clicking every second from my jig to make Small Thiele parameters Measurement

[magnets99]

Hi everyone,
I need a bit of help, i'm following along with this guide

which teaches me how to measure the small thiele measurement.
I need this measurement for some mystery speakers that i want to make a smaller non ported enclosure for.
I have done this before with the none amplified version of the rig and the results were inconsistent so i bought a Fosi audio tpa3116 amp and built the amplified testing circuit in the video.

Problem is, when i plug the two 3.5mm jacks into the sound card i get a 'click' out of the speaker about once a second.
I get this if i use my desktop onboard sound card, my laptop onboard sound card, a usb soundcard in either my laptop or my desktop. It happens on windows and linux.

The clicking gets louder if i turn the amp up.

I'm pretty sure i've made a mistake with my circuit but i can't see where. Here are some images:
This is the circuit i've built from the video (pause at 10:30 to see the original)

the pencil drawing is me drawing out the breadboard circuit as i have made it, which to my eye looks comparable with his circuit.

this is the top of the breadboard cicuit

and this is the bottom

it's a second hand breadboard, so ignore the line 4th from bottom, there is nothing soldered in there.

Heading to the right of the picture is the cable to the speaker, with the red positive and the black/red negative.
Heading to the left of the picture is the three dupont soldered connectors to the 3.5mm microphone stereo TRS jack.
Black is ground (sleeve), Red is Left (tip) and white is Right (Ring)
also heading to the left is the cable from the amplifier with Red being + and Black being - of the left channel out.

Can you see an error?

some notes:
clicking only starts when i plug the microphone in (and turn the amp on)
the speakers work
at the top left of the breadboard bottom image it looks like there is a solder bridge from the top rail to the 2nd top rail, there isn't. It's just my terrible soldering where it leans over.
both my desktop and usb soundcard have stereo mic inputs and i've built this rig as a non amplified version using the same computers and got a result (or at least didn't get clicking).

 

[phofman]

so i bought a Fosi audio tpa3116 amp

IIUC the circuit you connect to the amp output works only for non-bridged amps which have the "negative" speaker output connected to GND. However your D-class amp has bridged outputs

IIUC your measurement circuit connects one of the bridge outputs to GND - not nice.

IMO you would need to have mic/line-in balanced input and remove the wire short-connecting your amp - terminal to mic=amp GND.

 

[phofman]

Or theoretically you could use line-in input (not the mono microphone), connect each voltage divider to L/R channel of the line-in jack, and use the virtual balanced feature R-L in REW. However it remains to be seen what the 350+kHz PWM signal from the D-class amp mildly filtered by the simple output LC network of TPA3116 boards will do with inputs of your sound card - it will all depend on quality of the input filters (which is always a big question). The speakers work as the low-pass filter, removing the PWM signal. But maybe it will be OK.