aion COMET Manuale - Pagina 5

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BUILD NOTES

Pre-1994 version

The default parts list for the Comet is for the pre-1994 version, the only difference being the op-amp

since the original TA7136P IC is no longer produced and very hard to find. This involves changing three

capacitors (C5, C6 and C7).

The original diodes clipped near 1V, but since no equivalents are readily available, it's recommended to

use 1N914 (0.65V) and BAT46 (0.35V) in series for each diode pair. The "stock" clipping mode is the up

position of the toggle switch, and the down position is a little more compressed and lower volume.

Pre-1994 version

If you'd like to build the post-1994 version of the DS-1, make the following substitutions:

• C5: 470n → 68n

• C6: 250pF → 100pF

• C7: 1uF → 470n

Additionally, the "stock" clipping mode is now the down position of the toggle switch. You can change

out D6 and D8 for normal 1N914 diodes to raise the clipping threshold a little bit, providing more

contrast between the up and down positions.

IC selection

The DS-1 has undergone a few other minor circuit changes after the major revision in 1994, mostly

related to the IC:

• 1994-2000: Rohm BA728N

• 2000-2006: Mitsubishi M5223AL

• 2006-2016: New Japan Radio NJM2904L, later changed to NJM3404L, exact year unknown

• 2016-present: New Japan Radio NJM4580 (JRC4580)

The first four are single-in-line (SIL) dual op-amps, although the NJM2904 and NJM3404 have a DIP-8

version available. Since 2016 when BOSS made the switch to SMD, the DS-1 has used the JRC4580. It's

recommended to use either the NJM3404 or NJM4580 in this project.

Big Muff clipping mod

The amplifier stage formed by Q2 is identical to the first transistor stage of the Big Muff. The stock DS-1

does not have any clipping in this stage, but if you want to experiment, space has been provided to add

the two diodes and capacitor and convert it into something more like stage 2 or 3 of the Big Muff with

feedback diode clipping.

To try this modification, use 1N914 for D2 and D3 and a 100n film capacitor for C4. Omit these three

parts for the stock DS-1 circuit.

COMET VINTAGE DISTORTION