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Audio cliping with NJM2755 input selector
Audio cliping with NJM2755 input selector
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Old 8th February 2020, 10:22 AM   #1
smartroad is offline smartroad
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Join Date: Feb 2020
Default Audio cliping with NJM2755 input selector

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
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Old 8th February 2020, 12:28 PM   #2
smartroad is offline smartroad
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Join Date: Feb 2020
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 .


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!!
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Old 24th January 2021, 01:01 PM   #3
Thmr is offline Thmr
diyAudio Member
 
Join Date: Jan 2021
Quote:
Originally Posted by smartroad View Post
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.
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Old 24th January 2021, 03:29 PM   #4
davidsrsb is offline davidsrsb  Malaysia
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Join Date: Dec 2005
Location: Kuala Lumpur
Make sure you run the NJM2755 at 9V supply. It will work at 5V, but clip easily.
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Old 2nd February 2021, 11:33 AM   #5
Thmr is offline Thmr
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Join Date: Jan 2021
Hi, after some research I found this NJM2755 binding scheme involving PIC16F88. My question is is this a working circuit, and should the PIC16F88 be programmed? Regards.

Last edited by Thmr; 2nd February 2021 at 12:01 PM.
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Old 2nd February 2021, 12:25 PM   #6
Thmr is offline Thmr
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Join Date: Jan 2021
i-매거진
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Old 2nd February 2021, 12:36 PM   #7
Thmr is offline Thmr
diyAudio Member
 
Join Date: Jan 2021
Quote:
Originally Posted by Thmr View Post
Hi, after some research I found this NJM2755 binding scheme involving PIC16F88. My question is is this a working circuit, and should the PIC16F88 be programmed? Regards.
The site with the scheme is Korean, in the post above
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Old 2nd February 2021, 09:12 PM   #8
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Any microcontroller needs programming. It wouldn't be hard to switch the device with
a rotary switch though, the 1F/100k circuit used in the datasheet to reduce pops seems a
good idea.
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