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

[lolol2]

In standard stereo output, are you connecting and electrode wire to each output socket, two act as two pairs?
Then, with triphase switched on, do you run one from red, one from yellow, and one from either black output?

Yes there are two channels you can use for stereo mode, channel A with red + black1 and channel b with yellow + black2.
For triphase you bridge the both black common ports, you can do this with a cable or just add this little switch like in my build.
Then you only need three cables/electrodes, red + yellow for the both channels and black as common connected to black1 or 2.

For example one of my favorite electrode setup, common on glans, one channel on shaft and one channel under/on balls.

Also, on the input side, would I be correct in thinking that both sides of the stereo signal have their own volume / on-off controls?

The two volume buttons control each channel yes, mostly you want to to set two different volumes depending on your electrode placement.
For example an analtrode needs mostly more volume than an electrode on your glans.
So I would recommend to build a unit with an individual volume control for each channel



@TheElectrician
Sorry can't answer any of your questions.

Would you be kind enough to show a few internal pictures of your wiring?

Would also like to see a picture of your results.

[tudeloo]

On the left side of the diagram, am I right in thinking they are individual channel inputs, rather than something like a 3.5mm stereo have? Likewise, on the right side, are they individual outputs? I think that's the bit that confuses me the most.

Yes, they are, but they could easy be replaced with the connectors of your choice. I personally simplified by own design of my most recent build and bought a Nobsound amplifier that uses the TPA3116 amp chip. https://www.amazon.com/Nobsound-Channel ... 00WTOAC1M/
This saved on buying and wiring a few of the extra pieces and I just bought a 3.5mm to RCA cable. The amp is currently $33 and has a 5% "coupon" thing too. Be sure you use a 12 volt *double insulated* power supply (should have a depiction of a square inside a square). At least 3.8 amps should cover it.

I advice people who are interested in safety not to buy these chinese firecrackers. Bad components (cheap caps go boom), sub optimal design, bad layout design (might not care about thd) and sometimes even very dangerous (mains not secured internally, wires can touch output rails etc.), because they almost always neglect all safety-norms. Buy a named amp, you can use it for more than just your balls, but know this: take some hints from madrid and lolol2 design and isolate it and if not stated that you can connect the negative of channels A and B with each other, dont attach it to yourself and thus close the loop!

Why is there no fuse in this design anyways? I mean, it is such a simple measure to ensure low current-only and in case of failure of any component to limit high current tissue burns.

The reason for the high price of a stim device is simple: they give you a safety standard that is out of reach of most electronic amateurs. Tho, I do think some are overpriced without havnig a med-cert.

[phoopha]

On the left side of the diagram, am I right in thinking they are individual channel inputs, rather than something like a 3.5mm stereo have? Likewise, on the right side, are they individual outputs? I think that's the bit that confuses me the most.

Yes, they are, but they could easy be replaced with the connectors of your choice. I personally simplified by own design of my most recent build and bought a Nobsound amplifier that uses the TPA3116 amp chip. https://www.amazon.com/Nobsound-Channel ... 00WTOAC1M/
This saved on buying and wiring a few of the extra pieces and I just bought a 3.5mm to RCA cable. The amp is currently $33 and has a 5% "coupon" thing too. Be sure you use a 12 volt *double insulated* power supply (should have a depiction of a square inside a square). At least 3.8 amps should cover it.

I advice people who are interested in safety not to buy these chinese firecrackers. Bad components (cheap caps go boom), sub optimal design, bad layout design (might not care about thd) and sometimes even very dangerous (mains not secured internally, wires can touch output rails etc.), because they almost always neglect all safety-norms. Buy a named amp, you can use it for more than just your balls, but know this: take some hints from madrid and lolol2 design and isolate it and if not stated that you can connect the negative of channels A and B with each other, dont attach it to yourself and thus close the loop!

Why is there no fuse in this design anyways? I mean, it is such a simple measure to ensure low current-only and in case of failure of any component to limit high current tissue burns.

The reason for the high price of a stim device is simple: they give you a safety standard that is out of reach of most electronic amateurs. Tho, I do think some are overpriced without havnig a med-cert.

