The Boss LM-2B is a bass compressor pedal, and an older version of the well-known LMB-3 Bass Limiter/Enhancer1. It is built around a dbx 1252 VCA chip, the component that does the actual gain reduction, and it shares nearly all of its parts with the LMB-3 aside from that chip. Both pedals are built with the classic hard-to-kill Boss ruggedness1.
How it compresses
The LM-2B has a fixed compression ratio that cannot be adjusted. The reviewer at ovnilab.com, judging by ear, perceived it as somewhere between 10:1 and 20:1, which makes the pedal well-suited to peak limiting: clamping down hard on the loudest notes rather than applying gentle, even leveling1.
In subjective terms, that reviewer felt the older LM-2B has a smoother compression action overall than the LMB-3, and less distortion in the lows when hit with a big amplitude peak1.
"In subjective terms, I feel the older LM-2B has a smoother action overall, and has less distortion in the lows when hit with a big amplitude peak."
Controls
| Control | What it does |
|---|---|
| Threshold | The only way to get less squashing is to raise the threshold by turning the knob clockwise1 |
| Enhance | Cuts around 1 KHz and boosts at 2 KHz: a steep narrow mid cut followed by a steep narrow spike of boost1 |
Because the ratio is fixed, the threshold knob is the main tool for shaping how hard the pedal compresses1.
The Enhance knob and tone shaping
The Enhance control is the pedal's tone circuit, and it colors the signal in a few distinct ways1:
- Enhance on: the LM-2B cuts around 1 KHz and boosts at 2 KHz. It does not boost nearly as much in the range above 4 KHz, so it does not amplify noise quite as badly as the LMB-31.
- Enhance off: the pedal rolls down the high frequencies in a long wide slope, even more than the LMB-3 does, which can be considered a bass boost depending on output level1.
- Below the mid-cut point: the frequency response is very similar to the LMB-3, with no loss of lows1.
There is no way to get a flat signal from the LM-2B. With the Enhance off, the high-frequency roll-off always shapes the tone1.
Bypass and how it compares to the LMB-3
The LM-2B uses buffered bypass switching. Boss sometimes gets a bad rap for its buffered bypass, but the ovnilab.com reviewer found no complaint with it in this pedal: with unity gain and a flat frequency response, the buffer is transparent1.
Against its successor, the LMB-3, the differences come down to the VCA chips and the voicing around them: the LM-2B's reviewer heard smoother compression, less low-end distortion on big peaks, and less high-frequency boost above 4 KHz, meaning less amplified noise1. Players looking at current Boss bass compression may also come across the BC-1X Bass Comp, and the wider field is covered on the compressor pedals and bass pedals pages.
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Questions
Is the Boss LM-2B true bypass?
No. The LM-2B uses buffered bypass switching. Boss sometimes gets a bad rap for its buffered bypass, but the reviewer at ovnilab.com found no complaint with it here: with unity gain and a flat frequency response, the buffer is transparent in practice.
Has the Boss LM-2B been replaced by the LMB-3?
Yes. The LM-2B is an older version of the well-known LMB-3, which Boss still makes. Aside from the different VCA chips, the two pedals use nearly identical components, and both are built with the classic rugged Boss construction.
What is the compression ratio of the Boss LM-2B?
The ratio is fixed and cannot be adjusted. The ovnilab.com reviewer, judging by ear, perceived it as somewhere between 10:1 and 20:1, which suits the pedal to peak limiting rather than gentle leveling.
What does the Enhance knob do on the Boss LM-2B?
The Enhance knob cuts around 1 KHz and boosts at 2 KHz, a steep narrow mid cut followed by a steep narrow spike of boost. With the Enhance off, the pedal rolls down the high frequencies in a long wide slope, which can act as a bass boost depending on output level.
Can the Boss LM-2B give a flat, uncolored signal?
No. There is no way to get a flat signal from the pedal. Below the mid-cut point of the Enhance control the frequency response holds up well, with no loss of lows, but the high-frequency roll-off with the Enhance off means the signal is always shaped.
Sources (1)
- Boss LM-2B, ovnilab.com
