TH Custom Effects Pro-cessor 4.2 User manual

Overview
This is a must-have for your pedalboard. Depending how you use it, it can be:
Signal Splitter,
Signal Mixer,
24dB Highpass filter
24 dB Lowpass filter
Two parallel effect loops
….
The V4.2 release has a smaller footprint and cutouts on the sides.
General
The pro-cessor is designed around standard circuits like OpAmp Buffer, Sallen Key Filter etc. The combination is
unique leading to a very flexible workhorse in any effects setup.
Due to your personal needs regarding filtering you will want to choose other component values for the 4th grade Sallen
Key filters. The current values will set corner frequencies for the filters as follows:
Lowpass: 250Hz Highpass: 400Hz.
A lot of work has gone into the development of the filtering. The initial idea I had with variable filters (using pots) did
not work as the steepness only is 12dB which was not enough to do efficient frequency cutting.
Now with the 4th grade filters there is 24dB action which is highly efficient. Feel free to use other values for your build.
Example of usage (see more at the end of the document)
Pro-cessor 4.2
Not really an effect –better !
Ease of build Medium
-partscount Medium
-density Medium
Parts sourcing Normal
Enclosure fitting Advanced
Debugging level Easy

Schematic

Bill of Materials
Device#
Qty
Value
Comment
Resistors
R1, R2
2
33k
R3, R4, R5, R6, R13, R14
6
1M
R7, R19
2
3k9
R8
1
2k7
R9
1
3k3
R10
1
1k8
R11
1
3k9
R15
1
100R
R17
1
1k
R20
1
820R
R21
1
560R
Capacitors
C1, C3, C16
3
220n
C2
1
100n
C4
1
220nF
C5, C6, C7, C8
4
10uF
C9
1
47uF
C10
1
22uF
C11, C13
2
330n
C12
1
1u
C14
1
560n
C15
1
180n
C17
1
680n
Pots
BLEND
1
25k-B
linear
Diodes
D1
1
1n4001
D2
1
LED superbright
color of choice
ICs
IC1, IC2, IC3, IC4
4
TL072P
Use OPA2134 or TLC2272 for extra low noise
Other
Jack1-6
6
NRJ6-HM-1
Mouser Link.
alternative
6
NRJ4-
only metal nuts will fit!
Rotary Switch
2
rotary 2PT3
Musikding-Link
alternative on-on-on
2
on-on-on
alternative switch Mouser Link
Pay attention when selecting the jacks. Unfortunately there are no NRJ4 with metal tip anymore, so you need to buy
the stereo version (NRJ6) when you want them grounded to the enclosure (-HM).
You can also use the plastic version but you will need to ground your enclosure via a piece of wire. Also the plastic
nuts will not fit next to each other as they are too close. There are round metal nuts which will work on the plastic
shaft.
When ordering make sure you order the version with nut included or order the nuts separately!

Building
Start populating resistors and diode first, then IC sockets and capacitors. Then go the jacks. Last mount the BLEND
pot and the rotary switches from the backside(see detail). Due to the small size of the PCB and the narrow layout you
should check if the capacitors you choose do fit in.

Backside mounting detail:
This is how the rotary switches are mounted.
If you use the on-on-on switch you need to wire it externally. This will need a 125B enclosure!
First make the connection between pin 3 and 5 of the switch.
Then wire 2 to X_FILTER, 1 to X_DIRECT, 4 to LP, 6 to HP.

DRILLING
Drill template in 600DPI is available at the website: https://diy.thcustom.com/drill-templates/
Here are the measurements for the backside drilling:
1590B enclosure:
If you use a 125B or different make sure to measure the 21mm from the top.
1590B needs the holes to be slotted to the bottom (as shown above). Otherwise the PCB will not fit in.

EXAMPLES of use

Finally
I did develop this for someone telling me he needs something for his acoustic guitar setup where only the lower
frequencies should go through an Octaver effect whereas the higher frequencies should stay intact untouched.
The pro-cessor can do that by activating the LP-Filter for channel B, sending it via B_Send to the Octaver, returning
the signal via B_Return. Mixing it with the unaltered signal that runs via channel A at the same time.
This is only one out of the possible uses of this tool. And if you only want to put effects on your pedal board: Try it with
channel A running through LP, channel B running through HP and use the blend-control to apply 24dB filtering. That
can be called an effect for sure.
It will be interesting what you did with the Pro-cessor. Please let me know !
This is a picture of one of the prototypes.
Disclaimer & License
PCBs purchased from TH custom effects are intended for DIY / non-commercial use only. It is not allowed to
redistribute the PCBs and artwork from this document. However, you can uses these instructions and PCBs
to build and sell your own product based on PCBs ordered from TH custom effects.