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

[Ganiolin]

Another experiment that I want to do (and I still bought the amplifier) is to use the MONO amplifier below. This amplifier is based on the TPA3116DA same of the first two channel amplifier above listed. On aliexpress it cost around 4$ each one. i bought four with the hope to replace the two mono amplifier that i tried before.



DC12V-DC26V - Max 150 W - DC12V energia 50 W, DC20V 100 W, DC24V 150 W


Do you think that this amplifier would work in this configuration?


Thanks

[DefinitelyHere]

The "Thanks Bob!" made me chuckle; until recently that was part of a meme among flerf debunkers like SciManDan. (Dan has since retired the meme after Bob Knodel's passing.)

First of all, most people seem to have best results using the 8 ohm and 0.63W taps on those 70V line transformers. I wish I could explain the reason for this in non-technical terms, but it has to do with turns ratios on the transformer and the voltage delivered at the output. Using the 8 ohm tap allows the transformer to handle more power from the amplifier, and the 0.63W tap steps the voltage up to where it will reliably cause the nerve depolarization necessary for the e-stim effect with low current. If the voltage is too low, you'll need more current to get any sensation and will have a greater risk of literally cooking your flesh.

In terms of mains electrical safety, the main concern is that there isn't a direct path between the power supply primary and secondary. If there is, mains voltage can easily find a path to ground through you and you will have a bad time.

I'd like to address the fan noise issue. If you're comfortable with soldering and have a spare 7809 lying about, try putting that between the power supply and the fan. The fan will run a little slower but should still provide more than enough airflow. The regulator will completely decouple the fan from the amplifier.

Thanks for your help, nearly done building! Quick question, so I should be using the 8ohm and 0.62W 70v (purple wire) on my specific transformers? I included screenshots of the transformer that I have. Not looking for any extreme power, and would rather play it safe. If anyone else wants to chime in, it would be greatly appreciated. Thanks!

[pvsage]

Does it sound like I have a "bad" amplifier board or maybe something else weird may be going on?

How do you have the output transformers wired? For maximum energy transfer and output voltage, you should be using the highest impedance terminals on the 4/8 ohm side and the lowest current/highest impedance taps on the 70V side. If you're using 8 ohm to 0.67 A, you can get a bit more voltage at lower current (might feel stronger due to more nerve depolarization) by using the 4 ohm tap on what we're using as the primary.

[pvsage]

Thanks for your help, nearly done building! Quick question, so I should be using the 8ohm and 0.62W 70v (purple wire) on my specific transformers? I included screenshots of the transformer that I have. Not looking for any extreme power, and would rather play it safe. If anyone else wants to chime in, it would be greatly appreciated. Thanks!

Yes. 8 ohms attached in series with the resistor from the amplifier; lowest available "current" tap on the 70V side. Higher voltage at lower current will give more sensation with lower risk of physical injury.

The typical impedance for the 0.67A tap of a 70V transformer is 8000 ohms, assuming the other side is connected to a loudspeaker of the specified impedance. The effective output voltage will be pulled down by your skin, just like it is with a stun gun or taser...which is essentially what these home-built estim devices are.

[pvsage]

I have tried 4 amplifier of this type 2 bought on aliexpress and other two bought from amazon

It seems a lot of these boards sold via Amazon, eBay, and aliexpress are rejects that couldn't be sold via the usual scumbags (that it, the more reliable suppliers). Might want to try getting one directly from a source like Parts Express.

[icehash23]

Hi all! Veteran noob here, looking for some advice. Sorry for the wall of text.

I've been stimming on and off since I was 18 (~15 years ago). I first built a terrible mono "Davey Box" using the amp from a salvaged baby monitor (lol) with some silver solder/copper trodes. Boy, did I not know what I was missing out on! But I guess it did the trick at the time. From what I've read and experienced lately, it seems I've become pretty accustomed to the more intense stim levels...

