Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Headphone Systems Everything to do with Headphones

opamp/BJT headphone amp
opamp/BJT headphone amp
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 31st May 2005, 09:09 PM   #1
svokke is offline svokke  Belgium
diyAudio Member
Join Date: Apr 2003
Location: Leuven
Default opamp/BJT headphone amp

I am busy making this headphone amplifier as my first solid state project.
Click the image to open in full size..
What do you think of this circuit and how do I start choosing a suitable transistor/bias point?
What parameters do I have to look for?

Regards, Svokke
In illusion comfort lies
  Reply With Quote
Old 1st June 2005, 03:03 AM   #2
jcx is offline jcx  United States
diyAudio Member
Join Date: Feb 2003
Location: ..
1st order of business is deciding what impedance load you want to work with and how much power you need; dynamic headphones range from 16 Ohm to 600 Ohm, sensitivity from slightly less than 90 dB/mW to over 100 dB/mW

HeadWize faqs points to all sorts of good relevant headphone information - the link to Rane under headphone power requirements gives the sensitivity of many headphones

I always have to point out the difference between LOUDNESS and HEADROOM - read http://headwize.com/articles/hearing_art.htm twice, once for avoiding hearing damage from average LOUDNESS and again for the required dynamic peak HEADROOM of real music - that you should want to cleanly reproduce, but only for seconds per hour of listening

taking some dynamic range values from the headwize article you can see that while 10 mW average power into most headphones could lead to hearing damage with extended exposure, it wouldn't be totally unreasonable to want 100-500 mW peak power to reproduce natural music peak levels without clipping

Once you have load Z and peak pwr you can choose a bias current and current sink circuit as well as transistor sizes and if heatsinking is necessary
  Reply With Quote
Old 1st June 2005, 03:48 AM   #3
amplifierguru is offline amplifierguru
Account Disabled
Join Date: Aug 2004
Location: Earth
Hi Svokke,

So to pick up where jcx left off, and assuming you're happy with 100mW of class A power into (the minimum load) 16 ohms then you'll require a standing current of around 120mA from you're current source and a thermal load on your transistor of 1.8W so you'll need to heatsink a BD139 perhaps to the casework/chassis.
Perhaps a BD140 in the current source. Might be a good idea to put a current limiting resistor in just in case of shorts.
  Reply With Quote


opamp/BJT headphone ampHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
headphone amp with lm4562 opamp umut1001 Headphone Systems 23 15th April 2008 02:08 AM
THAT transistor headphone amp (250ma discrete opamp) design sanity check. Russ White Headphone Systems 19 13th December 2007 12:52 PM
CF-Opamp Onvinyl Parts 6 3rd April 2006 03:09 PM
Single supply opamp - unequal rail voltage and opamp selection Hans L Parts 8 19th February 2006 02:15 PM
Regulate the psu of a power opamp with a similar power opamp? Franz G Chip Amps 34 19th October 2004 10:49 AM

New To Site? Need Help?

All times are GMT. The time now is 06:48 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 16.67%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio