Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

Need help to get rid of noise
Need help to get rid of noise
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 11th August 2019, 02:34 PM   #1
deletecm is offline deletecm
diyAudio Member
 
Join Date: Aug 2019
Default Need help to get rid of noise

Hi,


I have an amp that somehow makes noise that looks like a square wave around 1kHZ, and it gets to the output amplified. It's only present when the amp is turned on, so it's coming from the amp itself. The output (both channels) looks like this when no input signal is present:
Click the image to open in full size.

I'm also attaching the schematic. The amp doesn't even have digital circuits apart from a digital clock IC, and that doesn't seem to generate 1kHZ at any pin. So where is that noise coming from?
Attached Files
File Type: pdf schematic.pdf (281.3 KB, 53 views)
File Type: pdf schematic(1).pdf (285.6 KB, 29 views)
  Reply With Quote
Old 11th August 2019, 04:00 PM   #2
MarcelvdG is offline MarcelvdG  Netherlands
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
Did you by any chance test it with a multiway loudspeaker with broken-down squawker or tweeter as a load?
  Reply With Quote
Old 11th August 2019, 04:12 PM   #3
deletecm is offline deletecm
diyAudio Member
 
Join Date: Aug 2019
There was no load at all, I only measured the output with an oscilloscope. Don't know if you can open that picture but it looks like a noisy 200mV peak to peak square wave.
  Reply With Quote
Old 11th August 2019, 04:26 PM   #4
MarcelvdG is offline MarcelvdG  Netherlands
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
That's a pity, because then I haven't a clue what might be the cause.
  Reply With Quote
Old 16th August 2019, 12:04 PM   #5
Mark Tillotson is offline Mark Tillotson
diyAudio Member
 
Join Date: May 2018
Location: Cambridge UK
Sounds like break-through from the 7-segment LED display circuitry. This is possibly getting to the amp's input section somehow (dried out decoupling capacitors perhaps).
  Reply With Quote
Old 31st August 2019, 06:17 PM   #6
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
The last time I had that type of problem turned out to be my desk top CFL lamp.
It was radiating near the amp and interfering with it.
__________________
PCBCAD51 download or CDROM October 2019 version out now ..https://www.murtonpikesystems.co.uk
  Reply With Quote
Old 31st August 2019, 06:31 PM   #7
scobham is offline scobham  United Kingdom
diyAudio Member
 
Join Date: Mar 2008
Location: Merseyside
Try to identify the problem area by scoping the various modules in the amp to see where the issue is generated. Usually this kind of problem occurs in a negative feedback loop or through coupling through the psu. I would suspect a faulty capacitor somewhere but without a bit more diagnostic info that's about all I can say.
  Reply With Quote

Reply


Need help to get rid of noiseHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
List of Tube Noise Measurements - please nominate lowest noise tubes TavishDad Tubes / Valves 339 5th September 2019 08:33 PM
Mad Scientist Noise Cancellation - Bass noise leakage bobthedespot Multi-Way 29 19th October 2018 02:58 PM
ultra low noise power supply and low noise amplifier ambrosia168 Power Supplies 8 13th October 2017 02:43 PM
Flicker Noise dominates triode noise in audio (AES) ruffrecords Tubes / Valves 68 22nd October 2014 07:59 PM
Overall noise, singnal to noise(db) & Distortion(%) obtain raha arya Solid State 2 12th December 2012 02:47 PM


New To Site? Need Help?

All times are GMT. The time now is 09:01 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki