Push Pull Output Stage Question - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 9th February 2003, 12:29 PM   #1
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Question Push Pull Output Stage Question

<big>Hello Folks ,</big><br>
I've been busy recently , rather heavy power supply built (it bends my workbench!) , a dual mono thingy with damper diodes , half a ton of oil caps and chokes . Now moving on to the output stage . It consists of triode strapped S11E12 in push pull , aiming for 65mA / -65V / 340V operating point 6.6k p-p . The bias circuit consists of a 470 ohm resistor in series with a variable cascode current sink running from a negative supply , with bias monitor meter . Sink can be varied from 100-150mA , rock solid and nothing on the sink board gets warm , a good start ! Output stage balance is via a pot , balance checking via a centre reading meter between the S11E12 cathodes . My question before I bolt the thing in and commit is : <i>I have used a 470 ohm resistor in series with the sink , mainly to keep dissipation of the sink down (so I can use smaller , higher Hfe transistors) , what are the disadvantages of this ?</i><br><br>

316a<br><br><center><img src='http://service.globalarray.net/user/bigdaddy/outputstage.jpg'>
  Reply With Quote
Old 9th February 2003, 01:41 PM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
A series resistor will limit the CS compliance a bit; Ohm's law will tell you that.
  Reply With Quote
Old 9th February 2003, 01:54 PM   #3
diyAudio Member
 
Join Date: Jul 2001
Location: Orleans, France
In my opinion, BC549 can't work properly at 100...150 mA collector current, and MJE340 can't work properly at low collector voltage (10 V min)

You have to chose lower resistor for the common cathode (220 Ohms) and use something like 2N2222 instead of BC549.

MJE340 need a small heatsink for correct reliability.

Regards, Pierre Lacombe.
  Reply With Quote
Old 9th February 2003, 05:24 PM   #4
316a is offline 316a  England
diyAudio Member
 
316a's Avatar
 
Join Date: Dec 2002
Location: West London
Default BC549

...you're right about the BC549 , I did not realise it was only rated at 100mA , still seems to work ok . I'll shove a BC184 or an MPSA42 in there instead . The MJE340 is already heatsinked , you may be right about the series resistor though , I'll shove a slightly lower value in


316a
  Reply With Quote
Old 10th February 2003, 01:04 AM   #5
diyAudio Member
 
Circlotron's Avatar
 
Join Date: Jun 2002
Location: Melbourne, Australia
Default Power long-tailed pair. Way to go!

I like this approach with the single current source. It makes the whole output stage into a long tailed pair. Should be very well balanced. For what it's worth, have a look at the constant current sink cct I made up a while back. I measured a slope resistance somewhat in excess of 400 megohms. http://www.diyaudio.com/forums/showt...7225#post67225
__________________
Best-ever T/S parameter spreadsheet.
http://www.diyaudio.com/forums/multi...tml#post353269
  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
Push-Pull Output Stage MOSFET Tester lineup Solid State 2 10th September 2008 11:00 PM
split push-pull output stage andrew_whitham Tubes / Valves 16 22nd March 2007 06:25 PM
Transformer coupled 6SN7 push-pull DAC output stage? cathode_leak Tubes / Valves 7 24th January 2005 07:26 PM
6BQ5 as a Push Pull Output Stage. ppl Tubes / Valves 7 23rd December 2004 09:32 PM
unity gain push pull output stage ergo Solid State 11 6th January 2003 10:32 AM


New To Site? Need Help?

All times are GMT. The time now is 12:38 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