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Rolls RM203X

Stereo Line Mixer
Published April 2005
By Tom Flint

Rolls RM203XPhoto: Mark Ewing

Rolls cram a very useful nine stereo line channels and a mono mic channel into a 1U box that's targeting keyboard players. 

Rolls have been in the audio electronics industry since 1989, producing accessories and slightly unusual products all designed to plug the holes in the market left by larger manufacturers. Their current range of products comprises mostly power amps, mixers, and signal processors, although Rolls also design bespoke items for other companies to brand as their own, and are prepared to modify existing models, even for small orders.

The RM203X is an unconventional mixer designed to please a fairly specific market that's probably best described as 'keyboard players with a rack full of sound modules'. For example, a musician taking a MIDI rig out on the road might have a number of keyboards plus a rack of modules, all with separate audio outs. The RM203X could be added to the rack, have everything plumbed into it, and would allow the keyboardist to create their own submix, complete with effects, so that the front-of-house engineer just has a stereo feed to deal with.

1U Rackmount Hardware

Being a 1U rack unit, this mixer has no faders, no EQ section, and little in the way of aux sends or bussing structure, and there certainly aren't any channel muting buttons, low-cut filters, or built-in effects. Its purpose is simply to mix (sum) together one mono microphone input and nine stereo line inputs into a left-right stereo pair.

Helping it do this are nine pairs of quarter-inch jack sockets on the rear, plus one XLR input with optional phantom power and dedicated trim pot. Curiously, instead of having a switch for phantom power, a small circuit jumper has to be relocated from one pair of pins to another. The pins can be seen through a hole in the metalwork at the rear, but it requires a pair of tweezers to reposition the jumper. What's also unusual is that 12V is applied rather than the standard 48V offered by most of today's mixers and preamps. I emailed Rolls in the USA about this and was told that they'd found that most mics operated normally on 12V, that the RM203X already had 'good solid 12V rails', and that generating 48V would have taken more circuitry. To test their wisdom I plugged in a condenser mic which I usually run on 48V, and found that it did indeed work perfectly well at the lower voltage.

The main mixed signal leaves the RM203X via two output jacks, but there is also a single Aux Send jack socket and a stereo return pair for use with an external effects device such as a reverb processor. A block of four RCA phono sockets provide an alternative route for stereo signals to leave and enter the mixer, and they are labelled Record to suggest that a cassette, DAT, or CD recorder could be connected to the two outputs.

Rolls RM203XPhoto: Mark Ewing

On the front panel are the controls relating to the rear-panel inputs. The XLR channel has a volume-level pot with corresponding Clip LED. Below it are two very small pots, one for stereo panning, and the other for controlling the aux send level. The small pots are unusual in so much as their orientation is different to that of the main level pot. For example, the level pot begins its travel at the seven o'clock position, and rotates clockwise to reach its maximum value at five o'clock. The small aux pots, on the other hand, start at a one-o'clock position and move clockwise to their stopping point at 11 o'clock.

The pan/balance pots also operate in the same strange way, so that each one has to be turned to the left to increase the right channel signal and vice versa. My guess is that Rolls have reversed the left and right so that they relate to what is heard in a theatre, venue, or studio when the musician using the RM203 is facing the audience, FOH, or control booth. The stereo channels have the same setup to the mic channel, except with balance pots in place of the pan pot.

At the very right of the rack there are three more pots making up what could be called the master section. The first control, labelled Tape In, adjusts the level of the signal arriving via the phono inputs, while the second pot attenuates the aux return signal. The third and final pot comes with its own Clip LED, and controls the signal level of the master outputs. The RCA outs remain unaffected by the Master Level knob, which means that adjustments for monitoring won't ruin a recording if a tape machine is connected.

To the right of the controls is a headphone output for monitoring the Master mix. Unfortunately there is no dedicated volume control for the headphone jack, so the Master Level pot acts as its attenuator.

In Use

The RM203X doesn't have many features, so you'd expect it to perform its basic functions well. I was quite impressed with the product's sound quality and it's no-nonsense, easy-to-use design. Even with all my available sound modules running through the inputs, the audio seemed clear and punchy. Inevitably, each signal path adds a little noise of its own, as all preamps tend to do, but I had to turn the gain almost all of the way up to generate any significant hiss. The 26dB gain offered by each channel proved to be more than enough for line-level signals from keyboard and sound modules, although more general-purpose mixers usually provide 40-60dB.

The aux sends offer plenty of gain, so it's possible to exercise a lot of control over how much signal gets sent to an external effects processor. The Tape In knob boosts signal by 20dB, so the phono inputs can also be used for another keyboard/sound module if required, which may be useful if you have lots of sound sources. In testing I tried overloading inputs so that every note triggered the warning LED, and tested both inputs and master level in this way. Obviously, the more overdriven the input, the more distortion occurred; however, the RM203X coped pretty well with signal excesses.

In terms of build quality, this mixer fares rather well. All the knobs are very solid, and don't flex as they tend to on much of today's gear. Even though the smaller knobs are fiddly, their diminutive size is understandable given that everything has to fit into 1U. Nevertheless, it was annoying that the phantom-power jumper switch required the use of tweezers, and the small trim knob on the rear would have been better placed on the front panel.


The RM203X will be of most interest to that select group of keyboardists wanting a space-saving box to submix their rig, although I'm sure there are studio owners who have similar requirements too. There are many features that could be added to broaden the product's appeal, but that's not really the point. Nevertheless, some improvements could be made. A second aux output would be welcomed by many who like to send independent left and right signals to effects processors, and a dedicated headphone level attenuator would be nice. I realise that the jumper switch makes it impossible to turn on phantom power by accident, but a proper button would still be an improvement in my opinion.

In its favour, the RM203X offers lots of inputs. A typical 16-channel mixer can cope with eight stereo sources, whereas the RM203X handles nine, plus a mic input. Add to that the RCA inputs, with their own dedicated level control, and you effectively have 21 channels, plus aux send and return facilities. With a UK price of £249, it may face competition from some mass-produced general-purpose mixers offering loads of channels. Nevertheless, it has to be accepted that a company producing products on a small scale for niche markets is going to have to charge for their trouble.

Published April 2005