I think so too !
All my amplifier was build with national semi "SAMPLE" and all is really NOISY !
I buy cheap china 2xlm3886 board with parts for 25$ on ebay and it work in silence.
That's proof ?!
dvrlfg
Before blaming the chips themselves, you should cast a critical gaze toward your particular implementation of the chip's support circuitry.
The fact that you have made more than one, presumably each with its own chip, and they are all noisy, makes you the only true common factor in all of those designs.
Also note that there are hundreds or thousands of others, here, who have done the same thing, but did not have the same problem.
Details of the physical layout can easily make a circuit very noisy. Many of the posts and threads, here, address exactly those types of issues.
If you would care to post a photo of a noisy amplifier, maybe we could all learn some things, and maybe you could end up with a quiet amplifier that you could enjoy.
On the other hand, if you have used the same types and qualities of layouts with OTHER chip amps, but they have been quiet, then you might have an interesting point for discussion.
The fact that you have made more than one, presumably each with its own chip, and they are all noisy, makes you the only true common factor in all of those designs.
Also note that there are hundreds or thousands of others, here, who have done the same thing, but did not have the same problem.
Details of the physical layout can easily make a circuit very noisy. Many of the posts and threads, here, address exactly those types of issues.
If you would care to post a photo of a noisy amplifier, maybe we could all learn some things, and maybe you could end up with a quiet amplifier that you could enjoy.
On the other hand, if you have used the same types and qualities of layouts with OTHER chip amps, but they have been quiet, then you might have an interesting point for discussion.
It depends. If the signal and ground wires from the input connectors to the PCB are not twisted, and not twisted and shielded, and they have any space between the two wires ("enclosed loop area"), and if there is also a significant EM field from the AC mains or transformer wiring (maybe from also not being properly twisted), then shorting the inputs or connecting a source will complete the loop with the two wires (signal and signal ground) and the time-varying magnetic field from the mains or transformer wiring could induce more hum than when they are just floating unconnected. See "Faraday's Law".
But if they are floating, unconnected, and are not twisted, and not shielded and twisted, then they could be good "regular" antennas. So if for some unexplainable, crazy reason there was no RF low-pass filter just before the input, on the PCB, then the floating inputs could cause noise or other problems, due to RF getting into the amplifier inputs. (And that can still happen, maybe to a lesser or different extent, when the inputs ARE connected.)
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.