Low-cost (~$40-60) DIY Stereo E-stim for Audio Input (based on TroniC's MidiStim)

[MilovanaFan]

I want to print this as a case for this project. Does anyone know if the hole spacings are equal across these pcbs?

https://www.thingiverse.com/thing:4254574

[JakofClubs]

Any one have stl files for a 3d printable case for this project?

If you are going to use a plastic case, you might consider mounting the resistors on an aluminum plate to spread out the heat.

[fritzp]

Hello,

Thank you for this tutorial and everyone for your contribution. I am tempted to try building my first device. I live in Europe so I don't have access to all the material you listed. I did a mixed between the material that you suggest and the material that lolol2 suggests in his tutorial.

Spoiler: show

lolol2's tutorial

Could someone confirm that the list i've made would work:
1. Amplifier XH-M189 TPA3116D2 (from your tuto) https://www.amazon.fr/Reland-Sun-amplif ... 168&sr=8-3
2. 100V transformer (from lolol2's tuto) https://www.conrad.de/de/p/elma-tt-iz18 ... 16104.html
3. 3.9 Ohm 50W resistors (from lolol's tuto) https://www.conrad.de/de/p/elma-tt-iz18 ... 16104.html
+ 22 Ohm 50W resistors (from lolol's tuto) https://www.conrad.de/de/p/widap-160082 ... 25118.html
4. Power switch (from lolol2's tuto) https://www.amazon.fr/Adaptateur-dalime ... Q==&sr=8-4
5. Banana 4mm pins (from lolol2's tuto) https://www.amazon.de/gp/product/B07X34SNGP/

Thanks for your help

[lolol2]

This should work fine.
The only problem is that you only have one volume knob for both channels.

Maybe I would just order two of the AMPs (if +10€ is no big deal) and use one for right and one for left channel, then you have an individual volume control for each channel. Using an 3.5mm y-splitter as input for both AMPs.

[fritzp]

Fabulous ! Thank you for your help!!

[edger477]

This should work fine.
The only problem is that you only have one volume knob for both channels.

Maybe I would just order two of the AMPs (if +10€ is no big deal) and use one for right and one for left channel, then you have an individual volume control for each channel. Using an 3.5mm y-splitter as input for both AMPs.

I have many amps and this is now my favorite: https://www.amazon.de/-/en/gp/product/B087FWWVB6/

It has separate knob for each of 4 channels, and is Bluetooth (no cables, no hum). When used in Bluetooth dual-channel mode, then you have RCA output (so you can connect another amp or 2B). I use it for 2B (don't have to stim with amp, leave all knobs at 0) because for some teases that are really quiet (i.e. Estim Bondage) any noise/hum from sound card can be an issue, and with Bluetooth transmission this does not get through.

[Odli.DPrincess]

[icehash23]

I live in Canada, and trying to find a suitable amp. I can figure for everything else but if anyone knows an alternative that's in-stock, please link it .

I have a budget of 70$, so if there's a prebuilt e-stim box that anyone here knows and likes please leave your recommendations!

I feel bad for posting this on here but thank you so much to anyone that can help.

Hey sorry this is late, but maybe it'll help others:

Also in Canada. I used a SMSL SA-36A, as AFAIK it was recommended by TroniC on Smartstim for the "original" MidiStim. I paid $69.99 CAD, so that fits your budget... but seems Amazon has it for $105 now

So far it's been worth it - I've since tried some other "module" amp boards, including a chinese TPA3116D2-based one from "Doudou". This one had bad spikes when you got close to the "off" position of the pot (I think solvable by replacing the switched pot with a dedicated switch and separate pot) but this meant a much more limited range of usable master volume control.

The SMSL's master volume pot is great, very smooth. I bypassed the amp switch on it so it's just on as long as I have the DC plug in. I still have individual channel pots (and even 4x individual trode bias pots) but the master one gets the most use. It's easy to spin down in an emergency or if I have to change something about the setup.

[Kevin77794]

1. Amplifier XH-M189 TPA3116D2 (from your tuto) https://www.amazon.fr/Reland-Sun-amplif ... 168&sr=8-3
2. 100V transformer (from lolol2's tuto) https://www.conrad.de/de/p/elma-tt-iz18 ... 16104.html
3. 3.9 Ohm 50W resistors (from lolol's tuto) https://www.conrad.de/de/p/elma-tt-iz18 ... 16104.html
+ 22 Ohm 50W resistors (from lolol's tuto) https://www.conrad.de/de/p/widap-160082 ... 25118.html
4. Power switch (from lolol2's tuto) https://www.amazon.fr/Adaptateur-dalime ... Q==&sr=8-4
5. Banana 4mm pins (from lolol2's tuto) https://www.amazon.de/gp/product/B07X34SNGP/

Does anyone have an instruction manual on how to put this together, for someone that has no experience in this type of project?

[Corndogville]

I finished my box, yay! I modified a bit the original build and now it feels great.
This is my final schematic, notice the extra resistors:


The default schematic worked but felt a bit painful, with a constant "static" that got unbearable at the higher levels. After adding the two parallel resistors the static is almost gone and the signal feels very smooth, strong but not painful.
Resistors are inexpensive and this modification barely adds complexity to the build. The quality increase is MASSIVE. I highly recommend this over the original schematic (unless you like pain of course).


