Phase of Pass Labs amps! - 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 March 2004, 08:15 PM   #1
diyAudio Member
 
Join Date: Jan 2004
Location: Croatia
Lightbulb Phase of Pass Labs amps!

Long time ago I red an Accuphase's article on the net. It said that the phase (or degree of phase inversion) is of most importance for the correct reproduction of instruments timbre. In Nelsons writings I didn't saw anything about phase invertion at the ends of frequency response (high and low frequencies). One University did a research on how do we react on inverted phase below 100Hz, and they said we hear that as unnatural sound, even unrecognizeable. Can someone (maybe Nelson) tell me something more about that in Pass Labs amplifiers. I would also like to hear your opinions on this subject.
  Reply With Quote
Old 23rd March 2004, 08:28 PM   #2
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
Pass Labs products do not invert phase, although the
original Zen design (not a real product) explicitly does.
  Reply With Quote
Old 23rd March 2004, 08:59 PM   #3
diyAudio Member
 
Join Date: Jan 2004
Location: Croatia
How do you achieve that? I mean, is phase invertion something you are trying to avoid in an amplifier with adding something in a circuit, or there just isn't phase invertion because of a good circuit construction?
  Reply With Quote
Old 24th March 2004, 01:17 PM   #4
diyAudio Member
 
Join Date: Jan 2004
Location: Croatia
Default What about phase distortion?

Is "phase distortion" similar to "phase invertion"? Somewhere on this forum I red that some Pass amps and preamps have phase distortion of 5 degrees. Is that true? Can that be void? Is it important at all for the music reproduction?
  Reply With Quote
Old 24th March 2004, 01:51 PM   #5
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
Are you perhaps asking about phase shift rather than phase inversion?
  Reply With Quote
Old 24th March 2004, 02:17 PM   #6
diyAudio Member
 
Join Date: Jan 2004
Location: Croatia
yes (I guess)! I don't know the proper word. What is the phase shift? Give me just brief explanation!
  Reply With Quote
Old 24th March 2004, 05:12 PM   #7
uli is offline uli  Austria
diyAudio Member
 
Join Date: Dec 2002
Location: Vienna, Austria
Default phase shift

Hi,

an ideal amp with a frequency range of Zero to Infinite

wil have theoretically zero degrees of phase shift.

If you insert poles you get some degree of phase shift:

the input dc-blocking caps add some phase shift to the

lower range of the signal. therefore good designs start

either at pure dc (e.g. X1000) or at the lowest possible

frequency. this cap produces 45° phase shift at its pole

frequency. the same is true for the upper end of the ampīs

range. therefore designers try to make these poles about

the factor 10 away from the audible range thus reaching

phase shift which is very lo, about 5 degrees or so

An amp with ideal square wave reproduction (0 - oo Hz)

does not necessarily sound perfect. this means that in

real life you always have to accept imperfect solutions

the art of design lies in the perfect blend of those imperfections

just as e.g. a SE power amp with one 300B or an Aleph 2!

Uli

__________________

'Jazz is not dead, it just smells funny' F.Zappa
  Reply With Quote
Old 24th March 2004, 05:22 PM   #8
diyAudio Member
 
Join Date: May 2001
Blog Entries: 5
Very lucid explanation, Uli
  Reply With Quote
Old 24th March 2004, 05:44 PM   #9
uli is offline uli  Austria
diyAudio Member
 
Join Date: Dec 2002
Location: Vienna, Austria
tx!

Uli

__________________

'Jazz is not dead, it just smells funny' F.Zappa
  Reply With Quote
Old 24th March 2004, 06:27 PM   #10
diyAudio Member
 
Join Date: Jan 2004
Location: Croatia
What about Aleph 5? I didn't find any info. Is there any way to minimise phase shift in this circuit without making it sound worse?

PS: Thanks for nice explanation!
  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
fullrange speakers and Pass labs amps MikeW Pass Labs 41 23rd March 2008 11:59 AM
Powercords and effects on Pass Labs amps mert Pass Labs 19 5th July 2007 11:12 PM
Recommend a Good Preamp for Pass Labs Amps misterdoggy Pass Labs 4 20th January 2007 04:43 PM
My opinion on Pass Labs and Mr. Pass (Nelson) himself b_online Pass Labs 11 21st May 2003 12:39 AM


New To Site? Need Help?

All times are GMT. The time now is 07:35 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2