F6 Amplifier - Page 126 - 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 29th August 2012, 02:01 PM   #1251
diyAudio Member
 
Join Date: Jan 2012
Location: Pennsylvania
Blog Entries: 1
Quote:
Originally Posted by lhquam View Post
I think I have stumbled onto the secret of the F6.
.
Parastroika! I understood it [back in the 1980s] to mean openess which you are doing.
  Reply With Quote
Old 29th August 2012, 07:12 PM   #1252
diyAudio Member
 
bobodioulasso's Avatar
 
Join Date: May 2008
R2=1k looks very strange.
What signal is left to the primary?

Last edited by bobodioulasso; 29th August 2012 at 07:16 PM.
  Reply With Quote
Old 29th August 2012, 08:34 PM   #1253
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
Originally Posted by bobodioulasso View Post
R2=1k looks very strange.
What signal is left to the primary?
My stupidity! The THD numbers were correct, but I neglected to notice that the output voltage was being reduced approximately by the ratio of the Z/(Z+R2||R1) where Z is the transformer impedance.

In fact, impedance curves show just the opposite: the input driver impedance should be low in order to flatten the output frequency response curve. In earlier posts, Zen Mod discussed the importance of secondary loading. Here is the transformer V(sec)/Vin vs frequency for different values of Rsec. From bottom to top they are 100R, 200R, 500R, 2K, 1meg. At 100R, the 20 Hz rolloff is only -.18dB vs. -.47dB with an Rsec=1meg. Unfortunately, secondary loading also reduces the open-loop gain.
Attached Images
File Type: jpg JT123-sec-load-bode.jpg (137.5 KB, 367 views)
  Reply With Quote
Old 29th August 2012, 10:16 PM   #1254
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
sim/calculate for prototype

then listen and measure

accent on listen

my remarks about importance of secondary loading are staying carved in stone , but if Pa is saying that SS gate impedance is low enough and flat enough for exact Jensen type , I would not argue for a second

especially if I'm not having Jensens on hand
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM

Last edited by Zen Mod; 29th August 2012 at 10:22 PM.
  Reply With Quote
Old 29th August 2012, 11:48 PM   #1255
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Quote:
Originally Posted by Zen Mod View Post
sim/calculate for prototype

then listen and measure

accent on listen

my remarks about importance of secondary loading are staying carved in stone , but if Pa is saying that SS gate impedance is low enough and flat enough for exact Jensen type , I would not argue for a second

especially if I'm not having Jensens on hand
Those Jenson trannies seem to be very good. Here are scope photos of the square wave response.

The first image is for a 1MHz square wave from a 50 ohm generator directly into both primaries and no load on the secondaries. The bottom trace is voltage across the primary. The top trace is voltage across the secondary. Horizontal scale is .2us/div.

The second image is for a 100kHz square wave from a 50 ohm generator directly into both primaries and 1nF load on the secondaries (similar to the SS100 JFETs). The bottom trace is voltage across the primary. The top trace is voltage across the secondary. Horizontal scale is 2us/div. There are some artefacts, but I would not call it ringing.

Is that a good transformer?
Attached Images
File Type: jpg DSC_0365.jpg (150.4 KB, 331 views)
File Type: jpg DSC_0366.jpg (168.9 KB, 322 views)
  Reply With Quote
Old 30th August 2012, 02:31 AM   #1256
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Does anyone know how much DC current through the transformer primary can be tolerated without added distortion? The question is motivated by the issue of the input JFETs not necessarily being well matched in IDSS. A potentiometer could be added to trim the input stage offset voltage at the cost of increasing the impedance driving the transformer.
  Reply With Quote
Old 30th August 2012, 03:55 AM   #1257
lhquam is offline lhquam  United States
diyAudio Member
 
Join Date: Mar 2010
Location: Olalla, Oregon: Land of the 100 Valleys
Here is a plot of open-loop gain vs. frequency. Too much roll-off at high frequencies for a no feedback amplifier.


Quote:
Originally Posted by buzzforb View Post
I have a fondness for no feedback designs. Try it without any and see if it is stable. Should be able t run the Pspice pretty easy, as you seem to be the bloody master of that program. DF wont be good, but plan to use it on FR with another amp driving woofers.
Has crazy, ridiculous thought today. OPa1632 feeding transformer. Fully differential input stage is definitely overcomplicated
Attached Images
File Type: jpg F6-R100-vb6-olg-bode.jpg (174.0 KB, 282 views)
  Reply With Quote
Old 30th August 2012, 05:57 AM   #1258
diyAudio Member
 
triode_al's Avatar
 
Join Date: May 2004
Location: Westland
Blog Entries: 1
Quote:
Originally Posted by lhquam View Post
Is that F5 nein?
Fsechs nein nein -the moderator does not accept that
__________________
DAC TDA1541 S1; Kondo post-I/V filter; MC30-Super --> two stage RIAA; Pre: SP-6 clone ; F5 ; 300B PP ; ESL 57

Last edited by triode_al; 30th August 2012 at 06:00 AM.
  Reply With Quote
Old 30th August 2012, 07:50 AM   #1259
diyAudio Member
 
bobodioulasso's Avatar
 
Join Date: May 2008
Some square waves from the output of your proto, Ihquam?
  Reply With Quote
Old 30th August 2012, 08:45 AM   #1260
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
Quote:
Originally Posted by lhquam View Post
Does anyone know how much DC current through the transformer primary can be tolerated without added distortion? The question is motivated by the issue of the input JFETs not necessarily being well matched in IDSS. A potentiometer could be added to trim the input stage offset voltage at the cost of increasing the impedance driving the transformer.
do not bother yourself - just make input buffer careful as usual
__________________
my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
  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 04:35 PM
Hi Vi F6 box ioro Multi-Way 4 15th April 2012 08:27 PM
Whats happening with F6? jugoslavija Pass Labs 1 1st November 2011 07:39 AM
Hi-Vi F6 kkosiba Multi-Way 14 9th November 2007 08:38 AM
F6 traw Pass Labs 7 2nd November 2007 07:09 PM


New To Site? Need Help?

All times are GMT. The time now is 02:25 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