Extensive compressor reviews and FAQ

RMI/Lehle Basswitch Dual Band: Lehle is known for making some of the best signal switching systems on the market. RMI is a pedal brand that uses Lehle technology. Their pedals are expensive, but the signal fidelity, functionality, and construction quality are top of the class. So when they told me they were developing a compressor, especially a dual-band VCA design, I was quite excited. I also had the honor of helping them with beta testing and some design elements.
For an explanation of dual-band compression, see this article in the FAQ. The short version is that your signal gets split into two "bands" of high and low frequencies; those bands each go to their own separate compression circuit, so that your lows don't trigger compression on the highs, and vice versa. Then the separate signals are mixed back together for one full-range output.
One of RMI's goals was to get as much control as they could out of the fewest possible knobs and switches. If you want to dial in every parameter of two bands of compression individually, you want the FEA DB-CL. But if you find the FEA's eleven knobs and extra switches intimidating, the Basswitch will get you similar results using only a few knobs. The tradeoff is that the parameters hidden under the hood are either preset, or dependent on the settings of the four knobs, or dependent on your input signal.
The knobs include Volume (output), Gain (input/threshold), Comp (ratio), and Freq (the crossover frequency between the two bands). Attack and release times are program dependent, meaning they change based on the volume of your notes, and they are preset differently for the highs and the lows. The Gain knob has a wide range, allowing a good match with both high and low output instruments and playing styles. The ratios go from 1:1 to 10:1, from mild to fairly strong. It does a decent job of peak limiting for normal non-extreme cases. It has a soft knee, meaning when your signal peaks are less intense it will apply a gentler compression, which becomes stronger (up to the maximum ratio set by the knob) as your peaks get more intense.
The Freq knob crossover goes from 250 Hz to 12 KHz. As a bass enthusiast, I often set the x-over on my FEA or Rane dual-band units to a setting lower than 250 Hz, to specifically target the excessive peaks from thumping the strings or the boomiest notes of my low B string, without applying such a strong squeeze to the majority of my signal. But the 250 Hz setting here is still good enough for that purpose, taking care of the thumpy bass and leaving the rest of my sound neutral. I can't think of a single practical case where crossing as high as 12 Khz would be useful. But the medium to high settings of the frequency range actually end up providing an interesting and pleasant tone control. There's only one output volume knob for both bands, so the balance between them compensates automatically within the circuit; this means as you choose different frequency settings, the highs and lows may change relative volume, shaping the tone. Of course it's not just a tilting EQ, since the signal is compressed on both sides, so the result can be more subtle or much more interesting depending on how strongly you set the Comp knob. The moral of the story is that the minimum Freq setting is the basic starting place I recommend for practical purposes on bass, but you should explore and experiment with the entire range just to find a unique voicing that suits you.
The tone is super clean and uncolored, apart from the EQ-like effect I just described. There is zero loss of highs or lows, and no scoops or humps in the middle. At many settings I would describe it as bright and crisp sounding. The action is smooth and even, with no squishy or swelling effects. The noise floor is very low; the only time I heard any noise was when I had the Gain set too low and overcompensated with the output volume.
Two of the knobs rotate "under" rather than the usual "over", so their midpoint is 6:00 instead of 12:00. Also none of the knobs have markings to indicate their value (e.g. ratio or frequency). So the knobs can be a bit confusing; you just have to go for an intuitive and experimental approach, and use your ears. The knobs are also very short and countersunk into the housing, to keep them from being damaged or accidentally rotated by your foot; but this also means you have to try a bit harder to turn them when you want to.
The construction quality is excellent, absolute top marks. The footswitch can be set to either a relay-based "true bypass" or a high quality transparent buffered bypass. You select the bypass type by removing and re-inserting the power plug while holding down the footswitch--a neat and convenient system! The housing is longer nose-to-tail than the small MXR size, but it's the same narrow width, and the jacks are all on the top end so it will fit neatly in a tight pedalboard. It runs on standard Boss-type 9V DC, or up to 15 V; either way, the voltage is brought up to 18 V internally for higher headroom (less chance of clipping). The on/off LED also indicates the amount of compression when engaged.
The RMI and FEA are equals in quality and tone; the main deciding point between them is really just the controls and form factor. Compared to the EBS, the RMI is much better built, and I never liked fiddling with the trim pots inside the EBS. The EBS has its Tube Sim mode which I like, but the RMI has a wider range of control, a more crisp articulate sound, and its gain knob is much better than the two-position switch of the EBS for matching different instruments.

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