F6 Amplifier - Page 106 - diyAudio
Go Back   Home > Forums > Amplifiers > Pass Labs

Pass Labs This forum is dedicated to Pass Labs discussion.

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 23rd August 2012, 06:51 PM   #1051
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally Posted by kasey197 View Post
has anyone figured out yet why two voltage rails for output stage vs input stage ?
I am making an allowance for dissipation ratings of the input Jfets. Their
bias figure is not degenerated, so with some devices the current can get
pretty high. Also, this design can be run at higher rail voltages, maybe too
high for those inputs.

  Reply With Quote
Old 23rd August 2012, 07:12 PM   #1052
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
Originally Posted by Antoinel View Post
Why burden your circuit with negative feedback? Without NFB, the output stage is Circlotronic, has high power [value?], and low distortion [value?]. What else are you seeking? Most probably you'll say a low output impedance; but where will its physical location be ? Will the low output impedance be at the junction of the power supplies and/or the joint between the source of upper JFET and the drain of lower JFET. Your thoughts!
You will see my answer soon. Circlotrons work with or without negative feedback, your choice.
  Reply With Quote
Old 23rd August 2012, 07:17 PM   #1053
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Quote:
Originally Posted by kasey197 View Post
on a completely different note - has anyone figured out yet why two voltage rails for output stage vs input stage ? It can't be something trivial given that they are shown as distinct in the simplified schematic. Any clues anyone ?
Mr. Pass, maybe throw us a bone or two ? )
First, I agree with Ihquam. As Papa has said, driving these transformers takes the lowest output Z for best results. Of coarse exactly what your trying to do is important also... for the complementary buffer to have the lowest output impeadance, you would want to use the Highest IDss parts you can. Some may argue but, that will ussually mean the highest transconductance. That will create the lowest output Z. If you are selecting 10mA or higher Idss parts, you probably want to keep the voltage down and the /part Pd to 100-120mW.
This low output Z thing is passed through the transformer (sometimes said to be reflected) to generate a source impeadance that drives the output FETs. The function is Buffer out Z * turns ratio^2 = Secondary output Z or the source impeadance the FETs sees.
Guess I'm a little late??
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 23rd August 2012, 08:09 PM   #1054
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Quote:
Originally Posted by lhquam View Post
You will see my answer soon. Circlotrons work with or without negative feedback, your choice.
Your circuit is special. I am glad you continue to unravel its potential.
  Reply With Quote
Old 23rd August 2012, 08:22 PM   #1055
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Default Balanced F6

Here is an F6 design that is fully symmetric in the spirit of a circlotron. The output power supplies float relative to ground, but not relative to each other. The harmonic distortion is primarily 3rd order. It will accept either balanced or unbalanced inputs.

I have simulated it with LTSpice and it looks very good.

The power spectrum plot in for 1 watt output at 1kHz into 8 ohms.
Attached Images
File Type: jpg F6B-v1b-bal-2-cleaned.jpg (140.1 KB, 347 views)
File Type: jpg F6B-v1b-bal-2-cleaned-AC.jpg (171.3 KB, 343 views)
File Type: jpg F6B-v1b-bal-2-cleaned-ps.jpg (134.6 KB, 334 views)
  Reply With Quote
Old 23rd August 2012, 08:35 PM   #1056
diyAudio Member
 
buzzforb's Avatar
 
Join Date: Oct 2010
Location: Burlington, NC
Quote:
Originally Posted by Nelson Pass View Post
I am making an allowance for dissipation ratings of the input Jfets. Their
bias figure is not degenerated, so with some devices the current can get
pretty high. Also, this design can be run at higher rail voltages, maybe too
high for those inputs.

How do you control offset? A pot will have a degenerative effect, correct.
__________________
...Shape the sound , Man!
  Reply With Quote
Old 23rd August 2012, 10:01 PM   #1057
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Quote:
Originally Posted by lhquam View Post
Here is an F6 design that is fully symmetric in the spirit of a circlotron. The output power supplies float relative to ground, but not relative to each other. The harmonic distortion is primarily 3rd order. It will accept either balanced or unbalanced inputs.

I have simulated it with LTSpice and it looks very good.

The power spectrum plot in for 1 watt output at 1kHz into 8 ohms.
Whao; you have a creative development. Is the underlined mean that your circuit satisfies the requirements of a "genuine" Circlotron?
  Reply With Quote
Old 23rd August 2012, 10:07 PM   #1058
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Quote:
Originally Posted by buzzforb View Post
How do you control offset?
I reference the positive half DC values to ground.

  Reply With Quote
Old 23rd August 2012, 10:12 PM   #1059
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
Originally Posted by Antoinel View Post
Whao; you have a creative development. Is the underlined mean that your circuit satisfies the requirements of a "genuine" Circlotron?
The only difference from a circlotron that I know about is the position of the power supply V1 relative to the output FET.
  • In my circuit, there is the clockwise loop: Rload - V1 - R4 - J3
  • In a circlotron the loop is: Rload - R4 - J3 - V1
All remains the same (except the bottom of the bias circuit remains attached to the bottom of R4).
  Reply With Quote
Old 23rd August 2012, 10:18 PM   #1060
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
Originally Posted by Nelson Pass View Post
I reference the positive half DC values to ground.

Like this?
Attached Images
File Type: jpg F6B-v1b-bal-2-cleaned3.jpg (157.2 KB, 323 views)
  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
New F6 diy coming soon ? Nounours18200 Pass Labs 37 31st August 2012 05:35 PM
Hi Vi F6 box ioro Multi-Way 4 15th April 2012 09:27 PM
Whats happening with F6? jugoslavija Pass Labs 1 1st November 2011 08:39 AM
Hi-Vi F6 kkosiba Multi-Way 14 9th November 2007 09:38 AM
F6 traw Pass Labs 7 2nd November 2007 08:09 PM


New To Site? Need Help?

All times are GMT. The time now is 01:33 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