TRIODE Voltage amp + Power OP output follower - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs 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

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 16th August 2010, 03:36 PM   #1
lineup is offline lineup  Sweden
diyAudio Member
lineup's Avatar
Join Date: Dec 2005
Location: the north
Default TRIODE Voltage amp + Power OP output follower

It is quite easy to build a good and simple 'tube amp'
if using a triode (like 6DJ8) as voltage amplifier
and add one Power Op-Amp as output stage, follower.

Getting 50 Watt RMS into 8 Ohm with less than 1% THD distortion is not difficult.
The dist that is there will be totally of TUBE characteristic
as the Op-Amp gives practically no dist at Unity Gain.

It is a bit like Tube-Buffered Gainclone.
Click the image to open in full size.
But problem with LM3875 and LM3886 is they can not work at Gain=1.
They are not true Op-Amps in this respect.

OPA541 can be used as a 'normal' opamp, at unity gain = 1.
And so easily work as output follower.
Power supply can be 70V for plastic models and 80V for metal package.
See images ...
Output current is 10 Ampere, so it drives 4 Ohm speaker, too.
Precision Amplifier - High Output Current - OPA541 -

My idea is very simple and works very good in SPICE.
I will post more detailed circuits later.
Here is the concept:
Attached Images
File Type: png 6DJ8_OPA541_1.png (4.0 KB, 527 views)
File Type: jpg opa541ap.jpg (23.4 KB, 522 views)
File Type: jpg opa541bm_2.jpg (5.1 KB, 510 views)
  Reply With Quote
Old 16th August 2010, 04:02 PM   #2
Bigun is offline Bigun  Canada
diyAudio Member
Bigun's Avatar
Join Date: Jan 2009
Location: Waterloo, ON or Herefordshire
Blog Entries: 2
I think this is a good looking approach, you could do a search to see what else might be helpful,

Synthesis Magnum, commercial tube-chipamp hybrid...

Connecting tube gain stage to LM3886 for guitar amplifier??? How can this be done???

Tube with Power IC Output Stage - JLTi
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote
Old 16th August 2010, 05:28 PM   #3
pedroskova's Avatar
Join Date: Dec 2002
Location: C'ville VA, USA
The JLTi is kind of the opposite of the OP. No gain from the tube, and all of the gain provided by the chip. The tube is pretty useless if a decent preamp is present in the system.

Lineup - could the OPA544 be used as a substitute, i.e., is it unity gain stable as well?
  Reply With Quote
Old 16th August 2010, 09:52 PM   #4
diyAudio Member
Join Date: Jan 2002
Location: nowhere
Sorry mate, the distortion will not be tube b/c it is driving an easy load (the IC). The IC is driving the difficult load and the distortion will be like a SS amp.
  Reply With Quote
Old 16th August 2010, 09:56 PM   #5
diyAudio Member
Wavebourn's Avatar
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
The distortion will be like a tube is driving SS amp, and SS amp is driving a complex load.
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 16th August 2010, 09:59 PM   #6
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
Join Date: Nov 2005
isnt amplification from the tubes just about 20 or so
thus still needs some amplification from IC too

would be interesting to reverse it, IC driving tubes

or maybe IC driving IC, with tube interstage trafo
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 17th August 2010, 07:23 PM   #7
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
Join Date: Nov 2005
would it have more interest in ChipAmp forum ?

I can move it over if you want ?
sometimes we know very little, and sometimes we know too much
  Reply With Quote
Old 17th August 2010, 07:35 PM   #8
diyAudio Member
Join Date: Jan 2002
Location: nowhere
Maybe. point is u're assumption is wrong, shouldn't matter which forum u chose. But that's the whole point about this site, discussing ideas.
The concept of a tube doing voltage gain and transistors doing current is fine, but the distortion will be just as Wavebourn said.
  Reply With Quote
Old 18th August 2010, 08:40 AM   #9
teemuk is offline teemuk  Finland
diyAudio Member
Join Date: Nov 2004
Location: Suomi, Finland
Circuit and method for a ... - Google Patent Search
  Reply With Quote
Old 14th November 2014, 08:11 AM   #10
lgqliu is offline lgqliu  China
diyAudio Member
Join Date: Feb 2005
Location: chengde
Default 6DJ8+OPA541


This figure has a problem?
  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
four transistor emitter follower (diamond buffer) as power output stage? capslock Solid State 114 22nd February 2015 10:51 AM
Choosing rail voltage in Class A, Power Follower Amp ervinl Solid State 1 5th August 2010 11:26 AM
Mosfet Power Follower with 1:1 Output Transformer questions AudioGeek Solid State 0 23rd February 2010 01:22 AM
N-channel only output devices in a power follower. x-pro Solid State 23 6th August 2009 01:50 PM
Low Voltage Plate Follower 6DJ8 Buffer Power Supply mwl6m Tubes / Valves 50 3rd August 2007 07:50 AM

New To Site? Need Help?

All times are GMT. The time now is 01:09 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