A question about diamond buffers - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

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
Reply
 
Thread Tools Search this Thread
Old 24th June 2008, 07:39 PM   #1
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
Default A question about diamond buffers

Hello everyone,

Recently (since this morning actually) I got very interested in diamond buffers and found several schematics. I understand the principle for the Walt Jung version and some derived ones but not this one for which I post the schematic. I may be a dumb question but how is the second stage correctly polarised? To me it looks like a class B or even C stage... Probably I'm missing something in the design...
Attached Images
File Type: gif diamondbuf.gif (18.3 KB, 864 views)
  Reply With Quote
Old 24th June 2008, 07:41 PM   #2
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
The Walt Jung design is limpid, with the emitter resistors on the first stage setting the second one in class A...
Attached Images
File Type: jpg diamondwalt.jpg (27.3 KB, 802 views)
  Reply With Quote
Old 24th June 2008, 07:43 PM   #3
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
And finally this one used in an Accuphase amplifier is very elegant with the first stage biasing the second one...
Attached Images
File Type: jpg accuphase.jpg (15.7 KB, 866 views)
  Reply With Quote
Old 24th June 2008, 10:14 PM   #4
juma is offline juma  Serbia
diyAudio Member
 
juma's Avatar
 
Join Date: Nov 2005
Location: Zemun
Take a peek here:
http://www.diamondstar.de/dDB_design.html
  Reply With Quote
Old 24th June 2008, 10:43 PM   #5
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
Thank you for your answer,

These ones have the emitter resistor for bias as it should. I just wondered about the scheme without them. I found it on a forum about headphones. They could be Sijosae design or something. I just wondered about the crossover distortion in a strict class B like that. It is better in class A.

And if the Vbe of the first stage is lower than the second, you get a nice class C one.

I may be wrong but I wanted a confirmation.

Anyone?
  Reply With Quote
Old 24th June 2008, 10:46 PM   #6
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
And I wanted to share the Accuphase one which I find very interesting with the autobias acting like a faint NFB too.
Very elegant...
  Reply With Quote
Old 24th June 2008, 11:17 PM   #7
forr is offline forr  France
diyAudio Member
 
forr's Avatar
 
Join Date: Dec 2004
Location: Next door
Hi Darian,
You are right, the first schematics you show is wrong.
I would be curious of the results obtained with the Accuphase circuit.
  Reply With Quote
Old 24th June 2008, 11:39 PM   #8
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Darian

I read the circuit (1) like this: -

The circuit is symmetrical and collector voltages in the first stage will be equally offset from the supply rails when the Hfe of the transistors is equal.

Since the bases of the input transistors are at the same voltage (connected), the differential voltage between the collectors is Vbe(337) + Vbe(327). This is insufficient to bias the second stage into conduction, because of the voltage drop across the 2*4R7 emitter resistors and because the transistors used are identical to the ones in the first stage.

So this is a class B push-pull amplifier and will have pronounced crossover distortion.

w
  Reply With Quote
Old 25th June 2008, 12:01 AM   #9
darian is offline darian  France
diyAudio Member
 
Join Date: Mar 2006
Location: Paris
Thanks for your answer,

So I was right about it. I guess no one complained about it in the headphone forum (Headwize I think). There may be some people listening to that badly designed circuit and thinking it's a good one. Too bad for them...

Anyway, I have my answer. If someone wants to try the Accuphase circuit, I'd be pleased to hear some feedback. It's so smart and so simple at the same time.

Thanx
  Reply With Quote
Old 25th June 2008, 08:10 AM   #10
Banned
 
Join Date: Jan 2008
Blog Entries: 2
Quote:
Originally posted by wakibaki


The circuit is symmetrical and collector voltages in the first stage will be equally offset from the supply rails when the Hfe of the transistors is equal.

Since the bases of the input transistors are at the same voltage (connected), the differential voltage between the collectors is Vbe(337) + Vbe(327)
Sorry

I was about to go to bed when I wrote that. I went to sleep and woke up thinking about it.

In both instances this should read emitter, not collector.

This is 2 cross-coupled emitter followers, so voltage gain < 1. It's purely a current buffer.

Since the Vbe's of the stages are likely to be close, the xover is probably fairly smooth.

If you wanted to run it AB, you could do this:-

Click the image to open in full size.

w
  Reply With Quote

Reply


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
HDAM / Diamond Buffers Q RnR Solid State 0 21st April 2009 09:59 PM
A question about diamond buffers darian Analog Line Level 3 24th June 2008 07:38 PM
Diamond buffers Nordic Parts 7 13th March 2007 02:13 PM
Mini Portable Headphone Amplifier, with Discrete Diamond Buffers cetoole Headphone Systems 3 30th May 2006 06:32 AM
Diamond buffers w. CFP outputs Christer Solid State 39 26th January 2004 11:08 PM


New To Site? Need Help?

All times are GMT. The time now is 06:55 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2