~10 years later, I've since built two MidiStim boxes. One (back in SmartStim days, rip climberr and tronic) was a mockup using the still-OEM-packaged SASL SA-36A , with some Speco T7010 transformers (the modern revision, from B&H Photo Video). It at least served as a platform for me to know what I was getting into, and plan my design, but...

On the next build (~3 years later, ~2 years ago), I broke everything out into a very large plastic clamshell case as a sort of prototype, in order to have an easier time breadboarding and diagnosing any issues. I'm still using that amp with the adapter it came with (SAP-1238-T - 12V/3.8A, Class II double insulated).

I guess I was never really sure which tap to use, because since building this second revision, I've gravitated from Yellow (1W, used for a vast majority of my time stimming), more recently to Orange (2.5W) and upon some very recent research, way down to Purple (0.5W).

Tonight, upon switching to the Purple (8000 ohm?) tap, the start of the session seemed to be going great. I was at a comfortable stim level, but still had tons of headroom.

~1.5 hrs later, after hitting my laptop's Realtek max output + amp output volumes (while frustratingly wishing there was more) and climaxing... I began packing up, only to find that the transformers and series resistors (3.9 ohm 25W) had gotten hot enough to melt my case into my bedsheets - more severely melted was the plastic around the right channel, corresponding to my bipolar anal trode, an Estim Systems Large Flo, which always seems to take a lot more juice.

This never happened when I used the "higher" power (Orange/Yellow) taps. I've since realized (...incredibly belatedly) that since we're running these transformers "backwards", the "lower" power taps correspond to a higher voltage output, which... I guess can generate more heat?

So my guess is that the limited turn count in the "higher" power taps (yellow 1W/orange 2.5W) were the bottleneck of my rig's output, preventing any severe overheating. But after dropping "below" that (to a higher turns ratio), said bottleneck was widened, causing the overheating issues I'm seeing now.


----


tl;dr I guess my question is:

I'm encountering heat issues while capping out volumes on an SA-36A amp with Speco T7010 (8 ohm:0.5W) transformers and 3.9 ohm 25W series resistors. Apart from adding heatsinking/active cooling via metal case + fan, is there anything else I can do to increase output power overhead?

For my next build I am thinking about trying:

• 12V/10A (120W) Class II AC adapter
• Nobsound TPA3116-2.1 (50W x2) Bluetooth amp (not sure whether the onboard DAC will be worth its salt - the usual AUX is available as backup)
• In a (Hammond HM3094-ND metal case, from DigiKey)
• Perhaps with an active blower fan, if heat is still a problem once the offending components are coupled to metal (thermal paste?), and given I can find one that will fit the case.

Any and all thoughts will be greatly appreciated! Build pics as payment

[edger477]

I'm encountering heat issues while capping out volumes on an SA-36A amp with Speco T7010 (8 ohm:0.5W) transformers and 3.9 ohm 25W series resistors. Apart from adding heatsinking/active cooling via metal case + fan, is there anything else I can do to increase output power overhead?

If tranformer has 4 ohm primary, try using that for input, but your issue comes from using the amp on max volume/power. Most of that power was converted to heat in resistor and transformer and not delivered to electrodes. If you say that purple is 8000 Ohm, that is about 10x more than human body (and for internal electrode resistance is probably below 500 Ohm). So more than 90% of that power was converted into heat inside windings (since most of resistance was there).

To reduce that, you need to use more powerful output tap. The least powerful output tap will give the most voltage/the least current, but it also has the highest internal resistance and it will produce least power when using internal electrode. We use least powerful output mainly for safety reasons (the least current will be there), but since you ran into "lack of power" issue, try using next one. You get less voltage when no load, but when connected to electrode you will get more voltage than on weakest tap, since there is less wire and internal resistance in higher power tap, so the current output will be higher. Lower internal resistance means less heat, but the main reduction in heat will be from reducing amp volume (and therefore overall power delivered to transformer).

On my transformers I am mostly using taps that have around 200-500 Ohms.

[diglet]

I have tried 4 amplifier of this type 2 bought on aliexpress and other two bought from amazon:
...

