class A Line level buffer - Page 2 - diyAudio
Go Back   Home > Forums > Source & Line > Analog Line Level
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

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 22nd February 2011, 09:25 AM   #11
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
my newest headphones are 95dB/mW

2.2Vac from a CDP will give ~120dB at the ear hole.
I doubt I'll need any extra gain. I suspect I'll be in attenuation mode !
But yes, to the idea. A switchable X1 (+0db), X2 (+6dB), X4 (+12dB) gain setting would be ideal. The difficult part may be adjusting the compensation so that each gain option operates as stabily as the best.

I was going to ask:
1.) would converting the lower 139 to a complementary and becoming a push pull ClassA reduce the performance?
2.) would using the dual soic8 as a two channel single ended ClassA output stage cause overheating? Rth j-a = 145C/W
I'm thinking to reduce the opamp bias slightly from 5mA to 4mA and reduce the voltage from 34Vdc to 24Vdc (this reduces opamp temperature by ~22Cdegrees)
24Vdc still gives ~+11dB of overhead above maximum signal.
regards Andrew T.
Sent from my desktop computer using a keyboard

Last edited by AndrewT; 22nd February 2011 at 09:37 AM.
  Reply With Quote
Old 22nd February 2011, 12:53 PM   #12
Bonsai is offline Bonsai  Europe
diyAudio Member
Bonsai's Avatar
Join Date: Jul 2003
Location: Europe
Interesting points Andrew

1. No I don't think this will reduce the performance. I basically did this design because good performance can be obtained with a very simple circuit. I think a complimentary class A should work very well, but it will probably be more complex due to the bias requirements. The loaded follower aproach used in this design is simple and very stable.
2. No, I if I understand you correctly, this should work quite well. Likewise, my constant current load on the op-amp outputs is probably a little heavy handed - I think 3mA will also work fine.

Re the point about the gain, the reason I propose this is that if you apply 2x to 3x gain to the headphone stage, I find the volume pot will typically sit between a quarter to to about 10past for most listening - so its setting is similar to where you set it when listening over the speakers.

That said, 3V pk into 32 Ohm headphones is incredibly loud - there's plenty of headroom if you listen at normal levels.
Amplifier Design and Construction for MUSIC!
  Reply With Quote
Old 19th March 2011, 02:54 PM   #13
robmil is offline robmil  United Kingdom
diyAudio Member
Join Date: Jun 2004
Location: London
Hi Bonsai

thank you for your brilliantly laid out information. As an aside...
What software do you use for the documentation. It looks absolutely first class!

  Reply With Quote
Old 19th March 2011, 03:52 PM   #14
Bonsai is offline Bonsai  Europe
diyAudio Member
Bonsai's Avatar
Join Date: Jul 2003
Location: Europe
Hi Rob - thanks.

I use . . . . Microsoft Word - nothing special. I am using MS Office and in my version there are some document templates or themses - I just selected one of them and stuck with it.

I'm busy working on a class A headphone amp based on the above BTW. Shown be able to publish something in a week or two.
Amplifier Design and Construction for MUSIC!
  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
RIAA Article and Line Level Buffer Bonsai Analogue Source 3 22nd February 2011 01:02 PM
Low-distortion Class-A line/headphone buffer linuxguru Analog Line Level 8 13th November 2010 07:00 AM
trouble matching line level to guitar amp input level...any help? mondogenerator Instruments and Amps 5 19th December 2009 10:00 AM
Simple Line level buffer/active crossover? gregorx Subwoofers 37 28th July 2008 04:56 PM
Line level op amp buffer hags Chip Amps 1 16th March 2007 09:22 PM

New To Site? Need Help?

All times are GMT. The time now is 09:36 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