Marantz discrete op amp (line stage or headphone amp) - diyAudio
Go Back   Home > Forums > Blogs > RJM Audio Blog
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
If I put my notes here, I might be able to find them again later!
Rate this Entry

Marantz discrete op amp (line stage or headphone amp)

Posted 10th November 2013 at 11:00 AM by rjm
Updated 10th November 2013 at 01:11 PM by rjm

Last one for today.

I was having problems getting this to work, the key seems to be adjusting R6 to null the voltage offset. Works fine now, but this is just a rough reverse engineer of the diagram, the parts values and the type of transistors are essentially placeholders.

The input jFET is shown as a dual package. The output bias current is most likely much lower than the 100 mA I configured, so the class A output power is proportionately smaller. For the rest of the currents and the types of transistors used, your guess is as good as mine.

edit: R7 should most likely be closer to 47 ohms, while another 5p capacitor should go in parallel with the feedback resistor, R17.
Attached Thumbnails
Click image for larger version

Name:	marantz-amp-rjmaudio.png
Views:	3744
Size:	34.3 KB
ID:	1163  
Attached Files
File Type: asc marantz headphone amp.asc (7.2 KB, 264 views)
Posted in The Lab
Views 1888 Comments 3
Total Comments 3

Comments

  1. Old Comment
    You might have to adjust R6 a lot less if you substitute a diode connected BC547c for D1. As is you get uneven contributions from each side of the diff pair.
    permalink
    Posted 11th November 2013 at 04:48 AM by mirlo mirlo is offline
  2. Old Comment
    rjm's Avatar
    I'll look into that. Thanks!
    permalink
    Posted 11th November 2013 at 12:00 PM by rjm rjm is offline
  3. Old Comment
    Why are R4 and R6 such drastically differently values? Shouldn't they be the same?
    permalink
    Posted 21st January 2014 at 11:08 AM by FoMoCo FoMoCo is offline
 
Hide this!Advertise here!

New To Site? Need Help?

All times are GMT. The time now is 05:25 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki