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yeah thats pretty good
neeed bad food bbl

Posted by renesis at 17:41 | permalink | 0 comments

whats flying colors?
like 0.1% THD from 20-20k?
60dB crosstalk would be pretty badass, 40dB is prob good enough

Posted by renesis at 17:35 | permalink | 0 comments

i once tested a 5kw amp at max load and the toroid made it sound like it was coming in for re-entry
shake itself out of the rack
it was
it was hooked to an AP, sub 1% THD, china amp was legit
circuit was a class-h qsc ripoff
naw thing was the size of a watermelon
was a 5U amp
probably if you could drive it hard enough to get away from the noise floor

Posted by renesis at 17:30 | permalink | 0 comments

so thats lots of switching, and thats a higher psu load
they can be microphonic, too
prob not
not in a useful way

Posted by renesis at 17:25 | permalink | 0 comments

shrug, above 100mhz, it starts to become a significant load
like, the ghz rf geeks at work are like I NEED A 6pF CAP and theyre not joking
yes it could be the smps
especially if its that old
my guess is something like 100khz
damn thats why
so i think its some sort of subharmonic effect
but shit that switches that low, that you shouldn't be able to hear, you can almost always hear that shit

Posted by renesis at 17:20 | permalink | 0 comments

so you could put it next to something that radiates, and itll couple into the loop that fixed the internal noise issue
just use like 14 awg
haha yeah
ground on one side
anyway, just try shit
bridging grounds with wire
poking at the circuit with your fingers
push all the analog shit on the left around
you need an emc analyzer or spectrum analyzer to do it well
like, antenna probes help
yeah but the scope is a load and wont pick up shit in the air well

Posted by renesis at 17:15 | permalink | 0 comments

you can also try splitting grounds and coupling through caps, inductors, usually some parallel combination of both
but this is tricky stuff
try bridging grounds
but it kind of depends
because in one situation something that helps might make shit way worse in other
like coupling through an inductor can help with noise
but can make it hyper sensitive to ESD
anyway, bridging grounds inherently introduces loops

Posted by renesis at 17:10 | permalink | 0 comments

try moving caps and inductors
parallel caps and inductors can couple even at audio frequencies if theyre close enough
just be careful and it needs to be grounded
if its ferrous, e and h
if it isnt, just e field
pretty much
e corresponds to voltages, h to currents
like if you have a 1GHz fet switch 1kV with no load, itll make an e field mess but wont do shit to h field
you bridge and cut grounds
you want short heavy wire
relative to whatever youre doing

Posted by renesis at 17:05 | permalink | 0 comments

100mhz wont couple across a board super easily
yeah but its square waves fool
so that edge is the equivalent of the slew of a much, much higher frequency
wtf is this
its prob just crackheaded singles ided grounding
if 70s audio trash, highly likely
anyway, touch the circuit with your fingers
when its making the noise, you maybe block where its coupling, or find a sensitive spot that goes nuts when loaded with body capacitance
but my guess is its coupling through grounds

Posted by renesis at 17:00 | permalink | 0 comments

if its not s strict star ground with well isolated power and signal grounds, its probably that
almost everything in the 70s was a bad design, everything discrete
you could have capacitors standing up in the same plane inches apart coupling some RF shit that is creating common mode trash at audio bandwidth
old shit versus new rf world is often pretty hopeless
if you can hear it, you have some sort of speaker or amp or whatever hooked up
so theres obviously noise on the output and the ground where it connects into your signal destination
yeah so use the headphone ground as your ref
or both
does it have electrolytics?
ha, an EMC scanner
or a spectrum analyzer, or a badass scope
but like, if youre into the 100s of mhz, dozens of pF start to matter
so hooking shit like a scope probe to it will usually change it

Posted by renesis at 16:55 | permalink | 0 comments

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