Broskie P-P Bridged Output Stage - 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 April 2012, 01:26 AM   #1
diyAudio Member
 
Join Date: Mar 2009
Default Broskie P-P Bridged Output Stage

Has anyone built John Broskie's H-Bridged output stage shown in his Tubecad blog number 192? (See the link below.) I've got it breadboarded, but getting enough balance in all those triodes to limit dc offset is challenging. Would be interesting to hear thoughts on possible routes to achieving balance. Thanks much.

OUTPUT STAGE DESIGN
  Reply With Quote
Old 9th April 2012, 03:32 AM   #2
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
There are several diagrams on that page. I built the one with 4 output tubes all driven by a driver transformer with 4 secondaries. I did it because I used to make some extremely high powered solid state amps that way back in high school. They used the same circuit to make 300 to 1200 watts, which was stupid power in 1970. Back then I used to wind my own driver transformers or use a pair of Heathkit transformers with their primaries in parallel.

Triode electronics has a tube type "universal driver transformer" with a center tapped primary and 4 independent secondaries. I bought a pair of the early ones and tried the BTL circuit with several different tubes. The results were the same. the driver transformer starts rolling off at 10KHz and is 6db down at 20 KHz. The low end isn't great either.

They now have a "version 2" of the driver transformer, but I don't know if I will try it or not.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 12th April 2012, 12:14 AM   #3
diyAudio Member
 
smoking-amp's Avatar
 
Join Date: Dec 2001
Location: Hickory, NC
While trying to figure out how Broskie's double bootstrap worked in that blog #192, I realized that there is another equivalent way to do the same using the more usual differential pentode driver stage driving a totem pole output stage. Usually the bootstrap from the output midpoint goes to the top of just one or the other of the diffl. driver plate resistors (per side, if talking an H bridge config, and a bootstrap cap is usually there too).

In one case the boot boosts the drive for the upper totem pole device, or in the other case it reduces the drive for the lower totem pole device. But it is possible to do both bootstraps at once like Broskie effectively did by reducing the bootstrap signal by 1/2. Connect both diffl. driver plate load resistors together to an R going to B+ and another equal R going to the output. The drivers sum to a constant current, so they only cause DC loading on the R/R divider. The two equal R's then divide the output AC level in half for the equal 1/2 bootstrapping to each side. I've never seen that done before. (one might have to play with the driver stage DC plate V or B+, maybe a bootstrap cap)

This approach eliminates two floating (filament issue) tube elements from the driver stage versus the Broskie version.
__________________
Without MS, how would we live without all those hackers?

Last edited by smoking-amp; 12th April 2012 at 12:24 AM.
  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
Controversy regarding Bridged Amplifier power output RishiGuru Chip Amps 91 22nd November 2012 05:27 PM
Measure the output of a bridged class D ocool_15 Class D 5 20th April 2008 08:12 PM
41Hz.com AMP8 - Output power when bridged MikeHunt79 Class D 8 29th March 2008 02:47 PM
Is the BASH Plate Amp Output Bridged? gmikol Subwoofers 1 26th October 2006 07:24 AM
Cap. at the output on bridged no DC avenger Chip Amps 20 11th November 2003 07:57 PM


New To Site? Need Help?

All times are GMT. The time now is 10:21 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