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Zoom RFX2200 & RFX1100

Multi-effects Processors
Published March 2005
By Tom Flint

Zoom RFX2200 & RFX1100Photo: Mike Cameron

Two of Zoom's budget studio effects processors have been re-released with a few modernisations. Are they still relevant in today's market?

The RFX2200 and RFX1100 are the immediate descendants of the RFX1000 and RFX2000 multi-effects processors reviewed back in SOS January 2000. Now, as then, both RFX models are based on the same set of effects algorithms, but the RFX1100 has fewer controls and less I/O, and therefore has the lower retail price.

The most obvious difference between the new and old RFX processors is their aesthetic appearance which, to my eye, is much improved. The sickly 'green on black' screen printing has been replaced with a combination colour scheme comprising silver, black, white, and blue. Both new units have also been given combi jack/XLR sockets on the front panel in place of the quarter-inch jack socket of old, so that most types of microphones can be directly connected to the units.

I can't imagine that anybody likes external power supplies, and thankfully Zoom have now replaced them with the internal variety, so that power connection is made via a standard IEC kettle lead. The rest of the processors' controls and effects appear to be the same as before, although I am reliably informed by UK distributors Exclusive Distribution that the sound chip governing the quality of the internal processing has been upgraded. I didn't have the old models to hand to find out if there really was any noticeable difference in sound quality, but it's likely that Zoom have upped the stakes somewhat to fend off competition from other manufacturers.

Inside The RFX2200

The RFX2200 is a 24-bit digital effects processor with one pair of quarter-inch jack sockets for signal input and a matching pair for output, providing 20-bit A-D/D-A conversion. It also has both coaxial and optical S/PDIF digital outputs, so outgoing signals can be kept in the digital domain. MIDI In, Out, and Thru sockets support the product's fairly decent MIDI implementation, and for those preferring remote control, there is a bypass footswitch jack too.

The input section on the front includes the aforementioned combi jack/XLR socket together with its own Mic On/Off switch and clip LED. Next door are controls governing the input, output, and wet/dry mix levels. Beyond these is a section containing the two-character display and 10 buttons dedicated to various programming duties. Beside the screen is a six-segment, 30dB LED meter for monitoring input levels.

The RFX2200 has 48 preset programs that are split into six banks of eight, so that particular effect types can be found relatively quickly. For example, the first bank is for reverbs, whereas the fifth is a collection of remix-specific algorithms. Pressing one of the buttons repeatedly switches banks, while the position of the Effect Type knob determines which of the eight effect algorithms is loaded. At the far right of the front panel are a set of four pots labelled Edit, each with its own status LED. Quite what is being edited by these knobs depends on the particular effect that is selected at the time, although Zoom have added some reverb-specific labels above each control so that the functions are always clear when the reverb bank is being used.

The first knob, titled Rev Character, has 11 positions that relate to reverb variations within each effect type. For example, the 11 Hall reverb variations are Large, Bright, Recital, Municipal, Wood, Cathedral, Medconcert, Strings, Castle, Small, and Gymnasium. Every other reverb type has its own set of character settings, meaning that there are a total of 88 presets to work from, not to mention the other esoteric reverbs, such as the Dimension, Gate, and Reverse that are buried in the SFX bank. The second editing knob is labelled Rev Time and governs the time it takes the reverb to decay away to nothing. The last two pots provide low and high EQ boost/cut control for each reverb.

The second effects bank is full of delay and combination effects, providing a respectable selection of mono, stereo, pan, and rhythmical options. This time the first editing knob performs a variety of adjustments such as changing the delay's panning depth or the amount of treble attenuation. The usual chorus, flanger, pitch, and phaser programs we've come to expect from multi-effect units are present in the third effects bank, plus a few more combination options.

The Direct Approach

The RFX effects will appeal to vocalists who want to plug their mic directly into their effects processor instead of going through a mixer. Zoom must be thinking of that group of live performers who want control over their own sound, many of whom will probably be solo acts singing to DAT or MIDI-file backing, and therefore inserting their effects between mic and PA. The mic input also promotes use of the in-built vocoder effect, which Zoom seem keen to point out in the manual.

