[Tutorial] Building your own DIY E-Stim Stereo Device

[Dramya]

I followed the listing of viewtopic.php?p=326644#p326644 and I could find most of the items with relative ease, but I think I have a few interesting links that could be added to the item list (German Amazon, but they deliver to other countries)

Power Supply:
https://www.amazon.de/-/en/dp/B0BF9T6X6 ... tails&th=1
This one has the same properties as the original listed item, 12V 10A 120W, and the show picture is accurate as it is indeed double insulated. Way better price then the one mentioned somewhere in this topic that is specifically meant for lab equipment.

Stereo Amp:
https://www.amazon.de/-/en/dp/B0B2K8KPP ... ct_details
Same exact board but with a TPA3116D2 chip, which is (as far as I can find) a better performing chip then the CS8673E chip one in the original listing. If it actually is I will find out soon enough. Also, it is of German make, so I'm reasonably sure it is not a fake one with a totally different chip under the heat sink.

I still have to get the rest of my orders, but as soon as I get to put it together I will post an update.


I also have a question, I have struggled to find the Stereo Amp that closely resembles the one listed but should I even have cared? Is there a lot of difference between those Amp's? Could I have chosen a different one, maybe of different make and type?

I also heard from Edger477 that the 22Ohm resistors are not actually needed, what was the reason to include them in the original design?

[Electro]

The TPA3116D2 chip is what you want and it has a good sized heat sink on it, so that looks like a good amp.
The power supply looks good, you'll never pull more than 5 amps from it.

[Dramya]

The TPA3116D2 chip is what you want and it has a good sized heat sink on it, so that looks like a good amp.
The power supply looks good, you'll never pull more than 5 amps from it.

This worries me for a tiny bit, I took a rather generic electronics enclosure without any air holes in it, does this chip generate a lot of heat? Enclosure is big enough, so it should have should have enough air in it to take a bit of heat, but I think I should consider punching some holes in it too.

[Electro]

This worries me for a tiny bit, I took a rather generic electronics enclosure without any air holes in it, does this chip generate a lot of heat? Enclosure is big enough, so it should have should have enough air in it to take a bit of heat, but I think I should consider punching some holes in it too.

The amp doesn't generate much heat, I bought a cased amp that has the TPA3116D2 instead of one of these and it doesn't have any ventilation at all and the case doesn't seem even slightly warmer than its surroundings.

The resistors do make heat though and they are mounted to a 3" x 5"(75mm x 150mm) thin metal sheet as a heat sink that's exposed to air and the metal sheet feels hot to where you can still hold your hand on it, but not for more than a few seconds during longer and more intense stim sessions. I wouldn't mount the resistors directly to plastic.

My resistors and transformers are inside a plastic box but the metal sheet is the lid and I mounted the resistors upside down onto that lid using a healthy amount of CA glue(standard clear superglue), no other ventilation for the box but the lid is exposed to the air around it. ..again I don't have my amp inside this since I have a cased amp. So my rig is the cased amp and the "speaker wires" from the amp run through drilled holes for each of the four wires and the output wires from the transformer come out of the box on the opposite side. So basically I've more or less got two boxes roughly the same size that are tethered together.

[JakofClubs]

I also heard from Edger477 that the 22Ohm resistors are not actually needed, what was the reason to include them in the original design?

Apparently, some older amps worked better with the additional resistor. Edger477 did fairly extensive research on the modern TPA3116 amps and found that they don't benefit from it and it's a waste of power. They aren't required for safety.

IIRC it was originally called a smoothing resistor. I have a pair in my box with no noticeable power reduction. I subjectively think it feels a little less spikey, but it depends on the track. I should add a switch to bypass them on my box to see if I still think that's true.

[edger477]

Edger477 did fairly extensive research on the modern TPA3116 amps

Actually, I did not research myself, I suspected that the reason for them might have been that older amps did not pump current until they detect some minimum load, and asked about it in Joanne's discord (there are some very good electronics engineers there). On modern amps, especially with a transformer that has static resistance (when you measure with Ohmmeter) that is 4 or 8 Ohms (the side we connect to amp), these parallel resistors are just waste of power, and also source of unnecessary heat.

[tommarr]

I liked the case lolol2 mentioned in his post here viewtopic.php?p=326644#p326644. However it was no longer available and there seemed to be nothing similar in amazon / ebay. After some searching I found that bahar sells the case from their website in all amounts.

