How much clearance around 12AU7s? - diyAudio
Go Back   Home > Forums > Design & Build > Construction Tips
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Construction Tips Construction techniques and tips

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
Thread Tools Search this Thread
Old 15th December 2009, 12:28 PM   #1
GregH2 is offline GregH2  Australia
diyAudio Member
GregH2's Avatar
Join Date: Oct 2009
Default How much clearance around 12AU7s?

Hi all,

I'm designing a preamp PCB and am wondering how much clearance (from other valves and capacitors) I should have around my 12AU7s. Your advice is appreciated.


  Reply With Quote
Old 15th December 2009, 12:29 PM   #2
diyAudio Member
ashok's Avatar
Join Date: Jun 2002
Location: 3RS
At least one tube diameter ?
  Reply With Quote
Old 17th December 2009, 02:16 PM   #3
diyAudio Member
MellowTone's Avatar
Join Date: Jun 2006
I think what ashok said is about right, one tube diameter should do it, perhaps a touch more to be safe. I'd be inclined to keep caps at least two diameters away, as I believe they are affected a bit by heat.
I Reject Your Reality And Substitute My Own
- Adam Savage, Mythbuster
  Reply With Quote
Old 18th December 2009, 01:26 AM   #4
diyAudio Member
ashok's Avatar
Join Date: Jun 2002
Location: 3RS
Yes as Mellow Tone says , caps should preferably be kept further away. A caps life depends also on operating temperature and as always elevated operating temperature shortens useful life for almost anything on Earth !

Remember that power tubes generate a lot of heat and things might need more clearance. I see some designs very tightly packed. I don't think they will last very long if used on a continuous basis. Ambient temperature and air flow also matters a lot. In cold countries many compact things might work well as it's so cold most of the time(?). Here in the tropics it's 35+ deg C ambient temp all through mid summer . Can't guess how long compact power tube amps will work here. Right now we are almost mid way in December and it's.....cold.....21degC .
  Reply With Quote
Old 9th January 2010, 03:30 AM   #5
Ivey is offline Ivey  United States
diyAudio Member
Ivey's Avatar
Join Date: Jan 2010
Location: Ann Abor, Michigan

There is no set rule for novar base tubes of 3/4" dia. In designing military tube equipment in the 1950's and 60's. Most tubes had a metal shields that dissipated the heat to the chassis. So I/we never worried about heat.

Your caps are also an item not to worry about as well. If your chassis is ventilated. The warm air will rise and natural cooling will occur. Your biggest concern is air moisture. Too little or too much. This dry out your power main caps and mare your plastic caps.

But then again, this will happen over years of time.

So, there is no fear in how you design tube preamp, but a power amp is not the same.

If using a 12AU7 in a "phase inverter/driver" it will draw a heavy current load. Cooling is needed. But in a preamp, there is no need.

Again on caps. Most plastic caps are sealed. Like Wima, Epco, Evox, etc.,
So you are pretty safe there. Electros are a different breed, but use good ones and you are looking at 6 to 10 yrs of service.

Take Care

  Reply With Quote


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
Driver Clearance jeffshort2000 Swap Meet 8 20th October 2010 03:11 PM
Oh, those 12AU7s again... Bamalama Tubes / Valves 11 23rd July 2009 04:58 PM
The Loudspeaker Kit Christmas Clearance LSK Scott Vendor's Bazaar 0 7th December 2007 09:51 AM
DIY parts clearance ultranalog Swap Meet 1 31st July 2003 12:59 PM

New To Site? Need Help?

All times are GMT. The time now is 03:25 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2