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Frap Audio Dynamics 2806

500-series Compressor & Expander By Neil Rogers
Published October 2023

With some neat features to control how the compressor and expander interact, there’s more to this module than meets the eye.

Frap Audio Dynamics 2806It’s always nice to try a product from a company you haven’t crossed paths with before, and it’s especially nice when it’s something that offers rather more than you first imagined. The product that brought this thought to mind is Frap Audio’s Dynamics 2806, a mono compressor and expander that comes in the form of a ‘double‑wide’ 500‑series module. Frap, who may be new to the world of studio processors but have been active in the Eurorack modular synth scene for a while, describe their 2806 as belonging to the same family of ‘advanced dynamics processors’ as the ADR Compex. That famous device was released in the late 1960s (see our SOS February 2014 article for more about it) and, legend says, was used for the iconic drum sound on Led Zeppelin’s ‘When The Levee Breaks’. Although I was pretty sure the 2806 wouldn’t help me play like John Bonham, I was intrigued and keen to hear what it had to offer.

2806 Overview

There’s a lot going on in this compact design and there are many controls, so I was impressed that the interface didn’t feel overly busy or cluttered. At its heart are two dynamics processors, each with its own control signal but sharing the same THAT 2181 VCA chip for signal processing. The inputs are electronically balanced, while the output runs through a Lundahl transformer.

One processor is a feedback compressor and the other a feed‑forward downward expander; the top half of the front panel hosts the compressor controls and the lower half those for the expander, with a few ‘global’ controls in the middle. The two processors can be used individually (either can be bypassed) or in tandem to sculpt your signal, and the LED bar meter on the left displays both the amount of gain reduction (down from the top) and the amount of expansion (up from the bottom). Clever and efficient though that is, it can make the meter pretty busy at times, and I did sometimes find it a little distracting. Both are surprisingly feature‑rich processors, and there are some clever ways to control their behaviour individually and the way in which they interact. There are extensive side‑chain capabilities too, both for refining the processors’ responses and for more creative triggering.

As you’d expect of a VCA compressor this one can be very fast and aggressive. This could be thought of as being its ‘default behaviour’, but the designers have included an impressive selection of controls that make it very malleable. For example, alongside the usual complement of controls (threshold, separate attack and release times, ratio and make‑up gain), there’s provision for parallel compression: Frap have opted for a Parallel knob that adds in dry signal without changing the level of the processed sound. The make‑up gain control can also attenuate the compressed signal, so there’s the option of starting with the dry and blending in as much processed sound as you need.

More novel features include the option to relax the compressor’s behaviour by switching to what Frap call Classic mode: the time constants become much slower and it’s easier to make the compressor ‘pump’ — think more ‘vintage’. The Priority control, just above this, is another thoughtful touch. This prevents the expander operating at the same time as the compressor (ie. the compressor always takes priority), so that it doesn’t counteract any gain reduction being applied. Yet more flexibility comes courtesy of a three‑position Ref toggle switch, which selects from where in the signal path the compressor gets its internal control signal. The centre position turns the compressor off (no control signal, so no gain reduction), while the Pre and Post positions take the signal from before or after the make‑up gain control, respectively (so always post the VCA). Set to Pre, the make‑up gain control does what it says on the tin: turn it clockwise to restore the level lost through compression. Switch to Post, though, and the make‑up gain serves as an input gain control into the side‑chain circuit, making it feel more like an 1176 in use. There’s also a variable Contour control, which is a side‑chain EQ that makes the compressor less sensitive to low frequencies. Full details of the filter aren’t given in the manual, but while the legend suggests it might be a shelving EQ I found in practice that it had much the same effect as using a variable high‑pass filter. Either way, it’s a really useful feature!

Moving on to the expander, as well as the typical controls you’d expect to find — attack, release, threshold and ratio (called ‘Expand’ here) — there’s a side‑chain filter section with variable high‑ and low‑pass filters (18Hz to 1.7kHz and 200Hz to 19kHz, respectively). Since the expander and compressor use the same VCA, the make‑up gain and parallel controls I mentioned above apply to both processes.

It Takes Two

Although this is a mono device, it occupies two 500‑series slots. Partly that’s to allow enough space on the front for all the controls, of course, but it also allows the 2806 to exploit two channels of the host rack’s inputs and outputs. The first channel is, naturally, for the main audio input and output, and the second input is used for the external side‑chain. But the second output is also used...

The Dynamics 2806 occupies two slots, and although a mono device, it makes good use of both channels’ I/O.The Dynamics 2806 occupies two slots, and although a mono device, it makes good use of both channels’ I/O.Between the main compressor and expander controls, a three‑position Ext SC toggle switch dictates where any external side‑chain signal is routed, and what’s sent to the second output (Aux). With Ext SC set to Expander (down position), the external side‑chain keys the expander and can be shaped by the low‑/high‑pass side‑chain filters; a copy of the unprocessed sound is sent to the Aux output and the compressor continues to react to its internal control signal. With Ext SC set to Compressor, the external input triggers the compressor and can be shaped by the Contour control, with a copy of the processed sound going to the Aux output; the expander reacts to its internal control signal. In the third position (sigma symbol), the compressor reacts to a sum of the internal and external side‑chains, the expander reacts to the internal one, and a copy of the processed sound appears at the Aux output.

