Newbie 3.5mm TRS Voltage Question - diyAudio
Go Back   Home > Forums > Amplifiers > Headphone Systems
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

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
Thread Tools Search this Thread
Old 29th December 2011, 02:48 AM   #1
diyAudio Member
Join Date: Dec 2011
Default Newbie 3.5mm TRS Voltage Question


I am trying to experiment with my phone. I have a 3.5mm TRS jack (naked) for headphones. When I plug it into my phone I would expect to read voltage yet I get nothing. Since the entire phone operates on DC voltage I figured 2 VDC would be a setting to go with but now I am wondering if that is too high? What kind of voltage should I expect out of my 3.5mm headphone jack?

  Reply With Quote
Old 29th December 2011, 06:41 PM   #2
diyAudio Member
Join Date: Nov 2011
-0dB sine wave should give you 0.8V or less on AC. DC would kill any set of headphones, so the chip has a charge pump to create AC. I'd actually expect more like 0.25-0.5V. It would be a miracle if you got 2V at full volume.

Last edited by ethanolson; 29th December 2011 at 06:43 PM.
  Reply With Quote
Old 31st December 2011, 02:00 AM   #3
diyAudio Member
Join Date: Nov 2011
I just realized that if you don't have a complete circuit on both channels that the phone may not put out any signal. There may also be a relay in the headphone port to switch power from the speaker to the headphone port when something is inserted.
  Reply With Quote
Old 2nd January 2012, 08:54 PM   #4
diyAudio Member
Join Date: Nov 2004
Location: Germany
1. If you measure from T or R to S (L/R to ground), there should be no DC voltage at all since, as stated, headphones don't generally appreciate DC.
The L and R outputs are either floating at half supply, which means you need a buffer for the return, or the headphone amp generates a negative supply of its own and can use a "real" ground for return. Of course the outputs may also be capacitor (AC) coupled.

2. Even if the outputs are floating at half supply, you cannot generally access the "real" ground from outside.

All in all, it's a very boring affair DC wise. AC may be more interesting, assuming your multimeter has low-level AC ranges (2VAC or lower). Always use 50/60 Hz sines for tests with non-TrueRMS meters.
  Reply With Quote


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
(DIY) 3.5mm jack adapter to 2.5mm output Rui Luis Instruments and Amps 4 6th September 2011 06:50 AM
Newbie voltage regulator question imperfectcircle Solid State 3 25th February 2007 03:37 PM
WTB: 2.5mm plug to 3.5mm plug cable Relax Swap Meet 5 10th February 2007 12:13 AM
newbie post, but hopefully not a newbie question wiredcur Solid State 3 24th August 2002 10:49 PM

New To Site? Need Help?

All times are GMT. The time now is 01:49 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2