When using the vocoder, the audio part requiring modulation is input via the left-hand jack on the rear panel, allowing a vocalist to use their voice to affect the filter envelope. If, however, nothing is plugged into the mic socket, the rear right input is taken as the trigger source.

Special, Remix, & Mixdown Effects

The special effects in bank four are actually quite fun, and well worth having onboard — they are the sort of thing that the BBC's Radiophonic Workshop spent most of the 1960s developing! The ring modulator is ideal for Dalek voices, while the playfully-titled Time Trip should do the voices for most of the Doctor's other foes! Also included here are a vocoder, a pitch-shifter with delay feedback loop, a rotary-speaker simulator, and the aforementioned Dimension, Gate, and Reverse reverbs. The vocoder is intended to be used in conjunction with the mic input (see 'The Direct Approach' box), and works reasonably well using a variety of trigger sources. It's a shame, though, that the RFX doesn't have a gate which could be used in the same way to rhythmically chop up synth parts.

The Remix bank contains a selection of filters for radical sound mangling. Isolator is a variable three-band filter for homing in on particular instruments or vocal parts in an arrangement, although it works equally well as an extreme EQ for solo tracks. Similarly, the Lo-fi EFX program is an aggressive EQ filter with added distortion for making vocals, or perhaps whole mixes, sound grungy and dirty. There is also a comb filter which will be a godsend to anyone who wants that 'through a plastic drainpipe' or 'down a concrete stairwell' kind of sound!

The last bank is titled Mixdown, and contains the sort of sound processing options typically used when bouncing a multitrack mix down to a stereo master. Understandably there are reverbs, compressors, and limiters on offer, but also worth a mention are the condenser-microphone and amp-cabinet simulators.

Edited patches can be saved internally with the RFX2200, and there are 100 memory slots for doing so. By default, the memory is loaded with presets which are designed to showcase the versatility of the effects. From the front-panel display these are merely represented by numbers, but a table at the back of the manual provides each one with a name and description. It actually seems a shame to record over the patches, since Zoom have gone to the trouble of programming and listing them so carefully!

Anyone For MIDI?

Apart from the Input and Output level knobs, just about every front-panel control on the RFX2200 can be remotely altered using MIDI Control and Program Change messages. The active controls output MIDI as well as respond to it, so it's possible to save adjustments by connecting a sequencer and setting it to record. Changes can then be reproduced by playing the sequence, regardless of the actual physical positions of the controls.

Zoom RFX2200 & RFX1100Photo: Mike Cameron

It is possible to assign a Program Change number to certain patches, so that, for example, an effect can be matched to a particular sound from a keyboard, synth, or sound module. Moreover, multiple Program Change numbers can be assigned to the same patch, meaning that a favourite reverb setting can be called up by different songs.

Being able to control the taps of a delay over MIDI is certainly something some thoughtful programmers will exploit, but others may prefer to lock things to the song tempo, and that can be done by engaging a MIDI Clock receive mode. There is also a data-transfer mode that can be used to program another RFX2200 or for storing settings in a sequencer.

RFX1100

While it is undeniably useful for many people to have their effects patches controlled via MIDI, there are also those who want to use effects on the fly rather than as part of a program, and therefore have no need for it. For those, the RFX1100 offers a more budget-friendly way to get many of the same effects, although, according to the manual spec, the A-D/D-A conversion is 18-bit rather than 20-bit. Digital interfacing is also absent, so the analogue jacks are the only way to get signals out, and there are no user memories for saving favourite settings.

With fewer controls than the RFX2200, the RFX1100's front panel has been arranged quite differently. One knob is given over to the task of selecting between effects banks, and the adjusters for reverb Time and Character have been grouped with the In, Out, and Mix pots. Some users may well miss a front-panel bypass button, but there is still the bypass footswitch input on the rear panel.

