10 V DC on audio in pin OK? - 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 19th January 2013, 04:12 AM   #1
diyAudio Member
 
Join Date: Dec 2012
Default 10 V DC on audio in pin OK?

Hi,
beginner question - I am trying to assemble a TDA2050 amp kit. I am seeing a 10V DC on my audio in for a Vcc of 20V for this attached circuit, is it ok? - especially for my android phone

Also I see a 10K pot at the audio in but they did not supply a pot nor is it marked on the PCB (attached). Would appreciate if someone would take time to explain.

Thanks
Arvind
Attached Images
File Type: jpg circuit dia enlarged.jpg (83.4 KB, 55 views)
File Type: gif pcb-front.GIF (191.9 KB, 54 views)
  Reply With Quote
Old 19th January 2013, 04:47 AM   #2
adason is offline adason  United States
diyAudio Member
 
adason's Avatar
 
Join Date: Nov 2004
Location: Maryland
no
  Reply With Quote
Old 19th January 2013, 05:08 AM   #3
sandyK is offline sandyK  Australia
diyAudio Member
 
Join Date: Apr 2007
Location: Sydney
Arvind
Connect a 10K resistor across the Input terminals in place of the non supplied potentiometer, and measure again.
You may be seeing capacitor leakage with your DMM , or perhaps have a faulty
C3 or C4
Regards
Alex
  Reply With Quote
Old 19th January 2013, 05:46 AM   #4
minsik is offline minsik  Australia
diyAudio Member
 
Join Date: Mar 2011
Location: Sydney NSW
When posting please specify precise information to help in people helping you. ie Input? One can assume the pcb input terminal, or the IC input terminal, or the input relating to a component?

If its the input to the IC Pin1, then this is correct with a 22k voltage supply and the input bias divider network of 2*22k should be 10V. (Also by nature of the dc gain of the ic and 100% negative dc feedback the output voltage on IC pin 4 and negative input pin 2 will all be 10V. )

If you mean the input to the pcb ie pin 2 of the non supplied pot then as previous poster said, put a 10k to ground and measure again with nothing input connected. The DC path to ground will have zero volts on it unless the caps are faulty. when connecting any other device to the input it depends on what they are outputting as reference to ground. Measure them before connecting to the amplifier.
Of course if there really is 10V dc present from the connected device and the dc on the positive side of the input caps is slightly lower then you have reverse bias on the caps. Not a good situation and can lead to failure of the cap and destruction of the IC.

Also I point out a cct drawing and possible wiring mistake. the input coupling c
acpacitors look like they should be in parallel and going between the pin2 of the pot position and the pin 1 of the ic input pin. C4 is shown as connecting to the input bias network of R1 and R6 but this is a mistake and and will seriouslt affect the freq responce limiting to a low pass cct. Perhaps you meant to draw the two capacitors in parallel and NOT connected to R 1 and R6 ????
If the cct is correct then the 1uf c4 is connected from the input via c10 to ground greatly providing a nice path for higher frequencies to ground. ie shorting them out. Hope this helps.


  Reply With Quote
Old 19th January 2013, 07:01 PM   #5
diyAudio Member
 
Join Date: Dec 2012
Sorry about not being clear enough.
Thanks for the suggestion - I put the 10K resistor and the amp works now !.

BTW I am using my computer 12V 10A output from my computer PSU via a DC DC boost converter (150W, 24V) and I am not noticing any distortion - at least not to my hears, I am no audiophile.

Another thing, the Lepai 2020A+ sounds louder and nice, for $20, it is nice.

Thanks again.

Arvind
  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
DC feedback at pin 7 of the LM 3886? Marc Vi Chip Amps 13 8th December 2011 12:23 PM
Audio Technology 10 C 77 25 10 KAP Advice domtweaker Multi-Way 9 6th August 2011 11:19 PM
Dc 25v at pin 3 lm3886 (help) jaffeth Chip Amps 6 25th November 2009 03:37 PM
Looking to re-house Tannoy 10" DC and 10" woofers in to other cabinets speedysteve Multi-Way 15 30th September 2008 04:27 AM
For Sale: Ceramic 9 pin tube sockets $1.00 each 12 for $10.00 Sal Brisindi Swap Meet 0 26th June 2007 11:45 PM


New To Site? Need Help?

All times are GMT. The time now is 05:43 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