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Overstayer 8755DM

Stereo Modular Channel By Bob Thomas
Published April 2019

Overstayer 8755DM

Overstayer's versatile stereo processor offers endless ways to manipulate — or obliterate — any input signal!

Digital audio virtually eliminated the problem of unwanted distortion, but in doing so, it probably reminded us that distortion can also be musical — and there are now many tools designed specifically to create such distortion, among them Overstayer's 8755DM Stereo Modular Channel. 

Staying Over

Founded by musician, engineer and producer Jeff Turzo, Overstayer have created a range of compact, high-quality analogue recording and mixing processors. This latest unit is a stereo mic/line/instrument channel with a unique combination of features and facilities, incorporating some functionality from their existing microphone channel, VCA compressor and analogue saturation and distortion processors. 

Apart from the separate left and right input gain controls and polarity switches, the 8755DM's two channels share a single set of controls; it's intended for stereo applications. Nonetheless, the sheer number of switches and vintage-style knobs, and the minimal metering, make it essential that you make an effort to understand its signal flow and constituent modules before you dive in. The first clue that the 8755DM is not your average stereo channel comes when you look at the I/O options on the rear panel, where you'll find XLR connectors for its two transformer-balanced microphone inputs, two sets of balanced line inputs, a set of balanced preamplifier outputs, balanced sends and returns for the left and right channel effects loops, and the left and right channel main outputs. In addition, there are quarter-inch jacks for the left and right channel instrument-level inputs, external side-chain and control voltage (CV) inputs for the VCA compressor, and separate left and right CV inputs that control the output level of the 8755DM's saturation section, of which more later.

The sheer number of analogue sockets on the 8755DM's rear panel tells you just how complex and versatile this device is!The sheer number of analogue sockets on the 8755DM's rear panel tells you just how complex and versatile this device is!

Input Routing 

Above the master input level control, you'll find a row of three switches. Selecting which input goes where involves the first two of these, plus another unlabelled, horizontally oriented 'floating' switch at the top of the Bandwidth Control section. The first switch selects which of the first three inputs (Instrument, Mic or Line 1) is routed through the main channel path. The second determines the source entering the mic inputs' balancing transformers, from the microphone input (Mic), the microphone input with a -20dB pad (Mic-20) or the fourth and final input (Line 2). Finally, the 'floating' switch overrides the second switch, routing Line 1 directly to the input of the mic transformer. Since, in this configuration, the line inputs replace the microphone XLRs, the first switch must be in its Mic position to route the selected Line inputs down the main channel path. A serendipitous result of the switching complexity is that the signal passing through the gain controls is always available at the preamp outputs. Another completely logical and very useful situation arises when Line 1 is selected on the first switch and the 'floating' switch is set to the left, at which point you'll find that the preamp outputs are carrying the signal from the microphone inputs, which remain active unless replaced at their transformer inputs by Line 1 or Line 2. The final three switches in the input section activate the filter (Bandwidth Control), the EQ (Frequency Control) and the compressor (Amplitude Control).

Filters & EQ

Under the front-panel heading of Bandwidth Control, you'll find individual high-pass (20Hz to 4.7kHz) and low-pass (220Hz to 22kHz) filters. Each has frequency and peak (resonance) controls, and self-oscillates at higher resonance settings. Like almost all the other rotary controls, these are marked only from 0 to 10 with four-division increments, so your choices of frequency and the amount of resonance will — as with every other continuously variable parameter on the unit — be primarily listening-based. The final control in this section is the horizontally oriented Curve switch. When active, this increases the low-frequency headroom in the harmonic saturation and distortion processes, in order to preserve power and dynamics in the low bass. 

The three-band Frequency Control (EQ) section follows, with shelving bass (±18dB) and treble (±15dB) controls offering corner frequencies at 50/150/300 Hz and 5/10/15 kHz, respectively, plus a wide-ranging swept bell‑curve Presence band (±12dB 260Hz-12kHz). This has a proportional-Q response that narrows the bandwidth at higher boost or cut levels. 

Sitting on either side of the bottom edge of the Frequency Control section (but having nothing to do with it!) are two switches and two green lenses. On the left, the insert switch activates the 8755DM's effect loop, and the lens next to it illuminates when the unit is powered up. The switch on the right controls the relay-switched hard bypass, with the green lens next to it going dark when that bypass is engaged. Sitting on the top edge, directly above these switches, are the 8755DM's only meters: two four-LED ladders that display the amounts of saturation and compression.


The Amplitude Control contains a variant of the stereo VCA compressor found in Overstayer's Stereo Voltage Control peak limiter/compressor. Attack and release times are set either manually, using two three-position switches (Fast, Medium, Slow), or by engaging the compressor's RMS detector side-chain (a pull switch on the threshold knob) to obtain programme-dependent timings. The threshold control is scaled from 10 to 0 so, once again, it's your ears that will be used to set the actual threshold. There's no ratio control as such, but Overstayer's unique Behaviour control is an equivalent, if somewhat unconventionally implemented, function that is capable of taking a signal from all transients to all ambience. In essence, this not only manipulates the compression envelope and its 'hardness', but also skews the ratio and timing. The make‑up gain control also has a dual function, switching in an internal 220Hz side-chain high-pass filter when pulled out. A three-position switch allows you to set the source of the side-chain to be post-EQ (switch up) or pre-filter (switch down). In its unlabelled middle position, this switch activates the external side-chain input. If no external source is present, this effectively bypasses the VCA; since the make‑up gain is active if the compressor is in circuit, you've got another source of gain (boost or cut) to play with. 

