Anti-Triode SEPP, how to do best? - Page 3 - 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 19th March 2009, 07:28 AM   #21
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally posted by Wavebourn
Hmmm.... I'm afraid you will need too many LEDs. Like a Green Light District (GLD, SY?)
Here it is Wavebourn. This is what I think I can do with recycling my post#2 CCS (the green LEDs one on the post#17 pic).
Does this count for a cascoded Mosfet gyrator (electronic choke)? Did I get it right at all?

I have included a 12AU7 common cathode simulation so to see how it reacts. The 420R resistor on top of the first Mosfet sets the current. It can be a 500R trimmer for using other tubes, namely my 6V6 trioded or a 12B4A in another preamp that I wanna test the gyrator too. The 33K 10W feeds 10mA so the LEDs can work low noise, and its Johnson noise is filtered by the 47uF not to reach the cascode's gate.
Attached Images
File Type: gif salgyr.gif (7.2 KB, 1666 views)
  Reply With Quote
Old 19th March 2009, 08:31 AM   #22
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Quote:
Originally posted by Michael Koster
It doesn't matter really how you
develop the fixed voltage. It can be used with fixed bias because it
can regulate the plate voltage.

Cheers,

Michael
Can I get the fixed voltage from a divider on B+ ? How higher than the anode voltage it must roughly be?
  Reply With Quote
Old 19th March 2009, 04:32 PM   #23
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
So what happens when you filter the best ideas of
Michael J Koster, Wavebourn, and Nelson Pass
through the strange mind of Ken? Heck if I know...

Pretend Zen is a Triode, same thing only sandy.
Only trying to show you the active source servo.
I'll bend it around a real triode here soon enough.

Good Ash? Bad Ash? I'm the one with the Aleph.
******* evil mirrored clones, what can you do?
Attached Images
File Type: gif badash1.gif (49.0 KB, 1540 views)
  Reply With Quote
Old 19th March 2009, 04:36 PM   #24
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
So in theory:

At DC: its a Voltage source

At some subsonic frequency:
Its a gyrator of aproximately
equal and constant current.

Above 20Hz: Its Anti-Triode
or Aleph or whatever...

---------------


And LTSpice seems to agree.


---------------

Just needs a sourceOdyne
to flip a ground level input
common to the bottom rail.
  Reply With Quote
Old 19th March 2009, 04:52 PM   #25
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
You might notice the oddball 3K3 in the lower Bootstrap.
Why? Cause currents in R7 and R8 tend to be the same.

With a Symmetrical 4K7, bootstrapping wasn't happening
at all for the lower end. Indeed, the collector lost a volt
or two somewhere.

Tweaking it to 3K3 gave it the same -30V peak as the
upper collector's +30V Peak. Problem solved...
  Reply With Quote
Old 19th March 2009, 05:05 PM   #26
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally posted by salas


Here it is Wavebourn. This is what I think I can do with recycling my post#2 CCS (the green LEDs one on the post#17 pic).
Does this count for a cascoded Mosfet gyrator (electronic choke)? Did I get it right at all?

I have included a 12AU7 common cathode simulation so to see how it reacts. The 420R resistor on top of the first Mosfet sets the current. It can be a 500R trimmer for using other tubes, namely my 6V6 trioded or a 12B4A in another preamp that I wanna test the gyrator too. The 33K 10W feeds 10mA so the LEDs can work low noise, and its Johnson noise is filtered by the 47uF not to reach the cascode's gate.
1. 47 uF in series with LEDs is odd. Instead of decreasing voltage variations it increases them. Remove it.
2. 220 uF in servo feedback is too high for 1 mOhm resistor. Recauculate it for a reasonable time constant.
3. Voltage divider in servo feedback is formed by equal 1MOhm resistors. You have to increase the value of a bottom one many times, or decrease a value of the upper one to set proper anode voltage. If you need voltage drop on the upper resistor about 3V, on lower resistor about 150V, what should be their values?
Start from selecting the value of the bottom one, like 10 MOhm. Actually, 1 MOhm will be high enough comparing with Rp of your tube, so 150/3=50, i.e. the upper one should have 50 times smaller value, i.e. in case of lower one 1 mOhm it should be 20 KOhm. Use 50K trimmer to set it properly. Then select the capacitance, say for 1 Hz corner with 20 KOhm resistor.
And the last, a mistake in your drawing: you connected servo feedback to LEDs. Disconnect it. Gate of the upper FET should go to the servo feedback divider.
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 19th March 2009, 05:17 PM   #27
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Problem is, how do I keep the upper Mosfet on, If I don't put LEDs on its gate? I guess with the upper divider Vdrop?
  Reply With Quote
Old 19th March 2009, 05:40 PM   #28
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Quote:
Originally posted by salas
Problem is, how do I keep the upper Mosfet on, If I don't put LEDs on its gate? I guess with the upper divider Vdrop?
It is the main point of my idea that Kenpeter described, "That is absurdly cool!"
Upper MOSFET generates current needed to keep a constant voltage on the plate!
__________________
The Devil is not so terrible as his math model is!
  Reply With Quote
Old 19th March 2009, 06:14 PM   #29
Salas is online now Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
OK, what to you think about this one?
Attached Images
File Type: gif salgyr2.gif (6.9 KB, 983 views)
  Reply With Quote
Old 19th March 2009, 06:33 PM   #30
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
I would add 3 more LEDs in series. You have plenty of voltage available, use it.

Also, I would remove that 600 Ohm resistor: it is not needed here (it was needed for your version of CCS with stable gate voltage), increasing that 330K about twice. Better, as I said, use 1M resistor and 50K trimmer for breadboarding. Also, 47 uF is too high value: I would decrease it to say 2 uF using a metal film cap.

And, finally, I would consider different transistors (smaller capacitances for better frequency response) since you need about 5 mA only.

__________________
The Devil is not so terrible as his math model is!
  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
SEPTOR AT-amp (Anti-Triode) being built revintage Tubes / Valves 36 16th October 2008 06:01 AM
ESLDD with "anti-triode" revintage Tubes / Valves 27 4th October 2008 08:37 PM
Screen Driven Dissimilar Pentode SE Anti-Triode Spud kenpeter Tubes / Valves 2 26th July 2008 02:22 AM
Sepp? Tim Wyatt Tubes / Valves 4 27th April 2005 06:34 AM


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 © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2