Denon 3801 -- strange whirring sound

jeberhart

OK, I'm totally puzzled. I need some help figuring out a rather unusual (in my opinion) noise from my Denon AVR 3801, which is hooked up to a whole arsenal of Polk speakers.

Basically, here's what's happening: At high volumes, during breaks between songs, I'm hearing a strange whirring noise from the Denon AVR 3801. It sounds kind of like a VCR rewinding. This only happens at volumes exceeding minus 8 below the zero threshhold db on the AVR 3801. What I THINK is happening is that the AVR 3801 is running pretty hot, and a fan in there is switching on to cool the unit. Questions: Is this normal at high volumes for the 3801? And if so, am I doing any damage here? I want to emphasize that everything sounds really clean and nice, even at the point where this fan or whatever the hell it is starts coming on. It's really weird.

I hear this between songs on any of my CD playback players. I've definitely isolated it to the 3801 -- the noise is coming on between songs on the CAL CD player, at high volumes. It's not a bothersome or annoyong noise -- just a whirring, like I said.

I'm probably going to call Denon next week during business hours, but in the meantime, I just want to make sure I'm not toasting my receiver. BTW, the front speakers -- old Polk Monitors 10B -- are running off my Adcom GFA-555, so the Denon is getting some help.

Any of your thoughts would be appreciated. There are some users of Denon on this board who are very knowledgeable, so I'd appreciate your ideas.

TheGrayGhost

That is the cooling fan in the 3801. Make sure that you have at least 4" space all around the Denon for proper cooling and check to ensure the fan is not blocked on the back of the receiver.

mantis

The Denon avr3801 doesn't have a fan inside.No exhaust anywhere on the back.I can't explain the noise your having.I have owned mine for a least a year now and I never experienced the niose you mention.I don't crank mine up that loud, maybe once in a blue moon.I run at loudest -15db and thats really loud for movies,-20 to 25db for music in direct.SACD and dVD audio I have gotten it up to -10db and still no niose at all.I run a pair of speakers in my masterbed and theater at the same time and no noise.
You should cal Denon on this issue,I really don't think theres a internal fan,if there is I never heard it.

TheGrayGhost

Mantis,

The 3801 does have a cooling fan mounted to the heat sink. Check page 6 of the operating instructions for the warning “Route the connection cords, etc. in such a way that they do not obstruct the ventilation holes”. The fan is mounted 90 degrees to the ventilation holes on the back of the receiver. I have confirmed the cooling fan when I had the cover off to check the build quality of the receiver.

jeberhart

I don't know, Mantis, I think Cliff may be right: There's GOT to be some kind of fan or cooling device in there, because I listened again today and it sounds like it starts up for just a few seconds, then winds down. And if you've never played your AVR 3801 above -10 db on the volume control, you never would have heard it, because this noise never occurs at anything below -08. Until recently, I'd never played mine that loud, either, but I've really been pushing the system hard the last few days (why? to test my new Polk surrounds, that's why ). It's not a very loud noise, either -- you have to be pretty close to the receiver to hear it. I've been burning a lot of old cassettes to CD lately, walking around up there fiddling with levels, and I think that's the first time I heard it, in fact.
Anyway, I also did some research on the Net today, using an engine to plug in "Denon" and "cooling." I didn't find any references to the 3801, but I did find references to fans in other Denon units, such as the 3300. At any rate, I am going to call them on Monday when the office opens to get a definitive answer.
Of course, I could just run the amp at any volume below -08 and never hear the thing come on, but no one ever accused me of doing things the easy way. :0

jeberhart

Well, Mantis, Cliff was posting his note just as I was writing mine, apparently. Looks like he's got us! Read the instructions? Gee, if only I'd thought of that. I'm still gonna call Denon and bug them about this -- why doesn't the fan kick on at lower volumes? Seems like it might help keep the unit cooler at all times, you know? But I guess the sound would be intrusive to some people.
BTW, Cliff, my 3801 is sitting in the catbird seat -- top shelf of my rack -- with absolutely no obstructions, front, back or sides. Clearance to wall behind back is probably two feet, clearance from top of receiver to ceiling is a good four or five feet, and the vents on the left side are at least 3 feet from the side wall of the room, so there's no way I'm crowding it.
Thanks to both you guys for responding -- Cliff for knowing the specs and Mantis for info on how you run your rig. And thanks to Polk, too, because I really love the forum space they provide us with here, you know?

mantis

Thanks,
I was unaware of the fan inside.I never heard mine run.
I have however heard the Onkyo's and Integra's run quite often when pushed hard for a period of time.

You shouldn't worry about it, the fan is there to help dissapate heat under hard use.Don't sweat it at all.when you play above 0db then start sweating for your speakers and the amp.You are asking for trouble in that range if there for a long peroid of time.
As long as you have proper ventilation,which it seems you have, you unit will serve you for a long time.

The avr3801 was the best 1200.00 and under receiver that mated the best with My Polk speaker system.I wouldn't trade it for any other receiver in that price class.