Notes
AquaboyDLX_2019
madbeanpedals
Calibration
Before starting, remove IC4. This is necessary to start the biasing process. Set the controls as shown.
• DELAY, MIX controls to their center position.
• FDBK at about 1/3 up.
• RATE and DEPTH controls all the way down.
• MOD switch to the center (off) position.
• BIAS1, BIAS2 and Cancel trimpots to their center position.
• T1 full CCW.
• If you have frequency measurement on your DMM, adjust the Clock trimmer to about 6.5kHz while
probing either pin2 or pin4 of IC5. If you don’t have this feature set the Clock trim half-way up.
1.
Audio probe pin7 of IC3 to confirm you have signal reaching the BBD. It is normal for this signla to
be loud and even somewhat distorted. You may hear clock noise, as well. If you have no signal at
pin7 you need to work your way back through the circuit to find out what went wrong (start at pin7
of IC2).
2. Audio probe pin3 or 4 of IC3 while either strumming the guitar or send some audio through the
input of the effect (a looper, etc). Adjust the BIAS1 trimmer until you get delay passing. The area
over which the trimmer will result in delay is usually about 1/4 of its range. Continue refining the
position of BIAS1 until you get the lowest amount of distortion on the delay signal.
3.
Now probe pin4 of IC3 to confirm it is also passing delay. If it does not, make sure that you have
clock frequency on both pins 2 and 6.
4. Unplug power and replace IC4. Repeat the same procedure above by audio probing pin3 of IC4
and adjusting BIAS2 for the lowest amount of distortion on the repeats. Confirm that pin4 is also
passing delay.
5.
Set the Delay pot to Max. Now finely adjust the CLOCK trimmer until just before you hear any high
pitch whine in the audio path. This is the maximum delay setting. The clock frequency should land
somewhere around mid-6kHz. Leave the Cancel trim in the center position.
6. T1 fully CCW is the lowest volume/# of repeats you can get with FDBK fully up. At about 3/4 up,
T1 is the stock setting of the DM-2. I suggest setting FDBK about 90% of the way up and then
adjust T1 until it just starts to go into self-oscillation. That should give you plenty of repeats on the
control with the possibility of going into oscillation if that’s your thing.
If you do have a scope, you can use it instead of an audio probe to make the proper adjustments to
BIAS1, BIAS2, Clock and the Cancel trimpots. When using a scope, set the Cancel trimpot so that the
two output waveforms from pins 3 and 4 of IC4 converge.
