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

Switching power supply for tube filaments possible???
Switching power supply for tube filaments possible???
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 2nd November 2017, 03:56 PM   #21
Sunsun22 is offline Sunsun22  Hong Kong
diyAudio Member
 
Sunsun22's Avatar
 
Join Date: Jul 2004
Location: Hong Kong
I have this thought because my friend has an electronic factory in China and when I talked to him, he said he can make such at a max of 5 amp, 12V with a minimum of 200 pcs at $25 each. The module has current limiter and voltage control that I think this could be good for DHT tubes. I'm not sure other than the above, is there any other criterion to determine a good DHT filament heater?
  Reply With Quote
Old 2nd November 2017, 06:11 PM   #22
artosalo is offline artosalo  Finland
diyAudio Member
 
artosalo's Avatar
 
Join Date: Feb 2010
I have used this sort of power supply when testing 813SE amplifier without any extra filtering (but series NTC of course).
I found no measurable problem in THD or S/N.
These power supplies have voltage adjustment, but I don't know about current limit.

12V 10A LED Strip Power Supply 120W LED 12VDC Switching Power Supply Led Adapter | eBay
  Reply With Quote
Old 2nd November 2017, 07:30 PM   #23
pcan is offline pcan  Italy
diyAudio Member
 
Join Date: Dec 2015
Switching power supply for tube filaments possible???
I believe that there is no shortage of single output low noise switched mode power supplies, no need to design a custom one. An example of a modern commonly available compact power supply of this kind is the Mean Well LRS-75-12: 75W, the output can be set between 10.2 and 13.8V at 6A, and the ripple and noise at 20 MHz bandwith is 120 mVpp. Switching frequency is 65 KHz. This UL listed industrial grade SMPS is better than most LED power supplies, and it costs way less than 25 USD. For a little more money, better specifications are available.
  Reply With Quote
Old 2nd November 2017, 07:33 PM   #24
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
Its like … people are forgetting good RF suppression tech? Seems so. The unsubtle answer is "separate cans": isolating one's crazy-noisy (potentially) switching power supplies in earth-grounded faraday cages is critical. Having tight little multiturn ferrite-core chokes right at the exit point of the cage is also critical. Do all the filtering IN-can, and then suppress the emission of anything RF'ish.

You can do this for Lo volt H+ supplies (heater); you can do this for B+ or S+ (screen) supplies. Copper sheeting isn't all that expensive, and does wonders. So do hand-made small ferrite RF suppressor chokes.

OR - if you prefer - you can do the Faraday cage thing in reverse. Put all the hash outside the amplifier cage. Enclose the amp in its own Faraday cage to keep out in-the-air RF. Put the little RF suppressor beads right at the power-feed-in points. "Think like an antenna" as my uncle used to say.

Anyway, my 2¢ worth. Not much these days.

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
  Reply With Quote
Old 2nd November 2017, 07:45 PM   #25
pcan is offline pcan  Italy
diyAudio Member
 
Join Date: Dec 2015
Switching power supply for tube filaments possible???
The faraday cage concept is actually almost a necessity for the compliance to EN-55032 anyway (I believe). This is the latest EMC emission standard for multimedia equipments. If you look at a modern EN-55032 compliant power supply such as the above mentioned LRS-75-12, it clearly shows the construction details you mentioned. Good earth ground is mandatory to avoid nasty EMC issues.
  Reply With Quote
Old 2nd November 2017, 07:58 PM   #26
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
Quote:
Originally Posted by pcan View Post
The faraday cage concept is actually almost a necessity for the compliance to EN–55032 anyway (I believe). This is the latest EMC emission standard for multimedia equipments. If you look at a modern EN–55032 compliant power supply such as the above mentioned LRS–75–12, it clearly shows the construction details you mentioned. Good earth ground is mandatory to avoid nasty EMC issues.
Finally "common sense" becomes "common law" for the "common good" of the "common man".

I'm an unrepentant ex-Ham, no longer on the air, but once 40 years back "into it". You learned early-and-quickly to use Faraday cages for all sorts of things Hammish. Its "the way" of RF.

Thanks for mentioning EN–55032.

Its surprisingly easy to do the right thing with copper wire mesh caging material. Just remember to solder the "little holes' mesh wires" where you intend to screw it onto the chassis.