Do you have an example of an amp that you'd consider both safe and suitable? (Preferably with a UK link for purchase? )

[Dust]

Just a quick update from me.
Today I put everything together using crocodile clamps as connectors and surprisingly... it works great :).
Finally the pain files no longer get filtered and oh boy, some of them are quite hard^^

There are a lot of teases waiting to be replayed with a proper box, can't wait for the weekend.

Would you be kind enough to show a few internal pictures of your wiring?

Thanks.

Uff, I forgot to add that my wiring is a total mess but I guess I can share it (but don't expect anything helpful^^). I really expected it to not work, so I did not put any effort in to make something clean. And now I don't want to touch it: Don't fix something that is not broken or something like that...

Let's start with the nice and pretty pictures from the outside.

The front:

Spoiler: show

The back:

Spoiler: show

The inside o.O:

Spoiler: show

Btw is it normal that with tri-phase on, the combined signal can feel completly different from the two separate ones? For example (and my most radical experience) two smooth signals resultet in a pointy one. This was while 3 electrodes where attached in a line (on some part of my body ) and the common one was NOT in between. Or is something fishy going on?

[lolol2]

That doens't looks soooo bad!
My first battery build was more messed up and also worked fine.

Spoiler: show

1.jpg (480.48 KiB) Viewed 5623 times

Thanks for sharing.

And yes triphase can feel completely different, when both channels have different frequencies you will get that amazing stroke feeling you can't experience with a stereo electrode setup.
With stereo you have the advantage that you have two channels you can control completely independent in volume.
With triphase the volume is always a mix of both channels, so when you turn down one channel to zero, the volume of the other channel will also drop a lot.

Both fun to play with, some files work better with stereo and some with triphase.

[tudeloo]

Sorry, I cannot recommend any normal audio amp for estim. There is inherent danger in shorting out - you being in the middle, touching another case of a device etc. - and thus creating a short with mains.
(see: https://www.youtube.com/watch?v=xaELqAo4kkQ )

I will only ever recommend an estim device or a certified medical device. Those are made with exactly these problems in mind, also current flow between channels in "triphase" mode that can damage amps.

[mantrid]

touching another case of a device etc. - and thus creating a short with mains.
(see: https://www.youtube.com/watch?v=xaELqAo4kkQ )

It shorts you with Earth which has the same potential as N(eutral). This itself may only be dangerous for Martians.

Did you watch the video? Because the DIY recommendations in this thread contain transformers which isolates you galvanically from the amplifier. I.e. There can't be any current from amplifier through the body to Earth. The guy in the video talks about that (isolation).

But even without that, the maximum potential difference between the amplifier and Earth is the voltage of the power supply (usually 12V), provided that you use either an unisolated supply (normal switching supply) or that the amplifier input is DC coupled to an unisolated PC.

Nevertheless, your statement is not completely wrong: If there is a power supply failure either of PC or of amplifier power supply or if there is a lightening stroke and if you are DC coupled to the amplifier output and if you touch Earth it will become dangerous. This is why transformers are used. (In order to protect against spikes I also recommend TVS diodes.)

[Electro]

On the left side of the diagram, am I right in thinking they are individual channel inputs, rather than something like a 3.5mm stereo have? Likewise, on the right side, are they individual outputs? I think that's the bit that confuses me the most.

Yes, they are, but they could easy be replaced with the connectors of your choice. I personally simplified by own design of my most recent build and bought a Nobsound amplifier that uses the TPA3116 amp chip. https://www.amazon.com/Nobsound-Channel ... 00WTOAC1M/
This saved on buying and wiring a few of the extra pieces and I just bought a 3.5mm to RCA cable. The amp is currently $33 and has a 5% "coupon" thing too. Be sure you use a 12 volt *double insulated* power supply (should have a depiction of a square inside a square). At least 3.8 amps should cover it.

I advice people who are interested in safety not to buy these chinese firecrackers. Bad components (cheap caps go boom), sub optimal design, bad layout design (might not care about thd) and sometimes even very dangerous (mains not secured internally, wires can touch output rails etc.), because they almost always neglect all safety-norms. Buy a named amp, you can use it for more than just your balls, but know this: take some hints from madrid and lolol2 design and isolate it and if not stated that you can connect the negative of channels A and B with each other, dont attach it to yourself and thus close the loop!

Why is there no fuse in this design anyways? I mean, it is such a simple measure to ensure low current-only and in case of failure of any component to limit high current tissue burns.

