This design is a variation of TroniC's MidiStim from the SmartStim forums.
https://www.smartstim.com/forum/viewtop ... 59&t=37175
eBay bare minimum Parts list:
1. "US TPA3116 Digital Power Amplifier Board 2*50W DC24V Two-Channel Stereo Digital" - $8.49
2. Speco T7010 $13.99 x 2
3. 3.9 ohm 10W resistor (3 pieces) $5.60
4. UL Listed 12V 3A 36W AC Adapter Power Supply $8.99
5. 20 Pairs 2mm Gold-Plated Bullet Connectors $5.45
Total before tax for eBay bare minimum: $56.54
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Added 10/3/2020: Parts Express replacements drop the price to just $43.12 before tax! ($6.95 economy shipping included)
1R. TPA3116D2 2x50W Class D Stereo Amplifier Board with Volume Control $7.98
2R. 70V 10W Speaker Line Matching Transformer $5.19 x 2
3R. 4 Ohm 10W Resistor Wire Wound 5% Tolerance $0.83 x 2
4R. 12V 5A DC Switching Power Supply Grounded AC Adapter with 2.5 x 5.5mm Tip Positive Plug (also UL listed) $9.97
5. 20 Pairs 2mm Gold-Plated Bullet Connectors $5.45
1P. 2.5 x 5.5mm Power Jack to Screw Terminals $0.73
(edited on 10/22/2020, seems like the 5V 2A adapter went out of stock.) You can save some money if you already have a 12V supply and a way to wire it to the amplifier.
Big thanks to hosenguy for helping verify this wiring diagram!
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This assumes you already have a soldering iron (soldering is easier than you think), wire, a 3.5mm audio cable, and something to mount the components to.
I recommend also getting some silicone wire for the electrode leads though since it's very flexible:
22 AWG 15ft x3 $7.59
Other instructions:
- Be careful, you are passing electricity through your body. However, the risk is very low if your electrodes stay below the waist.
- There will be a bunch of other wires on the side of the transformer with the 0.5W tap, just insulate the ends with tape or something and move them out of the way.
- The two major changes to the original MidiStim are a different amplifier and lower power resistors. I measured less than 2 watts at the input of the amplifier so it seems that 25W resistors aren't needed (maybe you need them if you're trying to shock your entire leg or something?).
- You can use a virtual audio mixer like Voicemeeter Banana (or other versions of Voicemeeter) to adjust left-right volume bias by passing the E-stim audio into the virtual input and then changing the L-R bias. Then you route the virtual input to the audio output that goes to the amplifier. Make sure all the audio devices going in and out of Voicemeeter are set to the same sampling frequency and bit depth (like 2 channel, 16 bit, 48000Hz) or else you'll have audio skipping and crackling.
- EarTrumpet is a useful app to have in general, it provides an easy interface to move programs to different audio outputs.
Ultimately I hope this helps get more people into E-stim since there is huge potential in it. The current E-stim teases on Milovana are just the beginning and they are already amazing!