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BUILD NOTES

BBD selection

The original bucket-brigade delay chips used in the CE-2 have been discontinued for many years and

old-stock chips are getting difficult to find. Fortunately, reproductions of both the MN3007 and the

newer MN3207 are available along with the corresponding clock driver, and they perform just as well as

the original devices in this circuit.

The original CE-2 uses the MN3007 (reproductions available from Xvive), while later chorus pedals such

as the CE-3 use the MN3207 (reproductions available from Coolaudio as the v3207). The Azure project

is set up to allow either type to be used by soldering two jumpers in one configuration or another.

So which should you use? The MN3207 has slightly better noise specs, but a lower maximum operating

voltage. In this application, the maximum voltage doesn't make much of a difference since we're running

it at 9V either way, so the added expense of the MN3007 probably outweighs any advantage.

However, the silicon shortage that began in 2021 has made all new-production BBDs somewhat scarce

as Xvive and Coolaudio's production has been delayed. So really, go with whatever you can find until the

shortage is over. Any BBD is better than no BBD!

Clock selection

The MN3101 clocks are only compatible with the MN3007, and the MN3102 and v3102 clocks are

only compatible with the MN3207 and v3207. There are currently no reissues or reproductions of the

MN3101, so if you use a reissue MN3007 then you'll need an old-stock MN3101 to drive it.

These are a lot easier to find than old-stock MN3007s, but be careful to order from trusted sources

since it's possible that a fake chip could damage the BBD.

Setting the jumpers

Underneath IC2, there are four jumper pads arranged in a square pattern. The MN3007 and MN3207

have their positive and negative supply pins inverted from each other, so the jumpers need to be set to

route the supply voltages to the correct pins.

The underside of the PCB has a legend on the silkscreen showing which way the jumpers should be

soldered. If using a MN3007, both jumpers should go horizontally. If using a MN3207 or v3207, the

jumpers should go vertically.

The MN3101 and MN3102 clock drivers have the supply pins reversed internally, so these two chips are

cross-compatible and IC3 does not require any of its own jumpers.

Setting the bias by ear

The trimmer adjusts the bias voltage to get optimum performance from the BBD. Set the Depth knob all

the way up and set Rate to a medium speed, around 12:00. Start with the bias control at halfway, then

adjust it up or down until you hear the strongest chorus and the least audible distortion.

AZURE ANALOG CHORUS