Multi-stage amplification - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 5th August 2007, 01:24 AM   #1
sam9 is offline sam9  United States
diyAudio Member
sam9's Avatar
Join Date: Jun 2002
Location: Left Coast
Default Multi-stage amplification

In the latest edition of Audio Express, Denis Colin presents data to show that overall THD can be lowered by chaining several op amps end on end rather than achieving all the gain in one stage. He is thinking mostly of phono preamps. The idea is that three opamps with a gain of 5 each (5x5x=125) will result in lower overall THD than a single stage with a gain of 125.

He used AD797's to test this and presented measurements (nor sims) to arrive at an optimized gain per stage, about 4.8.

This got me to thinking about the LM3886 and similar IC amps. A complaint I read on the site is that the ap notes always show these devices configured with a gain of 20 which some feel is lower than they desire. The suspicion is that at gains of 25 or 30 the THD figures deteriorate. It occurs to be that an opamp on the front end (perhaps part aof a "super gain clone" scheme) with just a little gain might be away to have one's cake and eat it too. Opamp gain = 1.5 x GC gain 20 = gain of 30. or 1.25x 20 = 25. Or 2 x 15 = 30. etc etc.

Anybody tried this? It seems to me that the "catch" might be noise, I noticed Colin always mentioned THD, never THD+N. But if you are using AD797s that might not be much of an issue. More cynically if you are just thinking phono amp, perhaps the LP surface noise covers iy all up anyway.
  Reply With Quote
Old 5th August 2007, 05:23 AM   #2
diyAudio Moderator Emeritus
lumanauw's Avatar
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Sometimes ago I asked a question here, why make 2 stages with each gain =3x when we can make a single stage with gain=9x. Someone answers that these 2 approach has difference in bandwith (where gain x bandwith = constant, so less gain gives more bandwith). Cascading several low gain stages will work in higher bandwith. Don't know about the noise, though.
  Reply With Quote
Old 5th August 2007, 04:49 PM   #3
diyAudio Member
myhrrhleine's Avatar
Join Date: Jan 2006
Location: Avalon Island
Multiple stages can work fine and has often been done.
One can even combine the 2 amps to create one, high gain amp, thus providing more feedback and lowering distortion.
[Grasshopper]:Old man, how is it that you hear these things?
[master]:Young man, how is it that you do not?
  Reply With Quote


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
UAS - Universal Amplification Stage Stee Solid State 70 12th November 2010 01:23 PM
Advice sought on building multi-channel amplification jwillans Solid State 10 3rd March 2009 08:31 PM
GAS - Global Amplification Stage Stee Solid State 17 19th August 2008 03:58 AM
multi amplification and different sensitivity drivers : drawbacks ? mbon Multi-Way 4 20th June 2004 03:16 PM
power amplifier with one-stage voltage amplification alex0 Solid State 5 7th February 2004 12:02 PM

New To Site? Need Help?

All times are GMT. The time now is 05:56 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2