As far as the sounds are concerned, the RFX1100 seems to provide more or less the same set of reverbs with the same choice of variations, albeit without the EQ controls. The rest of the options are significantly trimmed, so that, for example, there is only one delay option. Zoom have also left off many of the more unusual special effects and mix processors, and have cut down on the number of mastering options. Having just two Edit knobs rather than four has meant that the user can adjust fewer parameters, and the manual is needed for finding out what each knob does when a new effect is selected. Quite often, there is a choice of two parameter adjustments, one on the left and one on the right side of the pot's travel. Naturally, the dual-effect programs have very limited control, with just one knob for each effect.

Effective Testing

Like-for-like comparisons between competing products can be problematic, because most devices offer different levels of control over their parameters. Nevertheless, to provide some sort of perspective I matched the RFX processors with the closest equivalents I could find in my studio — a Lexicon MPX100, which retailed for £250 when released, and the multi-effects processors built into my Yamaha AW4416 recorder. The RFX2200 has far more reverbs than anything else, so the majority of my tests were reverb comparisons.

Listening to reverb tails, it was clear that, when compared to the RFX2200, my MPX100 began to sound slightly artificial as its effect decayed to nothing. The RFX2200 did produce some extremely minor processing artefacts during its decay, but it was still impressive. The RFX's reverb, in general, sounded less dense than that of the Lexicon, and in some ways was all the more natural for it. Nevertheless, the MPX did sound slightly smoother, and more akin to the character of the Waves Trueverb plug-in I regularly use. That's not to say Zoom's processor is coarse; it's still smooth enough, but I suspect that its algorithms are less dampened, and perhaps have a lower density setting than those of the Lexicon. The Yamaha effects exhibited the same attention to detail as far as reverb tails were concerned, but the Zoom could be said to have a warmer quality overall, which was a pleasing characteristic which made it all the more attractive.

A series of tables in the user manuals of both machines show what parameters the Edit knobs control for each effect algorithm, so you'll want to keep the manual close at hand.A series of tables in the user manuals of both machines show what parameters the Edit knobs control for each effect algorithm, so you'll want to keep the manual close at hand.Photo: Mike Cameron

Zoom obviously haven't skimped on processing, otherwise the various reverb's electronic origins would have been more noticeable at the ends of reverb tails or when up-front room settings were tried. However, Zoom's method of creating effects does produce an individual sound quality which will appeal to some listeners more than others, and doesn't quite have the same distinctive 'gloss' demonstrated by the Lexicon and Waves reverbs mentioned.

As far as I could tell from matching patches as closely as possible, the sound quality of the RFX1100 is very similar to that of the RFX2200, despite its marginally inferior converters. Selecting and editing effects is about as simple as it could be and presents no real learning curve, although it is necessary to have the manual to hand in order to find out what the Adjust and Variation controls are doing for each effect type. Obviously the RFX1100 isn't very editable, so it is a case of 'like it or lump it' most of the time.

The RFX2200 is also pretty easy to use, but again the manual is needed. Admittedly the controls are the same for all the reverbs, but reading the manual's Reverb Character Table is the only way to identify what type and size of hall is represented by patches within the Hall bank, for example. Zoom have tried to be consistent, but the Edit knobs still perform radically different functions from one effect to another. Lose the manual and you'll find it very difficult to remember if a knob is changing EQ, LFO, delay time, pitch, or gate threshold. Overall, the front panels of both products are clearly laid out, but the blue-on-black text used for two of the banks is hard to read in poor lighting.

Zoom RFX2200 & RFX1100Photo: Mike Cameron

MIDI Under The Microscope

Knowing that some programmers will want to use MIDI Control Change data to gradually adjust parameters during a performance, I tested the controls for zipper noise (see the 'Zip Fear' box for an explanation of this audio technology problem). As you would expect, changing from one reverb type to another produced a slight blip in the audio signal, but most people will want to stick to the same program during a continuous musical passage. Nevertheless, there are many circumstances in which a gradual adjustment of the Time and EQ parameters could be used to creative effect. Unfortunately, zipper noise was clearly evident as I adjusted both Low and High EQ parameters. At first the Time pot appeared to be free of the problem, but it still exhibited the familiar clicking when turned very fast.