Do so before drilling the screw-holes. Makes it SO much easier to get clean holes drilled in the mesh. Also, it serves as a nice buffer when tying the mesh cages to the chassis for the screws (which tend to crumble the naked copper wire over time).

GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
  Reply With Quote
Old 2nd November 2017, 08:01 PM   #27
GoatGuy is offline GoatGuy  United States
diyAudio Member
 
GoatGuy's Avatar
 
Join Date: Dec 2012
Location: SF Bay Area
PS: it also makes good sense to buy a small box or bag (if they still have them) of small, thin brass washers. Disks with holes. Really thin. You can solder these to the mesh too, to make both screw-holes and wire-port feed-thrus. Don't forget your grommets! Insulation is no barrier to gradual insulation wear. Grommets are. GoatGuy
__________________
John Curl's Golden Rule…: 100 kHz bandwidth, 3 μs risetime, 100 W mean output, 100 V/μs slew rate, 2 Ω dynamic load, 20 amp min current source/sink
  Reply With Quote
Old 2nd November 2017, 09:44 PM   #28
v4lve lover is offline v4lve lover  Netherlands
diyAudio Member
 
Join Date: Aug 2010
Location: Surrounded by glass
Switching power supply for tube filaments possible???
What about buck converters with a linear reg behind them? A LT1084 fed by a buck could work..

I've attached AN101 by Jim willams for reference.
  Reply With Quote
Old 2nd November 2017, 10:20 PM   #29
Koifarm is offline Koifarm  Netherlands
diyAudio Member
 
Koifarm's Avatar
 
Join Date: Aug 2005
Just ntc and smps.
Ntc protects overcurrent smps when starting with cold heater.
Buy smps with 2 times higher current as needed.
Attached Images
File Type: jpg IMG_0131.JPG (68.6 KB, 218 views)
  Reply With Quote
Old 3rd November 2017, 12:37 AM   #30
Sunsun22 is offline Sunsun22  Hong Kong
diyAudio Member
 
Sunsun22's Avatar
 
Join Date: Jul 2004
Location: Hong Kong
Thank you for all the input. The unit recommended by PCAN ?? ?? ??? DC12V?? ?? ???-??? is a high voltage switching supply from a 12V input. The filament supply is a 317 which is adjustable for various voltage output. Since I need a switching supply for DHT filament supply, this module is not for me.

I have this need because I failed to make my DHT preamp dated back 20 years ago because of hum. With today's technology, I THINK (only) we can fight against DHT hum problem with switching power supply.

A bit elaboration on what we are getting for $25. This will be an individual RF sealed box (just like 120W 12V switching supply from eBay) with TWO channels of 60W (total 120W) supply of switching power that can be adjusted between 1.25V to 12V therefore we can use it for different DHT tubes. There is an adjustable current limiter ranging between 100mA to 5A to avoid over supply of current at start up. The unit can plug into 100V-240V and is self adjusting to suit worldwide voltage.

According to my friend, considerable cost is making the RF sealed box because of mechanical machine tools. Break down of costs: -
RF sealed box $8 min 200.
1.25V-20V 60W with current limiter $5 per channel (two channels $10).
Universal voltage supply $7.
No minimum order quantity for the switching unit.

This really draw up my interest if we don't need the RF sealed box and universal voltage supply since there should already be 6.3V or 12V from the existing transformer. I will ask him to give me (free of charge of course) two 1.25V-12V modules and restart my DHT preamp that I stopped 20 years ago.

Last edited by Sunsun22; 3rd November 2017 at 12:41 AM.
  Reply With Quote

Reply


Switching power supply for tube filaments possible???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
Split Voltage Switching Power Supply for Power Amp vectorplane Swap Meet 2 24th April 2011 12:48 AM
Switching Power supply allanon77 Solid State 31 25th June 2010 07:41 AM
Tube filaments (heaters) power supply matejS Tubes / Valves 5 12th July 2007 06:50 PM
Switching supply for 300B filaments Zen Audio Tubes / Valves 7 2nd May 2007 03:38 AM
Switching power supply for tube-pre JasonLee Tubes / Valves 12 20th March 2007 01:26 AM


New To Site? Need Help?

All times are GMT. The time now is 06:38 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki