Highland Dynamics BG1 stereo compressor

The BG1 Stereo is a two channel tube compressor loosely based on the Altec 436 and also the British modified 436.

There are two compressors in one 3U chassis, linkable side chain amplifiers. Tubes are pre channel: 4BC8, 6SN7 and 6AL5.

Fully balanced circuit with transformer input and output, fuse is a 1 amp slow blow and is located in the power inlet at the back.

There is also a select in the fuse holder to switch to 240 mains voltage there too, change the fuse to a .5 slow blow if operating at 240 volts mains.

 Hook ups are located in the back as well and are balanced XLR.

WHAT IT DOES

Input and Output controls: This lets you set the input and output, they are continually variable to allow you to fine tune the compressors.

Output is after the output transformer so it is in essence a output pad, don’t be afraid to have this all the way at 10, if you need to turn the output signal down, you can do so with this control.

-600 or 150 ohm input taps. This switch lets you select the input impedance taps on the input transformer.

150 gives you more gain and color/character, also useful in running a microphone directly into the compressor.

-Feedback settings. This is like the BG2, B is for the classic British modify Altec 436 and A is the no feedback stock 436.

B gives you less gain with a smoother more Hi-Fi sound of the British compressor. A gives you more gain and more character, lets more harmonics through and gives the compressor more of a sound.

-Compression switch: This will remove the side chain signal making the compressor into a line amp.

You can use the different feedback and input impedance settings to achieve different tones with using it as a line amp.

Also different distortion character and sounds if you choose to overdrive the circuit.

-Threshold setting: The BG1 has 3 threshold settings, Low is stock, Medium gives you a little more signal going through the compressor before compression, and High even allows you to get some overdrive sounds when driving the compressor hard but still getting compression.

-Attack: 9 attack positions are available from very fast to very slow. 3 is around the stock Altec both American and British and similar to the fast setting on a BG2, 5 is around where the slow setting is on a BG2. 9 is extremely slow.

-Release: 9 release positions are available from very fast to very slow.

-Hold: This allows you to turn on the release, in hold the compressor will compress but not release back to full signal. When you switch back to operate, the release to go back to what ever speed you have the release setting set at.

-Link: This will link the two side chains together, a signal in either side will make both sides compress the same amount. It is like have the side chains in mono but the audio amps still fully independent.

-Meter: there is a trim pot through the small hole by the meter labeled “meter”. This lets you set the zero and calibrate your meters. Different line voltages can cause the meters to rest in slightly different places, use this to adjust back to zero with no audio going into the compressor.

Features

• Input and output controls
• Fast and slow attack
• 6 release positions
• Link switch for stereo use
• 600 and 150 ohm input impedance taps
• Switchable feedback settings