The modular format for preamps and studio processors continues to expand. Here’s our pick of recent 500-series releases.

Originally developed by API to populate and expand their large‑format consoles, the 500‑series format is hugely popular today, in home and professional studios as well as on location. Today, many manufacturers offer 500‑series modules and host racks, and the format can be a convenient and often cost‑effective way to get your hands on gear designs that were once reserved for big‑budget, high‑end facilities. Its modular nature means you can ‘mix and match’ to your heart’s content: fancy a channel strip that combines a Neve preamp, a Motown‑style equaliser and an optical compressor? Not a problem!

Whether you’re looking to make the leap into the 500‑series world, or simply want to fill empty slots in your rack, you can explore the format in detail in our SOS November 2020 articles that take you through what to look for in a rack (https://sosm.ag/500-series-chassis), and factors to consider when choosing modules (https://sosm.ag/500-series-modules). But there have been many new products since, so this month we’re shining our Spotlight on some of the key releases of the last year or two.

AEA RPQ503 & Snaqbox V2

As its name suggests, the RPQ503 is a 500‑series version of AEA’s praised RPQ3 standalone preamp. With a 68kΩ input impedance and a healthy 85dB of gain on tap, it’s optimised for ribbon mics, but as AEA are keen to point out, the RPQ503 makes an excellent partner for all other types of mic, too. The gain and output level controls are joined by a trio of buttons that handle mic/line switching, polarity and 48V phantom power. Much like its rackmount sibling, the RPQ503 also includes AEA’s CurveShaper EQ, which comprises low and high bands that each offer ±20dB of gain and sweepable frequencies.

Earlier in 2026, AEA also launched the Snaqbox V2, a new and improved version of their two‑slot 500‑series chassis, and thanks to upgrades to the power supply, the unit is now capable of delivering a chunky 500mA per slot, ensuring compatibility with the vast majority of 500‑series modules.

RPQ503 $799, Snaqbox V2 $349.

RPQ503 £799, Snaqbox V2 £399. Prices include VAT.

www.aearibbonmics.com

aearibbonmics.com/audio-products/rpq503

aearibbonmics.com/product/snaqbox

API 525A

Having invented the format, API have continued to support it. Their consoles can host modules, they make host racks, and their product range includes a healthy selection of modules. The most recent addition is the 525A, a FET compressor that builds on the 525 that was introduced in the 1970s. The new version maintains the discrete signal path, employs API’s own proprietary transformers and 2510/2520 op‑amps, and retains the sonic characteristics of the original unit. It also features an aesthetically pleasing 1970’s‑style analogue gain‑reduction meter. Ratios range from 2:1 to 20:1, and the module includes a Ceiling parameter that combines the 525A’s threshold and make‑up gain controls. Updates to the classic design include variable attack times (15μs‑15ms) and a choice of seven release modes (50ms‑2 seconds).

$1195

£1195 including VAT.

www.apiaudio.com

apiaudio.com/product/525a-fet-compressor

Atomic Analog Tonograf EQ

Atomic Analog’s Tonograf EQ faithfully recreates the signal path of the TAB W95, a transistor‑based EQ module that was originally developed in the early 1960s. With the germanium transistors used in the original design now unavailable, the company set about trialling components that could replicate its sound and behaviour. They settled on Lundahl input and output transformers, along with custom‑wound inductors and other high‑quality components from the likes of Panasonic and AVX. The resulting module pairs capacitive high‑ and low‑shelf bands with an inductor‑based proportional‑Q mid band. There are also a few additions to the design that inspired it. Firstly, the original’s fixed 10kHz high shelf has been expanded, with 7 and 16 kHz options, while the boost‑only mid band now offers ±9dB of gain and an extended range of centre frequencies (500 and 700 Hz, and 1, 1.4, 2 and 3 kHz).

$1175

£1025 including VAT.

www.atomicanalog.com

www.soundonsound.com/reviews/atomic-analog-tonograf-eq

atomicanalog.com/tonograf1

Cloud Microphones TRUE BLUE CL‑520

Revealed at NAMM 2026, Cloud’s new CL‑520 module is built around an updated version of an acclaimed TRUE Systems preamp design. Aiming for neutrality rather than character, the module boasts ultra‑low distortion and noise measurements, along with high resistance to interference from neighbouring modules and power supplies.

Its frequency response is quoted as ±0.25dB from 10Hz right up to 250kHz! Up to 76dB of gain is controlled by a detented pot, while functions such as gain range, polarity, phantom power, a dedicated ribbon/dynamic mode and the unit’s high‑pass filter (25‑420 Hz) are handled by relays and controlled by the company’s Touch‑Control interface. The mic input is joined by a front‑panel instrument input, which sits below a Thru connection that allows the signal to be passed on to an amp or other gear.

