Breaking my head over AC+DC heater reference - Page 3 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 21st March 2014, 12:35 PM   #21
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by grommeteer View Post
I like Ketje's solution.
If feeding all the filaments with DC is required, it is an option; however, it will also increase accordingly the peak rectified current waveforms, which the OP wanted to reduce. Depends on the priorities...
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪
  Reply With Quote
Old 21st March 2014, 02:29 PM   #22
diyAudio Member
 
Join Date: Apr 2012
Location: Kiel, Germany
This is Ketje´s idea - with a choke and an AC path for the more power hungry tubes.
Not sure about the snubber and the choke´s value, though.
Of course there is a reference from the DC heaters to the AC heaters. You are not free to connect/reference them in the way you ususally would.
The LM317 is not really needed, the DC voltage could just as well be adjusted with a choke of exactly the needed impedance, if line and load regulation is not what you want.
Attached Files
File Type: pdf AC_DC_heat.pdf (8.7 KB, 17 views)
  Reply With Quote
Old 21st March 2014, 08:46 PM   #23
Ketje is offline Ketje  Belgium
diyAudio Member
 
Join Date: Dec 2012
Location: Flanders
Oh no, not my idea at all.
If you take the 0V as a groundlevel the the 12V6 heater is pulsed by more then 30V positive.This is because a diode in the bridge is clamping one side to 0V = ground.
Mona
  Reply With Quote
Old 21st March 2014, 09:44 PM   #24
diyAudio Member
 
trobbins's Avatar
 
Join Date: Feb 2009
Location: Melbourne, Oz
Grommeteer, normally the choke is placed after the diode bridge, not before.

If a rectified and regulated DC is used for some of the valves using a bridge rectified supply, then it may be better to make the positive regulated output as the "0V", and make the 0V a negative regulated voltage terminal, as the new '0V' will provide a better 'balance' of the AC heater voltage around 0V. However, the AC heater voltage is only referenced to the 0V for a very short portion of each mains period when the diodes are conducting - otherwise it is floating, which is by far the majority of time.

Also probably worthwhile putting a capacitor across the AC heater winding, so that leakage inductance induced noise doesn't find the output valve heaters as the easiest path to take.
  Reply With Quote
Old 21st March 2014, 10:07 PM   #25
diyAudio Member
 
Join Date: Apr 2012
Location: Kiel, Germany
Trobbins, agreed.
The beauty of a choke supply is that the diodes will be forward biased for a greater portion of the time. I think what is called conduction angle is larger and current peaks are not as high as in a standard circuit.
  Reply With Quote
Old 21st March 2014, 10:18 PM   #26
sbrook is offline sbrook  Canada
diyAudio Member
 
Join Date: Feb 2007
Location: Ottawa Canada
Personally I'd go for a second tube / valve of the same type acting as a dummy for the 6.3V filament. Reason being is that the filament resistance changes as it gets hotter until it reaches stable. That can change the balance of the humdinger. Although, I do like the balanced approach of the resistor on either side of the 6.3 V tube.
  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
AC Heater reference to B+ toufu Tubes / Valves 14 4th February 2012 12:21 PM
dc and ac heater supply in Aikido Jaap Tubes / Valves 2 7th March 2010 08:08 PM
AC or grounded DC for heater? rouslan Tubes / Valves 1 18th August 2006 02:16 PM
heater voltage: why ac, and not dc? alex278 Tubes / Valves 18 7th October 2005 12:21 PM
AC or DC Heater? sauuuuuce Tubes / Valves 2 27th October 2004 12:57 PM


New To Site? Need Help?

All times are GMT. The time now is 03:17 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