L5 PREAMP DRIVE CHANNEL
10
BUILD NOTES, CONT.
LM13700 vs. CA3080
The original L5 Preamp used CA3080s as in the original amp. These have been discontinued for a long
time, and while they have been reissued and are not terribly hard to find, they are expensive.
The LM13700 is essentially a dual version of the CA3080/CA3094 and is still readily available. Since the
L5 circuit uses two CA3080s, it seemed like a good opportunity to replace them with a single LM13700.
The only change that this required was to add a second 100k resistor (R53) to cut the compressor LED’s
voltage in half, since the LM13700’s I
ABC
pin sits at twice the voltage of the CA3080’s pin. This extra
resistor prevents the LED from staying on all the time, which was the only side-effect of substituting the
LM13700 in place of the CA3080.
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.
