Starting new project - double DIY midstim box - plans and ideas

[andyupnaway]

Been a couple of months since last post. Curious about your experience / satisfaction with the new box. Any surprises or advice for others considering doing this? Does it meet your expectations? Thanks!

[edger477]

Been a couple of months since last post. Curious about your experience / satisfaction with the new box. Any surprises or advice for others considering doing this? Does it meet your expectations? Thanks!

I can say I am happy with the build, the 4mm sockets are great since you don't have to build cables, you can just buy as many as you want, and most of the better cable have female socket on them so you can connect any to any for multiple electrodes setup, creating commons without using switch etc.

I guess you could make simpler version of box without any switches at all, with this system it is easy to create common by connecting 2 cables together and also swapping 2 cables is not a big deal, if you are not good at soldering you could leave the switches out.

Aside from that, I think this amp would work fine if I did not wait for 4Ohm resistors, I already had 6Ohm in same shape and form, and I did try using other taps on transformers (8 Ohms for input and 2.5W on output) and I can confirm that the initially chosen ones are the best.

[andyupnaway]

Thanks for the update. This will be my next project.

I plan on taking a slightly different approach. Will use the same Douks amp as you but will have two identical DIY boxes, mainly because I already have a working two channel system that has switches on the input side to swap channels and switches on the output to change polarity. Did not include a triphase switch, easier to make up a y-cable. Would be nice to have a single chassis like yours but also like having the compactness of the single stereo box when not at home.

[froog]

Hello,

Coming to this late - but wondering if anyone can answer a question or two about these designs. I notice that there are diodes (zener diodes?) across each of the input lines for each stereo channel, as well as a capacitor on each of the ground input lines. These do not appear in the midistim original design.

Can someone explain what the purpose of these? I have basic electronic knowledge. I assume the diode is a sort of protection against the spikes in the input voltage, but not sure what the capacitor is for

[edger477]

Hello,

Coming to this late - but wondering if anyone can answer a question or two about these designs. I notice that there are diodes (zener diodes?) across each of the input lines for each stereo channel, as well as a capacitor on each of the ground input lines. These do not appear in the midistim original design.

Can someone explain what the purpose of these? I have basic electronic knowledge. I assume the diode is a sort of protection against the spikes in the input voltage, but not sure what the capacitor is for

Hey... the diodes would short in case the voltage over them goes over 17 Volts (around, don't remember exact spec), which is above what the amp can make (since I use it with 12v PSU). Basically, it can only happen if some kind of catasthropic event (lightning?) destroys the PSU and then the amp, it prevents the spike from getting through transformers.

The capacitors are basically high-pass filter, these that I used are starting to filter out frequencies below 600Hz (the proper cutoff is lower, below 300 I think)... basically it allows to play files that aren't very good, that have very low frequencies (which are unhealthy), sometimes there are files like that that work fine for 312 or 2b.

Neither of these components are essential nor they change the box output in a meaningful way during my normal use scenario. I guess it is just overengineering :)

[froog]

...Neither of these components are essential nor they change the box output in a meaningful way during my normal use scenario. I guess it is just overengineering :)

thanks for quick response. I'm learning a lot through looking into this.

[froog]

Hello,

I had another question if you don't mind - I'm building a 4 channel box with same amp, same transformer as this build, and just a 3.3ohm 25W resistor in series before the transformer on each channel. No parallel resistors, or switches for triphase, or other extra bits)

But I really want to add an LEDs on each output channel - for prettyness - that would show when current is flowing, and maybe even flcker/throb a bit as I am using it. I wondering how I might work out which to get, and whether I need any other components to go with them (ie see you have athem in pairs). Can someone point at any advice on how to design this added extra bit?

Thankyou in advance - hope it's OK to jump on this and ask questions!

[picofarad]

Hi
I too have a question. I built a stereo stim setup and I'm very pleased with it. However. I'd like to get sound feedback. As it is setup I don't hear anything but
what if I connected an 8-ohm speaker in parallel to the output of each channel?

I do have 4 ohm resistor in series between the amp and the transformer.

[edger477]

Hi
I too have a question. I built a stereo stim setup and I'm very pleased with it. However. I'd like to get sound feedback. As it is setup I don't hear anything but
what if I connected an 8-ohm speaker in parallel to the output of each channel?

I do have 4 ohm resistor in series between the amp and the transformer.

Why would you want to listen to estim signal? If you have anything that you want to listen to, you use different sound card so that estim only goes to box.

[picofarad]

Why would you want to listen to estim signal? Because I want to (see Pavlov's dog)

If you have anything that you want to listen to, you use different sound card so that estim only goes to box.
Not what I want to do. I will try some experiments and measurements.
[/quote]

[edger477]

It would be better to use headphone splitter or rca to 3.5 jack (for example on this amplifier when in bluetooth mode the rca output the signal, so you could connect headphones or another amp with speakers)

[diglet]

Or use voicemeeter to send the audio to your stimbox, as well as to your speakers.

[picofarad]

Or use voicemeeter to send the audio to your stimbox, as well as to your speakers.

I had never heard of Voicemeeter. Downloaded it. Not the easiest thing to configure but I think I got it setup. I now need to test it, likely do some tweaking on the levels between the speakers and my blue tooth linked Fosi amp.

I'm sure this is the right solution, thanks for the reply and the helpful information.