$899

£899 including VAT.

www.cloudmicrophones.com

www.cloudmicrophones.com/products/true-blue-520-precision-mic-preamp

Cranborne Audio Brick Lane 500

Cranborne Audio like to do things differently, and their first compressor is unlike any other — but at the same time, like lots of them! While the signal path is all‑analogue, it’s one of the few modules to employ a PWM‑based process (that’s Pulse Width Modulation) for gain reduction, rather than one of the usual suspects (FET, VCA, optical and so on). The approach delivers an incredibly fast response and ultra‑low distortion, but although this translates to an exceptionally transparent, neutral sound character (often useful in itself), Cranborne have painted this ‘blank canvas’ with a range of more colourful options for those who prefer more ‘vibe’.

With seven different operating modes (Velvet, Float, Smash, Tame, Glue and two versions of Polish), the Brick Lane can emulate the key characteristics of a range of traditional compression topologies. A mode‑dependent Stress control also lets you dial in up to a filthy 20% distortion! Furthermore, an Enigma mode lets advanced users access all manner of parameters not obvious on the front panel.

$699

£679 including VAT.

www.cranborne-audio.com

www.soundonsound.com/reviews/cranborne-audio-brick-lane-500

www.cranborne-audio.com/bricklane500

Dangerous Music BAX500

T

he Baxandall EQ, which dates back to 1950, remains as useful today as it was then. In their BAX EQ, Dangerous Music brought it up to date, delivering hugely impressive technical specs and useful additional features. It’s been with us now for a couple of decades, so was an obvious candidate to port to the 500‑series — but the company didn’t want do that until they could do so without compromise.

Now, they’ve achieved that: the single‑channel BAX500 EQ benefits from the same design and components as its rackmount sibling, and is hand‑assembled at the company’s US facility. It’s equipped with high‑ and low‑pass filters, plus the broad Baxandall‑style low and high shelves so famed for their smooth, musical response. With a ±5dB gain range, it’s obviously not a surgical tool, but the broad, multi‑octave sweeps can have a more dramatic musical effect that you might think, and the filters can further shape those curves or counter unwanted side‑effects, such as lifting subsonic rumble.

Dangerous say it’s equally well suited to tracking, mixing and mastering duties, and tight component tolerances and stepped controls make it easy to match multiple modules for stereo or other multi‑channel material.

$1299

£1299 including VAT.

www.dangerousmusic.com

www.dangerousmusic.com/product/bax-500

Drawmer MQ‑1 / MQ‑2

Inspired by the legendary Motown EQ units, Drawmer’s MQ‑1 and MQ‑2 modules promise to capture the sound and feel of the iconic 1960s studios. Both feature the same EQ facilities, with seven proportional‑Q bands at 50, 130, 320 and 800 Hz, and 2, 5 and 12.5 kHz. Each band offers a ±10dB gain range, and a master gain control offers a further ±10dB of level adjustment.

The MQ1’s EQ bands are complemented by Drawmer’s Crush circuitry, which delivers additional harmonic ‘warmth’ at the push of a button. The double‑width MQ2 is intended for stereo processing, but as well as giving you two channels of the same EQ, it features a handy one‑knob compressor. (On the subject of Drawmer compressors, also check out the On The Horizon section at the end of this article.)

MQ‑1 $379, MQ‑2 $579.

MQ‑1 £299 MQ‑2 £430. Prices include VAT.

www.drawmer.com

www.soundonsound.com/reviews/drawmer-mq-1-mq-2

drawmer.com/products/500_series

Gainlab Audio Auditor

Gainlab Audio have delivered some impressive rack gear in recent years, and have now launched the first in a forthcoming range of 500‑series modules. Called the Auditor, it’s a ‘double wide’ Class‑A headphone amplifier that aims to provide high‑quality monitoring in a compact format.

It boasts impressive specs: the published frequency response is within ±0.005dB between 10Hz and 20kHz, while THD sits at <0.005% (measured at 200mW). The headphone output offers protection from DC offset, overcurrent and power‑on transients and, helpfully, the incoming line‑level signal is also passed on to the host rack’s outputs for connecting additional monitoring or recording gear. Along with its volume control, the Auditor is equipped with mute and mono‑sum switches.

