THESEUS DUAL OVERDRIVE
6
BUILD NOTES
Clipping diodes
The King of Tone uses MA856 diodes, which clip at a slightly higher threshold than standard silicon
diodes such as 1N914 (approximately 0.82V compared to 0.7V). These diodes are long out of production
and have almost entirely disappeared from the old-stock market, likely all bought up by Analogman and
other cloners.
The BA282 and BA283 are very close to the MA856, and were the popular substitute among builders
for awhile... until they dried up too.
Now, the closest option is the BAS33. These clip at around 0.8V, still significantly higher than the 1N914
and only slightly lower than the MA856. We’ve compared the curves on a Peak DCA75 and confirmed
that they closely match the MA856 across the current test range.
The only problem is that the BAS33 went end-of-life in early 2022. Availability is still high, but
eventually they’ll join the ranks of the others.
Omitting the send/return jacks
The loop between the two channels is a modification that is not in the original King of Tone. This loop
automatically shorts together if nothing is plugged in, so it’s fully backwards-compatible if you don’t use
this feature. However, if you do want to omit it entirely, see the alternate wiring diagram on page 11.
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.
