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

[arig4711]

I would never ever use a 24V power supply. This is far too much for a stereostim.

Ohms law:
12V / 8 Ohm = 1.5A (18W per channel )
24V / 8 Ohm = 3A ( 72W per channel)

( I hope my physics knowledge from school is right)

The 12v 10A isn‘t Class II.

There shouldn’t be any difference between a 12V 5A and a 12V 10A power supply.

[Spielers]

The 12v 10A isn‘t Class II.

There shouldn’t be any difference between a 12V 5A and a 12V 10A power supply.

the power supply need a electric coil to work properly, a transformer with a electric chip get you an interrupped signal.

[edger477]

I would never ever use a 24V power supply. This is far too much for a stereostim.

Ohms law:
12V / 8 Ohm = 1.5A (18W per channel )
24V / 8 Ohm = 3A ( 72W per channel)

( I hope my physics knowledge from school is right)

The 12v 10A isn‘t Class II.

There shouldn’t be any difference between a 12V 5A and a 12V 10A power supply.

That is not how you calculate power...

You would need to measure current and voltage that goes into amplifier to calculate wattage. Power supply only gives power to the amplifier, and amplifier uses that voltage and current to drive transistors that amplify the input signal. The output voltage will not be 12 or 24V, it will depend on amplifier volume, input signal, and the load connected to the amplifier. It does not matter how many volts the power supply is as long as it provides stable enough power (too weak power supply can cause amplifier to start behaving very weirdly and even cause very painful spikes). If you give it more power than it needs it simply will not pull all of the available current and that is it.

If you use amplifier that can use either 12 or 24 as input, and provide same output power, then at 24V it will simply draw half the current that it draws on 12V (with same signal and volume).

[arig4711]

Well, it is Ohms law.

Anyhow I just wanted to help. And this is imo a risky thing.

Why not use a 48V power supply?

[edger477]

Well, it is Ohms law.

Anyhow I just wanted to help. And this is imo a risky thing.

Why not use a 48V power supply?

Criteria for power supply is
- double insulated
- voltage and power within amplifier specifications (some amplifier will require 12V, some will require at least 19, some work with 10-30)

You can apply Ohm's law like you did if you connect the power supply directly to 8 Ohm load (which some transformers are even for constant input). However, none of us do that, we all use amplifier, so it is irrelevant - power supply needs to provide sufficient power (voltage x current) to drive amplifier. Its voltage needs to be in range specified by the amplifier, and current needs to be sufficient to handle maximum output by the amplifier (of which most ends up as heat in parallel resistor).

Output of properly powered amplifier (with power supply within its specifications) will depend entirely on the input signal (estim) and volume of amplifier - this is what the voltage and current on transformer terminals depend on, not power supply.

Your usage of Ohm's law sounded like you are connecting power supply to electrodes on your body, please don't do that.

[arig4711]

Well, it is Ohms law.

Anyhow I just wanted to help. And this is imo a risky thing.

Why not use a 48V power supply?

Criteria for power supply is
- double insulated
- voltage and power within amplifier specifications (some amplifier will require 12V, some will require at least 19, some work with 10-30)

You can apply Ohm's law like you did if you connect the power supply directly to 8 Ohm load (which some transformers are even for constant input). However, none of us do that, we all use amplifier, so it is irrelevant - power supply needs to provide sufficient power (voltage x current) to drive amplifier. Its voltage needs to be in range specified by the amplifier, and current needs to be sufficient to handle maximum output by the amplifier (of which most ends up as heat in parallel resistor).

Output of properly powered amplifier (with power supply within its specifications) will depend entirely on the input signal (estim) and volume of amplifier - this is what the voltage and current on transformer terminals depend on, not power supply.

Your usage of Ohm's law sounded like you are connecting power supply to electrodes on your body, please don't do that.

Ohms Law is right.

Most of the energy of the power supply goes into the outputs, and through the resistors and transformers into the electrodes.

If you take the TPA3116: this one has 18W per channel with 12V and definitely much more with 24V. The sheet says 120W/channel (and unrealistic 50W/channel with 12V) , which isn't possible, because of Ohms law. More realistic is 72W / channel and this would blast your genitals away, when you max the volume.

I had long discussions about this thing in the old smartstim-forum. Also the veterans only used 12V or at max 15V power supplies with the TPA3116. More would be dangerous.

I don't want to discuss the obvious anymore, but please be aware of the risks (also the recommended 12V Power supply is not Class II).

[edger477]

Most of the energy of the power supply goes into the outputs, and through the resistors and transformers into the electrodes.

Man, please just stop commenting, you are spreading misinformation.

Maybe you are not completely clueless about electrotechnics but this statement is. If even 10% of power available from good power supply ended up in electrodes this thread would have no users (most would not be dead but would have no interest in estim ever again). If you really believe what you write here, then you should really get battery power for your amplifier, because your wall socket probably can supply more than 3kW of power and you are connecting power supply to it, so it must all go through, right?

I feel it is completely pointless to try to explain what happens with power supplied to amplifier, what is its output, and even from there - because output stage of stim box were very well described in earlier posts, roles of serial and parallel resistors etc... It all respects Ohm's law but you have to understand and apply it to each of those subcircuits. And yes, without parallel resistor it is possible to push more than 10% of available power to transformer, but we all have volume knob and we use it. Most of us also have parallel resistor which together with losses in transformer consumes almost all of the output power of amplifier (and provided power from supply), electrodes receiving only very small fraction of it, by design (because like that output power depends on static components, not on conductivity and area of electrode contacts). Having more power than needed just means less distortion, it does not mean that all of it HAVE to be used. Just like having 200HP engine in car does not mean you always have to be accelerating.

And BTW, I personally use that exact model of Leicke 24V power supply linked by @lolol2, not because it can provide 120W, but because it is double insulated (represented by two boxes one inside of each other on sticker on its back).

The linked one for 12V does not have it, but who wants to use 12V, this one does and 3A should be enough for estim (if you don't have speakers you connect to amplifier when not stimming)

[arig4711]

Man, please just stop commenting, you are spreading misinformation.

Maybe you are not completely clueless about electrotechnics but this statement is. If even 10% of power available from good power supply ended up in electrodes this thread would have no users (most would not be dead but would have no interest in estim ever again). If you really believe what you write here, then you should really get battery power for your amplifier, because your wall socket probably can supply more than 3kW of power and you are connecting power supply to it, so it must all go through, right?

I feel it is completely pointless to try to explain what happens with power supplied to amplifier, what is its output, and even from there - because output stage of stim box were very well described in earlier posts, roles of serial and parallel resistors etc... It all respects Ohm's law but you have to understand and apply it to each of those subcircuits. And yes, without parallel resistor it is possible to push more than 10% of available power to transformer, but we all have volume knob and we use it. Most of us also have parallel resistor which together with losses in transformer consumes almost all of the output power of amplifier (and provided power from supply), electrodes receiving only very small fraction of it, by design (because like that output power depends on static components, not on conductivity and area of electrode contacts). Having more power than needed just means less distortion, it does not mean that all of it HAVE to be used. Just like having 200HP engine in car does not mean you always have to be accelerating.

And BTW, I personally use that exact model of Leicke 24V power supply linked by @lolol2, not because it can provide 120W, but because it is double insulated (represented by two boxes one inside of each other on sticker on its back).

The linked one for 12V does not have it, but who wants to use 12V, this one does and 3A should be enough for estim (if you don't have speakers you connect to amplifier when not stimming)
[/quote]

ok, once again, but then I definitely stop. Of course there don't flow 18 watts into the electrodes (because of the resistors, transformers). I am not stupid. There is a body current-calculation-sheet (I think from Tronic), perhaps you know that sheet.

Power from Amplifier - body current (with typical stereostim setup)
10w - 30mA
20w - 42,9mA
50w - 67,9mA

A body current over 50mA could be dangerous. And why risk that?

Sorry, but I think you are spreading misinformation.