$390

£349 including VAT.

www.gainlabaudio.com

gainlabaudio.com/auditor-professional-headphone-amplifier

Neve 88R LBC / LBEQ

The 500‑series format can be a cost‑effective way to get your hands on a slice of high‑end large‑format console tech, and Neve’s 88R preamp has been available in module form for some time. More recently, they introduced the 88R LBC and LBEQ, which recreate the channel compressor and EQ from the same console in module form.

The VCA‑based LBC is perhaps more ‘forgiving’ than the company’s famous diode‑bridge compressors. Its variable ratio control ranges all the way from 1:1 to brick‑wall limiting. A clever dual‑circuit adaptive attack allows it handle fast transients or more sustained sounds appropriately, while the release can be controlled manually (30ms‑3 seconds) or set to auto.

Unusually for an analogue compressor, the 88R LBC also offers automatic make‑up gain. Setup, then, can be super quick and easy, making it particularly useful on tracking sessions. The LBEQ features four overlapping bands with ±20dB gain ranges. The high and low bands can be switched between two shelf modes (standard/resonant) and two bell modes (narrow/wide), while the fully parametric low‑ and high‑mid bands feature a Q control with a 0.3 to 7 range.

$995 each.

£954 each including VAT.

www.ams-neve.com

www.soundonsound.com/reviews/neve-88r-lbc

www.ams-neve.com/outboard/500-series-range

Sound Skulptor LA502T

Sound Skulptor’s wide range of modules revives classic designs and aims to make them more accessible, not least by offering them in both DIY kit and fully assembled form.

Their latest offering is the LA502T, an optical compressor inspired by the much‑loved Teletronix LA‑2A. It expands on their earlier LA502 by pairing the same optical cell and transformer‑based input/output stages with a valve‑drive make‑up gain.

The control set has also been expanded, with a new ratio option sitting between the default LA2A and limiter settings, two side‑chain high‑pass filter options, and additional 10 and 20 ms attack times. While the fully assembled price isn’t bad, the DIY version could prove a bargain for someone who’s confident in their soldering skills!

Assembled $689, Kit $399.

Assembled £549, Kit £299. Prices include VAT.

www.soundskulptor.com

www.soundskulptor.com/en/dynamics/58-110-la502t-tube-optical-compressor-for-500-series.html

Trident Audio SC2

Trident Audio’s new SC2 aims to faithfully recreate another classic design: the Joemeek SC2 optical compressor. Renowned for its ability to apply some ‘glue’ to vocals, individual instruments and full mixes, the module’s photo‑optical circuitry is said to react ‘naturally’ to incoming signals, applying musical‑sounding levelling that helps to maintain a track’s emotion.

Trident say that thanks to its ‘forgiving’ nature, the SC2 excels at subtle dynamic control, but will still deliver pleasing results even when being pushed harder for effect. We’ve yet to review it, but if it does sound like an SC2 it should make a lot of people happy!

$599.99

£525 including VAT.

www.tridentaudiodevelopments.com

tridentaudiodevelopments.com/product/sc2-500

Wolff Audio W1

Launched at NAMM 2026, the W1 brings the preamp section of Wolff Audio’s flagship console to the 500‑series format. It fully replicates the console’s signal path, including the custom Cinemag input and outputs transformers, and boasts a socketed op‑amp design so users can install alternative op‑amps that offer a slightly different tonal character.

The main, stepped, 0‑50 dB gain switch is joined by a ±6dB trim control for fine adjustments, and the company say the low minimum gain makes it possible to place a mic extremely close to loud sources without sacrificing clarity. Along with a handy front‑panel mic/instrument input, the W1 is equipped with an output level control and a set of switches to toggle phantom power, signal polarity and a ‑20dB pad, and to select a high‑impedance instrument input option.

$787

£785 including VAT.

www.wolffaudio.com

On The Horizon...

Finally, there are always more 500‑series releases on the horizon, and we’ll keep you up to date as news arrives. But, just before we went to press, SOS welcomed over 150 brands to our GearExpo UK show in London, where French company H‑Labs showed us their brand‑new CL089 PWM compressor, the launch of which was imminent. Like their other recent hardware, this draws inspiration from a vintage Studer processor.

We also enjoyed a sneak preview of two upcoming compressors from Drawmer (one a FET type, the other optical) that we hope to review very soon. But arguably the biggest talking point was Make Noise Pro Audio’s tongue‑in‑cheek AI Slop Machine — a joke that started life as a humble novelty sticker but evolved into a fully mocked‑up 3D ‘module’. Make Noise say more than a few people fell for that one!

hlabs.audio

www.drawmer.com

makenoiseproaudio.com