IOW: don’t sweat it! Build the version with the parts you can get and forget about it. If you like the way the Memory Man
sounds then you will love the
DirtBag Deluxe
.
If you plan on building the MN3005, you will need to utilize a Road Rage board, or similar charge pump design, to supply
the board with 15vDC (regulated) instead of 9v. Please refer to the Road Rage documentation on the Projects page of the
madbeanpedals website for more info. You should use an LT1054 charge pump and an LM7815ACT or similar regulator
(the T0220 type which provides up to 1A of current).
REVISION (CRITICAL): Some builders of the v3205 version of this project have run into distorted repeats. There
is a simple solution to this issue. Replace R21 (1k) with 100k and C14 (33n) with another 100k resistor. This forms
a voltage divider which eliminates overloading the lower headroom of the v3205. The original 1k/33n forms a low
pass filter with a corner frequency of about 4825 kHz. Even though this fix eliminates this filter, it seems that the
low overhead of the v3205 does not impact the delay tone in a significant way. Further tests also found that R10
could be omitted from the compressor portion of the NE570, but this is not critical. As a reminder, you will want
to use 47k for both R11&R12 when building the v3205 version.
Let’s Build It
There are three jumpers to set on the board under IC5 depending on which BBD you are using. Note
that you don’t want to mix and match BBDs. You need to use two MN3005, two MN3205 or two
v3205 devices.
MN3005
v3205 (MN3205)
These jumpers connect the VDD, ground and VGG pins of both BBDs to their proper sources simultaneously. The
MN3005 takes the VD voltage on pins 1, ground on pin5 and VGG is connected to ground on pin8. For the v3205, pin1
connects to ground, pin5 connects to approximately 8.2v (VD) set by D5 and VGG is about 14/15 of the VD voltage
through the voltage drop over D2.
Note that if building the MN3005, you should omit D5 from the board. The 8.2v Zener is only
used for the v3205/MN3205. You should also omit D2 and C17.
After setting the jumpers, I recommend populating the board with all the resistors IN ORDER. This will lessen the chance
of placing the wrong value resistor in a place that could later cause problems. Solder the resistors in place on the bottom
of the board.
Note that for the MN3005, R11 & R12 need to be 68k. For the v3205/MN3205 they should be
47k.
If you want to go the extra mile you can topsolder the resistors, too. This is not necessary for the effect to function
properly provided you have used good technique on the bottom side, but it does lend itself to a more professional look.