Here is the one I believe lolol2 had in his pictures https://bahar-enclosure.com/products/bd ... 70-x-60-mm
Ordered a bit larger one to have more space to lay out things https://bahar-enclosure.com/products/bd ... 10-x-65-mm

Will see if the shit ever arrives from China via bahar website Shipping to EU was around 25eur, not cheap but bleh whatever. Ordered two and will probably build and sell the second one to cover costs a bit. Amazon.de also has nice 25eur shipping for under 100eur purchases, conrad also 25 eur. Costs just going up everywhere

Stereo Amp:
https://www.amazon.de/-/en/dp/B0B2K8KPP ... ct_details

And sorry guys, I think I ordered the last ones Already have few TPA3116 but the form factor ain't that nice so that amp was easy pick

But I think I finally got enough of my wire mess without any enclosure minimalistic diy-estim. Time to dig the soldering iron from closet and make a nice box

[JakofClubs]

Edger477 did fairly extensive research on the modern TPA3116 amps

Actually, I did not research myself, I suspected that the reason for them might have been that older amps did not pump current until they detect some minimum load, and asked about it in Joanne's discord (there are some very good electronics engineers there). On modern amps, especially with a transformer that has static resistance (when you measure with Ohmmeter) that is 4 or 8 Ohms (the side we connect to amp), these parallel resistors are just waste of power, and also source of unnecessary heat.

My mistake. Perhaps it was Diglet that did the testing?

[edger477]

We did some tests together with scopes and different loads but I would not call that extensive since it did not involve different amplifiers for verification. I did rebuild my boxes without these resistors (old boxes had them) and can confirm that output did not become worse for it.

[diglet]

Edger477 did fairly extensive research on the modern TPA3116 amps

Actually, I did not research myself, I suspected that the reason for them might have been that older amps did not pump current until they detect some minimum load, and asked about it in Joanne's discord (there are some very good electronics engineers there). On modern amps, especially with a transformer that has static resistance (when you measure with Ohmmeter) that is 4 or 8 Ohms (the side we connect to amp), these parallel resistors are just waste of power, and also source of unnecessary heat.

My mistake. Perhaps it was Diglet that did the testing?

I did some testing with a tpa3116 clone, scope and parallel resistor, was not able to identify any useful effects.

Tests available here: https://github.com/diglet48/restim/wiki ... l-resistor

[fishyfish]

All the rest of the schematic seems clear to me but can somebody clarify how to connect the triphase switch?

Below is an example where I would use the outer connectors. I suppose the correct wiring depends on the switch too? I don't know if this is right, I'm just providing the picture to make it obvious what I'm asking.

triphase.png (103.49 KiB) Viewed 8544 times

[Míchael]

All the rest of the schematic seems clear to me but can somebody clarify how to connect the triphase switch?

Below is an example where I would use the outer connectors. I suppose the correct wiring depends on the switch too? I don't know if this is right, I'm just providing the picture to make it obvious what I'm asking.

triphase.png

Thats correct for triphase you connect both "-" with the switch as seen in the schematic.

[fishyfish]

Thats correct for triphase you connect both "-" with the switch as seen in the schematic.

Thank you. I notice I got the wrong kind of a switch for this (two pins, not three) - I suppose it would also work if the only purpose of the switch is to either bridge the "L&R -" outputs or separate them?

[Míchael]

Thats correct for triphase you connect both "-" with the switch as seen in the schematic.

Thank you. I notice I got the wrong kind of a switch for this (two pins, not three) - I suppose it would also work if the only purpose of the switch is to either bridge the "L&R -" outputs or separate them?

Yeah the purpose is to simply connect the two. The 2b doesnt do it as a hardware solution for example and you could also just use a wire that shorts / connects both "-" pins.

For the switch as far as I know is the third pin (middle) common so just dont connect anything to it and it should work.

[limitsky]

Hi, I'm currently collecting the parts to make the tronic Midistim for the first time and was wondering what is a good electrode socket to purchase for 3.5mm size so I can solder it to the transformer wires. I have a 2B and want to use the 3.5mm to 2mm output cables that they gave.


Parts I plan to use were:

Transformer: Parts Express 70V 10W Speaker Line Matching Transformer

Amp: Nobsound HiFi 2.1 Channel Bluetooth 5.0 Power Amplifier Board Case Stereo Subwoofer Amp

Power: [UL Listed] Chanzon 12V 5A 60W AC DC Power Supply Adapter (Input 110V-220V, Output 12 Volt 5 Amp 60 Watt) DC Converter LED Driver Lighting Transformer for 12 V 5 A Flexible LED Tape Strip Light

Resistor: Uxcell a12040600ux0286 Chassis Mounted Aluminum Housed 25W 3.9 Ohm 5% Wirewound Resistors