Ok, I admit i don't make any sense out of this - 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 26th September 2004, 02:03 PM   #1
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Default Ok, I admit i don't make any sense out of this

PD was recently kind to post a fragment of the ML38 schematic.

For the last couple of hours i've been staring at the PS arrangement and feeling very dumb. Power to the collectors of the matched transistors seems to be supplied on both sides from CCS feeding a unity gain opamp. What's the point?
  Reply With Quote
Old 26th September 2004, 02:47 PM   #2
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Frank,

Very strange indeed. Could there be a drawing error in the interconnection of the terminals of those matched pairs? That doesn't make sense.

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 26th September 2004, 02:54 PM   #3
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
I'm not sure if you read it right, but the dual transistor is in 8-DIP package, so it is represented by the frame outline on a drawing. The power is supplied to one of the collectors, the other collector is connected to the emiter (of the other transistor).
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 26th September 2004, 02:59 PM   #4
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
This appears to be a funny and exotic way of cascoding

All transistors appear to work at a fixed Vce of about one diode drop
  Reply With Quote
Old 26th September 2004, 03:36 PM   #5
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
But that transistor that has the collector to the emitter of the other, that places its collector-base diode in conduction, isn't it? That would influence the operation of the input, no?

Edit: that collector doesn't appear to get any supply, as it is connected (with the other emitter) directly to the output via 10 ohms.


Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 26th September 2004, 04:00 PM   #6
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Left side transistors work with Vc = Vb so its Vce is one diode drop
Right side transistors work with Vc = Vb + diode drop so its Vce is two diode drops

Note that left side transistors have its bases tied together while right side transistors have its emitters tied together

Note also that small signal transistors may work with Vce as low as 0.1 V [ie: collector potential between base and emitter potential

Redrawing the schematic may help to understand it
  Reply With Quote
Old 26th September 2004, 04:10 PM   #7
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Here's the redrawn version. It looks much clearer now.
Attached Images
File Type: jpg buffer.jpg (36.8 KB, 1652 views)
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  Reply With Quote
Old 26th September 2004, 04:56 PM   #8
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Thanks Peter, that's MUCH better.
Eva, does that mean that the right side transistor works in what looks like bootstrapped common-base?

BTW, who designed this?

Jan Didden
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W. S. Maugham
Check out Linear Audio!
  Reply With Quote
Old 26th September 2004, 04:59 PM   #9
andy_c is offline andy_c  United States
Banned
 
Join Date: Apr 2003
Default Is this better?

Here's yet another interpretation. It's a diamond buffer with the input collectors bootstrapped to the output emitters, and the output collectors bootstrapped to one diode drop away from their respective bases.
Attached Images
File Type: png diamond_bootstrap.png (6.5 KB, 1564 views)
  Reply With Quote
Old 26th September 2004, 05:04 PM   #10
diyAudio Member
 
Peter Daniel's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Send a message via AIM to Peter Daniel
Quote:
Originally posted by janneman

BTW, who designed this?
This circuit is used in Mark Levinson ML380 preamp, as well in some other ML units.

Is there a need for dual NPN/PNP transistors here?
__________________
www.audiosector.com
“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC
  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
Linear voltage regulator: how to make good use of "sense" and "ground sense"? NeoY2k Analog Line Level 7 6th September 2008 11:35 PM
does this make sense? nosegoblin Solid State 9 14th February 2004 02:19 PM
Does this make sense? Illusus Chip Amps 11 25th September 2003 01:59 PM


New To Site? Need Help?

All times are GMT. The time now is 01:44 AM.


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