Gainlab Audio GLA-MP1 Bishop

Gainlab’s channel strip delivers high‑quality valvetube preamplification and optical compression, along with some interesting tone‑shaping options.

We’ve looked at a couple of Gainlab’s products in the pages of SOS already. The Dictator variable‑mu compressor (SOS December 2021) and the Empress equaliser (SOS April 2022) both impressed us with their combination of good build quality, great sound and value for money. So when I was offered the opportunity to test their Bishop Channel, a recording channel strip, I was keen — and I wasn’t disappointed.

Controls Overview

The first stage in the signal path is a valve mic/line/instrument preamplifier. Its large, stepped gain knob is surrounded by a busy‑looking legend, with two concentric circles; each one indicates the setting for a different gain mode, with the modes selectable using an adjacent metal toggle switch. In the low‑gain mode, this stage can apply up to 40dB boost, while in high‑gain mode it can add up to 60dB. All this is achieved using three vacuum tubes. A neat yellow lighting system clearly indicates which mode you’re in, with two backlit circles around the legends as well as the switch LED lighting up to give you that confirmation, meaning you don’t have to squint to see how the toggle is set: a pleasing combination of style and substance!

There are seven metal toggle switches nearby, most relating to the preamp. Three are for features you’d expect on any modern preamp: 48V phantom power, a pad (for the mic input only) and polarity inversion. There’s also a power on‑off switch for the whole unit, a selector switch for mic, line or instrument mode, and another to choose between a front‑panel input and one on the rear. A dedicated saturation stage for the instrument input allows you to add some colour to clean DI signals using a smaller Drive knob that’s placed top left of the main gain control. As well as allowing deliberate coloration of the sound, this can be really helpful when used more subtly to tame any spikiness in a guitar signal before it hits the valve stages. I was a little surprised to find on some online images that the front‑panel input appeared to be an XLR, rather than a combi type into which you could plug a bass or electric guitar directly... but fear not! That must be an early version, since the review unit featured just such a combi. (It’s perhaps worth noting that, when active, phantom power is present on the XLR whether you have the mic, line or instrument setting selected.)

This is an optical compressor that, I think, is broadly based on the Teletronix LA‑2A design, but it’s not a direct clone and is actually more sophisticated.

To the right of the gain knob and in the centre of the 2U rackmountable unit is a large backlit moving‑coil VU meter that displays the output level. A recessed preset allows you to calibrate the meter’s zero point with a small screwdriver or similar, and next up we have the compressor stage, with its own LED metering. This is an optical compressor that, I think, is broadly based on the Teletronix LA‑2A design, but it’s not a direct clone and is actually more sophisticated. While it’s a single compressor (there’s only one optical cell) there are, as Gainlab put it, two slopes at play. Each has its own threshold control and independent 11‑LED gain reduction meter. The top 10 LEDs indicate 1dB of gain reduction each, so the meter has plenty of resolution in the most useful range (if you’re crushing a signal...