excited about my new smaller thinner preamp cards using 1.27mm headers.
so far they seam to work as before. I kept some space by the optical relay as I expect there to be more front end circuitry. I hope to find a smaller 1 form c opto relay to use. found a toshiba that looks promising that's 1/4 of the size. The 60v 1Amp clamping protection diodes have started to loo very large so working on finding some smaller diodes to. the gold caps to the right are DC blocking caps before the ADC. The PGA2500's output some DC which needs filtering out.
Although I was fairly happy with the shrinking down of the 1st cards ( still more to do ) the 3.3v 2amp power card was a complete fail!!!
1st I messed up the voltage divider traces. I tried adding the correct resistor to ground to set the TI tpsm84209 output voltage to 3.3v
Without the regulator IC in circuit the output fluctuates all over the place.
I'm thinking so far using the through hole resistor made the voltage divider loop to large. ( the datasheet warns against making that loop large ! )
Although the caps are within voltage spec I'm not sure about the in series resistance. This is were to be honest I'm entering a new area. I don't have a LCR meter and I don't even know if there is LCR mode on my keysight 34461A bench meter. ( better check the manual but dont think so )
maybe if I generate 100khz square wave with the mixer recorder I could get the in series resistance of the capacitors I used that way ( the old mixer recorder prototype is still working ) . never used an LCR , no idea yet how it works. looks like I'll need one eventually.
Even the picture I took of this little 1 x 1 cm board failed. it came out upside down and blurred. it cost 1$ , so I think the best thing is to make a better effort with the pcb design and start from there!
These 4 cards will slot into a backplane to make
+/-15v(+/-1A) line drivers and headphone
+/-5v(+/-1A) preamps and adc + dacs
48v(135mA) phantom power
3.3v(2A) digital power