15 July 2013


With so much of the world running headlong into a landscape dominated by digital manipulation and mass production, it’s nice to occasionally run in the opposite direction…

Text: Andy Stewart

“Oh s**t, not again!” was the first thought that crossed my mind when I finally clapped eyes on the Retro 176. What was I thinking, asking to review equipment like this yet again? I’d seen the pictures and I’d heard the rants from other engineers who’d used it… I should have steered well clear after reviewing Retro’s versions of the stereo Pultec and Gates STA Level and simply gotten on with living in the real world. You know the real world? That tedious place where you haggle to get 20 bucks off the price of that already discounted dishwasher, or resist the temptation to buy that $29 Aldi DVD player because the one you already own works fine. Sure it whirs a bit, and the sound drives you crazy sometimes, but it seems wasteful and rash to just throw it out!
The world of the Retro 176 is not that world. This is a world where reason and convention are tossed out the window faster than a cheeseburger wrapper from a P-plater’s car. It’s a world of audio compression par excellence, where a vocal chain glows luminous (like the compressor’s enormous VU meter) and
every moment of the performance rivets you to the spot like a stun gun from Star Trek. It’s a world where the weak notes inherent in a bass guitar are ironed out with little fuss: a turn
of the input gain here, a fiddle with the release there; and where thin sounding, amateurishly recorded electric guitars suddenly get their comeuppance, lose their clattering top-end and grow some midrange.
Very few compressors on earth can place such comprehensive control over an audio signal without causing its sound to lose vitality or tone, but you can certainly add the 176 to this very short list.


Like all Retro gear, the 176 takes its cue from a vintage classic; in this case the much loved (though rarely sighted) UA 176, which first appeared out of Bill Putnam’s laboratory in around 1966. This ’60s single channel vari-mu valve compressor – which itself was the younger sibling of the fixed ratio (12:1) UA 175 limiting amplifier, released in 1961 – is still regarded by many who use it as the ultimate valve limiter. From the success of these units eventually came the cheaper (and valve-less) 1176LN ‘black-faced’ compressor; a more ‘modern’ take on the 176 design, this time designed using solid-state circuitry and a FET – rather than vari-mu – gain reduction circuit. The 1176, although similar in terms of its control set, was quite different under the bonnet, possessed a significantly faster attack control and was more aggressive overall. These days the 1176 is by far the most famous member of the original UA family.
Like the much loved and oft emulated 1176LN, the Retro 176 (like the UA 176) has very familiar controls, albeit with a few curve balls thrown in for good measure. As with all the models in Bill Putnam’s original range, setting the gain reduction on the Retro 176 is a two-handed process whereby the input control manipulates the threshold – more input generates more compression – and the silky smooth output knob compensates accordingly. Ratios of 2:1, 4:1, 8:1 and 12:1 are selectable via a rotary switch while attack and release setting are independently manipulated in the typical fashion via standard rotary pots.
Actually, there’s more to the attack control than first meets the eye. Pulling this knob clicks it into an alternative mode of operation that’s slightly more bombastic and distorted sounding – and more in keeping with the original circuitry of the UA 176. I’ve not actually used a UA model for years so I can’t confidently compare the two in my mind, but suffice it to say one setting is more elastic than the other. The ‘in’ setting seems more relaxed and invisible while still retaining the ability to push back powerfully against a strong incoming signal. And the stronger the gain reduction, the thicker, more harmonically rich and vivid things become, just like you want your audio to sound… but more on that in a moment. The backlit VU meter, which casts a magnificent glow over its immediate surroundings is switchable to Input, Output, or Gain Reduction, and like almost no other compressor I know, its swing and trajectory seem perfectly in tune with the performance of the compressor itself – as the gain reduction circuit puts the squeeze on, so the needle seems to press with conviction to the left and release only after the signal has submitted to its will.
Also, like the original, the build quality of the Retro 176 is remarkable. The construction is that of heavy-grade steel, although most of the unit’s considerable weight seems to be in the input and output transformers, which are hefty indeed. Ironically, the nature of this classic ’50s/’60s design makes for an extremely fragile unit overall. With all the valves and transformers (bar one) being rear-mounted and very exposed on the back panel, the Retro 176 must always be treated with great care when it’s out of the rack or when you’re connecting XLR cables. This design type hails from an era when packing up your studio and heading over to a mate’s place for some overdubbing was all but inconceivable. The 176 is not designed to travel without a proper protective roadcase, and you’d never dream of throwing it in the back seat of the car with your mic stands and guitar cases, that’s for sure. In the rack is where it belongs.


The main input and output controls of the 176 feel magnificent to the touch, and provide super accurate tweaking of their respective values – I only wish the smaller knobs were as convincing. The front panel is hinged at the bottom and tilts forward as per the original, and opening up the unit reveals hand-wired point-to-point wiring and very little else. All the circuitry is mounted either on the front or rear panels; there’s nothing placed horizontally on the tray itself, apart from wiring.


There are three other major controls on the Retro 176 that you won’t find on the original. Two of these can be found on the left side of the unit above the chunky bypass toggle switch, and these are manipulated via more of the same. The uppermost control is an ‘Interstage’ switch that affects the tone of the compressor by inserting an additional transformer into the circuit between the input and output stages. Depending on the program you’re feeding it, this can add anything from an almost imperceptibly subtle tonal shift to extra amounts of distortion and punch. I’m yet to fully appreciate the benefits of this control, to be honest, and suspect it will only be after spending more time with it that I’ll have a better sense of when to switch it in (or not). At this stage my perception is that it seems to invigorate slightly dull and mellow sounds by raising the percentage of distortion in the signal, making them more obvious in a mix.
The second unusual feature is what’s called an ‘Asymmetry’ switch, which betrays Phil Moore’s background in broadcasting (Phil being Retro’s President and designer). This is an unusual control that feeds only the positive or negative sides of a waveform to the compression circuit; a concept that was apparently originally designed into broadcast limiting amplifiers to protect AM radio transmitters from overload. Essentially what this control does is reduce the amount of information funnelling into the detector, and in cases where a waveform is decidedly asymmetrical – like voices and percussion, for example – it allows you to choose (using your ears) which side of the waveform best suits your needs. In cases where a signal still sounds too harsh or spiky, switching the Asymmetry switch from positive to negative offers you the opportunity to find the harder edged side of the waveform (if one exists) and feed only that side to the compressor, thus making the tone at the output smoother overall. Conversely, a sound that feels a little too mellow can have its softer side fed to the detector, leaving the harder side to pass through to the output unscathed, thus compressing and simultaneously clarifying the sound somewhat. It’s an esoteric concept but a logical one nonetheless, and for certain voices it works well. Again, this is something you’d only develop an instinct for over time but there’s no question it does make a difference.
The final feature on the Retro that doesn’t exist on the original 176 is a sidechain high-pass filter, a control that’s becoming more and more commonplace on newly released compressors. The concept is simple enough: the sidechain HPF is inaudible to all but the compressor’s detector circuit, allowing whatever low frequencies are filtered from the detector’s path to pass through the compressor without incident, reducing pumping and a general over-sensitivity to bottom-end. This is a great feature to have in a compressor. It allows the control circuit to react to something other than the kick drum in a stereo mix bus situation; it allows more of the midrange component of a signal to be controlled without the bottom-end being annihilated in the process, creating a fuller rounder tone; and it gives you the ability to preserve and maintain some dynamic in the signal below the HPF’s crossover point where other compressors might otherwise force you to simply back the gain reduction off.


Sonically the Retro 176 really is a classic piece of esoteric outboard. It brings dynamic vocals into line with so much richness and delicacy it’s just plain unfair. On bass it provides fullness and depth without pumping or overreacting, and electric guitars just sit in the mix and glow. It’s one of those devices where the more I’ve played with it, the more indispensable it has become.
I’m sure I’ll find countless other roles for the 176 over time, but I must admit, every time I’ve been in the studio with it lately, it has almost always found its way onto centre stage as a lead vocal compressor. No doubt this will be the role it performs in the vast majority of cases in studios around the world, and in this situation it is simply sublime. Vocals are often wildly dynamic and hard to control without generating unwanted side-effects, particularly distortion, but with the 176, 10dB of gain reduction is perfectly manageable and 15dB still holds together nicely.


This is the third time I’ve looked at a piece of Retro gear and mercifully – for the time being at least – the last. As a writer and engineer, it seems there are only two possible outcomes of a Retro review: going nuts or going broke! In the six weeks I’ve had the 176 I’ve grown more accustomed to its sonic qualities than I would have liked, so once again the struggle to return it will be immense. Like no other compressor in my outboard rack, the Retro 176 seems to sound better the more it compresses, and in the window between two and 12dB of gain reduction it’s unmatched by any compressor in the rack.
I’m sure ‘the haves’ – those lucky enough to buy a 176 at some point in the future – will snigger when they screw this unit into their racks for the first time. Meanwhile the ‘have-nots’ – the vast majority of us – will have to be content for now to pray for a miracle: that one day 176s will simply rain from the sky! I, for one, will be firing arrows from my crossbow at the tyres of the courier van (à la Wez from Mad Max II) as it drives away next week. When I win Tattslotto I’m going to buy all the Australian stock of 176s in one second flat, no questions asked. Until then, I guess I’m hangin’ with the have-nots.


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