F4 power amplifier - Page 299 - 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 27th January 2010, 01:31 PM   #2981
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Quote:
Originally Posted by Nelson Pass View Post
If you have a source which can drive 5 Kohm and a couple hundred pF,
you can dispense with the JFETs altogether and simply drive the Gates
of the Mosfets.

A little more work, and you can use a single pair of Mosfets and raise
the impedances of the bias circuit, and then it would be about 22K and 70 pF.

I would like to try without the JFET buffer and connect my Tube preamp (cathode follower output 12AU7) directly to MOS-FET output stage.

#1: Would there be any issues with bias setting (drift, optimal values, etc.) with one set of MOS-FETs? I would like to make bias selectable (low and high), where low would be for muzak and around 100-300mA...

#2: If the two 220uF capacitors are lifted from ground and connected to output terminal instead, they would bootstrap the input and making the input impedance higher (and load lighter for the preamp), correct?
  Reply With Quote
Old 27th January 2010, 01:47 PM   #2982
Zen Mod is offline Zen Mod  Serbia
diyAudio Member
 
Zen Mod's Avatar
 
Join Date: Jan 2003
Location: ancient Batsch , behind Iron Curtain
if that's plain Jane CF - just forget . in that case - leave buffer stage in .

you can find one pair mosfets output iteration on few first pages of thread .... bufferless little later
__________________
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
Old 27th January 2010, 04:31 PM   #2983
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Of course you could try it and see what you get.

  Reply With Quote
Old 27th January 2010, 04:58 PM   #2984
diyAudio Member
 
vitalstates's Avatar
 
Join Date: Jan 2006
Location: uk
Quote:
Originally Posted by diyray View Post
I can't find any info. other than 1 volt .05 (pre-out). Maybe it does I don't know. They don't give enough info. in the manual to know.

Onkyo Europe - PR-SC5507
here are some figures I took some time back...I can't remember why I did them so You'll have to take them as they are....they might address your question
Attached Files
File Type: doc test-op.doc (20.0 KB, 65 views)
__________________
There is nowhere you can be that isn't where you're meant to be
www.vitalstates.org
  Reply With Quote
Old 28th January 2010, 09:07 AM   #2985
Skorpio is offline Skorpio  Denmark
diyAudio Member
 
Join Date: Mar 2004
Location: Denmark
Quote:
Originally Posted by Nelson Pass View Post
Of course you could try it and see what you get.

I have tried and found the following up till now:

Standard: input impedance= 5k, gain approx. 0.93gg
Bootstrapped: input impedance= 64k, gain approx. 0.93gg

I have added a switch to be able to select between the two, but with my tube prestage bootstrapping is best.
Next step will be lowering the two 220uF input capacitors to 10uF PS

I will also like a switch to change bias from approv 1A to 0.3A, will this could operate without major problems during operation?
  Reply With Quote
Old 28th January 2010, 06:53 PM   #2986
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
No. But the DC offset is likely to change.

  Reply With Quote
Old 15th February 2010, 09:18 AM   #2987
generg is offline generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Hi Zen Mod,

why didn´t you tell me how wonderfull F4 with Pumpkin sounds.........?

.... in the moment F5 lies in the corner.
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 15th February 2010, 03:05 PM   #2988
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Zen Mod is a man of great modesty.

  Reply With Quote
Old 15th February 2010, 03:23 PM   #2989
generg is offline generg  Germany
diyAudio Member
 
generg's Avatar
 
Join Date: Jul 2009
Location: Near Frankfurt
Quote:
Originally Posted by Nelson Pass View Post
Zen Mod is a man of great modesty.

He will be happy to hear this from You!
__________________
and the First Wtt is......a really First Class PSS Idea
  Reply With Quote
Old 15th February 2010, 03:25 PM   #2990
diyAudio Member
 
Audiofanatic's Avatar
 
Join Date: Oct 2002
Location: The Netherlands, Utrecht
Default Zen Mod, Choky !

Quote:
Originally Posted by generg View Post
He will be happy to hear this from You!

He already know this

Best regards,

Audiofanatic
__________________
Be nice to animals.
  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
Rockford Fosgate Power 20001 bd amplifier power rating?? pachoorion Car Audio 8 8th May 2011 10:49 PM
Power transformers versus amplifier output power..what is your option? destroyer X Solid State 38 9th May 2009 05:23 PM
McIntosh Power Amplifier Power Guard johnnyrt Solid State 2 23rd August 2007 10:22 PM
Output power for a power amplifier Progg70 Solid State 33 10th September 2006 08:44 AM
Amplifier 3000 Wats Rms Power + Smps Higcht Power Bestiality MARAVILLASAUDIO Class D 1 5th November 2004 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 02:55 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