Amplifier Orientation?

Power tubes should NEVER be run horizontally unless the amp / tubes were designed to do so. Not only does this create hot spots on the tube due to uneven cooling, the plates can sag over time and short out. Some tube manufacturers in the old days actually had slightly different manufacturing methods for vertical and horizontal oriented tubes.

Line level tubes are typically not a problem to turn sideways. Due to their lower plate voltages, current consumption and heat generated, one typically need not bother worrying about that.

I have no idea which, if any, orientation would be lower in microphonics. Sean
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Do not change the orientation of the VT-100s... They should sit on their feet... You really do not want to have all of the heat rising to the circuit card that is on the top. One of the things that will happen is shortened tube life. With that in mind - the biggest "no-no" of this all is having 1/2 of the tubes in this amp operating base up.. Just a bad thing to do to tubes.. A quick consultation with the owner's manual will also confirm ARC's position on how the amp should be orientated.

Per Sean's post, the best way to run tubes is base down. Audio Research has made the choice to run the tubes horizontal, which is why the later units have fans to assist in the convection process and reduce issues with horizontal tubes.

The next problem you will have is that the amps are not on their feet. ARC has done a decent job of providing feet that actually do some good in terms of vibration isolation. You will find this out of you ever experiment with isolation tweeks and the VT-100..

Thanks all. Didn't seem intuitively like an issue, but I wondered, and the points you raise make more than a little sense. I didn't think about the effect on the upper circuit board, for example. I'd always seen base down tube configurations, but the ARC, as some noted, have the tubes positioned horizontally, so I wondered if orientation was a problem. That's why I figured I'd consult the experts.

Thanks again. Guess my floor will just be messy...

i was completely unaware that this amp ( or ANY for that matter ) ran the outputs horizontally. Hopefully, they've done their homework and this will not turn into a problem in the long run. Sean
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Sean - ARC horizontal tubes have not been a long term problem for me (4 yrs)... but my amp has plenty of air space.