[sdiy] Elektron Digitakt teardown

[Julian Schmidt]

Am 09.07.2017 um 12:42 schrieb Julian Schmidt:
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> Am 09.07.2017 um 12:28 schrieb rsdio at audiobanshee.com:
>> Interesting stuff, particularly the enhanced analog isolation.
> yes! how does it actually work?
> I see two SI8660 digital isolator ICs that are probably used to 
> isolate the data lines for the DAC/ADC from the digital to the analog 
> part.
> +/-12V is only used for the analogue side.
> But how are the GNDs isolated?

I had a closer look at the PSU.

12V DC input from the external wallwart go in.
https://www.elektron.se/wp-content/uploads/2016/11/PSU3b.jpg

GND isolation for the digital part seems to be achieved with a LT3575, 
an isolated 5V flyback converter.
http://www.linear.com/product/LT3575

but the analog PSU is not completely clear to me.
They have a VPH2-0066 fixed inductor with 6 coils with 6.6uH each
http://www.mouser.com/ds/2/87/BUS_Elx_PM_4301_VERSA_PAC-335903.pdf

A lot of 1117 LDO regulators to the left of the coils, but how is the 
negative voltage generated from the +12V input?
I can not spot a switching regulator IC near the coils, nor a MOSFET or 
similar to generate a PWM for a switching PSU.

Any ideas?