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previous: Winnie Thomas Okay, Here's my newest question: -- 6/6/2000 2:53 PM View Thread

Re: Horizontal tube placement

6/6/2000 4:36 PM
Ray Ivers
Re: Horizontal tube placement
I think the major issues are 'grid sag' (grid misalignment over time due to gravity; the main reason why tubes are not supposed to be stored horizontally), cooling, and physically keeping the tubes in their sockets under shock loads. The grid sag issue should less important with beam-power tubes, and more important with 3-grid power pentodes like the EL34 / EL84. GEC was quite specific about KT88 horizontal mounting ("pins 4 and 8 of each tube are in the same vertical line"), i.e. plate-structure 'holes' if any top and bottom, plate-structure 'wings' (main heat-dissipation area) left and right.  
Steve at VHT told me that to date they have had no VHT rack-mount power amp tube failures directly attributable to horizontal mounting, but these are fan-cooled amps. I personally would not recommend this type of tube mounting, for reliability reasons, but I really haven't too much experience with it so don't necessarily take my word for it.