To find out what was going on I took a look at the MIDI data in my sequencer's event list and found that when the knob had been turned fast, only the occasional MIDI value had been recorded, which I believe contributed to the noise. Turning the knob slowly allowed every intermediate data value to be recorded, and the problem was gone. Practically speaking, if a fast change is required, slowing down the sequencer's tempo to record a slower pot movement, and then speeding it up for playback does the job. Unfortunately, the same careful measures do not remove the zipper problem from the EQ knobs. Turning them both fast and slowly creates clear zipper artefacts, even when all the Control Change value increments have been recorded.

Obviously, other effects in the RFX2200 assign different Control Change values to the Edit pots, and offer different parameter adjustments, so I picked one or two to see if the zipper problems were localised, but I found that the zipper problem was common to the controls regardless of the program or parameter.

Zip Fear

Zipper noise is very descriptively named, because it sounds very much like a muffled zip being undone! It's a specifically digital problem which is commonly found on low-budget products, although it is not always immediately apparent. Let's see how it can occur with a volume fader. When you adjust a fader on an analogue mixer, the waveform level changes smoothly as you sweep the fader, so you just hear the volume changes. When you sweep a fader on the most basic of digital mixers, it increments and decrements the volume in steps, the size of which depends on the resolution of the mixer's internal volume parameter. If nothing is done about these volume steps, each is heard as a small unwanted 'blip' noise. A fast series of these noises is what creates the zipper-noise effect. And the problem isn't just limited to volume controls, because almost any digital processing parameter has the potential to create stepped changes in the processed waveform.

So why don't all digital systems suffer from overwhelming zipper noise? Well, one way in which manufacturers combat the problem is by making the parameter steps so small that the zipper noise becomes negligible. Another approach is to program the internal processor to smooth out its response to stepped parameter changes. However, both these approaches require higher-spec processing chips and extra DSP programming, which increase the cost to the consumer.

Conclusion

On the front cover of manual, Zoom claim that 'the convincing sound stage created by the RFX2200 far surpasses anything else available in this class,' which is quite a boast. Zoom don't go as far as classifying the processors, but judging by their UK retail prices, I think we're talking about the budget market. In my tests, both Zooms fared pretty well when put up against some of the other modest processors I own, although I couldn't say whether there is anything else out there with a better sound for the price. I can certainly imagine finding a use for the RFX2200 in favour of some of my other processors on the basis of its sound alone, but if I wanted to tweak a sound precisely I would have to look elsewhere.

Aside from user-friendliness and sound quality, I think most people will be impressed with the number of effects that are on offer, the most unusual of which being provided by the RFX2200. The downside is that editing them all requires constant reference to the manual. For this reason, I'd really like to see a version of the RFX2200 with an LCD instead of the two-character display, so that a description of the relevant parameter is recalled whenever a knob is turned.

The RFX2200 is greatly enhanced by having MIDI functionality. Being able to assign patches to several Program Change messages is particularly useful, as it allows the processor to be added to a pre-programmed arrangement without altering the sequenced MIDI data. There are, unfortunately, some zipper-noise problems, although nothing more than I expected from a budget effects unit. In practice, you'd probably use a single Control Change message to set up the EQ positions for a patch in order to avoid problems, but at least the more important Time control sounds smooth when adjusted moderately.

Even though the RFX1100 offers the same quality effects for less money, for me the higher price of the RFX2200 is well worth paying, and that's not just because of the MIDI, digital outputs, bypass button, display, and user memories. The extra Edit knobs offer quite a lot more control, making the effects far more useable for more applications. Without them, some of the more esoteric effects are destined to become mere novelties instead of genuinely useful sound-creation tools. Having more controls is also vital for the combined effects, where the total number of Edit controls available to each effect is halved. Plus the Tap button is a much better way to adjust delays and modulation times than the Edit-knob method offered by the RFX1100. The bottom line, however, is that both these units offer pretty decent, no-nonsense effects for very little money.

Published March 2005