Sizing a Regulator - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 May 2005, 07:35 PM   #1
diyAudio Member
 
Join Date: Dec 2003
Location: Denver, CO
Default Sizing a Regulator

Is there any down side to using a larger sized regulator chip? I need 1.2 amps for the heaters I'm planning to feed, which seems a bit close to the 1.5 amp limitation of the LT1086. Is it OK to use the 3 amp LT1085? I don't know if that means a larger heat sink requirement, or what, but I'll bet that somebody here does. Thanks!
  Reply With Quote
Old 17th May 2005, 01:31 AM   #2
Stocker is offline Stocker  United States
diyAudio Member
 
Join Date: Dec 2003
Location: Austin
You may need to waste a very small amount of electricity as heat in order to achieve minimum current required to regulate properly with your powered circuits idle. Do not worry too much about a larger regulator unless its datasheet says not to use it for low currents.
__________________
Jesus loves you.
  Reply With Quote
Old 17th May 2005, 01:40 AM   #3
hermanv is offline hermanv  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Northern California
Default Heater Inrush

Seems I recall that vacuum tube filaments have very large inrush currents, so make sure the regulator you use is safely current limited. With current limiting heaters will take longer to stabilize but tube life will possibly improve.

Tube fans; someone verify my recollection of filament inrush current at 10 to 1?
  Reply With Quote
Old 17th May 2005, 01:47 AM   #4
diyAudio Member
 
Tom Bavis's Avatar
 
Join Date: Jun 2002
Location: Macedon NY
3 to one is more like it, though some may be worse... current limiting will slow warmup, may haelp life.
  Reply With Quote
Old 17th May 2005, 01:50 AM   #5
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Dr. Ruth said that size doesn't matter but you probably aren't old enough to remember that. I think that Helen Gurley Brown had a different opinon.

Don't forget that the regulator has its own "overhead" -- some voltage which is going to get chewed and spewed out as heat -- depends upon whether it's low dropout regulator, or the garden variety 7812 etc.

Have you considered just using a beefed up zener (i.e. a zener on the base of the transistor and a little bias current) -- there really is no need for "regulation" per se since the load on the tube filament is invariant.
  Reply With Quote
Old 17th May 2005, 04:55 AM   #6
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
An optional Plan B,
Allen Wright in his Tube Preamp CookBook recommends using separate LM317 as CURRENT regulator for each tube heater. A small, device mounted, heatsink will then suffice. No switch on surge to worry about. Having said that, I don't remember when I last changed a tube because the heater had gone open circuit so I don't believe switch on surge is a major problem for tube heaters. Don't worry about power tubes - just run them from the 6.3V AC.
Cheers,
Ian
  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
Help sizing psu smoothing cap riotubes Parts 5 8th July 2009 08:07 PM
Sizing PP OPT alexg Tubes / Valves 14 11th June 2007 08:19 AM
Sizing capacitors preiter Power Supplies 5 29th May 2006 05:48 AM
Sizing thermistors eeka chu Parts 7 19th December 2004 08:03 PM
help w/ enclosure sizing mp3z24 Multi-Way 4 8th June 2002 01:36 AM


New To Site? Need Help?

All times are GMT. The time now is 03:04 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