A40 Clipping Point - 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 May 2014, 01:08 AM   #1
diyAudio Member
 
Join Date: Jun 2007
Default A40 Clipping Point

Can someone help with understanding Clipping in Pass A40? Feeding a 1khz signal into a 5.5 ohm resistor. The amp puts out 19.8 vrms when it justs starts clipping. The voltage rails are at +/- 31vdc. Don't think anything is wrong just want to understand the math.
  Reply With Quote
Old 23rd May 2014, 01:27 AM   #2
diyAudio Member
 
Join Date: Nov 2009
E squared over load or 19.8 x 19.8 = 392 divided by 5.5 = 71.28 watts
  Reply With Quote
Old 23rd May 2014, 02:56 AM   #3
diyAudio Member
 
Join Date: Jun 2007
Yes I understand that. I'm running dual mono with 650VA xfmr's per side. So surely my supply voltage isn't sagging at the 19.8 volts correct? I realize I'm dropping some across the emitter resisters but only about 6.5vdc per channel. Again just want to understand the specifics. BTW power supply is CLC. Might need to look across inductors.
  Reply With Quote
Old 23rd May 2014, 03:11 AM   #4
diyAudio Member
 
Loudthud's Avatar
 
Join Date: Nov 2007
Location: Near Dallas Texas USA
19.8 VRMS is 28V Peak. So it seems your amp is operating normally.
  Reply With Quote
Old 25th May 2014, 08:58 AM   #5
AndrewT is online now AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
find info on
Vpk (peak voltage of an AC signal)
Vpp (peak to peak voltage of an AC signal, measured by reading the oscilloscope waveform)
Vac (the measured voltage using an AC voltmeter)
Vrms (the heating effect of the AC waveform)
Vdc (the steady voltage from direct current supply or load)
Vripple (the variation of voltage on a nominal DC supply).

Then read about sinewave signal and how to convert from/to Vac, Vrms, Vpk, Vpp
__________________
regards Andrew T.

Last edited by AndrewT; 25th May 2014 at 09:00 AM.
  Reply With Quote
Old 25th May 2014, 10:32 AM   #6
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 Freecrowder View Post
Can someone help with understanding Clipping in Pass A40? Feeding a 1khz signal into a 5.5 ohm resistor. The amp puts out 19.8 vrms when it justs starts clipping. The voltage rails are at +/- 31vdc. Don't think anything is wrong just want to understand the math.
lazy to calc exact losses across mosfet-Rs combo in peak , but assume that you're having 60V clean PSU , including losses resulting in some 55Vpp sine

then divide with 2 to have Vp

then divide with 1.41 (root of 2) to have Vrms

P=(Vrms^2)/R

so , P = (((55/(2 x 1.41))^2)/8=47W

incidentally , that's exactly around 19.5Vrms

disclaimer - I really don't care how much Wpeak is that

__________________
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 25th May 2014, 11:31 AM   #7
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 Zen Mod View Post
......exact losses across mosfet-Rs......
meaning , of course , about bjt-Re , but I'm sure that everyone is already accustomed on Mighty ZM's brainfarts

__________________
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
Lots of craziness (weird noises and osc) happening in point to point 5W EL84 Amp 777funk Instruments and Amps 17 2nd March 2014 06:20 PM
Point 2 Point (no PCB) for TDA7293, TDA7294, TDA7295, TDA7296. danielwritesbac Chip Amps 149 10th July 2013 08:18 PM
SE guitar amp - point to point with vvr jeffe Swap Meet 2 5th November 2011 04:02 PM
Recovery from clipping, soft clipping hahfran Solid State 49 23rd February 2010 01:03 AM
Audio Note's Kit One done in point-to-point wiring Wram Tubes / Valves 18 29th April 2003 10:59 PM


New To Site? Need Help?

All times are GMT. The time now is 03:58 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