Axiom Home Page Forums General Discussion Home Theater H/K 525 and temperature

I finally put the doors on my entertainment center a couple weeks ago, finishing a project that I've been working on for 3 years (rather sporadically!). Anyway, I also decided to stick a thermometer on top of the receiver to check temperatures now that the airflow has changed. Yesterday, while watching a movie at reasonable levels (and not a big bombastic movie, either-A Mighty Wind), the thermometer, which is sitting on top of the reciever, read 120 degrees F. Should I consider sticking a fan in the entertainment center? I've got cutouts on the back for cables and cooling, but I am a little concerned. The reciever didn't show any ill effects, and neither did the DVD player sitting on the shelf above it.

Hi Ken,

I'm on a brief vacation break but bored already, so I decided to try out my new wireless link. Sitting on a dock in the wild Canadian North (not at Axiom) at an island in Georgian Bay.

Anyway, can you tell if the 525's fan is kicking in? I've only detected the fan on mine coming on once, but it may run a lot more than that since I only have about 1 inch clearance or so above the receiver. A secondary fan wouldn't hurt. Cooler is always better with any electronics. It would need to be silent otherwise it could get annoying.

Regards,

I leave the doors open on my stand, it seems to reduce the temp significantly. 120 degrees sounds extreme though. I have 2 HK amps in there, the receiver and a 5 channel power amp, they both get pretty hot but I have never had any problem with them shutting down or sounding bad. Here is a link that is interesting http://www.htguide.com/forum/showthread.php4?t=14210 I think I will look into installing a small fan in the back of my cabinet soon.

Either the H/K's fan is really quiet, or it hasn't come on. As soon as I noticed the temp, I opened hte door and turned off the receiver. Of course, i was done with the movie by then... I think in normal TV watching (DTS:Neo6) and CD playing (again, DTS:Neo6), I've seen it around 100-110. But I didn't measure the temp before I put on the door.

Hey Ronno, glad to see that you visit htguide! I contributed several posts at that thread (very interesting one). Most of them were questions though :-)

Good thread, yeah. I kind of like the laptop cooler idea, but I couldn't find one off the link. My TiVo does have an available USB port, though.. It makes me nervous to think about running a PC power supply without a significant load on it, though.

This looks like a nice unit:

http://www.zipzoomfly.com/jsp/ProductDetail.jsp?ProductCode=370855

Decent price, compared to the 120 MM AC fan that I found on Radio Shack's site ($24+shipping, presumably).

Interesting that you record these kind of temperatures Kcarlile. By the way, how are you recording these temps. Are you resting the thermometer on the top of the unit? What kind of thermometer?

That is one thing that I immediately noticed when I tried out the 525 was the amazing amount of heat that it put out compared to my ONKYO at the same volume level. Actually even when the h/k was idle it put out so much heat that I thought I would have to install a sprinkler system in my house just in case.

Perhaps it just has really efficient heat sinks that get rid of a lot of heat, but it seemed REALLY excessive to me.

Let us know how things go and if you install an external fan let us know how much temperature drop that you get. It would be really interesting to know.

I don't know if this is still true, but back in the dark ages one of the hard decisions to be made when designing an amplifier was how much bias to apply, ie how much idle current to run through the output stage. The idle current is what makes the amp a class AB rather than a pure class B, ie the output transistors are always on just a tiny little bit. This results in waste heat but reduces or eliminates the "crossover notch", a non-linear response around zero caused by the fact that transistors need a bit of voltage (~0.7 ish volts) to turn on so a pure class B amp will have some distortion at low levels.

If you have the bias too low the idle current is very small or non existent but the distortion is pretty bad at low signal levels. if you crank up the bias "enough to be sure" you get a very clean sound but the amplifier gets hot even when it is sitting around doing nothing.

All the HK amps seem to run hot; I presume this is a "good thing" caused by having a high enough bias on the output stage to push it solidly into class-AB land at the cost of wasting some power at idle.

Again, this may no longer be true and I may not be remembering it correctly after 25+ years, but...

I've got one of those little rotary thermometers onna stick things you can get at Home Depot, etc. Looks like a small meat thermometer, or a really big nail. The "tail" is resting on top of the 525. Right now with the 525 on standby, and the ambient temp in the house at 69 degrees (according to a different probably inaccurate thermometer), the 525's thermometer reads 75 degrees.

I may put in an AC fan on the other side for the TiVo. On hotter days, it's getting up to 51 degrees C, which is pushing into my "not happy" zone.