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Golden Age Project 500 Series

Mic/Line Preamplifier, EQ & Compressor By Matt Houghton
Published September 2017

Golden Age Project 500 Series

These modules can be mixed and matched to create a versatile, high-quality, Neve-esque channel strip for an impressive price.

Golden Age Project (GAP) were one of the first of the modern crop of affordable-clone manufacturers and their raison d’être seems to be to make high-quality discrete preamps and processors, based on classic designs but at a price that project studio owners will find affordable. We reviewed the first iteration of their Pre-73, based on the classic Neve 1073 preamp circuit, way back in 2009, and regular readers may recall reviews of several more of their devices since.

Before I delve into this review of their latest 500-series modules, it’s worth pointing our that, without exception, I’ve always been impressed by the quality that’s on offer from GAP for the asking price. Typically, the competitive pricing has been achieved by a combination of the adoption of low-cost manufacture in the Far East, and the swapping out of some of the more expensive components for carefully selected, unbranded replacements from China. So, for example, the Carnhill transformers used in most of the more expensive Neve homages have been eschewed in most models in favour of unbranded Chinese-made transformers, and the same approach has been taken to the capacitors. The PSUs have often (not always) been external OEM wall-wart types, and in some cases less money seems to have been lavished on the enclosures and switches than on either the classic devices on which GAP’s products are based, or on higher-cost clones from other manufacturers.

While I’ve seen plenty of self-declared ‘gear nuts’ dismiss this approach, I’ve never had a problem with it, for a few reasons: first, GAP offer higher-priced versions of some products featuring ‘name’ components for those who want them (some of their distributors also offer modifications); second, there are already plenty of cost-no-object clones available from other manufacturers; and third, and perhaps most importantly, when I’ve compared different versions of the same GAP product — for example the Pre-73 with and without Carnhill transformers — I’ve heard subtle differences, certainly, but I’ve also been very hard-pressed to say which sound I actually preferred. What all this boils down to is that while there may be more painstakingly authentic clones around, owner/designer Bo Medin has exercised very good judgement in bringing down the manufacturing costs without sacrificing much by way of sonic and tonal quality, and the great news is that those cost savings mean the asking price is, for this sort of gear, very competitive.

Balancing Act

GAP have offered 500-series models for a few years now, and with the release of their new Comp-554 (the original half-rack version of which was reviewed in SOS April 2011:, I was invited to try out the latest versions of each module in the current range. For review Bo sent us a Purple Audio Sweet 10 500-series power supply/chassis already populated with two full GAP recording/processing channels. Each channel featured a Pre-573 MkII mic preamp, a Comp-554 diode-bridge compressor, and two EQ-573 inductor EQs — one to process the signal itself, and another to sculpt the compressor’s side-chain. As the Comp-554 is a ’double-wide’ unit, the two full channels described above together occupy all 10 of the Sweet 10’s module slots.

Pre-573 MkII

In terms of functionality, the Pre-573 MkII offers pretty much everything you’d normally want from a mic preamp, and more besides. There’s 70dB of gain available via the main switched rotary Gain control for mic signals, from 20 to 70 dB in 5dB increments, and a further 5 or 10 dB of gain can be applied via a toggle switch — so the total gain range is actually 20 to 80 dB. At the end of the signal chain is a variable Output attenuator (this time a pot rather than a switch), which means you can drive the input transformer and gain stages as hard as you like into distortion and still set a sensible level for the next device in the signal chain (in fact, you can achieve some crazy amounts of distortion if you really wish to abuse things). If you’ve coupled the preamp with an EQ-573 module (more on that later), this output control allows you to adjust for any overall gain that’s added by that module courtesy of EQ boosts.

48V phantom power is delivered when another small metal toggle switch is in the up position, and a red LED shows at a glance when phantom is active. Level metering takes the form of another red LED labelled Signal — it starts glowing when the output level hits +4dBU, and the hotter the output level the brighter the LED becomes. That’s a minimal but sensible arrangement given the limited availability of front-panel space.

The main input, received through the host chassis’ sockets, is switchable between Mic and Line level via another toggle switch, and there’s a front-panel DI input jack. The user needs to juggle three metal toggle switches to select the appropriate source. The lowest one in the left column of switches chooses the 1.5MΩ FET-buffered Active DI input or the Mic/Line input, and when this is in the up position, the toggle immediately above it is used to select Mic or Line. The lowest toggle of the right-hand column selects the mid-impedance Passive DI when in the up position, whereby the front-panel jack is routed directly to the gain stages, bypassing the input transformer. The down position is off, and it must be set to that position if you wish to engage the Active DI. The Mic, Line and Active DI are all routed through the input transformer. It may sound complicated to describe on the page, but it’s all very obvious and intuitive in practice.

The Mic input impedance is switchable between 300Ω and 1.2kΩ, with each setting potentially offering a slightly different tonality when used with some moving-coil and ribbon mics. Generally, I preferred the 1.2kΩ setting, but it’s nice to have the option — I sometimes like, for instance, guitar cabs miked with the duller/more mid-rangey sound of a dynamic mic such as an SM57 when used with a lower-impedance preamp. The load on the output transformer can also be tweaked, but only via an internal jumper — the default position sets the load to 600Ω, the idea being that this will retain the ‘vintage’ character when connecting the Pre-573 to modern devices’ high-impedance inputs. If you’re plugging it into an older device with a 600Ω input impedance (eg. an LA-2A compressor), you can move the jumper accordingly. Without the load, connecting to a high-impedance device such as your audio interface line input will result in a brighter-sounding high-end.

Another interesting tonal option is presented via the three-position Air toggle switch: the up position engages a 6dB 30kHz bell boost, which provides a fairly subtle lift to a signal well below that frequency; the central position switches that facility off; and pushing the toggle down inverts the signal polarity (you can’t apply Air and polarity inversion simultaneously). Finally, there’s an alternative Pre-573 MkII Plus model with Carnhill transformers. And if that’s not enough by way of tonal options, you can always hook up an EQ-573...


Golden Age Project 500 SeriesThe EQ-573 inductor EQ cannot be used alone, but is intended to be used as an insert with either the Pre-573 MkII or the Comp-554. A short cable connects the units via sockets on the rear — you can see one of these connectors shown in the rear view of the EQ.The EQ-573 inductor EQ cannot be used alone, but is intended to be used as an insert with either the Pre-573 MkII or the Comp-554. A short cable connects the units via sockets on the rear — you can see one of these connectors shown in the rear view of the EQ.One consequence of offering the preamp and EQ as separate modules (some competitors offer the preamp plus EQ as one double-wide module) is that the front-panel of the EQ-573 is a touch congested. I tended to catch the controls adjacent to the one I wanted to turn, particularly when adjusting the HF band at the bottom — it was nothing too problematic, as the knobs aren’t easily knocked out of position, and the knurled edges and switched and detented nature of the different controls made it easy to select the desired setting with only my fingertips, but it’s worth mentioning. Yet the separation of the two modules also offers some advantages to the user, not least that you only pay for what you need. For example, if you require a bank of eight preamps, you’ll only need to budget for one 500-series chassis and eight preamps. You can add eight EQ modules in a second chassis, of course, but you could also choose to have only a couple, and decide how you wish to deploy them.

The one thing you can’t yet do is use the EQ on its own — it’s designed only to be used as an insert for the Pre-73 MkII or the Comp-554, with those modules’ transformers taking care of the signal levels and balancing. Each module has a small white socket at the rear, and a short cable is used to connect things — I was pleasantly surprised to find that these cables didn’t make getting the devices in and out of the rack any more difficult than is usually the case with 500-series modules. I say ‘you can’t yet do’ because Bo tells me he has been considering adding transparent IC-based balancing to the design, to allow the EQ to accept line-level signals without significantly increasing the costs. To be clear, the mooted arrangement would allow you to use the EQ as at present, without the ICs in the signal path, or as a stand-alone unit with the ICs in the signal path. I hope he does do that, as the EQ sounds rather nice to my ears and it would be lovely to be able to use it in tandem with my other mic pres, or to use the EQ alone on line-level sources where I might prefer not to hear a tonal contribution from the transformers .

In this three-band plus high-pass filter design, rotary switches select each band’s frequency and centre-detented pots apply gain or attenuation. The top-most controls physically govern the lowest frequency band, a shelving type which can be set to Off, or 33, 55, 100, 175 or 300 Hz, and can be treated to ±15dB of gain. Below, another pair of knobs control the MF bell EQ: Off, 240, 350, 500, 700 Hz, or 1, 1.6, 2.4, 3.2, 4.8, 7.2 or 10 kHz, and ±15dB gain. The bottom-most two knobs govern the HF shelf: Off, or 8, 10, 12, 16 or 20 kHz, this time with ±18dB. Above and a little to the right of this last pair is a single rotary switch that engages the high-pass filter: Off, 50, 80, 160, or 300 Hz. The only other control is a Bypass toggle switch. It’s a console-style EQ for broad tonal shaping rather than precision sculpting and the bands overlap usefully: it’s possible, for example, to apply a chunky low-end boost at 55Hz, while also high-pass filtering at 50Hz to pull back down any low-end detritus that’s been boosted along with the signal. And don’t forget that both the compressor and the preamp, one of which you’ll be using with this EQ, feature 30kHz Air boost options.


Like the EQ and preamp, the 554 compressor is a mono device, but unlike them it occupies two adjacent vertical slots in the host chassis. That amount of front-panel space is certainly justified: not only is there more circuitry to accommodate, including three transformers, but the Comp-554 also requires a second input from the host chassis to accept external side-chain signals. Happily, this means there’s plenty of space for the profusion of controls and the usefully large, backlit moving-needle VU meter. That meter can be switched to display GR (gain reduction) or the output level — and the latter can be switched between +4 and +12 dBu reference levels. Whichever setting you use, you’re always reading left to right: I’d half-expected in the GR mode for the needle to move left from 0VU as more gain reduction was being applied, but it moves the other way, and is indicated on a second scale with smaller numbers, from 0 to 100 percent. Somewhat curiously, I found that with drastic settings I could apply more than 100 percent gain reduction, but the meter is useful nonetheless.

Rotary switches set the Threshold (16 positions, marked from -20 to +10), Attack time (eight positions, ranging from 0.5 to 50 milliseconds), Release (six positions from 25 milliseconds to 1.5 seconds, along with two Auto release positions, the second of which is faster acting than the first), Ratio (1.5:1, 2:1, 3:1, 4:1 and 6:1) and a high-pass filter for the internal side-chain (Off, 50Hz, 100Hz or 7kHz). A toggle switch above the Ratio control allows you to choose between the default internal side-chain signal, (which may or may not be subjected to the aforementioned filter), the external side-chain input, and ‘Insert’. The last position allows you to use an EQ-573 module to fine-tune the internal side-chain signal. You could, for example, boost the mids and cut the lows and highs, to make the compressor more responsive to the mids. The greater number of high-pass filter options on the EQ module, compared with those built into the compressor, might also come in handy. There’s no overall input or output level control on the EQ, so you may need to tweak the compressor’s Threshold as you boost or attenuate EQ bands.

I’ve already mentioned the preamp’s 6dB Air EQ boost, but the compressor goes one better: the three-position Air EQ switch can boost the signal by 3 or 6 dB at 30kHz (the other position being Off). Obviously, the 3dB setting is subtler than the 6dB one, and I found it a useful addition — adding top end can become addictive, and it’s easy to overdo it as your ears grow tired if you’re not careful!

There are two different ‘bypasses’: Out routes the signal through the module but suspends the compression (but does not bypass the EQ-573, if inserted), effectively turning the 554 into a transformer saturation processor (you’d use the previous device in the chain to drive the input), while Bypass provides a traditional hard bypass of the whole module, including the EQ-573, if inserted. Finally, there are two more small metal toggles. One sets the output termination to 600Ω, 2kΩ or Off. The other allows two 554 units to be linked for stereo operation — which is a wonderful facility to have, since these things can sound superb on a rock track’s drum bus, particularly with the internal 100Hz side-chain high-pass filter engaged!

The standard model I was sent for review contained Chinese-made transformers, but as with the preamp a more expensive ‘Plus’ model is available, with Carnhill models fitted. Seriously, though, I don’t think I’d bother with the Plus version as this thing sounds great already! Other than for the additional options, the sound is pretty much indistinguishable from that of the stand-alone Comp-54 as described in the review I linked to above. In other words, it’s a lovely, characterful sound, and the compression action is wonderfully smooth and forgiving on a range of sources. But if you push it hard it can add a real smack. It’s worth noting that, as with all diode-bridge compressors (including the original Neve from which this design is derived), the Comp-554 can be a little noisy: if you’re compressing hard and adding loads of makeup gain, you’ll hear a distinct hiss. It’s not a problem, but an inherent characteristic of the design — and it’s easy enough to low-pass filter the result to remove the worst of it (though not with the EQ-573, which has no low-pass filter...). But if you’re tempted to keep piling on those high-end Air boosts you should definitely listen out for it!

Mod(ule)s That Rock?

Taken on their own, each module offers remarkably good value for money. In practical terms, they’re fairly versatile, and in sonic terms they all offer oodles of wonderful character. Any criticisms I have are trivial — the lack of finger space on the EQ controls, for example, or the fact that the legends on some controls were a few millimetres offset from the switch position — and none would deter me if considering a purchase. But when you combine them they really come alive. With just one preamp and one EQ you have a very capable tool to add bags of character to any mic, line or DI signal, and to massage a source to fit your mix. Add the compressor, and you have such a versatile, controllable channel strip that, again, seemingly has warmth on tap. And I’d recommend the full stereo setup that was sent for review without hesitation, whether as an analogue ‘front-end’ for recording to a DAW, or a line-level processor for use in mixing. It sounds great, and the switched controls make precise recall easy. Yes, it would be possible to pay significantly more money for slightly more polished Neve clones, but if you can’t get a cracking sound out of these tools it really isn’t the tools you should be blaming!


At this price per module, there are quite a few characterful preamps, EQs and compressors, from the likes of JoeMeek and Warm Audio, but none I can think of deliver that Neve-esque character quite so obviously. Further up the food chain, you’ll find a number of high-quality recreations from BAE, Heritage Audio and AMS Neve, as well as Mr Neve’s own current models courtesy of Rupert Neve Designs.


  • All units sound great.
  • Air band boost on preamp and compressor.
  • Manufacturing cost savings well judged, so these modules represent superb value.
  • Useful output-impedance options.
  • Solid build quality.
  • ‘Plus’ versions available with Carnhill transformers.


  • Some EQ controls feel a little cramped.
  • EQ can’t (yet) be used alone.


As with all GAP products, these all-discrete modules represent great value for money — it’s high-quality professional-sounding vintage, vibey gear at a project-studio price.


Pre-573 MkII £259; Pre-573 MkII Plus £429; EQ-573 £175; Comp-554 £389; Comp-554 Plus £576. Prices include VAT.

Pre-573 MkII $299; EQ-573 $269; Comp-554 $399.