Switching off amplifier (dumb question inside) - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips

Construction Tips Construction techniques and tips

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 29th January 2010, 08:34 AM   #1
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Default Switching off amplifier (dumb question inside)

So fellas, I just thought about the following design "feat" of the amp I'm going to build. The power switch turns on the mains to the transformer which in turn powers the rest of the amp. Say I have like 50000F of caps in the power supply. Now if I switch off the amp, the mains get cut off BUT there is still plenty of charge inside the caps that may continue to power the amp for quite a while. How can I get rid of this? I want the amp to be dead silent when I turn it off.
  Reply With Quote
Old 29th January 2010, 09:11 AM   #2
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
Muting transistors
  Reply With Quote
Old 29th January 2010, 09:18 AM   #3
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Thanks, I got a private message that gave some insights how to do that: a set of relays that cut the power from the amp circuit as soon as the secondary's voltage is down.
  Reply With Quote
Old 30th January 2010, 02:26 AM   #4
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
If you are looking at relays to open the power rails, why not use the relay to simply open the speaker connection?
  Reply With Quote
Old 30th January 2010, 03:48 AM   #5
wwenze is offline wwenze  Singapore
diyAudio Member
 
Join Date: Mar 2008
Quote:
Originally Posted by Enzo View Post
If you are looking at relays to open the power rails, why not use the relay to simply open the speaker connection?
And this serves a double purpose of eliminating the on-off boom. Neat.
  Reply With Quote
Old 20th February 2010, 09:34 PM   #6
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Another dumb question. What relays should I use to prevent a possible degradation of the sound?
  Reply With Quote
Old 21st February 2010, 05:24 AM   #7
tomchr is offline tomchr  United States
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Greater Seattle Area
You should always have a bleeder across the supply caps. A bleeder is a large resistor that will drain the charge off the supply caps. Calculate the resistor following ohms law to ensure a current through the bleeder of about 10 mA.

To avoid the turn-on/off pops, use a relay on the speaker connection. Siemens makes some good ones. As does Omron. Look for one that can switch 10~20 A with gold or silver-nickel contacts.

~Tom
  Reply With Quote
Old 21st February 2010, 10:12 AM   #8
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Yes, bleeder resistors are included in my design. Thanks for the hint on the realys! I have two Omron relays here, capable of switching 20 amps: click me! Guess they're fine then. *happy*
  Reply With Quote
Old 21st February 2010, 10:19 AM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I'd suggest you look at the possibility of using input mute as well.

Then you have a number of options that can be added later.
DC detect, triggering the input mute.
Higher voltage dc detect triggering the output relay with latch that requires operator action to unlatch, eg switch off power.
__________________
regards Andrew T.
  Reply With Quote
Old 9th May 2010, 12:15 AM   #10
diyAudio Member
 
EBM_dude's Avatar
 
Join Date: Aug 2009
Location: Germany
Good idea! 8-)
  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
Dumb question? Phil Olson Multi-Way 3 23rd October 2009 07:52 PM
Switching power supply inside NAD S170 (110V to 220V) yoke Parts 3 14th February 2009 10:58 AM
Dumb question, but... johnm Tubes / Valves 3 13th June 2008 10:14 PM
Dumb question. G Tubes / Valves 2 16th January 2008 08:16 PM
maybe this is too dumb a question... dannyspencer Solid State 6 18th April 2004 04:57 PM


New To Site? Need Help?

All times are GMT. The time now is 08:43 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