Triple Function Generator project

tip: if you use cheap fake LM6172 ic’s , you get funky blurry outputs!
tip2: Ebay sucks at certain times…

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Hmmm… Do I sense a LM6172 group buy coming on???

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I would get in on that

I could set this up. (with prepayments)
Mouser pricebreaks: (ex VAT)

[1:] € 4,23
[10:] € 3,80
[100:] € 3,11
[250:] € 2,92
[500:] € 2,65
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I’d probably get in on this too.

see here:

I’ve updated the BOM with alternative resistor values and switch info

I just noticed that the pads for normalling the inputs together have (unless I’m mistaken, tried this out with an IDC power socket since it’s what was handy) 2.54mm pitch, so if you solder on right-angle pin headers you could use jumper wires to select how the normals work rather than permanently soldering wires to them. Awesome! I’ll have to order some headers.

yes, idc will work. or dupont pin headers.
You have version 1 on the pcb
1: IN-------- (tip of the input jack)
2: OUT----- (switch of the input jack)
3: GND

connect pin 1 on pcb1 to pin 2 on pcb2
connect pin 1 on pcb2 to pin 2 on pcb3

Version 2 has this:
1: IN-------- (tip of the input jack)
2: OUT----- (switch of the input jack)
3: CHAIN—(tip of the output jack)
This is for routing in series and parallel.

Parallel: (one input source gets routed to all three inputs.)
connect pin 1 on pcb1 to pin 2 on pcb2
connect pin 1 on pcb2 to pin 2 on pcb3

Series: (the output gets routed to the next Function Generator input, three in a row)
connect pin 3 on pcb1 to pin 2 on pcb2
connect pin 3 on pcb2 to pin 2 on pcb3

@csboling: you can still route the boards in series if you would like to. Just wire it from the output jack.
I can make a drawing if you need it.


version 2 schematic.
note: the BOM remains the same. If you want ‘modular’ routing, add pinheaders & cables as needed

my only question would be,
how do you people clean the pcbs?
I use 99% isopropanol and a toothbrush, but at the end it always ends up with a sticky residue.

The same as you. sometimes I use a toothpick or flat screwdriver to remove flux blobs.

Some earlier discussion on PCB cleaning:

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I do nothing cleaning-wise, and i’ve never had any problems.
YMMW wrt. flux use, of course.

Two pictures from the TFG:


My PCB kit arrived last week, still trying to track down a couple of components though.

With the 4.2k resistor, 4.32k is listed as an alternative; I have 4.3k resistors on hand, would they work as well?


4.2k is hard to find, so anything that comes close is usable

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Question on switch wiring - can someone indicate which numbers on the DPDT pinout diagram on
correspond with A B C D on the pcb? Thanks!

the dpdt switch has 2 rows of 3 pins.
1 2 3
4 5 6

connect A & B to row 1 (2 & 3)
connect B & C to row 2 (5 & 6)

the switch makes or breaks a single connection between A & B and C & D
So two of the pins are not used, they are ‘open connections’

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Just finished one channel of my build. My video setup is still a work in progress but this makes a fun waveshaper/folder(?)/rectifier for audio, especially when gradually adjusting audio input level before going into the TFG :star_struck: