Two quick questions
how best to cut the jumper on the bottom of the board, a razor blade? it’s really tiny
if i have a earth ground point for the AC-mains to ground the chassis, should i just run a wire from THAT1646 to that, or do the ring of wire around the unit as is done in the demo/example
We have a [tutorial here that should help you with your jumper question.
For the grounding question, as long as chassis and earth ground are tied together on the device, you could run a wire over to that if it’s more convenient.](How to Work with Jumper Pads and PCB Traces - SparkFun Learn)
excellent, thank you
TS-Chris:
We have a [tutorial here that should help you with your jumper question.For the grounding question, as long as chassis and earth ground are tied together on the device, you could run a wire over to that if it’s more convenient.
[/quote]hey there, one last question
so i’m using a USB pre-amp (miniDSP UDAC8) which has 8ch unbalanced outputs
the goal was to push the RCA outputs to these boards for a conversion
V+ and V-, check, powered by the +/-15v meanwell SMPS sold here
Chassis, check, have it wired to a common ground point to the chassis. jumper cut, verified with a multi-meter
IN (input), check, ‘tip’ or ‘hot’ from the RCA output
GND, does this run to the SMPS ground? or to the Input ground? i feel like the demo indicates it should be the power supply GND, but where then does the RCA input ground go?](How to Work with Jumper Pads and PCB Traces - SparkFun Learn)
after a number of different tests, i found the proper wiring, and encountered a new issue
based on the ‘demo hookup’ you guys cut the chassis jumper because it was in a metal case
i had the same scenario, but apparently should not have taken that action
i since rejoined the ‘gnd’ and ‘chassis’ pin, and all my hum went away
i also found that the ‘gnd’ pin should be to BOTH the SMPS ground, and the audio shield. once i did both of those (well, more so the audio shield than the SMPS gnd) i was able to get a nice clean line to my amplifier
my next issue is, when the THAT boards are powered down, i get a nice clean signal to my amplifiers. however, when powered up by the meanwell +/- 15v power supply recommended by sparkfun help to pair with the THAT boards, i get a larg ‘hissing’ on the line
i’m not sure the cause at this time, but obviously it’s when the boards are powered up, so its either the boards or the SMPS, but something between the two seems amiss
any ideas? some folks on other forums have suggested that the SMPS is not a good fit to power the THAT boards because it’s too noisey and unregulated. they suggested i’d need to supplement with a regulation board to meet the stringent standards of the THAT boards
i purchased that SMPS based on sparkfuns recommendations, do you still standby that it’s compatible to provide good output from the THAT boards?
If so, what do we need to do to troubleshoot the hissing?
It’s possible the hissing might be coming from the power supply, have you tried a different power source to rule that out? We’ve not had any other customers have issues with this combination of products but it is possible the power supply is at fault.
thanks, do you have a recommendation of a SMPS that would be suitable for your product, still getting a decent amount of hiss even after including this post the SMPS you recommended in your demo project: https://www.ebay.com/itm/LT1963-LT3015- … 2837704363
Switch mode power supplies can be pretty noisy, you might need to add some additional filtering between the power supply and the rest of your project to eliminate the noise.
Another thing you could do is use batteries or switch to a linear power supply.