aion ACHILLES Instructions Manual - Page 5

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BUILD NOTES

Clipping diodes

The Prince 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.

Clipping switch

The DPDT on-off-on switch allows for three settings: soft clipping (diodes in op-amp feedback loop),

hard clipping (diodes to ground after the second op-amp stage) or no clipping (all diodes lifted). If you do

not need the clean boost setting, you can instead use a DPDT on-on switch.

However, note that since the diodes are shared between the two settings and "relocated" in each

position, you cannot use an on-on-on switch to use both sets of diodes or it will cause issues with the

circuit.

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