Stacking power amps mono blocks

I have two tube mono blocks that are stackable. However when I put one on the other there is only 1/2" space for heat dissiation between the two of them. I am worried that the lower unit will fry over time if it gets to warm and the heat from the tubes can't escape. I can obviously put a 2" x 4" to create space. However, the look may not be great. Anyone that has figured out a nifty thing or purchased something that creates a nice 3 to 4 " gap between two pretty heavy (at least 50 lbs each) power amps. By the way if I put them into my Target stand (the ampsare 8 " tall (mono blocks) I need to remove one shelf and loose three shelves and not great look for putting in two amps. I am I just not getting it?
if you have the space, some nice amp stands (single shelves, basically) look nice. Target makes some that are cheap, or you can make your own pretty easily. I'd avoid stacking, esp. if they are tube monos.

I had the same problem with solid state amps. I stacked them using 3/4" stock aluminum, 1/8" stock plate, that is routed and sandwitched with marbles. This works similar to Symposium Rollerblocks. Not only does it help with heat dissappation it also helps with sound quality. The top amps are smoother with less noise--it might be even more significant with tubes. I also painted the aluminum black for cosmetics. You can see how it looks at:
I do not believe a half inch is enough space. Not only should you be concerned about the lower unit, but also the tube amp above, so much heat in a tight space is probably not good for either of them. I would take ed's advice and buy a couple of amp stands. If you do get the stands, take a look at a thread here on agon about spk cable verses interconnect lengths, I don't personnally have any experience on cable lengths but the people who commented on the thread made some interesting comments. I would try both ways short interconnect and then long inter, with spk cables going short and then long. You may end up achieving a new level of performance. Good luck and let those amps breath. Pete
Thanks everyone. Seems as I am not the only one struggling with this. Since I do not like the empty shelf in the stand, it look weird with a hole and 8 inch of air. I need to look into one of two options.
1. Move the stereo so I can have one poweramp on each side of the target stand. Preamp on the bottom shelf. Interconnects of 3 ft will work.
2. Buy a stand that can take the ams and maybe has something like a 12 " space between the amp shelves.
Does and amp stand improve the sound? This is too much for me?
Amp stands will improve the sound of most tube amps (I haven't experimented with SS) even top of the line amps. I personally use long speaker cables (Dunlavy to match my speakers). I have my monoblocks side by side with amp stands on top of oak platforms isolated from the floor with inner tubes. There have been several good threads about isolation as well as amp stands.
Abstract, would you please explain? What do you mean by "routed and sandwitched with marbles"? I am thinking of using aluminium tubes of about 2.5 inches for the same purpose. Please enlighten..thanks
I agree that stacking the amps is NOT a good idea in terms of heat dissipation. If the amps are high bias designs, i would recommend appr 8" of free space above them. This lets the heat rise out of them unimpeded. In your case, not only is heat trapped in the bottom amp, what does rise out is only helping to cook the top amp. NOT a good thing in any aspect.

Unfortunately, I can't offer any good suggestions. I was also in that boat but ended up changing racks for similar reasons. Since all of my amps ( except two ) are all very richly biased and run hot, i didn't want then cooking to death. As such, i hated loosing a shelf or having a giant "dead space". To correct this situation, i ended up changing racks. I can now adjust the shelf height on several of my racks. This now gives me the ability to accomodate ANY situation or component AND the looks that i was searching for. Sean
Detlof: I routed the aluminum plates, just two routes per plate. They are about 3/8" wide and almost as long as the plate, stopping about 1 inch from either end (long being side to side in this case--if that makes sense). Then you have one with the grooves on the top, put two marbles near the ends of each groove, then put the other aluminum plate with grooves downward onto the four marbles. That's my recipe for my aluminum marble sandwitch. As to the concerns of heat dissappation--these concerns are probably correct for tubes or other types of amplifiers which do not have the heat sinks located to the outsides as mine do. Also, the ambiant tempurature and air flow around the units play a significant role. My units are only about 2" separated, which is adequate, although I have been considering increasing the flow under the bottom amplifier. In this situation it's really how much airflow you can get around the heat sinks--how much heat dissapation per hour. With tubes, this is probably much more difficult to accomplish since the heat generating device is located centrally in the amplifier--rather than on the external sides with massive heat sinks. I should have considered this with my original post.
Thank you. I am starting to get convinced. Need to run to look for amp-stands for my mono blocks.
Thanks for your time and consideration Abstract7. You make very good sense to me. I 'm thinking of following your footsteps and doing something similar.
You can also try a couple of very quiet running fans...I've rigged 2 three inch cooling fans to blow across the top of each of my VTL monoblocks (they're on their own shelves above each other). I don't actually run them when I'm listening, but for the warm up period (approx. 1/2 hr.) and in between songs- whether I'm changing CD's or albums, a 2 min. or so cooling will quickly bring the temp. of the upper shelf back down to "reasonable limits". I'm using a standard [adjustable shelf] Salamander #5 rack and have about 4"-5" between the top of tubes and bottom of shelf above.What I did was simply rig a wire from the front right vertical support rod straight back to the aft one at the very top just below the shelf above it.Pull the wire very tight and then a couple of cable ties or whatever,to hang the fan on the wire. Rig yourself a switch and a plug and you've got yourself a "cross-flow" ventilated rack.Obviously this will only work with an open design rack(no side panels),but if you really wanted to (depending on the material) you could conceivably drill a hole into a side panel type,and mount it somehow? - Where there's a will.... Bottom line,it can be done and still be effective and neat looking. Regards
Dcaudio, I also have a Target rack (5 shelf) with two VAIC 52B monos stacked inside it. These amps are very tall, and I removed a shelf apiece for each amp to fit them inside the rack. They each have 8" overhead clearance, which seems enough for heat dissipation. I put the extra shelves under the mono blocks and a layer of rubber beneath them to make a sandwich support. The whole set-up looks fine enough for my wife who is a scrupulous interior design aesthete (with a soft spot for the Bauhaus-chrome-castle VAICs anyhow).