The reason for the high price of a stim device is simple: they give you a safety standard that is out of reach of most electronic amateurs. Tho, I do think some are overpriced without havnig a med-cert.

I've seen the inside of this amplifier and don't feel it has any of the issues you are trying to suggest an amplifier might have. Some of your other statements like cheap caps go boom is somewhat misleading because a popped capacitor can happen in any device with capacitors and the result is they basically stop performing their function, one down isn't going to be a major concern apart from the noise made when it happens.

Regarding fuses a carefully chosen double insulated power supply that isn't overpowered for the rest of the design is the safety factor. The resistors and transformers also work together in adding extra layers of safety by effectively wasting power in a calculated way.

At this point, the way you are trying to come in and say a bunch of safety issues suggesting to buy an expensive device with a med cert without knowing what was behind this type of design with a track record of over a decade of people building this type of device successfully while people who use estim also find numerous undesirable qualities of many estim devices on the market as well makes me think you are affiliated with an estim manufacturer and working to defend them.

"sometimes even very dangerous (mains not secured internally, wires can touch output rails etc.), because they almost always neglect all safety-norms."

mains isn't inside this box, this isn't a giant surround sound amplifier with a built-in power supply. It's a small bookshelf speaker type of amplifier design with a double insulated 2-prong 12 volt power supply(you clearly glossed over this part about a double insulated power supply) external to the box, because of the double insulated power supply, there is 12 volts going into the box by design, not mains.

[phoopha]

I seem to be struggling to find all the parts in the UK.☹

Any other UK members had any success in sourcing the components for a build?

[tudeloo]

statements like cheap caps go boom is somewhat misleading because a popped capacitor can happen in any device with capacitors and the result is they basically stop performing their function, one down isn't going to be a major concern apart from the noise made when it happens.

This is just false. If a component fails you dont know if you get a "just not working" component (open circ), a short or due to some unlucky incident more damage to other parts of the circuit creating more shorts.

Regarding fuses a carefully chosen double insulated power supply that isn't overpowered for the rest of the design is the safety factor.

It is ONE safety factor. That alone wont get you a med cert. But I wont go into small currents and problems with them: there is no such thing as perfect isolation. Manufacturers suggest using fuses with transformers, because they can - and will - fail due to many reasons.

At this point, the way you are trying to come in and say a bunch of safety issues suggesting to buy an expensive device with a med cert without knowing what was behind this type of design with a track record of over a decade of people building this type of device successfully while people who use estim also find numerous undesirable qualities of many estim devices on the market as well makes me think you are affiliated with an estim manufacturer and working to defend them.

For what it is worth: i am not. However, since safety is a real issue, I will make suggestions that are appropriate for people who did not study computer engineering.

For all the excited amateurs out there, here is my sole reason for caution:
if the design is not properly isolated - like this one here is to some degree, but it is not medically safe (wouldnt be allowed to be used on humans by european or US standards in medical facilities) - you can by just touching a wrong part with your left hand provoke current to flow over your hand, arm, chest to your privates. If that current just comes close to something of 40-50mA (your typical USB port uses about 1000mA) your heart has a real risk of stopping or working incorrectly (pumping irregularly).
Why is it an issue here? Because you reduced your bodies impedance greatly: lupe, maybe even inserted something in your urethra/anally. Another problem is component and device failure without failsafes in place. Those might not pose the risk of death, but electrical burns can also be very very bad and destroy tissue. Just know, there is a real risk if you dont know what you are doing.

Stay safe!

[lolol2]

if the design is not properly isolated - like this one here is to some degree, but it is not medically safe (wouldnt be allowed to be used on humans by european or US standards in medical facilities) - you can by just touching a wrong part with your left hand provoke current to flow over your hand, arm, chest to your privates. If that current just comes close to something of 40-50mA (your typical USB port uses about 1000mA) your heart has a real risk of stopping or working incorrectly (pumping irregularly).

Thanks for making this clear, now I'm understanding about what scenario you are talking.
I have just added a basic health warning at the top of my first post.
Noticed that I kind of forgot something like that, when you post about estim over years you start to forget to inform about warnings more and more.

Not sure if there is any estim audio device which is based on an amp and has any medical certification?
I guess all the commercial estim devices are based on some TENS base?

