Common negative on LM3875? - 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 13th May 2004, 01:57 PM   #1
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Default Common negative on LM3875?

Hi All-

I was wondering if I could use a common ground headphone jack with the output of BrianGT's LM3875 gainclone?

I am constructing my office desk unit now and would like a headphone jack on the front for private listening.

I searched and found lots of stuff saying it was overkill , but nothing saying I couldn't combine the two negative leads from the separate chips to the headphone jack.


Thanks in advance,

Troy
  Reply With Quote
Old 13th May 2004, 03:20 PM   #2
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Default Tickle, or bump...

TTT
  Reply With Quote
Old 13th May 2004, 03:29 PM   #3
diyAudio Member
 
Join Date: Nov 2003
Location: NW Washington
Send a message via MSN to officeboy
I don't see how it would be a problem, it's just a ground for AC. So be sure your grounding stars are all grounding to each other, for both channels.

Just don't be hooking negative leads up together, There is an OUT pin. the other side of the connection is the ground.
  Reply With Quote
Old 13th May 2004, 04:16 PM   #4
HDTVman is offline HDTVman  United States
diyAudio Member
 
Join Date: Aug 2001
Location: Chicago area
I'm a little confused here. The question was

"
I was wondering if I could use a common ground headphone jack with the output of BrianGT's LM3875 gainclone?

I am constructing my office desk unit now and would like a headphone jack on the front for private listening.

I searched and found lots of stuff saying it was overkill , but nothing saying I couldn't combine the two negative leads from the separate chips to the headphone jack.

"
It's this part about the "two negitive leads from the separate chips" part that has me confused. If you mean the Negitive Power Supply rail then the answer is NO. If your talking about the signal/power supply common / Ground other wise known as the speaker negitive, then the answer is YES. You can connect the two channels together. I would suggest resistors in series with the headphone jack to reduce the signal level to the phones. 220 to 330 ohms should be fine. With out these you will be buying lots of new headphones and hearing aids before long.

Have fun BZ
__________________
What ever makes the tunes flow
  Reply With Quote
Old 13th May 2004, 04:33 PM   #5
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Sorry for the ambiguity.

I was hoping to use a 3 connection headphone jack(TRS) and use the tip as right spkr +, ring as left spkr + and sleeve as COMMON spkr -.

Would that pose any problem for the separate chips?

Thanks again to those who replied!!

Troy
  Reply With Quote
Old 13th May 2004, 05:05 PM   #6
diyAudio Member
 
Join Date: Nov 2003
Location: NW Washington
Send a message via MSN to officeboy
Should be no problems, Just be sure that the "sleeve as COMMON spkr -" is ground, and NOT a negative connection.

And yeah, major overkill for headphones.
  Reply With Quote
Old 13th May 2004, 05:36 PM   #7
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Well, its MAIN purpose is as a desk amplifier for a small line array.

But for those quiet days I would like to jack in my phones.

Thanks again!!

Troy


Edit: spelling
  Reply With Quote
Old 13th May 2004, 06:06 PM   #8
Alcaid is offline Alcaid  Norway
diyAudio Member
 
Alcaid's Avatar
 
Join Date: Nov 2003
Location: Klepp
I would suggest to lower the gain. The chips are stable down to a gain of 10 I think, and for headphones, that would be a good place to start.
  Reply With Quote
Old 13th May 2004, 06:35 PM   #9
diyAudio Member
 
Join Date: Nov 2003
Location: NW Washington
Send a message via MSN to officeboy
You could also just add a switch to shunt some signal to ground.
Kind of a headphones level thing, use it to drop your signal 20-30dB.
It would at least help to give your volume control a more usable range when your using the headphones.
  Reply With Quote
Old 13th May 2004, 09:00 PM   #10
troystg is offline troystg  United States
diyAudio Member
 
troystg's Avatar
 
Join Date: Apr 2004
Location: In a dream... Please don't wake me.
Thanks all for the help, now this thread can be achived for future searches..

Death to the thread!!

Troy

P.S.- I'm really a positive person.
  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
Common Source versus Common Drain output stages alaskanaudio Solid State 36 1st June 2014 02:35 AM
common ground or not? Mordor Car Audio 5 7th October 2008 12:08 PM
Common cause of distortion in SS eeka chu Solid State 1 24th May 2005 10:54 PM
common mode choke and negative lead filtering? AudioGeek Power Supplies 1 22nd May 2005 07:36 AM


New To Site? Need Help?

All times are GMT. The time now is 12:26 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