I wonder why Dave was so impressed by this transformer.
I reverse engineered the entire design and ran a cost analysis on a 10 piece basis.
The BOM cost is 110.84 including nominal labor/machining fees.
That's PTFE coated wire - 1USD a foot and there is about 24USD worth of wire on that core. I'll build one and characterize it.
What tells you it's PTFE? I see some deformation of the insulatoe on the BNC solder, that shouldn't happen with PTFE...
For running small batches I could machine those my self and all labor so all that would come to my pocket but I'm trying to find the customs fees for importing the cores and then exporting the devices, that could ruin my budget to sell them at any reasonable price...
I intend to order a few cores to test and see what happens, worst case I end with an injection transforner for myself and a few nice cores for other applications, I probably will find them useful in audio, but before they arrive I could make some with any cheap core and look at the HF response where permeability doesn't play a big role. LF response will be anything but nice, I know that.
JS
Damn, just went to post my DIY effort and found I'd been beaten to it!
I too used a nanocrystaline core, this one scavenged from a Wurth 3-ph CM choke:
https://katalog.we-online.com/pbs/datasheet/744839047160.pdf
Looks to be a little bigger than the one linked earlier, and encapsulated inside a plastic shell (I removed the protrusions in the pic before winding it).
Made a twisted pair with a drill and some random hookup wire and put 40 turns on it, as this coincidentally both matched the original number and also gave the same magnetising inductance as the SPICE model of the original indicated (actually 39 would have been the correct number in restrospect).
Took maybe an hour all up to build (not including measurements) and gave:
Xm = 222mH
Xl (per winding) = 1.25uH
Cpri-sec = 140pF
Unfortunately I couldn't do the whole sweep from 1Hz-10MHz in one hit, so there are four graphs here (corresponding to Floyo's "abs" and "rel" measurements - filenames should be descriptive enough of what's being measured).
While the low-freq performance of mine is slightly better, it only makes it to ~7MHz before falling apart. Possibly because I wound it while clothed, and don't fulfil the other two criteria either?
Building a transmission line transformer like this appears quite a challenge ...
Anyway, here's my results (using random cores from the junk box, didn't record the µH/n² values):
-3dB from 48hz to 14Mhz
Why is there no ground fill ont that main PCB?
Anyway, here's my results (using random cores from the junk box, didn't record the µH/n² values):
-3dB from 48hz to 14MhzI would be rather happy with that one in many applications.
Is that a 3577A you used for the test?
Is that a 3577A you used for the test?Yes, it is mine. Located in my home lab, we don't have such fancy stuff at work, but quite a variety of EMC chokes ...