4ch estim? Douk Audio M4

[darthjj]

Anyone have experience with 4 channel e-stim? I've been considering building a new box, since I would like to be able to use either 2 * triphase or triphase + 2 * normal 'trode pairs. It would be cheaper to just build an identical box to the one I have, but it would make the whole setup more impractical, since I stow it between use.

The Douk Audio M4 looks pretty good specs-wise. It's compact, reasonably priced and having individual volume controls for the channels makes calibration much easier. It also has bluetooth which is great, assuming it doesn't play sound effects or voice lines every time the volume is changed or if it loses connection, like most bluetooth speakers and headsets tend to do..

What I don't really know is if it's suitable for driving estim.. When building my first box I followed recommendations from people who know more about electronics than I do, and I think they wrote that some amps were better for this than others. I'm also wondering if 50W (assuming those numbers are true) could be too much. My current amp is 25W and even a volume of 33% is enough to deliver powerful shocks. A stronger amp would probably be usable, but I'm thinking that if I'm going to run it at less than 20% (?) volume then the hardware volume knobs won't be very easy to finetune the intensity with.

[edger477]

viewtopic.php?p=339484#p339484

Note that volume controls are digital (the pots seem to be some kind of rotary encoders, with limits for min/max) the volume steps are good enough to create relationship between electrodes but not really really "fine", I use volumouse for that, with step at "100" (which is around 0.3%, so more fine than volume mixer).

[darthjj]

viewtopic.php?p=339484#p339484

Ah, I thought I had seen it somewhere before, but I didn't get any search results for Douk so I couldn't find it now.

Great resource! Going to take me a while to read through it all, but have you noticed if the built-in bluetooth player add sounds on events, or if it is pure playback of the audio signal?

[edger477]

Great resource! Going to take me a while to read through it all, but have you noticed if the built-in bluetooth player add sounds on events, or if it is pure playback of the audio signal?

To be honest, I have not tried it with speakers, and I don't think I was ever wired up when BT connection status changed. However, I just checked with box turned on, disconnecting and connecting BT did not cause any signal output (LEDs light up even before I can feel the signal).

[darthjj]

Great resource! Going to take me a while to read through it all, but have you noticed if the built-in bluetooth player add sounds on events, or if it is pure playback of the audio signal?

To be honest, I have not tried it with speakers, and I don't think I was ever wired up when BT connection status changed. However, I just checked with box turned on, disconnecting and connecting BT did not cause any signal output (LEDs light up even before I can feel the signal).

Thanks! Good to know, since those things could lead to some unpleasant surprises otherwise :D

Do you also know if it's possible to send 4-channel surround signals over BT, or if it's limited to 2-channel stereo? Surprisingly difficult to find an answer for that on Google, all I'm getting are links to stores selling different speakers and sound systems :(

[edger477]

Do you also know if it's possible to send 4-channel surround signals over BT, or if it's limited to 2-channel stereo? Surprisingly difficult to find an answer for that on Google, all I'm getting are links to stores selling different speakers and sound systems :(

In control panel sound device settings you can only change format between 1 channel and 2 channel 16 bit 44100Hz. Amp itself has a button for 2 or 4 channels, when you switch it to 2 then the other 2 output the signal from first 2 (or bluetooth) so you get 3rd and 4th channels being clone of 1 and 2.

To stim with 4 channels, I'd use 2 sound cards (or one that has 4 channels and connect 2 3.5mm to rca cables, so not use bluetooth)

[darthjj]

In control panel sound device settings you can only change format between 1 channel and 2 channel 16 bit 44100Hz. Amp itself has a button for 2 or 4 channels, when you switch it to 2 then the other 2 output the signal from first 2 (or bluetooth) so you get 3rd and 4th channels being clone of 1 and 2.

To stim with 4 channels, I'd use 2 sound cards (or one that has 4 channels and connect 2 3.5mm to rca cables, so not use bluetooth)

Ah, that's unfortunate. Was hoping BT would allow me to skip a bunch of wires, making for even easier setup and stowing, but I forgot that digital multi-channel audio already is quite complicated with proprietary formats, and that BT might not support it at all :( Thanks for the answer anyway!

Not a lot of cheap multi-channel soundcards in local stores nowadays but scAmazon has a bunch of dubious looking cheap surround cards, might buy one and hope it works.

[diglet]

I have this usb soundcard built into my 4-channel box, so my box is connected with 1 usb cable, and it just works.

https://www.aliexpress.com/item/1005003985806714.html