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 7th July 2008, 11:37 PM   #1
NV&H is offline NV&H  United States
diyAudio Member
 
Join Date: Feb 2005
Location: Charlotte, North Carolina
Default What's the Idle Current of the F5 Power Amp

In his AudioXpress article, Nelson wrote that a power supply with a 6 amp continuous rating is needed. Does that mean that when the thing is powered up with no input signal, it's drawing that much?

Perhaps it draws less than that at idle with the 6 amp specified to ensure reliability?
__________________
NV&H
  Reply With Quote
Old 8th July 2008, 12:55 AM   #2
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
1.3A, with +/-24Vdc rails makes ~62.5W dissipation per channel.

It's a Class A power amp, so you want the PS to have a nominal power rating a couple of times as much.
The F5 is also a Push-Pull design with an output stage that is strong enough to deliver a lot of peak current, another reason for desiring a bulky powersupply.
Read the first 15 to 20 pages of the F5 thread for continuous and peak current rating of the PS.
  Reply With Quote
Old 8th July 2008, 12:56 AM   #3
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
The rating refers to the capacity of the secondary windings.

The draw of the amplifier is about 80 watts per channel at idle,
which results in an (rms) draw of about 1.5A from the wall
at 120V for 2 channels. In Paris, that would be more like 0.75A.
  Reply With Quote
Old 8th July 2008, 07:20 AM   #4
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
180W as in 2 x 62.5W x sqrt2.
  Reply With Quote
Old 8th July 2008, 10:52 AM   #5
MEH is offline MEH  United States
diyAudio Member
 
Join Date: Feb 2007
Where'd the sqrt2 come from?
  Reply With Quote
Old 8th July 2008, 12:18 PM   #6
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
Smoking Californian oak ?

The F5 manual reads 1.3A per leg, 25Vdc rails max, 62W dissipation per channel, makes 124W for stereo.
But also : power consumption = 180W and slow fused for 300W Max.

The amp is supposed to do 10A peak, 10A times 18V rms= 180W.
(if you add the bridge rectifier dissipation it becomes 133W/stereo)
  Reply With Quote
Old 8th July 2008, 02:06 PM   #7
The one and only
 
Nelson Pass's Avatar
 
Join Date: Mar 2001
You're right, 60 watts. I had 1.6A stuck in my head.
  Reply With Quote
Old 8th July 2008, 02:54 PM   #8
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
If only,

none of the F5 scavengers noticed that the mains fuse is rated at 2.5A.
The production F5 has 1 transformer and 1 fuse, means the power supply is sized at 180VA to 225VA Max for both channels.

Basically means the F5 is dimensioned for 4 Ohm use : 20V rails /(4+0.47)~ 4.5A peak aka ~3.15A continuous.
3.15A times 25Vdc per channel times 2 comes to ~160VA, with a little cherry on top makes 180VA.

For 2 Ohm use the peak output current would be around 8A, makes ~5 3/4A continuous, results in a single 300VA transformer for both channels.
Some already indicated to use a 800VA biggy for the F5 they're assembling, they'll probably laugh at a 50W Accuphase P102 Class A amp that runs on a chicken-leg 160VA transformer per channel.
  Reply With Quote
Old 9th July 2008, 01:26 AM   #9
Formerly "jh6you". R.I.P.
 
Babowana's Avatar
 
Join Date: Jul 2006
Thanks, Jacco.
Helpful info!
  Reply With Quote
Old 9th July 2008, 01:30 AM   #10
diyAudio Member
 
mpmarino's Avatar
 
Join Date: Jun 2004
Location: Crunchville, where I don't fit in.
Quote:
I had 1.6A stuck in my head.
Yeah.... I hate it when the dang Grado short circuits.

__________________
Crazy Yankee.
  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
Idle current adjustment for NAD gvelim Solid State 0 5th August 2008 03:56 AM
nad 3020b idle current reddish75 Solid State 4 4th July 2008 02:46 PM
idle current for bryston 4B Danielll Solid State 2 3rd October 2005 05:25 PM
chip amp idle current maylar Chip Amps 2 29th December 2004 03:25 PM
XM-1502SX Idle Current sdoom Solid State 1 9th July 2004 07:35 AM


New To Site? Need Help?

All times are GMT. The time now is 01:29 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