[mantrid]

As I wrote earlier, protection against dangerous potentials is ensured by the transformer. There can't be any current from amplifier through body to Earth (potential of PC chassis, heater, ...).

Dangerous potentials can only occur in case of a malfunction (otherwise touching a connector and touching Earth at the same time would be dangerous too). But malfunctions can occur. And it's not just the amplifier, It's also the PC which is connected to the amplifier. I would consider everything before amplifier output as unsafe.

That's why safety has to be ensured by the output circuit.

[tudeloo]

As I wrote earlier, protection against dangerous potentials is ensured by the transformer.

Consider electrode placement, tho. What about nipple clamps and chest pads? You still see them in every darn shop. Those will be output circuit protected against faulty currents regarding earth. But we both know current will flow. Will it reach lower tissue? Probably not in most cases. But what if it does? What if by some chance the path over the heart (maybe because the potential shift in your heart muscle was JUST RIGHT at that moment) will lead to that deeper current flow ...

Just be safe, keep it below the waist and isolated

Also to say it clearly: I think you all are doing a good thing trying to bring open source hardware into this field and also considering isolation etc. Better than just hooking up to an audio amp. So, dont get me wrong, keep up the good work! We can always improve upon good things :)

[JakofClubs]

Tudeloo,

I'm using a medical grade isolation transformer for my stimming laptop and 12v power supply, that I got off EBay for $70 shipped. Like this one linked below. I realise that mains power isn't the only safety concern, but it's a big step in the right direction. I didn't get this just for stimming, but I had it for my electronics hobby, so why not use it?

https://www.ebay.com/itm/Toroid-Medical ... 3843870273

[Caius1]

I'm looking into building my own box so I've been reading stuff on this forum.

So the current consensus is that a fuse is not a necessary safety feature but I also take it that a fuse wouldn't have any negative effects either. Negative as in having to rethink the wiring or specs too much.
I know a little about electronics and have interest in them so at least from a theoretical view: Where should you put the fuse if you wanted to add one to the build? Would it be correct to put it on the black (-) wire between the 12V DC power supply and the rest of the circuit? See the black S-shape in the picture below, it's the symbol for fuses, right?

Fuse placement in circuit?

fuse.png (45.13 KiB) Viewed 5383 times

Another thing about the fuse, how "big" should it be, I mean how many Amps (A)?
With all the parts in your shopping cart you can just add up their individual A requirements and get a fuse that's rated a little over the total?
If we go with the amplifier lolol2 originally listed being the only thing using power, you be good with as little as 0,25A fuse when the amplifier requires 0,2A? Something as little as this for example.

And couldn't you just use a circuit breaker in place of the switch to work as a fuse and power switch simultaneously?

EDIT
I also started to think more about the high pass filters.

So my recommendation:
Low cut-off frequency option: 100µF + 20 Ohm or 220µF + 10 Ohm
High cut-off frequency option: 100µF + 10 Ohm
In both cases, highest winding ratio that deliver sufficient power should be used.

I have 0 experience with the estim files/teases (only xp with basic Mystim device) so I don't really know if I should build a higher or lower cut-off. So I thought, why not go crazy and build them both? Usage would be like when there's a stim file with higher frequencies you connect the trodes to the high cut-off filter and vice versa and maybe flip a switch to change where the amp box feeds the output. Through which filter, I mean.
That would just mean more connector holes and somewhat increased cost but then you'd have the right cut-off filter for every situation. I think.

Another edit
I'm trying to work out a shopping list now, if I look at mantrid's list in the spoiler below, where's the 5,1 Ohm resistors supposed to go? I can't see it in the high pass filter diagram and it's only supposed to have 2 resistors, 10 Ohm for each channel in the filters.

Spoiler: show

I already posted Digikey part numbers for the output circuit in the past:

• Transformer: 237-1146-ND
• Capacitor: 493-17272-ND
• TVS-Diode: 1.5KE15CALFCT-ND (plenty alternatives, search for 1.5KE15CA)
• Resistor 10Ohm/2W: A138253CT-ND (plenty alternatives)
• Resistor 5.1Ohm/2W: A138346CT-ND (plenty alternatives)
  ...

Also this list would be super convenient for me because there's a Digikey webstore in my own country.