Audio cliping with NJM2755 input selector

smartroad

Member
2020-02-08 10:11 am
Hi all!


I have been building my own mini amplifier system and ran out of inputs. I decided to use an NJM2755 4 to 1 stereo audio switch to increase my input availability.


I have done a test circuit with it, following the application circuit diagram in the datasheet to start. The device works very well when switching. However I have found that with my CD player, Minidisc and DAT the audio is being clipped at higher volumes, only my tape cassette doesn't clip but I think that is more as tape cant get loud enough! I can't figure out why it is distorting. It is being supplied with the required nominal 9V.



I am asking on the off chance anyone has any experience on using this chip (NJM2755 | NJM2755V | 4-Input / 1-Output Stereo Audio Selector)


Here is my amp that I have made and it is feeding into: Customizable 20W Amplifier | Hackaday.io
 

smartroad

Member
2020-02-08 10:11 am
I'm an idiot! I was trying to figure out where in the system the audio was distorting. I discovered that when I connected the CD player directly to the amplifier (missing out the tone controller in my amp) then the audio was crystal clear. I then connected the CD player to one of the inputs on my amp and the distortion was there again. So it isn't the NJM chip causing the issues.


I figured out that the problem was the way I have setup the various volume controls. The main volume is controlled using the amp boards built in control. However the TDA selector and tone chip also has a volume control. Long story short, I had set that volume to high and THAT was causing the distortion :headbash:.


On the bright side I've updated the firmware to break out that setting so I can adjust if needed in the future without re-compiling!


Lesson here for me, methodically diagnose the problem first and don't jump to conclusions!!
 

Thmr

Member
2021-01-23 11:22 am
Hi all!


I have been building my own mini amplifier system and ran out of inputs. I decided to use an NJM2755 4 to 1 stereo audio switch to increase my input availability.


I have done a test circuit with it, following the application circuit diagram in the datasheet to start. The device works very well when switching. However I have found that with my CD player, Minidisc and DAT the audio is being clipped at higher volumes, only my tape cassette doesn't clip but I think that is more as tape cant get loud enough! I can't figure out why it is distorting. It is being supplied with the required nominal 9V.



I am asking on the off chance anyone has any experience on using this chip (NJM2755 | NJM2755V | 4-Input / 1-Output Stereo Audio Selector)


Here is my amp that I have made and it is feeding into: Customizable 20W Amplifier | Hackaday.io

Hello dear smartroad, I will be very grateful if you explain in more detail or run a diagram on how you have implemented the control of the inputs of NJM2755.