electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  electro-music.com September Equinox Concert Various artists

poster

Please visit the chat
 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Tube Synth PSU 6.3V output
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [3 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
xto



Joined: Feb 22, 2016
Posts: 2
Location: Canada

PostPosted: Mon Feb 22, 2016 8:39 pm    Post subject: Tube Synth PSU 6.3V output
Subject description: Please clarify importance of voltage accuracy on vacuum tube heaters
Reply with quote  Mark this post and the followings unread

Hi everyone,
i have built a few power supplies for my tube synth modules following Eric Barbour's design at the Power Supplies for Tube Synthesizers page from Ken's site.
The voltage output from the 6.3V circuit with no load will vary between 8.8 and 9.1 depending on the voltage fluctuations on the mains. This is as expected: 6.3 / 0.707 = 8.91VDC.

However, in the article Eric states: "The +6v is suitable for tube heaters (all of our tubes use 6.3v heater supplies - it need not be exactly 6.3v.) .... (Heater power need not be extremely clean - regulation is not really required.) "

Four of my modules when used together require a total of 2.5A for the heaters. When I plug the modules to my psu, the voltage drops to 6.1 - 6.2V and gives me exactly 2.5A current. This is excellent.

My worry comes when I use my psu as a bench supply (non-regulated) and I wish to experiment with single tubes.
I was recently working with a 12AX7 miniature tube with heaters in parallel which has a current rating of 0.3A, 6.3V.
If I remember correctly, the voltage on the psu dropped to approximately 8Volts, but current measured exactly 0.3A on my meter.

Should I be using a voltage divider or a voltage regulator circuit to always get 6.3 volts when using single tubes (or combinations that use less than 2.5A of current)?
Is it acceptable to use a higher voltage than 6.3volts as long as the tube uses the current required for its operation?

Any insight would be greatly appreciated.

Chris
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 3419
Location: Moon Base
Audio files: 516

PostPosted: Tue Feb 23, 2016 4:03 am    Post subject: Re: Tube Synth PSU 6.3V output
Subject description: Please clarify importance of voltage accuracy on vacuum tube heaters
Reply with quote  Mark this post and the followings unread

xto wrote:
Is it acceptable to use a higher voltage than 6.3volts as long as the tube uses the current required for its operation?

I have no experience with tubes so don't take my word for it but I would say yes. Actually I'd be very surprised if you would still get
the same current with a lower voltage. However it could be that the resistance increases becauses it heats up more than it should
dropping the current. Still if it is rated for 0.3A and that's what you measure it seems ok to me. But maybe someone else has some
actual experience with it. If you have a way to vary the voltage (probably not with a voltage divider since that already limits the current)
you could try and see what happens with the current when using a lower voltage. You could use a simple regulator, either something
like a 7806 or make one using a transistor.

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/ http://www.acidtrash.com/ Stickney Synthyards
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
xto



Joined: Feb 22, 2016
Posts: 2
Location: Canada

PostPosted: Tue Feb 23, 2016 3:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks PHOBoS, your answer echoes my suspicions. I will be trying out the 7806 in the next few days.

The datasheet specifies 10% tolerance at 6.3V which swings from 5.67V to 6.93V which is a bit far from the 8V I have been getting.

Hopefully, I won't burn out any tubes before I find the correct way of balancing my voltage output.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [3 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use