BETA PREAMP
7
BUILD NOTES
Series & parallel operation
While the original Beta Lead and Beta Bass amps each had two channels, the channels were identical
with the same internal circuitry and external controls. This would normally only be useful for effectively
switching between two presets, except for the unique feature that the channels could be run in parallel
and blended together.
We are planning to release a full dual-channel Beta at some point, but in the mean time, you can run two
of these single-channel units in parallel using a passive splitter and mixer to get the same sound.
You can also try running two of these units in series, which is a trick mentioned in the owner’s manual of
the original amplifier that is accomplished by patching the preamp output of “A” into the input of “B”.
Enclosure size
This project was designed for the
Hammond 1590BBS
enclosure, which has the same height as the
125B or 1590N1. If you don’t use the Hammond brand, be careful—not all 1590BBS enclosures are the
same. For example, Love My Switches sells two different types, and the
version is correct while
the standard one is too short.
The 1590BB2 seems like a close equivalent, but it’s about 4mm shorter. It may be possible to fit this
circuit in a 1590BB2, but we have not tested it, so you’re on your own!
Another alternative is the 1590C (also available from Tayda and Love My Switches). It’s about 10mm
taller than necessary, but if that’s all you can find then it will definitely work.
