Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Power amp vs preamp topology
Power amp vs preamp topology
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
Thread Tools Search this Thread
Old 28th January 2012, 08:32 PM   #1
johnguitar is offline johnguitar
diyAudio Member
Join Date: Jan 2012
Default Power amp vs preamp topology


I have the following problem that I cannot fully understand.
In literature it is said that in a common preamp stage the topology for taking the output is as in attached figure top02.
However, when it comes to Power amplification they always put the output transformer in the place of Ra (plate resistor) like in attached figure top01. Is it possible to create a topology like the attached figure top02 (which is similar to a preamp stage).?

What are the differences between these two topologies??
They say that power amps must amplify also current (not only Voltage amplification). If do we amplify the voltage, the current is amplified also (according to the resistance), isn't it?

So, is it possible to have power amplification with topology in figure top01?

Thanks in advance
Attached Images
File Type: png top01.PNG (19.5 KB, 109 views)
File Type: png top02.PNG (21.1 KB, 105 views)
  Reply With Quote
Old 28th January 2012, 09:11 PM   #2
DF96 is offline DF96  England
diyAudio Member
Join Date: May 2007
The resistor drops a lot of DC voltage, so requires a high supply voltage. It also absorbs AC power. You can afford this in a small signal stage, but not in a power stage. Despite this, it is sometimes used in low power outputs.
  Reply With Quote
Old 28th January 2012, 09:59 PM   #3
ryuji is offline ryuji  United States
diyAudio Member
Join Date: Feb 2011
Location: massachusetts
Originally Posted by DF96 View Post
The resistor drops a lot of DC voltage
I dont know the state of mind in other designers, but in my signal gain stages i was counting on this, i assume im likely not alone. (brought 440v b+ down to 250 quiescent, from too high to proper operating point.
  Reply With Quote
Old 28th January 2012, 11:01 PM   #4
Palustris is offline Palustris  United States
diyAudio Member
Palustris's Avatar
Join Date: Aug 2006
Location: Cape Cod
Topology one will work fine as a preamp or amp. Topology two is probably intended to be parallel feed so you need a cap between the tube and transformer or the transformer and ground. It will then work as a preamp or amp.

The advantage of parafeed is that it is easier to make a high inductance transformer if the transformer doesn't need to have an airgap. Without the airgap the quiescent current would saturate the transformer.
  Reply With Quote


Power amp vs preamp topologyHide 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

Forum Jump

New To Site? Need Help?

All times are GMT. The time now is 10:06 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio