Drop-in SC-Pure clocks on AF200 DDC
4Blue pill: Just enjoy the music
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Red pill: ... go back to blue pill
On clocks,
Make sure which pin is 1 for clock installation on the PCB, and which one is 45M or 49M clock for placement.
SC-Pure clocks can be purchased here, not affiliated.
https://iancanada.ca/products/sc-pure-extremely-low-phase-noise-audio-clock
Used 45M and 49M clocks here for replacing the bundled clock, or Crystek 957 is prob good enough.
For SC-Cut 10MHz option, this can be customized to 45.1584MHz (44.1K*1024), 24MHz (replaces USB clock) and 49.152MHz (48K*1024), with 45M and 49M separated by 24MHz (lower intermodulation). https://s.click.aliexpress.com/e/_oDSDzNj need to ask seller to customize the frequency such as most DAC clocks 22.5792M, 24.576M, CDP clocks 11.2896M, 16.9344M, and 33.8688M, 24M (intel) / 25M (AMD) for USB and LAN clock and some other 48/54M etc.
Good and cheap SC-cut OCXO is probably Morion MV197 (used from Aliexpress) if external 10MHz word clock is required with some resistor temperature stability on the regulator board.
https://s.click.aliexpress.com/e/_oFp8DVF
with Model12: Third edition 3627/2525-12V version MAX6350 from below
https://s.click.aliexpress.com/e/_onj1ypR
Fine tuning these 10MHz can be done with additional GPSDO (https://s.click.aliexpress.com/e/_oo9G1Nx) and frequency counter (https://s.click.aliexpress.com/e/_olsdEGl or calibrated cesium/rubidium/DOCXO (https://s.click.aliexpress.com/e/_oEQ0HlF standard frequency counters).
On power supplies,
Regulated (linear with B-field shielding or switching with EMI filter, though filtering doesn't mean it becomes 0) 5V power supply would be required for AF200.
Additional powerful capacitor buffer with ultra low noise regulator can be helpful for uV level or lower noise.
Isolated transformer is good to source these power supplies, especially when there are a lot of heaters, motors and digital devices (clocks with various harmonics). Just use it to begin with.
On USB delivery,
Additional galvanic isolation on USB port would be helpful,
Analog devices UM3165/3166 or UM4165/4166, Texas instrument ISOUSB211 or 7055-C Intona devices.
They can require a good power supply design, connectors and clocks.
LHY UIP (https://s.click.aliexpress.com/e/_oFNBUDR) or Singxer (https://s.click.aliexpress.com/e/_oCYT0tR) reclockers are good (requires some shielding) or better regulated and shielded high end ones. Some pulse transformer like in Soekris DAC or optical isolators like May DAC (https://s.click.aliexpress.com/e/_oEZpfNx) design can be enough, depends on your DAC, I2S, SPDIF & AES receivers.
On shielding,
Electrical field shielding and far-field shielding is probably enough with the provided aluminium shell. Additional can be done on top of the STM and other IC chips (copper tape with GND connection on PCB) and shielding box dividing each section with GND connection.
Magnetic field shielding (low frequency, especially 50/60Hz and its harmonics + possible intermodulation with other circuit components') can be done by using high permeability mumetal (high nickel + iron, https://s.click.aliexpress.com/e/_olfhjJR with https://s.click.aliexpress.com/e/_omHZHtF) or equivalent (high in cobalt + iron), added top/bottom and sides after the video, not shown here. (Why Sansui and Accuphase amps have fine grain texture and ppl can listen to music all day, even early 90s tin can digital recording drum sounds :D)
To make sure,
EMC probes and VNA or (noise source, square clock) + spectrum analyzer can be used to measure for near field. Oscilloscopes with probes for conducted noise. Don't bother with TEM waves, far-field, if there is chassis with less than lambda/20 holes and GND connection.
or just trust your ears & take the blue pill.
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