Breaking my head over AC+DC heater reference - 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 16th March 2014, 03:38 PM   #1
diyAudio Member
 
funk1980's Avatar
 
Join Date: Sep 2011
Location: Groningen
Default Breaking my head over AC+DC heater reference

Can this be done:
I have a transformer with just one 12.6V winding. I really want the first stage's heater supply to be DC (6.3V) for noise reasons. The second stage (2x ECC99 PP) draws so much current that regulating is impractical and AC is fine there anyway. Is it possible to properly use one winding for both regulated DC and AC?? How about ground reference. Charging peaks etc.
  Reply With Quote
Old 16th March 2014, 03:59 PM   #2
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
how much current you want on the 6.3V filament?
LM317 constant current source from rectified and filtered 12.6
all floating, may be a problem if the 1st stage is a rectifier at B+
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust

Last edited by infinia; 16th March 2014 at 04:09 PM.
  Reply With Quote
Old 16th March 2014, 05:21 PM   #3
diyAudio Member
 
funk1980's Avatar
 
Join Date: Sep 2011
Location: Groningen
Reading black my own post, I probably should have mentioned that the transformer only has one heater winding. There's one for B+ as well.
I need 6.3V @ 300mA DC and 12.6V @ 800mA AC from the same winding.
  Reply With Quote
Old 16th March 2014, 05:36 PM   #4
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
rectify 12.6 either full or half wave and run a LM317 and 4.7 ohm to set a constant 270 mA into the 6.3 filament, heat sink on LM317.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 16th March 2014, 05:39 PM   #5
diyAudio Member
 
KatieandDad's Avatar
 
Join Date: Nov 2011
Location: UK
A linear regulator would indeed waste a lot of the available power.

Why not try a buck regulator which would be much more efficient.
  Reply With Quote
Old 16th March 2014, 05:44 PM   #6
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
yes tubes waste a lot of heat too ,
I'd imagine trying save power, little here and there isn't their priority esp if quiet DC filament power.
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust
  Reply With Quote
Old 16th March 2014, 06:01 PM   #7
diyAudio Member
 
funk1980's Avatar
 
Join Date: Sep 2011
Location: Groningen
Quote:
Originally Posted by infinia View Post
rectify 12.6 either full or half wave and run a LM317 and 4.7 ohm to set a constant 270 mA into the 6.3 filament, heat sink on LM317.
Yes, that's what I did. And I tied the DC 0V line to the GND of the rest of the circuit for reference. But I'm getting a lot of 50Hz interference and suspect the culprit being the unbalanced AC heater wiring. The AC before the rectifier is no longer a nice sine wave and I don't see a way to balance/ reference it.

Buck SMPS is a bit out of my comfort zone at the moment
  Reply With Quote
Old 16th March 2014, 06:07 PM   #8
infinia is offline infinia  United States
diyAudio Member
 
infinia's Avatar
 
Join Date: May 2005
Location: Californication
cant you float the whole filament string and run the LM317 straight from 12.6 using full wave and a tiny cap for lower distortion?
using half wave cuts one side of the sine trading distortion for a just a little power saving. so bad for balance. full wave use a very small filter cap and a little series R
__________________
like four million tons of hydrogen exploding on the sun
like the whisper of the termites building castles in the dust

Last edited by infinia; 16th March 2014 at 06:36 PM.
  Reply With Quote
Old 16th March 2014, 06:16 PM   #9
Elvee is offline Elvee  Belgium
diyAudio Member
 
Elvee's Avatar
 
Join Date: Sep 2006
Quote:
Originally Posted by funk1980 View Post
Yes, that's what I did. And I tied the DC 0V line to the GND of the rest of the circuit for reference. But I'm getting a lot of 50Hz interference and suspect the culprit being the unbalanced AC heater wiring. The AC before the rectifier is no longer a nice sine wave and I don't see a way to balance/ reference it.

Buck SMPS is a bit out of my comfort zone at the moment
Here is a "creative" solution: it is not too wasteful, it remains balanced, and all filaments share a common that may be grounded if desired.

I assume the 12.6V filaments F1, F2 have a CT.
F3 is the 6.3V 300mA filament. The current can be fine-tuned with R5.

R4 is a dummy load, required to rebalance the bridge formed by the two high current filament.
The dissipation is the same as in the low-power filament, which is still tolerable
Attached Images
File Type: png SmartHeat.png (85.5 KB, 113 views)
__________________
. .Circlophone your life !!!! . .
♫♪ My little cheap Circlophone© ♫♪

Last edited by Elvee; 16th March 2014 at 06:19 PM.
  Reply With Quote
Old 16th March 2014, 06:46 PM   #10
DF96 is offline DF96  England
diyAudio Member
 
Join Date: May 2007
Difficult. You somehow have to stop rectifier hash, charging pulses etc. from the DC supply getting onto the AC supply for the ECC99 - because this noise will be worse than simple AC.

Does the 12.6V winding have a CT? If so, it can be done by producing a bipolar DC supply (e.g. +-8Vish after rectification and smoothing) with the CT grounded.
  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 01:21 PM
dc and ac heater supply in Aikido Jaap Tubes / Valves 2 7th March 2010 09:08 PM
AC or grounded DC for heater? rouslan Tubes / Valves 1 18th August 2006 03:16 PM
heater voltage: why ac, and not dc? alex278 Tubes / Valves 18 7th October 2005 01:21 PM
AC or DC Heater? sauuuuuce Tubes / Valves 2 27th October 2004 01:57 PM


New To Site? Need Help?

All times are GMT. The time now is 11:28 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