I ordered three from this seller: https://www.aliexpress.com/item/1005002780447560.html, with a few months in between orders, they all work fine even though the chip is not a real TPA3116.

Someone on discord ordered a few from amazon, they were all crap and needed big modifications to work.

[pvsage]

I'm encountering heat issues while capping out volumes on an SA-36A amp with Speco T7010 (8 ohm:0.5W) transformers and 3.9 ohm 25W series resistors. Apart from adding heatsinking/active cooling via metal case + fan, is there anything else I can do to increase output power overhead?

Try doubling up the resistors in parallel for an effective resistance of 2 ohms in series with each transformer. More of the output voltage will be dropped across the transformer, so the resistors will dissipate less power, and it will be spread out over two resistor bodies per channel.

[icehash23]

Thanks for the advice, edger and pvsage! I ended up going back to the yellow tap (~280 ohms or so) with this new build. Heat seems not to be a problem any more, and with the new amp/PSU there are miles of overhead.

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!

IMG_20230806_160836.jpg (418.98 KiB) Viewed 11069 times

IMG_20230806_160855.jpg (248.41 KiB) Viewed 11069 times

Aaand the dirty insides:

Spoiler: show

IMG_20230806_160746.jpg (474.7 KiB) Viewed 11069 times

IMG_20230806_160755.jpg (457.41 KiB) Viewed 11069 times

Schematic & other docs: Relevant Docs
(thanks to Stimaddict for archiving)
See attached for some drill templates! Use spring clamps to hold them on while you center-punch, because 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

Total, about $375? But I don't think I'll ever need to build another!

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).

[cbttorturelvr]

Ok looking to build one after getting tired of the 2b not working on a lot of teases.
Is there a go to build at this point preferably with US sources.

[Nobody81]

Uhh...lads? Did I fuck up with soldering directly to the pins on the amp because I thought the wire that came with it was too thin? I'm getting 0.8V out of it but no amps.[img][https://drive.google.com/file/d/1F776aZ ... p=drivesdk]

[Míchael]

Uhh...lads? Did I fuck up with soldering directly to the pins on the amp because I thought the wire that came with it was too thin? I'm getting 0.8V out of it but no amps.

That shouldnt be a problem if soldered properly. 0.8 volt is way too low In either way from a current perspective you will only get milliamps from the output. Putting more than 70mA is dangerous, for example 3 seconds of 7mA directly through the heart will result in a certain death. I would not measure the amps just measure voltage.

Back to debugging:

• Make sure that your amp volume is set.

• Make sure every connection is working and you dont have a short. you can test most of them with a multimeter

• Make sure that your pots are working. Test the ressistance with the multimeter. Terminal 1 and 3 should always be the value of the pot. Test the if terminal one and two (or two and three depending on your wiring) are changing values while turning the knob

• Measure the output of the amp. In my case my amp gives out 10v per channel.

EDIT just got access to the image you provided:
Just saw the image you provided:


Its not clearly visible but there could be a short in the audio input. But in general that does not look clean at all i would probably throw away the amp and redo it with wago's

[Electro]

Uhh...lads? Did I fuck up with soldering directly to the pins on the amp because I thought the wire that came with it was too thin? I'm getting 0.8V out of it but no amps.[img][https://drive.google.com/file/d/1F776aZ ... p=drivesdk]

Not sure how you are measuring things, are you supplying input audio to the amp, are you measuring after the output of the transformers, multimeters are designed to work in either DC or 50 or 60hz AC, so measuring things with a multimeter to determine that things are working well can be a crap shoot. Not enough information to even tell you if it's not working.

[Nobody81]

Just measured the voltage output of the amp itself and now I'm getting 12.5-12.6V. I also confirmed the pots worked so there's that. But when i try feeling for amps from the transformers (one's input to 4Ω, the other's at 8, and I checked the outputs at 0.5W-5W and 1.5W-10W) and nothing's coming from them. Is there a way I can test the transformers and also figure out what winding ratio they are? I got them from here.