrillic, click the EN button hidden in the bottom right corner ☭

Download it for free.

10. TDR Kotelnikov (FREE)

If you were a fan of their Feedback compressor then you’ll love this update. Label-come-plugin developers Tokyo Dawn Records (or TDR for short) have been developing free and cheap plugins for a few years now and have established themselves as one of the more reliable and high quality options.

According to their site Kotelnikov is “proudly digital” and isn’t trying to emulate any of the big hitters we are so familiar with, and in a age of vintage-emulation everything you have to commend them for that.

As for its sound; I’ve always found TDR stuff very flexible without overtly colouring the sound too much. Easily one of the more transparent compressors in this list. One feature I am a huge fan of is the high-pass filter inside the sidechain analysis circuit – more developers should include this as it’s invaluable for sidechain compression!

Be sure to check out all of their plugins.

Notable  Omissions

KUSH Audio Ωmega pre-amps (£22/$29)

I love KUSH stuff after being introduced to it by a good pal of mine. Initially skeptical about the subscription model (I still think this is a flash in the pan any plugin developers reading) but from quite early on I was hooked on these plugins.

While KUSH do produce some excellent traditional compressors it’s their Ωmega pre-amps I reach for time and time again, there are three in total, the Model 458a (a rarefied tube mic pre), Neve-style Model N and lastly the API-like Model A, all priced at a very reasonable £22/$29 each.

While not technically compressors they do work in a not hugely dissimilar fashion and I use them extensibly in my pseudo vintage recreations – much as I use compressors.

Click here and scroll to the bottom of the page.

digitalfishphones BLOCKFISH

This plugin seems to be as old the internet itself, or, at least to me. Along with Green Oak Crystal Ichiro Toda’s Synth1, this was one of the earliest freeware VSTs I ever downloaded, so its inclusion is perhaps more nostalgic than anything else.

HOWEVER the developers have not maintained the code for Intel based Macs and I’ve not been able to test to see if their VST or PC versions work, but I felt it difficult to compile a list without at least giving them a cursory mention, as if this was some sort of eulogy.

Sound wise, BLOCKFISH  has two modes, VCA or optical compression. From what I remember it was super aggressive and really brought out all the breathiness in vocals and room sound in close mic’d drums. Perhaps more of an effect than a tool, but perhaps that also says more about where I was with music production when I was first using the plugin back in the early 00s!

Lastly here are some compressors that I am yet to try but are under the £30/$40 mark and have come highly recommended from various colleagues and friends:

• Resonance Sound MasterMix Buss Compressor – a hybrid compressor sitting somewhere between a VCA-style and tube ’60s compressor. Hmmm!
• Minimal System Group Punch Compressor – an ultra-fast attack time FET/1176 stye compressor.
• Minimal System Group Punch Evolved – presumably an update on the above that has EQ and mid/side processing built in.
• FXPansion DCAM – a VCA compressor free to those with an FXPansion account.
• Minimal System Group Master Compressor – an ultra clean bus compressor with optional added harmonic distortion.

That’s it. Is there anything I’ve missed? I’ve scoured every corner of my audio unit library to try and dig out the best free and cheap compressors but no doubt there’s some total open goals I’ve overlooked so leave a comment to tell me what you use.