written by
Ziga Rezar

Free hardware "Gold Can" VCA Compressor!

Gear 9 min read

A certain British console revolutionised the way music is mixed in a way so profound, that it's sometimes hard to truly comprehend and appreciate. Nothing like it existed before and its sound defined whole genres in the decades following its release. And it may all be due to a little circuit invention called the Gold Can VCA.

After more than 40 years, there is a surprising die hard core of world renowned engineers who would choose this one piece of equipment as the only piece of equipment, the so called desert island pick - in a blink of an eye. And the first version was made in 1977!

You guessed it, we're talking about the SSL 4000 mixing console. From soaring rock guitar solos to R&B and even jazz music, this console's sonic fingerprint is touted to be the epitome of clarity, solid stereo image and low end punch. It's the perfect combination of transparency that lends itself to any genre, and subtle color when pushed to near and beyond its limits.

However, don't just take our word for it. Bob Clearmountain, Chris Lord-Alge aka "CLA", Tom Lord-Alge, Andy Wallace, Mark "Spike" Stent, Will Schillinger and Alan Moulder are just a few of the heavy-weights that are notable "SSL 4k" users, with enough awards under their belt to fill a truck.

chirs lord agle cla looking at grammys
Chris Lord Alge aka CLA looking at all his Grammys like they ate his cookies.

So what goes into this sound? Well, one of the most sound-defining features of this console is its master bus compressor. The so called "glue" and punch that's many times attributed to its summing bus circuitry is in fact mostly the job of this unassuming little stereo compressor found in the centre section.

About the mix:analog Gold Can VCA Compressor

And what's so special about it? It has a very interesting main gain control element - the Voltage-Controled-Amplifier VCA instead of vari-mu tubes or FETs. Solid State Logic, the company behind the design of the console used a third party electronics expert to get this circuit, the company called DBX.

Originally the DBX VCA was a discrete circuit, packed into a gold or black-colored sealed aluminum enclosure. Called the DBX-202 it was a pretty novel design at the time and it's not hard to see why SSL chose it as their gain control element in such a crucial part of the console.

"For those that don't know, the SSL stuff is some of the most famous gear in the entire industry. They're like the Fender or Gibson of the music gear."
- Hatsubai

Its fresh new sound superseded the Vari-𝛍 tubes and FET transistors as gain control elements in dynamics processors. It can be best described as "silky" or "smooth", as it retains the perceived transparency even when pushed hard, which is mainly due to its pleasant distortion characteristics even when operating close to its limits.

vca gold can circuits
DBX 202c "Gold can" VCA element as featured in our interpretation of the SSL 4K buss compressor

The original design in the SSL 4000 console, utilizing these VCA elements, even when modernized was a classic stereo compressor, with stereo-only and fairly basic controls. It does one job, and it does it well. But now we're well within the 21st century, and at mixanalog we thought that with all the advances in the audio engineering practices, a design like that could use a refresh.

Here's the result:

mixanalog vca gold can gui
mix:analog Gold Can VCA compressor GUI

Added timing constants and ratios

  1. The original selection of timing constants and ratios could be expanded with very little effort. Admittedly, it wasn't exactly limiting as it was, but I've found myself wanting an in-between setting of release between 100ms and 300ms, and medium attack setting between 3ms and 10ms.
  2. The 1.5:1 ratio can be really amazing too - its sweetness just brings things a little bit closer together, congealing an otherwise too "spacey" mix in an unobtrusive, transparent way.
While there is now more choice, you can still use the original settings (without modification) simply by dialing them in as usual.

Variable Side Chain Link

To accommodate for the up-and-coming M/S functionality upgrade, we both made the controls and electronic side-chains completely separate, effectively making it a true dual-mono design. Additionally, the link between the side-chains is variable, so it's possible to operate it as the original, fully linked, or only partially linked.

This makes for an interesting buss compression trick - when switched to MS mode, the thresholds can be set low, to achieve the desired gain reduction and movement on mid and side channel, then link the two for only around -10dB.

This way, the side channel will not be pounded by low frequency content in the mid channel, but the reverbs and other stereo effects will gently move with the rhythm of the song giving a great feel of rhythm and sway. Nice, huh?!

