My version of the Simple EL84 or rise of the anti-triode. - 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 26th August 2009, 05:07 PM   #1
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Default My version of the Simple EL84 or rise of the anti-triode.

Hi all,
I have just finished my latest amp. It is loosely based on the self splitting DiyParadise Simple EL84 amp. This has been a project in the planning and evolution for at least 5yrs now so its a great relief to have it finished and working.
It differs in a number of key areas though. I chose to use PL84's (16V EL86) because they are cheap and readily available and allow for lower impedance ratio Output Transformers. I also chose to use a 6AU6 as the driver. I am running both the PL84 and the 6AU6 in pentode mode, and this allows me to run the input and driven valve as a partial feedback combination. I have used LM317's in the tail of each of the outputs as CCS and have linked them for the self splitting using back to back 1000uf caps to allow fixed DC standing current and full differential output. The antitriode is run as a pentode. I am running 8V toroidal power transformers as outputs. Almost everything in the amp is salvaged so it has cost me almost nothing.

I was expecting it to sound good, but am a little surprised at how good it sounds. It has a slightly warm but very detailed presentation, and has masses of bass punch. I would have to agree with others impression of this configuration in describing it as having SE warmth with PP punch and extension.

If anyone is interested I will attempt to lash up a schematic.

Shoog
  Reply With Quote
Old 26th August 2009, 05:35 PM   #2
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by Shoog View Post

If anyone is interested I will attempt to lash up a schematic.
Yes please.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 26th August 2009, 05:37 PM   #3
Merlinb is offline Merlinb  United Kingdom
diyAudio Member
 
Merlinb's Avatar
 
Join Date: May 2006
Location: Lancashire
Sounds very interesting- I'd like to see a schem!
What do you mean by 'antitriode'?
  Reply With Quote
Old 26th August 2009, 05:39 PM   #4
diyAudio Moderator Emeritus
 
Bas Horneman's Avatar
 
Join Date: Apr 2002
Location: The Netherlands
Blog Entries: 18
I've read about the 6AU6 being an undiscovered gem several times. Or as they say in the states: sleeper

Once again it is confirmed.
  Reply With Quote
Old 26th August 2009, 05:53 PM   #5
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
Originally Posted by Bas Horneman View Post
I've read about the 6AU6 being an undiscovered gem several times. Or as they say in the states: sleeper
Me too (was suggested by one of my gurus before i read of it -- was suggested as an alternate to EF86)... i got some cryoed and have a box overflowing with them, at some point i'll get a chance to use some of them up.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 26th August 2009, 06:57 PM   #6
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
The thing with the 6AU6 is that it can handle respectable current (ie 5mA+) which is way more useful than most of the piddling little small signal pentodes which seem good for just about 1mA. this is especially important with partial feedback amps because the feedback current is liable to swamp the output signal otherwise. I have used it in my Tabor clone and now this one and both have sounded sweet without any hint of pentode harshness. There are also different voltage versions which makes it quite an economical tube.

The antitriode is the slave valve in a self splitting output stage which simply supplies the current to balance DC and AC signals in the output transformer. The stiffer it is the better it forfills its intended role - so configuring it as a pentode works best.

I will attempt a schematic tomorrow.

Shoog
  Reply With Quote
Old 26th August 2009, 07:30 PM   #7
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
6AU6 is a good tube, but I've found EL84 still the best driver tube. Try it. Using PL84 as drivers you have an option to power filaments from the same source.
  Reply With Quote
Old 26th August 2009, 08:20 PM   #8
diyAudio Member
 
Michael Koster's Avatar
 
Join Date: Jan 2008
Location: Eureka, CA
Quote:
Originally Posted by Merlinb View Post
Sounds very interesting- I'd like to see a schem!
What do you mean by 'antitriode'?
It's an "asymmetric" push-pull amp using a triode on one side and an antitriode
on the other. An antitriode can be built from a pentode, MOSFET, BJT, or even
a triode. THe circuit works a lot like an LTP.

It's called "antitriode" because it follows the inverse transfer function of the
triode, i.e. it exactly mirrors the triode. When the mirrored signal is combined
in the OPT with the original signal, there is no cancellation of the 2nd harmonic
as there is in a conventional push-pull circuit. The result is a push-pull topology
with the harmonic signature of a SE amplifier.

I have built a few amplifiers using this idea in one form or another (series, parallel,
parafeed...) and they all have the same SE harmonic signature.

Another kind of hybrid
Spud-Assist: Totem-Pole Current-Mirror PP Hybrid
  Reply With Quote
Old 26th August 2009, 08:37 PM   #9
diyAudio Member
 
Shoog's Avatar
 
Join Date: Aug 2002
Location: Eire
Quote:
Originally Posted by Geek View Post
The 6AU6 is a fine tube in its own right, but not an EF86 by a longshot, IMO.

The key to a 6AU6 is to find one that's not microphonic or even far more common, really, really hummy from bad h-k leakage.

Cheers!
Neither Microphonics or hum have been issues with the 6AU6;s I have. Did you hit a bad batch.

Shoog
  Reply With Quote
Old 26th August 2009, 09:34 PM   #10
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: West Virginia panhandle
Quote:
The key to a 6AU6 is to find one that's not microphonic or even far more common, really, really hummy from bad h-k leakage......Neither Microphonics or hum have been issues with the 6AU6;s I have. Did you hit a bad batch
I have a bunch of 6AU6, several hundred, maybe 1000. So of course I have experimented with them. Yes many are microphonic, some ridiculously bad, you can talk to it and hear yourself in the speakers. There are some hummers too, and some that snap crackle, pop, or hiss at you. Granted all of my tubes are old military stock and many are used, and all at least 50 years old, but there are a significant percentage (10 to 20%) that work fine except for hum, noise or microphony. If I were the only one to observe this, I would say that my tubes are just junk, but others have observed the same thing.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  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
Anti-Triode SEPP, how to do best? Salas Tubes / Valves 182 22nd September 2011 07:09 PM
SEPTOR AT-amp (Anti-Triode) being built revintage Tubes / Valves 36 16th October 2008 06:01 AM
Screen Driven Dissimilar Pentode SE Anti-Triode Spud kenpeter Tubes / Valves 2 26th July 2008 02:22 AM
My EL84 Triode PP Amp sorenj07 Swap Meet 7 19th June 2008 04:13 PM


New To Site? Need Help?

All times are GMT. The time now is 09:15 AM.


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