EBS MultiComp: OK, I have been avoiding saying this for some time, but it needs to be said. EBS pedals seem to "go bad" over time, more noticeably than other pedal brands. They are great when new, and the positive comments in my review apply in that case. But over just a few years they can develop issues such as distortion, switches failing, increased noise, or erratic behavior. So I do recommend buying new EBS pedals, but I don't recommend buying older used ones. The MultiComp has been on my list of "the best" bass comp pedals ever since I started doing reviews, but I may have to take it off that list because of this problem with older units. Also, frankly, the new MXR Bass Comp pretty well beats the "old king" EBS in many ways.
Aside from all that, the tone and functionality of this pedal are quite good. It has fairly low noise, and turning the compression knob up to higher settings does not increase the noise. The "multi-band" and "normal" (single-band) modes are clean and close to transparent. The "tube sim" setting adds a nice thickness and boost to the mids, and has a rich tone; it does seem to roll off the highs just a bit. In the other two modes there is not much rolloff of highs or lows, although it is not quite as "boomy" or "bright" as some other comps. The tube-sim mode sounds great for both fingerstyle and slap, at any Comp setting from 12:00 to max, and I could happily leave it switched on all the time at that setting. But don't ignore the multi-band mode! If you set the compression to max in the MB mode you can get a very articulate and defined slap sound. The maximum compression ratio is only 5:1 however, so it is not much of a peak limiter for the very aggressive players. Be sure to check out the article in my FAQ explaining what multi-band compression is all about.
The attack of the compression is a bit slow (and not adjustable), so it allows your natural initial attack spikes through, which can be good or bad depending on the rest of your gear--it's great for a more articulate or aggressive sound, but those sharp attacks can clip your amp momentarily. Otherwise the compression itself is very smooth and natural. High-output instruments (such as certain -but not all- active basses) can distort the EBS. It has a switch for "active" and "passive" modes, but my results with that were mixed. So if you are getting distortion, and if the active/passive switch doesn't help, then you can either turn down the output level of your instrument, or you can open up the pedal to adjust two internal trim pots. Turning the pots clockwise lowers the threshold, meaning the compression will kick in at lower signal levels. In MB mode, each trim pot ("high" and "low") adjusts the threshold independently for high and low frequencies. In the Normal and Tubesim modes, the "low" trim adjusts the threshold for the whole signal, and the "high" trim is not active. Your results and settings will vary depending on the output level of your instrument, and how much you want your signal compressed. You may find that raising the threshold (trim pot counter-clockwise) helps you get a more "natural" sound. To be clear though, I'm not saying you shouldn't use the EBS with an active bass, I'm only saying you may have to do some extra adjusting to make it work well with a high-output instrument signal.
There have been three editions: the oldest was a grey box with buffered bypass, then a black box with buffered bypass, and most recently a black box with "true bypass". The buffered bypass is just as good as the true bypass, however I have to recommend going with the newer true-bypass ones just because the older pedals may not be working as well anymore. The housing is the small size of MXR or Keeley, and it runs on standard Boss-type 9VDC.