Current sourced heaters in a CF - 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 23rd May 2005, 09:20 PM   #1
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default current sourrced heaters in a CF

Hello

Can I use a current source heater PSU (LM317 R=1.25/I type) for a cathode follower and still bias it with voltage so to keep the cathode no more than 100V DC positive in respect to the heater?
I want to use 0.3A current source for 12AU7.
Do you prefer the sound of a current sourced heater?
  Reply With Quote
Old 23rd May 2005, 10:26 PM   #2
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
I don't think you need constant current source for 12AU7 - indirectly heated filament. You can simply use DC regulator instead.

Johnny
  Reply With Quote
Old 24th May 2005, 08:11 AM   #3
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default hmm

I have read many times that a CS heater sounds better. That is why I want to try it.
Why you think its not needed?
  Reply With Quote
Old 24th May 2005, 08:20 AM   #4
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Default Re: hmm

Quote:
Originally posted by salas
I have read many times that a CS heater sounds better. That is why I want to try it.
That's what i've heard... i've not built anything with DC heaters yet so i can't talk from experience.

It is pretty easy to implement why not just try it.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 24th May 2005, 11:37 AM   #5
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Default got the parts already

I have got the parts already (he he) but I was mainly interested in floating CT with voltage to avoid exceeding over 100VDC difference between heater and cathode. So I asked if they do this and how on a current sourced heater. I will listen to it anyway and let you know p10.

PS did you see that?:

My ''TB3'' mini bipole plans

you are right to be a proponent
  Reply With Quote
Old 24th May 2005, 12:54 PM   #6
kmtang is offline kmtang  Canada
diyAudio Member
 
kmtang's Avatar
 
Join Date: Nov 2004
Location: Vancouver
The constant current source for filament supply is mainly used for Direct Heated Tubes like the 300B and 2A3. The reason is that the filament forming part of the cathode circuit which would affect the sound.

However, the indirectly heated tubes like the 12AX7 having the filament separated from the cathode, I don't see what CCS could do anything at all.

If you want to float the filament voltage, I think you can connect the -ve side of the CCS supply to the B+'s divider.

Just my 2 cents.

Johnny
  Reply With Quote
Old 24th May 2005, 04:59 PM   #7
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Quote:
I don't see what CCS could do anything at all.
The advantages are a gentler startup (heaters have lower resistance when cold) and a somewhat better potential efficiency. There's a nice treatment of these issues in Morgan Jones's book. The main thing to avoid is CCS operation of parallel heaters.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 25th May 2005, 03:23 AM   #8
diyAudio Member
 
Join Date: Oct 2004
Location: Adelaide South Oz
The Allen Wright "Tube Preamp CookBook" recommends exactly this method - example circuits of current sourced heater supplies at elevated DC voltage abound. A RECOMMENDED book for any serious DIY Audio Nutter.
Cheers,
Ian
  Reply With Quote
Old 25th May 2005, 07:05 AM   #9
diyAudio Member
 
Join Date: Nov 2003
Location: flyover country
I've used a slightly different approach - a voltage regulated heater circuit that is current limited only a little higher than the required heater rating for soft start up.
  Reply With Quote
Old 25th May 2005, 08:29 AM   #10
Salas is offline Salas  Greece
diyAudio Chief Moderator
 
Salas's Avatar
 
Join Date: Oct 2002
Location: Athens-Greece
Thanks people!
  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
Tube current regulation for series heaters' supply. engels Tubes / Valves 4 5th August 2007 10:49 PM
Current Sourced Cathode Follower dr._sleep Tubes / Valves 8 27th February 2006 08:46 PM
Current sourced heaters Salas Tubes / Valves 3 26th January 2004 11:09 PM
current sourced cascoded BLS schematic SteveG Pass Labs 48 24th July 2002 07:16 PM


New To Site? Need Help?

All times are GMT. The time now is 09:06 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