My F5T V3 build - Page 8 - 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 26th October 2012, 10:20 AM   #71
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
What is the current draw of the ClassA amplifier?
Now at the instant you pull the mains plug from the mains supply socket, what is the current draw of the ClassA amplifier.
Now take a guess at how slowly, or how quickly the smoothing capacitors will discharge.

Why do you need to add extra resistors to draw more current from the PSU?
Put your thinking cap on.
__________________
regards Andrew T.
  Reply With Quote
Old 26th October 2012, 11:06 AM   #72
flg is offline flg  United States
diyAudio Member
 
flg's Avatar
 
Join Date: Jul 2005
Location: North East
Bleeders are still a good safety measure. let's say the amp needs trouble shooting? You are not garunteed the supply will discharge it's caps and could get burnt, blinded, etc. It's only a few mA extra draw vs. Amps for the output section.
__________________
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 26th October 2012, 11:13 AM   #73
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally Posted by flg View Post
Bleeders are still a good safety measure.
so good? I have never seen the need for them and despite my reputation for safety have never used them.

I have looked at relay connected discharge resistors that ONLY connect AFTER power down. That is a quite different topology.
__________________
regards Andrew T.
  Reply With Quote
Old 26th October 2012, 11:21 AM   #74
Nikitas is offline Nikitas  Greece
diyAudio Member
 
Join Date: Nov 2011
Location: Amsterdam
"I have looked at relay connected discharge resistors that ONLY connect AFTER power down. That is a quite different topology."


Like?
  Reply With Quote
Old 26th October 2012, 11:25 AM   #75
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
They don't conduct while the amp is operational.
They don't get warm/hot.
They don't increase current draw.

They do conduct when required.
They do discharge high voltage capacitors in a controlled way.

I even bought lots of 24V tungsten bulbs to gain some advantage in non linear resistance characteristic as the capacitor voltage drops.
__________________
regards Andrew T.
  Reply With Quote
Old 26th October 2012, 11:31 AM   #76
Nikitas is offline Nikitas  Greece
diyAudio Member
 
Join Date: Nov 2011
Location: Amsterdam
No, I meant do you have an example of a circuit. I haven't seen something like that so far.
  Reply With Quote
Old 26th October 2012, 01:35 PM   #77
diyAudio Member
 
Join Date: Mar 2003
Location: midwest
Quote:
Originally Posted by AndrewT View Post
What is the current draw of the ClassA amplifier?
Now at the instant you pull the mains plug from the mains supply socket, what is the current draw of the ClassA amplifier.
Now take a guess at how slowly, or how quickly the smoothing capacitors will discharge.

Why do you need to add extra resistors to draw more current from the PSU?
Put your thinking cap on.
I never thought of it that way but it explains a lot. On my Tube amps with large power supplies or various Class A/B amps, I would always wait a period of time after switching off the power amp before switching off the pre amp. As they would continue to play after switch off otherwise, I always thought this was a good idea for bleeder resistors. With the F-5, I always noted it was "Dead" immediately with switching it off, and immediate switching off of the preamp caused not a sound.

I would imagine it bleeds off almost immediately. I have noted several have noted in F-5 builds these bleeders werent necessary, now I know why.

Russellc
__________________
Pass DIY B-1, Pass DIY F-5
  Reply With Quote
Old 26th October 2012, 01:48 PM   #78
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Quote:
Originally Posted by Odysseas View Post
No, I meant do you have an example of a circuit. I haven't seen something like that so far.
I wouldn't have said it was exactly hard...

Drive the relay with the secondaries of the transformer which switch the caps power to the amp or through the bleed resistors. This gives a much more controlled power down of the amps too and eliminates the possibilities of one rail draining faster than the other.
__________________
I thought about it once, but then thought again.
  Reply With Quote
Old 26th October 2012, 01:57 PM   #79
Nikitas is offline Nikitas  Greece
diyAudio Member
 
Join Date: Nov 2011
Location: Amsterdam
"Oh really?"
Well have you done it?
  Reply With Quote
Old 26th October 2012, 02:00 PM   #80
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Quote:
Originally Posted by Odysseas View Post
"Oh really?"
Well have you done it?
What's your problem I'm trying to help!?
__________________
I thought about it once, but then thought again.
  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
GB for F5T Convertible amplifier boards Tea-Bag Group Buys 127 13th July 2014 06:48 PM
F5T Premium kit GB buzzforb Group Buys 646 18th May 2014 09:34 PM
V3 trident coolhead Twisted Pear 7 14th March 2012 02:18 PM
Lepai V3 with TDA8566 Electro-Chip Chip Amps 4 3rd January 2012 05:04 PM
LAB Subwoofer v3.0 hulkss Subwoofers 3 23rd May 2004 08:27 PM


New To Site? Need Help?

All times are GMT. The time now is 08:35 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