Harmonics, Saturation & Distortion

Although the Drive knob sits amongst the compressor's controls, it's actually part of the harmonic amplifier, and its role is to set the amount of distortion delivered by the MAS, Sat and Hex stages. These stages are arranged in descending order of headroom and are switched in individually, so you can cascade the three together should you feel the urge to do so (I'm fairly certain you will!). The MAS (Multi Analogue Stages) stage allow you to add both second- and third-order harmonic character, and the peak-rounding limiting characteristic of vintage analogue recording chains to a signal. In SOS November 2016, I reviewed Overstayer's MAS 8101 Stereo Analogue Distortion Processor ( and in that review you'll find more detail on the MAS process featured in this stage. Similarly, the Sat stage is derived from that in the NT-02A Stereo Analogue Saturator (reviewed by Matt Houghton, SOS May 2014: The final Hex stage is an interesting one. It's based around a complementary metal oxide semiconductor (CMOS) hex inverter, which is a chip type that's usually associated with microprocessors rather than distortion amplifier stages. As its name implies, a CMOS hex inverter contains six inverters, each based on FET circuitry. When overdriven it produces a valve-like distortion — a quality that's often exploited by guitar effects-pedal manufacturers.


In recent years, parallel processing has become de rigueur in both digital and analogue effects processors, but the 8755DM takes this concept further than any other audio processor I know of. It does this by providing a continuously variable mix of three discrete feeds, each with an individual mute switch: Dry, which can be pre filter, post filter, post EQ or post both filter and EQ; Compressor, which is a post-compressor feed that can be driven dry or by the Dry feed's post‑filter/EQ options; and Sat, a post-harmonic amplifier feed that can be driven dry or by the Dry feed's post‑filter/EQ options and/or the compressor. The final switched front-panel function engages something called an output Ceiling, which is a limiter that sits in the signal chain in between the three Feed faders and the final Output level control. The Ceiling is set so that, with A-D converters calibrated to -18dBFS, 6 on the output level control gives 7dB of headroom, 7 gives 4dB of headroom, and 8 gives 0.1dB of headroom.


As I've come to expect of Overstayer devices, the 8755DM delivers world-class sonic sculpting facilities. It sounds great and allows an almost bewildering degree of control, but it's also massively versatile, offering everything from master-bus subtlety to full on dirt and distortion. When you combine its superb-sounding mic preamps, it resonant filters, its powerful, well-configured EQ and its wide-ranging compression, with the harmonics generation, saturation and distortion, and the various series/parallel processing configurations, its qualities and subtleties as a high-end stereo channel strip come together to create something that's most impressive indeed. All the more so, in fact, given what is a very reasonable price, considering the quality and number of processing stages and the fact there are two channels of everything.

Since it can be so subtly effective, I'd have absolutely no hesitation in using the 8755DM across a master bus. When it's not doing that, I'd happily unleash its harmonics generation, filter resonance, EQ and occasionally crazy compression on drums, synths or guitars. Vocals would probably need to be treated with a much lighter touch, but it's capable of that too. And if you're into modular synthesis, or have a CV source, there's endless inspiration to be found in driving the compressor's side-chain from its CV input. Special mention has to go to the Curve function, though, as the reduced harmonic saturation and distortion in the low bass not only means it maintains its power and articulation, but also makes the mid-range and treble distortion appear subjectively clearer and more dynamic — a quality that can be enhanced by the CV-driven virtual fader between the Saturation and the Hex distortion. Finally, if, like me, you're a guitarist, I have to say that the 8755DM is, hands down, the best-sounding, most inspiring and most expensive distortion 'pedal' that I've ever encountered.

Up until now, I hadn't discovered a channel strip quite like the Overstayer 8755DM Stereo Modular Channel, and I certainly don't recall anything else that can act equally well as a subtle mastering EQ/compressor, a source of inspiring musicality and a sonic mangler of epic proportions. The 8755DM isn't going to be to everyone's taste, but for those who get drawn in by its web of flexibility, performance and potential there is, I fear, little chance of escape!


I know of no hardware that's quite like the 8755DM, but units such as the Black Box Analog Design HG-2, the Looptrotter Emperor, the Thermionic Culture Vulture, Elektron's Analog Heat, Amtec's 500-series DST-5A and, of course, Overstayer's own MAS 8101 and Saturator NT-02A can cover aspects of its performance.


£2640 including VAT.

KMR Audio +44 (0)20 8445 2446.


Overstayer Audio +1 323 628 7067.