[Spielers]

Power from Amplifier - body current (with typical stereostim setup)
10w - 30mA
20w - 42,9mA
50w - 67,9mA

A body current over 50mA could be dangerous. And why risk that?

No. edger477 is right. how much amper flow into the body depends on so much more. how is the circuit? how big is the resitor? is there an parallel resistor? how is the transformer transmission? But not directly how big is the power supply. Normally there are 2 circuits one with the powersupply and the amplifier, and one with the signal - the amplifier- transformer - body. so there is no direct connectiion with the power supply, in the most cases.

And in IEC479 is defined you should max 10mA alternating current connect to the body.

[lolol2]

I don't want to discuss the obvious anymore, but please be aware of the risks (also the recommended 12V Power supply is not Class II).

Can't hop into that discussion because I'm not that deep into electronic stuff but let me add that the Leicke power supply's should be all class 2, also the linked 12V one (Model NT03015).
The shown picture on Amazon is just a general one, not representing the actual device.

p.jpg (491.36 KiB) Viewed 6034 times

[InfamousPlantain]

Notes:
1) I have switched to 3.9 Ohm resistors before the transformers and also added a 22 Ohm restistor in parallel to each transformer like recommended in another thread.
The result is a very clean and dry feeling of the signal, I really like it, the v1 device was already good but this is a bit smoother.

Hi! Thanks for the update into your adventures. I'm curious of how this resistor value is chosen. I've seen some use 10, some use 15, and now you've chosen 22.

[arig4711]

Power from Amplifier - body current (with typical stereostim setup)
10w - 30mA
20w - 42,9mA
50w - 67,9mA

A body current over 50mA could be dangerous. And why risk that?

No. edger477 is right. how much amper flow into the body depends on so much more. how is the circuit? how big is the resitor? is there an parallel resistor? how is the transformer transmission? But not directly how big is the power supply. Normally there are 2 circuits one with the powersupply and the amplifier, and one with the signal - the amplifier- transformer - body. so there is no direct connectiion with the power supply, in the most cases.

And in IEC479 is defined you should max 10mA alternating current connect to the body.

That calculation is based on the advanced stereostim design from Tronic which is the standard design (series resistance 3.9Ohm, parallels resistance 10Ohm, trafo 8Ohm, 1.25W).
BTW I don’t discuss this because I want to be right, it is just about safety.

[edger477]

The shown picture on Amazon is just a general one, not representing the actual device.

This is most important info on this page of the thread :)

That picture on Amazon doesn't look anything like my power supply, but yours does, so now I understand why recommendation - it is almost identical like mine just 12V (and less power).

EDIT: now I see is same power, yours is 12V 10A (120W) and mine is 24V 5A (also 120W)

POST EDIT: I also see your amplifier can provide more power at 24V (I would not really trust this but it says 2x120W so you would need 10A 24V power source, I think that would melt the board but ok, maybe it can handle 240w peaks)... In that case is true that this would translate to more power on output/transformer inputs (if you would turn the volume knob up enough) and for that particular amp is much better to have 12V supply because of more fine volume adjustment when it runs on lower power mode.

So this is important detail and valid argument for 12V supply - amplifier can provide more power (which we do not need) with 24V supply, making 12V is much better for estim (because of finer volume adjustment when max power is closed to max needed power).

[InfamousPlantain]

Hi All,

Just bumping this question for the parallel resistor value choice as it may have seemingly got lost in the midst of the other discussion :)

Thanks!

Notes:
1) I have switched to 3.9 Ohm resistors before the transformers and also added a 22 Ohm restistor in parallel to each transformer like recommended in another thread.
The result is a very clean and dry feeling of the signal, I really like it, the v1 device was already good but this is a bit smoother.

Hi! Thanks for the update into your adventures. I'm curious of how this resistor value is chosen. I've seen some use 10, some use 15, and now you've chosen 22.

[lolol2]

Easy answer... I have seen people using the 22ohm in combination with the 3.9ohm and decided to use them too.
There was no big math behind that decision.

So I can't tell what exactly the diference to smaller ones would be.
I only can say that this combination is working for me.