@steelhorse545
My audio card was indeed damaged. After trying the estim box with the faulty amp, the left channel had a massive drop in volume. Super annoying and a even bit disorienting, even with the balance corrected in Windows settings. I will have it repaired asap.

I ended up using the box via USB audio interface, configured at 100% volume. Turns out my amp is a bit weaker than expected and I had to raise its volume way up before getting any feeling. Not a big deal but led me to believe that the box wasn't working at all. I believe I was feeling more "distortion" with the USB interface simply because the interface had more power than the broken audio card, but with the extra parallel resistor the noise is gone and that's solved.
Thanks again for the help.

My parts are coming today, but I didn't order an AC adapter yet.

Since this is 12v and center positive, can't I just use the power supply from my 2B? The A channel died in less than a couple months of owning it, and there's no way I'm paying $85 to ship it back to the UK to have it fixed when, at the price I paid for it, it should have lasted forever (and been under warranty).

Not to mention what a garbage job it does at stereo stim. I went back to my homemade Davey Box.

[edger477]

can't I just use the power supply from my 2B

2B PSU might be too weak for DIY box. It is 12W and these TPA3116 amps produce (and need) more power, since audio devices are order of magnitude less efficient than pulse boxes.

Also, you should look for electronics shop that can repair your 2B, it is most probably driver blown off, and repair should be half of the price to send it back.

Also, some people in Joanne's discord modded 2B with stronger drivers so they don't burn out when you use Moaner and similar large electrodes :) You can check there what they repaired and then use it to check if yours has same problem.

[Corndogville]

Also, is there any final verdict on the 10 ohm 10w parallel resistors? I got a pair of Dayton Audio ones, figuring they'd be high quality:

https://www.parts-express.com/Dayton-Au ... quantity=1

For the 3.9s, I got Jantzen Audio:

https://www.parts-express.com/Jantzen-3 ... quantity=1

Also, I got these power jack to screw terminals, which will hopefully be compatible with the 2B adapter:

https://www.parts-express.com/2.5-x-5.5 ... quantity=1

[Corndogville]

can't I just use the power supply from my 2B

2B PSU might be too weak for DIY box. It is 12W and these TPA3116 amps produce (and need) more power, since audio devices are order of magnitude less efficient than pulse boxes.

Also, you should look for electronics shop that can repair your 2B, it is most probably driver blown off, and repair should be half of the price to send it back.

Also, some people in Joanne's discord modded 2B with stronger drivers so they don't burn out when you use Moaner and similar large electrodes :) You can check there what they repaired and then use it to check if yours has same problem.

It's not worth it to me to try and fix the 2B (nor do I relish explaining to an electronics shop what it does, but maybe it's different in Germany!), but what AC adapter do I need then in volts and amps? A link would be awesome, since it's not something I want to get wrong. What about the whole "class 2" thing, also? I think I've heard folks saying it had to be class 2, in regards to safety. I assumed the 2B one would be as safe as you can get, but obviously not if it's too weak.

[edger477]

Also, is there any final verdict on the 10 ohm 10w parallel resistors?

The resistors look good, but I'd try first building it without 10 Ohm resistors. Your box will be more efficient, and almost all modern amps work just fine if load connected is more than 8 Ohms.

That parallel resistor just converts part of amp power into heat. For old amps it was mandatory since they wouldn't produce output on low volume if there is not 8 Ohms or less load connected (some required 4). I think all modern ones will work even with 32 Ohm headphones (of course with less power but the extra power does not go into transformers anyway, it goes into that resistor and gets turned into heat).

what AC adapter do I need then in volts and amps?

Which continent are you at? Something like this is fine if you can get it https://www.amazon.de/-/en/gp/product/B00NWH1FTS/

[Corndogville]

Also, is there any final verdict on the 10 ohm 10w parallel resistors?

The resistors look good, but I'd try first building it without 10 Ohm resistors. Your box will be more efficient, and almost all modern amps work just fine if load connected is more than 8 Ohms.

That parallel resistor just converts part of amp power into heat. For old amps it was mandatory since they wouldn't produce output on low volume if there is not 8 Ohms or less load connected (some required 4). I think all modern ones will work even with 32 Ohm headphones (of course with less power but the extra power does not go into transformers anyway, it goes into that resistor and gets turned into heat).

what AC adapter do I need then in volts and amps?

Which continent are you at? Something like this is fine if you can get it https://www.amazon.de/-/en/gp/product/B00NWH1FTS/

I'm in the USA and this is the amp I bought:

https://www.amazon.com/gp/product/B099F ... UTF8&psc=1

Also, being a universal power supply, it's still not confirming what I need as far as amps/watts. Please explain it like I'm 5.

I also have a whole basket full over AC adapters, so I may already have what I need, I just need to know what to look for on the sticker....as well as anything I need to look for, safety wise.

Edit: It's probably overkill, but I own this one already:

https://www.amazon.com/gp/product/B08BL ... =UTF8&th=1

I'd rather use a fixed supply though, so if you can tell me what numbers to look for, I probably have it.