Battery-powered chipamp has an intermitted DC-offset issue - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 7th May 2009, 01:52 PM   #1
eisnerd is offline eisnerd  United Kingdom
diyAudio Member
 
Join Date: May 2009
Default Battery-powered chipamp has an intermitted DC-offset issue

As suggested by the subject, I have a simple battery-powered chipamp, using two ex-UPS 12V lead-acid batteries and the TDA2050V chip in a non-inverting arrangement, specifically. The DC offset is usually negligable, and there's very little switch on pop, however, on switching off I sometimes get a mid/high pitched sucking/wizzing sound, which I've heard from other amps or powered speakers before. From the look of the driver, while this happens there's a more substantial offset, though not enough to do damage (so far, at least to these speakers).

I have the batteries arranged -12V; 0V; +12V straight to the supply caps & chip, except for a simple DPST rocker switch on the +-12V lines. My suspicion is that the effect I described is caused by the rocker engaging or detaching slightly out of time.

Any suggestions as to switches that may improve this or circuits to guard against this imbalance either at the supply or output? Or perhaps I'm barking up the wrong tree and have another problem or should ignore this.
  Reply With Quote
Old 7th May 2009, 02:20 PM   #2
diyAudio Member
 
Join Date: Jul 2006
Location: Edinburgh
Schematic at hand?

One thing that your switch will cause the the caps to discharge through the amp. Because for each rail they'll discharge at different rates this could be causing the problem.

I would suggest adding diodes across your switch (just like you do on relays, or regulators) that will discharge your caps back to battery. Alternatively use a DPDT and add discharge resistors on one side, move the battery input on the other side and take the output from the middle.

I assume that the sound only lasts a second or two... or you mean permanent?

Also because with batteries things can be slightly different than PSUs make sure your grounding is correct.
  Reply With Quote
Old 7th May 2009, 04:24 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Can you measure the voltage across the smoothing caps as they discharge?
Sometimes one side discharges much faster than the other and the charged side then forces the discharged side into reverse polarity.

If this is the case then a pair of diodes solves the problem.

Fit reversed diodes from +ve to zero volts and again from zero volts to -ve. This limits the reverse voltage to <=700mV
__________________
regards Andrew T.
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Battery powered XO? MikeHunt79 Solid State 2 17th March 2008 02:19 AM
Battery powered amp Shpoop Chip Amps 8 26th January 2007 03:41 PM
anyone using a battery powered pre? whatsnext Solid State 15 30th October 2006 11:26 AM
battery powered gc in a tin digi01 Chip Amps 11 25th December 2004 04:11 AM
DC-33 DC Battery Powered Amp?? moe29 Pass Labs 2 26th April 2004 06:41 PM


New To Site? Need Help?

All times are GMT. The time now is 01:11 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2