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Old 20th May 2005, 07:02 AM   #1
G.Cesar is offline G.Cesar  France
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Default Tubes operating in horizontal position

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.
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Old 20th May 2005, 07:09 AM   #2
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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.
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Old 20th May 2005, 08:02 AM   #3
EC8010 is offline EC8010  United Kingdom
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Default 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.
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Old 20th May 2005, 08:45 AM   #4
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...........................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 ..
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Old 20th May 2005, 09:48 AM   #5
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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
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Old 20th May 2005, 11:14 PM   #6
Zen Mod is offline Zen Mod  Serbia
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VTL make some pretty nice looking preams in 1 and 2 HE cases ,partly because 12AT and 12AX7s are just lying .......
hehe

even in geetah amps you can find some preamp tubes in horisontal orientation- like you know -in that sort of amp cold air is pretty rare .....
so - turn your tubes in any way you like
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Old 21st May 2005, 05:36 AM   #7
Enzo is offline Enzo  United States
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It is not piffle, but it usually is only a concern in larger tubes. Check the data sheet. The small preamp tubes are fine that way as are the 6BQ5s. We mount them in guitar amps that way all the time, so if they will take that, you are OK too.
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Old 21st May 2005, 06:04 PM   #8
dhaen is offline dhaen  Europe
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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.
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Old 21st May 2005, 07:02 PM   #9
G.Cesar is offline G.Cesar  France
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Thank you all.
I will go for the horizontal mount, considering that
the risk is not too high.
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Old 23rd May 2005, 08:02 PM   #10
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I have a AMC 30 watts Class A amp with the 2 EL34 horizontal in the case. And no problems here.

Just try it.
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