Side Chain Filters

Modern music tends to get bass-heavy and extends to very low frequencies, so to complete our modernization we implemented some side-chain filters as well. Two of them are "tilt" types, inspired by a certain American bus compressor, and the other four are 6db/octave high-pass filters.

The result

There are some other very subtle tweaks in the circuit as well, mostly to improve transparency on input and output, and what we ended up with is a fabulously smooth compressor that's even more versatile than it's role model, but still proudly carries the family tradition into the next generation.

How it works inside mix:analog

Inside the mix:analog real-time gear access web app, we are going to GIVE AWAY access to the Gold Can VCA Compressor hardware unit that we built for you, FOR FREE. Yes you read that right!

It will not cost you any money to use it. All you need is a modern web browser, at least a 5 megabit/s internet connection and a free account at mix:analog and you can use this iconic bus compressor as much as you want!

This offer will be available at least until the end of February 2019, possibly longer if we're feeling generous ;) Just let us know in the chat box if you feel like you REALLY NEED it for longer and we will certainly do our best to accommodate you!

How do you access this legendary compressor?

Get it from the same screen as the rest of the mix:analog devices. After you log in, click the "Gold Can VCA" tab, then click a square with a time slot that works for you. You can book up to four days in advance, from 15 minutes to up to an hour at a time.

Click the "Gold Can VCA" tab and then a free slot to begin your free booking

You should drop by a few minutes early to upload your files in advance before the session starts, then you can activate it and use the compressor directly from the web browser in real time with a screen, similar to the following:

gold can vca in studio app
Gold Can VCA compressor in mix:analog studio app

In order to dial in your sound, just use the mouse to turn the knobs and adjust the settings - just like in your DAW. When you're happy with what you're hearing, use the Bounce button in the bottom-right part of the screen to bounce your file, wait for the progress bar to complete and get a download link.

Suggested settings

Pulling out detail and texture

starting point settings
A good starting point for gentle compression.

If your mix seems a bit dry or if it could use some added density, use low ratio settings of 1.5:1 or 2:1. These have a very wide "knee" and will start gently reacting well before the actual threshold value.

Next, choose a medium attack setting that works well with both low and high frequency transients (3ms is a good starting point) and the release setting that either "breathes" with the rhythm or lets go fast and allows reverb tails to come forward un-attenuated.

Aggressive, punchy mix

aggressive punchy settings
Adjust threshold to just get the needle move on kick hits.

It's the sound of rock music. Start with the 1:4 ratio, 10ms attack and 100ms release settings, then adjust the threshold so the needle only floats between "0" and "4". If the kick drum drives the compression too much, try one of the side-chain filter settings and listen to which one gives the best overall frequency response with the right amount of compression.

Many mixing engineers prefer the "AUTO" release setting in this use case, which is a combination of long-term RMS levelling and faster reaction to transients, so it could be a good idea to give it a listen and decide if it fits your song's dynamics.

Stereo drum room

stereo drum room settings
Adjust the threshold to only compress the transients, or hit it hard and later blend it in with the original track for "New York style" - parallel compression.

You won't believe how much you can extend the length of that room's reverb tail! Go for the higher ratios, fastest attack and release times and adjust the threshold to start shaving off transients and pulling up more and more room reverberation.

Again, if the original recording isn't high-pass filtered, you can use the side-chain filters to compensate for kick drum triggering the compressor too much.

Tip: you can get a better idea of the timing constants by cranking the threshold really low (counter clockwise) and listening to the "spike" that happens and the release speed after that.

Are you still here?

Reading about it is all good and some history about a classic audio unit can be a fun diversion, but you have to hear it in action to really know what I'm talking about. And now is a perfect time to give it a go - it costs nothing to do!

I went straight to re-evaluating my software emulations and shortly after, I bought a hardware unit that now lives on my master bus 90% of the time! It's a killer sound and since then, I've gotten quite a few "...what did you just do!?? That's the sound!" comments from my clients in the studio. But maybe that's just me...?

Give it a try HERE and contact me in the chat for further info. I'm always happy to help!

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ssl 4000 vca gold can