So there’s plenty of versatility here, including the ability to use the second output and input as a send and return to allow external processing of the side‑chain signal. A two‑position Listen switch allows you to monitor the post‑filter side‑chain signal, which is great for fine‑tuning a trigger. But it’s worth noting that to switch both processors to their internal side‑chain, you must physically remove the cable from input 2 — in a rackmounted chassis you may need to think your way around that using your patchbay!

In Use

Inevitably for a unit with so many controls and options, there’s a learning curve if you’re to get the best out of the 2806. But after a little orientation I found myself very impressed with the range of jobs I could get it to perform well. For instance, my first impression of the compressor was that it seemed pretty aggressive and heavy‑handed, but once I got a feel for using the Contour control and the approach to parallel compression, making the compression less obvious was a breeze. Used just as a conventional compressor, the 2806 works very well for controlling transient‑heavy sources and for adding heavy pumping effects to drum character mics. The ‘extra’ compression controls, though, make it excellent for sculpting strummed electric guitar parts to sit better in a mix, and for transparent dynamic control of vocals and bass parts. I quickly settled into a nice workflow of compressing a source in a slightly exaggerated way to hear the ‘groove’ of the compression, and then dialling things back so that the effect wasn’t overly audible.

In use on its own, the expander section was a pleasant surprise. It’s not the kind of tool I usually look to when working ‘outside of the box’ since we have so many software options now, but even when used for basic gating‑style functions I was pleasantly surprised at how effortless it felt to dial in settings with my hands rather than with a mouse. It seemed really easy to isolate snare drums and toms, and while I’m not sure quite how often I would use such a tool in my everyday work here at Half‑ton Studios (I’d be a little nervous of committing to this kind of thing whilst tracking), I have to say that, sonically, it seemed to produce more natural and (in a good way!) ‘softer’ sounding results than when doing the same job digitally, and it generally encouraged me to approach some tasks in a different way, which I think is a good thing.

Being able to use the expander whilst also adding a few dB of compression was a real joy. It often produced excellent results. For example, it was great that I could use the expander to clean up a noisy vocal take that had lots of mouth and paper noise between lines, and compress the vocal at the same time. It took me a little while to get comfortable with the interaction between the two ‘sides’ of the 2806, but I often found that just using a little of the expander (often dialling back the range control after setting it up) had the pleasing effect of rounding out the sound of the compressor as a part came in and out of a track. The Priority setting is really helpful there too.

The extensive side‑chain options are welcome too. I found the filtering options really useful and enjoyed my experiments with side‑chaining, and I reckon electronic music producers and those who like to get creative with hardware routing could find an awful lot to play with here.

Final Thoughts

Appearances can be deceptive. When I first saw at the 2806, with its clean look and plentiful controls, my perception was that this was going to be a clean‑sounding and very technical sort of tool. It can be used that way if you want, but its ‘default’ sound and vibe is more what you might expect from a stylised, vintage‑looking device. The compressor section’s natural setting is not subtle, and if you want saturated, pumping ‘character’ compression (think ‘When The Levee Breaks’) or, more generally, compression that you want to be heard, then this unit will happily oblige. Given the designer’s nod towards the ADR Compex, perhaps this shouldn’t have been such a surprise!

I’m not sure that I can recall an analogue compressor that allowed me to dial back its natural tendencies to such an extent.

But I’m not sure that I can recall an analogue compressor that allowed me to dial back its natural tendencies to such an extent, whilst still offering me firm dynamics control — that’s thanks largely to the Contour control and the way parallel compression is achieved. I suspect that many prospective customers will view the expander section more as ‘bonus content’. Indeed, I did so initially, but I have to say that I found a ‘hands‑on’ approach to using this style of tool enjoyable and productive, and it was great to have the control over the way the two processors interact.

In this price range, you have a lot of choices when it comes to hardware compression, but if you want a compressor that will suit every task in your studio the Dynamics 2806 is well worth consideration — and if you’re looking for an all‑round analogue dynamic processing tool with lots of flexibility, and hidden depths that you can explore over time, then you should definitely check it out: the 2806 is going to be right up your street!

Audio Examples

I have created some audio examples to show off the 2806's capabilities. You will find them here:


  • Characterful compression that can be easily controlled.
  • Onboard parallel and Contour controls are excellent.
  • Huge flexibility throughout the design.
  • Full‑featured expander with internal and external side‑chain options.
  • Encourages an enjoyable and extended learning curve.


  • Could be a bit fiddly for some perhaps.
  • Shared metering can often be unhelpful.


The Dynamics 2806 from Frap Audio is a versatile dynamics processor that packs a great‑sounding analogue compressor and highly flexible expander into a double‑wide 500‑series module.


€1329 including VAT.

Alex4 +49 (0)30 61 65 100 40.

€1329 (about $1400).

Alex4 +49 (0)30 61 65 100 40.