My Headphone amp series resistor on output - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Solid State Talk all about solid state amplification.

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 February 2012, 04:18 PM   #1
diyAudio Member
Join Date: Sep 2009
Location: Pretoria
Exclamation My Headphone amp series resistor on output

I built myself an headphone amp about a year ago. It uses one half of a jrc4556 opamp per side(L/R), for the output. Its a single supply design with 1000uf output coupling caps
I recently changed the design by taking out the two 100ohm resistors in series with the outputs. I use a 6m headphone cable extension with it.
My question is, is it ok to run it without those resistors? I have never had any problem with oscillations since taking them out.
I want to keep the output z low!!!
  Reply With Quote
Old 21st February 2012, 09:08 PM   #2
agdr is offline agdr  United States
diyAudio Member
agdr's Avatar
Join Date: Sep 2010
No output resistors on the JRC4556/NJM4556 are OK.

The O2 headphone amplifier uses NJM4556 chips as the output with 1 ohm output resistors. Even at that the 1R resistors were needed for balance since the amp uses both halves of the chip in parallel per channel (two chips total). With just one half of the chip per channel, like yours, the amp probably would have had no output resistor at all. That amplifier has been measured on good equipment, with capacitive cable loads, and the published results are very good.

One of the keys is the chip apparently has current limiting. The data sheet does not say it explicitly, but the data sheet graphs show it. So the output resistor isn't needed to protect against TRS plug shorting. The data sheet doesn't give a load capacitance graph, but with 70mA per half capability it seems to be fairly stable.

An interesting read on the benefits of low output impedance for head amps:

The "0-Ohm" Headphone Amplifier: The Sonic Advantages of Low-Impedance Headphone Amplifiers | Benchmark Interaction
  Reply With Quote
Old 22nd February 2012, 05:31 AM   #3
diyAudio Member
Join Date: Sep 2009
Location: Pretoria
Thanx! Thats exactly why i want low z. Increased damping factor!!
  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
Eliminating series resistor at line output? Omega_Void Analog Line Level 11 13th November 2010 01:11 PM
Resistor for Amp output testing Eric Pass Labs 12 8th January 2010 02:40 PM
Silicon Chip July06 / EPE Feb08 Studio Series Pre-Amp with remote and Headphone Amp pgamble Headphone Systems 6 8th November 2009 09:50 AM
Using resistor at output to reduce volume of headphone wwenze Headphone Systems 5 16th September 2009 10:16 AM
How to put fixed attenuation between preamp and amp. Lpad or just resistor in series? PUCK Parts 1 19th November 2003 03:59 PM

New To Site? Need Help?

All times are GMT. The time now is 07:51 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