• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Tubes operating in horizontal position

G.Cesar

Member
2005-05-02 1:39 pm
Paris
I intend to use, in a preamplifier, one or more of the following tubes, fixed
in a horizontal position :
6SN7GT - ECC82 - 12AU7 - ECC83 - 12AX7 - 12AT7 - 6H30 - 6N1P
6BQ5/EL84.
Are there some precautions to take into consideration ?
Which kind of tubes should be discarded ?
Thanks for your help.
 

ashok

Member
2002-06-06 4:43 am
3RS
This information is found on some tube data sheets. They will mention the tube orientations that are acceptable. You better check it , but I think the ECC and 12A series can be used in a horizontal position.
Not sure of the other two. Apart from horizintal operation check to see if they specify if there is any restriction specifying pin positions ( eg. like say pin 7 on top etc ).
Cheers.
 

EC8010

Ex-Moderator
2003-01-18 7:57 am
Near London. UK
Fiziks

As you know, the electrons are accelerated towards the anode, and it's the velocity of collision that heats the anode. If you lay the anode flat, then the electrons hitting the upper plate will strike it rather slower than the ones that travel downhill and strike the lower plate assited by gravity. At low anode voltages, electrons travelling upwards may almost make it to the upper anode before falling back through the grid structure to strike the lower anode, causing considerable confusion and a congested sound - rather like the rush hour on a tube train.




Sorry, I can't keep up this pseudo-technical piffle! There's no earthly reason at all why you shouldn't use any of your suggested valves in any orientation you like. It's only the high-powered valves where there's a danger of the grid sagging onto the cathode that have preferred orientations. The manufacturer's data sheets always say if there's an orientation issue.
 

ashok

Member
2002-06-06 4:43 am
3RS
...........................As you know, the electrons are accelerated towards the anode........................... If you lay the anode flat, then the electrons hitting the upper plate will strike it rather slower..................strike the lower plate assited by gravity........................... At low anode voltages........................ electrons travelling upwards may almost make it to the upper anode ....................rather like the rush hour on a tube train.

Ha...ha .. ha ..:D
 
I'm pretty sure all the tubes listed are safe in any position, except the ruskies, which I know little of.

Usually the reason is creep, sag or uneven cooling. For the first two cases, you want to mount horizontal sweep (e.g. 6CD6) and filamentary rectifiers (5U4 et al) so the elements are edge-on to gravity, so they don't flop or sag into the neighboring electrodes and cause nasty things. Many tungsten filament transmitting tubes may not be suitable in any horizontal position due particulars of their construction. I can't think of any types offhand that are restricted by convective cooling in a particular orientation; certainly this would be easy to correct with a fan.

Tim
 
I have observed increased microphony in phono preamps that happen to use horizontally oriented valves. This may be due to the mounting details too. It shouldn't affect valves run at more normal signal levels.
There is no reduction in reliability or life as long as the manufacurer's orientation and spacing guidelines are observed.