ST-120 and Heat question

I would like to move my ST-120 down one shelf space so that it sits next to the preamp. That would put a shelf above it rather than ”looking at the ceiling”.

I have a low RPM 4.5” thermostatically controlled fan that I can mount in the back of the cabinet. I can orient it such that it either pushes air across the amp or draws air across it and exhausts out the back.

The reason for this is that I now have a top loading CD player that needs to go on the top shelf along with the turntable.

Any thoughts? If I do it which way should the fan blow? Front to back or back to front?

Here's a picture of rack:



It should be noted that the back and sides are completely open.

THANX!

Funny - I'm in the same situation and was considering posting a similar question - I'm going to be putting the M 125 Mono blocks in a stereo HT type cabinet each on a shelf (they each will have a shelf above them) - shelfs are 1/2 press board - back is open and the front has a glass door - shelf is about 1-2 inches above the transformer. My plan is to watch this very carefully - if it does feel too hot - I'll have to find another home for these.

this will probably be open to several viewpoints, I've considered this before, but not actually done it.
I think I would opt to suck air across the amp rather than blow air on the amp. Also consider the fan noise,
I've always figured I would use two fans in series connection (half the voltage to each) so they actually run fairly slow and not at high RPM.
Just an opinion I'm sure there will be lots more!

Well I tried it last night. Not good.

While I don't think the amp ran any hotter and the fan did a good job of moving warm air the plywood shelf directly above the amp got VERY hot. Not scorched or smoking but I wouldn't feel comfortable with that arrangement in the long term. Back to the top shelf it goes.

Time to work on "Plan B". I guess I'll need to track down a low profile turntable or perhaps one with the drawer that slides out. HMMM...

jhoak wrote:Well I tried it last night. Not good.

While I don't think the amp ran any hotter and the fan did a good job of moving warm air the plywood shelf directly above the amp got VERY hot. Not scorched or smoking but I wouldn't feel comfortable with that arrangement in the long term. Back to the top shelf it goes.

Time to work on "Plan B". I guess I'll need to track down a low profile turntable or perhaps one with the drawer that slides out. HMMM...

Just a thought. You might try a thin sheet of rigid fiberglass insulation under the top shelf. Put the foil side down.

Best Regards,
Charlie

I would put the amp on the floor or on a pedestal between the speakers, but never on a lower shelf. My monoblocs will go on the floor right next to the speakers.

Basically same setup here, 2ea MKII's in a cabinet with glass front doors and open in the back, a good 2 inches of clearence above the amps, the amps sit right next to eachother. As long as the doors are open when I'm running them I have never had any heat problems. Considering a fan or fans also.

I used a similar setup a while back and found that after a while the rack itself got heated up because the mass of the wood is able to absorb heat. This led to residual heat being retained by the amp chassis as well because the air had to flow under the amp through the narrow space between the amp and the shelf.
It also looks like you have little overhead clearance and so the heat from the tubes is heating the top shelf. Those tubes get plenty hot and there is a good possibility that the wood so close above the tubes could get burnt or at least scorched.
At the very least the tubes will run hotter due to the restricted flow around them.
My solution was to go to a stainless steel wire type rack that is open below and above and does not restrict the natural convection of air over the amp. There are numerous types and some are very attractive. I found one at Costco for $40.00.
At $100 approx. a pair for KT'120 output tubes that could shorten the life of the tubes and do some damage to your wallet. I would leave the amp on top. Nice looking rack though but better suited to a sand amp setup.
p.s.
All Fans make noise and may produce some electronic effects on a nearby tube amp. None of them are really silent.

Baddog1946

Most of the heat from the amp is radiated by the hot tubes, and to a lesser degree the transformer. As a result, both my M-125s and ST-120 amp function as terrific-sounding radiant electric heaters. Putting any surface near the amp that will reflect or absorb/store heat will increase the amp's operating temperature. A cooling fan will help to reduce the tube and surrounding surface temperatures. If I were to enclose the amps, I would try to blow clean, dust-free air across the tubes (perhaps with a small filter on the back of the fan that can be cleaned periodically). The best way to keep the amp cool is to allow it to radiate to cooler and more distant surfaces -- like the ceiling and walls (and Dark Side of the Moon, if available).

Mount the turntable on the wall and put your CD player where the turntable is.

RMG wrote:Mount the turntable on the wall and put your CD player where the turntable is.

Thank you for the suggestion but in my case wall mounting the turntable is not an option. I have an IB subwoofer mounted in the same wall. It would be much like setting the turntable on top of a subwoofer. Not good at all.

Mount the CD player on the wall?