Got my M3 hardware today, so the build is done! Only waiting on the swap channel switch, but that'll be pretty easy to splice in later.
I had a couple errors. First the L+/L- output from the filter (input to the amp) were swapped via cable miswire. Caused some pretty alarming buzzing, but I caught it quick enough - no smoke, transformers and amp tested fine after. Second, the master volume pot's ends were reversed - also via cable miswire. Luckily both L and R were backwards, otherwise I'd have been really confused by the symptom. I would've liked to use some header pins and an IDC connector, rather than hacking up some ribbon cables and directly wiring them...
ALWAYS ohm out your circuits!! A DMM that does continuity is super cheap and extremely worthwhile... Building the discipline to follow through on using it though, that's priceless
Anyway, here's some pics. Parts list to follow!
Aaand the dirty insides:
- Spoiler: show
Other docs: Relevant Docs
(thanks to Stimaddict for archiving)
See attached for some drill templates! Use clamps to hold them on, tape doesn't stick to this coating very well.
I built sections 2, 7 (ish), and 8 into this build. Section 1 will come later, if I really find that I need it. I think the standard is mostly A/Left glans, B/Right prostate... The times when I really need to channel swap, I can just reverse my electrodes and try to remember which volume knob is which
Parts (priced in CAD):
- 1x CONSOLE ALUM 10.18"L X 7.48"W - $63.15
- 1x Nobsound HiFi 2.1 Channel Bluetooth 5.0 Power Amplifier Board Case Stereo Subwoofer Amp - $49.99
- 1x AC/DC DESKTOP ADAPTER 24V 120W - $78.27 (overkill, 12V at 60-80W will likely be enough, as TroniC says)
- 1x CORD 18AWG 1-15P - C7 3.28' BLK - $5.56 (longer if needed)
- 2x Speco Technologies T7010 70V 10W Line Transformer - $25 (USD)
- 4x POT 1K OHM 5W WIREWOUND LINEAR - $34.48
- 2x POT 10K OHM 1/2W CARBON LINEAR - $17.38 (Panel mount pref., I used vertical through-hole Alpha pots from Thonk)
- 10x CONN BANANA JACK SOLDER TABS RED - $18.40 (much cheaper on Amazon, but lower quality too)
- 10x CONN BANANA JACK SLDR TABS BLACK - $18.40 (much cheaper on Amazon, but lower quality too)
- 2x RES CHAS MNT 3.9 OHM 5% 50W - $13.48
- 1x DC POWER JACK 2.5MM PNLMT SOLDER - $2.87
- 1x Panel mount audio jack - $5-10 (I had some already, PJ3410 from Thonk, $2 or so)
- M3 screws to mount amp/resistors/transformers - $13.19
- Optional bigass rubber feet - $8.26 (helps airflow, makes more room for screw heads)
- 1x Bog standard SPST switch ($2-5) for triphase (joins L-a and R-a banana jacks)
- 1x Bog standard DPST switch ($2-5) for channel swap (inverts L/R signal after the audio jack)
- Various perfboards to make wiring pots/filters easier, scrap cables, heatshrink, zip ties, a step drill bit
Some notes... you'll have to be comfortable with desoldering an 8-pin ganged pot-button to recreate this build. It could be made a lot simpler by using the bluetooth function on the amp, with software volume controls (individual left/right, plus master). This would skip wiring the 3.5mm input jack, wiring the swap channel switch, wiring the L/R pots and filters, modifying the amp, and wiring the master pot knob.
Also big note, this amp defaults to bluetooth mode. The master volume is also a push button, which you press to switch to 3.5mm, but once it's in the box there's no real indicator of which mode it's in. I don't really like this, but apart from cutting traces to insert audio between the BT DAC and the amp, seems like it has to be done every time. All the other pots can be left at max inside the box, and the EQ switch left to "normal" (didn't seem to matter when the pots are maxed).