Tubes and forced air cooling ...

Hello,

Time for another tube question. First of all, thanks to the folks who post good information on this site. I know the sharing of information freely can be a pain but it's the backbone of Audiogon in my opinion. You all help to keep my tube equipment in good health and that makes me happy.

Ok, down to business. I am running the following setup in a home made rack.

ARC VT-60 and a Mark Levinson ML 27.5 on the bottom shelf the amps have about 6" of vertical clearance to breathe before the next shelf.

The next shelf has a Levinson 360S DAC and a No 37 Transport side by side and they have about 2 inches of vertical clearance to breathe.

The next shelf holds my Modwright SWL 9.0 Linestage and my Dynalab Tuner side by side they have about 3" of vertical clearance.

The amps get hot ... especially when I add ale on a Friday night. Too hot? I'm not sure ... but hot enough for me to put a small desk fan behind them to keep the air flowing. The fan works well but my question is :

How does this affect the amplifier? Tube amplifiers are designed to get hot ... that's the idea ... right? At what point do I risk negative impact on sound quality? Do I even want to go down this road? I see that ARC has put fans in the VT-100 so I don’t think I'm too far off base. I don’t like the fan noise so I am having fan mounts built and I am going to use 12 volt 120mm ultra silent PC fans. A little less air flow but very, very quiet. They will be easily replaceable and will only cost about $7-12. I figure I will get a couple years out of a set. I'll run one across the pre and one across the amps.

What do you think?