Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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

Filaments DC or AC?
Filaments DC or AC?
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
View Poll Results: What do you prefer for heating AC or DC?
AC 38 38.78%
DC 60 61.22%
Voters: 98. You may not vote on this poll

Reply
 
Thread Tools Search this Thread
Old 27th May 2018, 04:01 PM   #11
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
The manual twisting of the heater wiring is enough for me to use DC Hand twisting 22 solid core isn't very fun, and an SMPS is cheaper than a transformer, bridge, CLCRC filter.
  Reply With Quote
Old 27th May 2018, 04:05 PM   #12
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Filaments DC or AC?
If I hand twisted I'd go that route too, but I use a drill. I've had problems in the past with noisy filament SMPS so I either use AC or linear regs.
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 27th May 2018, 04:12 PM   #13
Lingwendil is offline Lingwendil  United States
Now with high-fructose ASSAULT-gluten!
diyAudio Member
 
Lingwendil's Avatar
 
Join Date: Apr 2008
Location: Oakley California
Filaments DC or AC?
I use a drill to twist mine. Takes all of ten seconds max. Easy peasy
__________________
Check out My 6SN7 Push-pull Flea Amplifier project! PCB COMING SOON!
  Reply With Quote
Old 27th May 2018, 04:18 PM   #14
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
When I need to run AC heaters I use UTP from a CAT5 Ethernet cable... Works great if you run separate runs, 28AWG isn't good past about 1 Ampere. I use chassis ground, so running DC saves some wire, too.
  Reply With Quote
Old 27th May 2018, 04:30 PM   #15
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Filaments DC or AC?
I don't use the chassis as a return for either AC or DC filaments, this seems to have been an acceptable practice in guitar amps and radios decades ago. I don't use the chassis for signal ground either. (I do connect it at one point to circuit ground) I also pretty much put everything on PCB these days..
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 27th May 2018, 04:33 PM   #16
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
All mine are 1950s style chassis grounded for safety, signal, and B+ return, all point to point wired. They kind of look like the under chassis of an old RCA colour TV!
I use aluminum as it's not ferromagnetic, and is a pretty good conductor (compared to steel, anyway).
Here's one I build with 12AV5GA outputs triode connected.


The SMPS on the left side powers the boost converter (bottom right) for 440V for the signal stages, the SMPS on the bottom left in the cage powers the heaters. The power is 230VAC rectified to 330VDC for the output stage.
Attached Images
File Type: jpg IMG_20180527_124217.jpg (871.9 KB, 409 views)
File Type: jpg IMG_20180527_124017.jpg (978.0 KB, 400 views)

Last edited by kodabmx; 27th May 2018 at 04:48 PM.
  Reply With Quote
Old 27th May 2018, 04:37 PM   #17
Gopher is offline Gopher  United Kingdom
diyAudio Member
 
Join Date: Nov 2005
Location: UK
So why do some people swear by regulated DC powered heaters? Are they hearing something different to those who prefer AC heating?
  Reply With Quote
Old 27th May 2018, 04:46 PM   #18
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
If they hear a difference they are either hearing hum from AC heating, or they are dreaming IMHO. I just use DC because it's easier and cheaper for me.
  Reply With Quote
Old 27th May 2018, 04:53 PM   #19
kevinkr is offline kevinkr  United States
diyAudio Moderator
 
kevinkr's Avatar
 
Join Date: Sep 2004
Location: Boston, Massachusetts
Filaments DC or AC?
In very low level circuitry it definitely makes a difference such as a phono, tape amplifier or I/V converter, otherwise I mostly heat with AC. (Note that noisy DC with 120Hz ripple may well be worse than AC!)

In the case of DHTs it makes a pretty big difference particularly with 5V filaments and above. AC heating in DHTs results in measurable intermodulation distortion at 2x the fundamental which you can see as side tones on the fundamental in an FFT measurement - this is measurable even with 2.5V filaments although I cannot say I hear it. There are ways to minimize it, but it's there. I would post new measurements (I can now easily measure with my RTX) but I don't currently have such an amplifier in house.

Koda, very nice clean looking build. I use aluminum chassis for the same basic reasons you state, but don't use them as ground references anymore. (I did at one time)
__________________
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
  Reply With Quote
Old 27th May 2018, 04:58 PM   #20
kodabmx is offline kodabmx  Canada
diyAudio Member
 
Join Date: Oct 2011
Location: Toronto
Quote:
Originally Posted by kevinkr View Post
Koda, very nice clean looking build.
Thank you, Kevin. It's one of the neater ones, that's for sure. I made an integrated amp in a 2" high chassis with a line stage, two buffer stages, a phono stage, and an EL34 output stage with VR regulated screns for a total of 22 tubes (separate power supply), complete with relay switched inputs and a relay based attenuator. It's a rat's nest but it works perfectly...
  Reply With Quote

Reply


Filaments DC or AC?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Filaments for 307A merlin el mago Tubes / Valves 58 24th December 2017 06:25 PM
What to start first B+ or filaments? merlin el mago Tubes / Valves 18 20th November 2017 03:46 PM
SMPS for Filaments? dshortt9 Tubes / Valves 2 16th January 2010 07:32 PM
CCS Design for DHT Filaments dsavitsk Tubes / Valves 9 29th April 2008 06:56 PM
Alloys for filaments Calvin Tubes / Valves 6 16th August 2007 12:41 PM


New To Site? Need Help?

All times are GMT. The time now is 01:34 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 13.64%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki