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

Amp troubleshooting... what kind of sound is this?
Amp troubleshooting... what kind of sound is this?
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 14th July 2018, 04:12 AM   #1
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
Default Amp troubleshooting... what kind of sound is this?

Trying to troubleshoot a Swan M200MKII which has a LM4766. Below is a video of ARTA measuring the amp's right channel via soundcard:

2018 07 13 22 28 24 - YouTube

The video goes: Off, on, minimum volume, back to original volume, off

So I can understand the "eeooon" part (lightsaber sound?) caused by clipping from insufficient Vcc at powerup and powerdown - the amp continued running for a while after power down so the bulk caps look ok.

But two things I don't understand:

1) Upon power up, why does the amp spend a while at a lower volume while having lots of harmonics of 200Hz?

2) The unstable bass noisefloor is due to a repeating "ts-ts-ts-ts-ts-ts-ts-ts-ts" sound which sometimes last a bit longer like "tssss-brszks" and is only audible on the right channel. (Although no guarantee what's on the left channel until I measure the insides)

I'm thinking the amp chip is a goner.
  Reply With Quote
Old 14th July 2018, 05:01 PM   #2
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
And when left powered on for a long time it starts whining in both channels

YouTube

YouTube

The whine seems to be dependent on impedance seen at the chip's input; Softest when connected to source and volume control max, medium when volume control min, loudest when disconnected from source and volume control max.
  Reply With Quote
Old 14th July 2018, 10:33 PM   #3
tomchr is offline tomchr  Canada
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Calgary
I would replace the local bypass caps and check the main supply caps. It's a shot in the dark, but a pretty cheap thing to try.

Tom
__________________
Modulus-686: 240W/8Ω @ <0.00025% THD. Modulus-86: 40W/8Ω @ 0.000054% THD. DG300B & Other Tube Circuits.
Neurochrome : : Audio - www.neurochrome.com - Engineering : : Done : : Right
  Reply With Quote
Old 14th July 2018, 10:48 PM   #4
nigelwright7557 is offline nigelwright7557  United Kingdom
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
Quote:
Originally Posted by tomchr View Post
I would replace the local bypass caps and check the main supply caps. It's a shot in the dark, but a pretty cheap thing to try.

Tom
If its of any age the electrolytics might need changing and same with coupling capacitors.
__________________
PCBCAD51 pcb design software. 2018 version out now with lower prices >> http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 14th July 2018, 10:48 PM   #5
P.Lacombe is offline P.Lacombe  France
diyAudio Member
 
Join Date: Jul 2001
Location: Orleans, France
Tom : +1 !
  Reply With Quote

Reply


Amp troubleshooting... what kind of sound is this?Hide 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
Differences in tweeter's sound by different kind of crossover andreaemme Multi-Way 75 12th May 2018 03:13 PM
My DIY speakers all sound kind of muffled aclup3 Multi-Way 42 13th April 2018 03:58 PM
troubleshooting tpa3116 amp. no sound Ensoniq Class D 28 18th September 2014 12:20 AM
Troubleshooting: T-amp with SLA battery, no sound output Sarco3 Class D 13 11th August 2014 05:22 PM
What kind of sound does a noisy 12B4 make ?? jj2 Tubes / Valves 5 16th March 2011 07:33 AM


New To Site? Need Help?

All times are GMT. The time now is 12:52 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki