output drive from PC headphone jack?? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 21st October 2010, 04:57 PM   #1
diyAudio Member
Join Date: Feb 2010
Default output drive from PC headphone jack??

I am building an LM3886 amp to drive speakers, with my MAC/iTunes as the source. I will start off using the analog L/R headphone outputs to drive the input of the amp.

My question is ... what kind of load can the headphone jacks drive?
I am having a hard time finding such info in the MAC specs.

Eventually I will add a DAC. For now, I plan to use a volume control POT in the AMPs input stage. My plan was to use a stereo, 10K POT. Thus, the MAC would have to be able to drive the 10K load impedance. Is this an issue?

  Reply With Quote
Old 21st October 2010, 05:06 PM   #2
diyAudio Member
Join Date: Feb 2010
I found this online .... still doesn't tell me the output drive current capacity ...

"Headphone sound output port

The iMac has a 3.5 mm sound output port for stereo sound output. The headphone sound output port is suitable for connecting a pair of headphones or amplified external speakers. When a plug is inserted into the headphone sound output port, the internal speaker and the Apple Speaker minijack are disconnected.

The sound output through the headphone sound output port has the following electrical characteristics:

output level 2.0 V peak-to-peak (0.7 V RMS), open circuit
source impedance 44 Ω
signal-to-noise (SNR) 90 dB unweighted (typical)
total harmonic distortion (THD) 0.03 percent or less "
  Reply With Quote
Old 23rd October 2010, 04:51 AM   #3
diyAudio Member
Join Date: Mar 2007
Considering there are not many headphones around approaching 10k, think you will be fine using the headphone jack.

I would use a simple preamp with volume control myself. In fact, that is how I have my setup working right now. PC analog out to a passive pre/switchbox.

My Pot is 100k. It will be replaced with fixed resistor values soon enough.

I am curious if you have a line out or a way to set the headphone jack to line out mode. This is possible both ways on my machine. The card has a standard line out and I can additionally set the headphone jack to line out with the software.

If so, that would be more desirable. The headphone output is amplified so you could end up with little to no pot travel.
  Reply With Quote
Old 23rd October 2010, 01:52 PM   #4
diyAudio Member
Join Date: Feb 2010
I may just keep the amp as a power amp, with no volume control. Then I can find a DAC with volume control.
  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
MAC or PC headphone L/R output drive? albireo13 PC Based 3 22nd October 2010 08:54 PM
Need help with headphone jack DJelly Headphone Systems 3 22nd July 2009 05:39 PM
4 Pin Amp output to 3 Pin headphone jack? StrayS2k Headphone Systems 3 17th February 2009 04:46 PM
breadboard headphone jack mbates14 Headphone Systems 2 9th November 2008 03:11 PM
which is which in a headphone jack? jarthel Headphone Systems 7 15th April 2007 08:52 AM

New To Site? Need Help?

All times are GMT. The time now is 07:02 PM.

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