Amps with fans

Mathew_M · « **on:** 26 Mar 2003, 04:10 am »

No I'm not talking about taking sides on either the AVA or Odyssey battle but those who have experience with an amp that has a built in fan to cool. The AVA modded Hafler 500 amp I'm looking at buying has such. The seller says it is about as loud as a computer fan when idle. This seems too loud to me though he says that he doesn't notice. My setup is in a small room and I do listen to a lot of subtle stuff.

thanks

Pez · « **Reply #1 on:** 26 Mar 2003, 05:07 am »

I had the same problem with my QSC power amp. The fan was as loud as a computer fan which is completely unacceptable. The reason I kept the amp is because you can buy an ultra quiet fan and mod. the QSC. Once the new fan is inplace the amp is completely inaudible from the listening position. Perhaps there is a low noise fan you can have put into the modded hafler.

Mathew_M · « **Reply #2 on:** 26 Mar 2003, 05:49 am »

...not sure about the low noise mod. I will ask Larry from AVA. I was all set on buying this amp until now. Damn, there's always a catch.

nathanm · « **Reply #3 on:** 26 Mar 2003, 06:48 am »

Those 20db fans are amazingly quiet. You can just hear a slight whirring in a dead quiet room. Anything louder than that and you'll be kicking yourself. I know I was when I got my QSC. Thank goodness they OKed the use of a Panaflo. The stock fan was still audible with the amp in a nearby closet but with the quiet one I was able to put it in my rack with the other stuff. Sweet! I improved my signal to noise ratio considerably!

If the Hafler won't melt down with lower air flow I'd go for it, otherwise I think it would be annoying.

Pez · « **Reply #4 on:** 26 Mar 2003, 02:13 pm »

Which QSC do you have Nathan?

nathanm · « **Reply #5 on:** 26 Mar 2003, 04:20 pm »

I have the PLX-1602 (er, I think that's the number).

Raj · « **Reply #6 on:** 26 Mar 2003, 05:33 pm »

Hi,

Check this fan out only 12db!!!!!
http://www.overclockers.co.uk/acatalog/Online_Catalogue_Papst_Fans_61.html

Thanks
Raj

Carlman · « **Reply #7 on:** 26 Mar 2003, 06:43 pm »

Why not just route some plumbing via a central system like big house vacuum cleaners...? That way the fan is nowhere near the equipment and you can increase the airflow!

nathanm · « **Reply #8 on:** 26 Mar 2003, 06:52 pm »

Or how about a big metal heatsink?!

Tyson · « **Reply #9 on:** 26 Mar 2003, 06:55 pm »

Noisy fans absolutely suck in amps. I have a crest pro amp with fans, and even stuck in the closet the fan noise is annoying. I do have to say that the fans in the QSC amp that Jason has are very quiet and I could live with those amps. Anything louder than that and forget it!

Raj · « **Reply #10 on:** 26 Mar 2003, 07:14 pm »

Incase no-one noticed the fan I mentioned is only 12db, hardly audible at best, couple this with a 0.40 oC heatsink and you'd get cooling in the region of 0.15 oC, what's wrong with that? I agree that loud fans are a problem when listening at low levels, but at 12db you should have no problems whatsoever.

Thanks
Raj

bubba966 · « **Reply #11 on:** 26 Mar 2003, 07:30 pm »

Raj,

I built a 'puter for a friend a month or so back and used 4 of the 12 dB Papst fans.

They are very, very quiet.

If they'd have sufficient airflow for the application in the amp, it certainly wouldn't be bothering you noise wise...

Eduardo AAVM · « **Reply #12 on:** 26 Mar 2003, 11:42 pm »

I do not like it in my experience sooner or later you get mad about the fan sound. Even the noise from the one in the Onkyos 989's is enough to have some of my customers crazy and thinking about using separate power amps instead. And remember that Onkyo target it's product as higher end so you can expect worse performance from conventional power amps with fans.

Raj · « **Reply #13 on:** 27 Mar 2003, 05:46 pm »

Hi Eduardo,

What was the noise output of those fans in question?

Thanks
Raj

ABEX · « **Reply #14 on:** 27 Mar 2003, 07:55 pm »

Tyson I agree and it's the only reason I pass on some amps

.Almost or is as bad as HUM!

agattu · « **Reply #15 on:** 27 Mar 2003, 08:44 pm »

I own the Rogue Tempest Tube Integrated Amp. Rogue Audio's amps uses damn near dead quiet cooling fans. They are nowhere near as noisy as computer fans and are never a nuisance.

Eduardo AAVM · « **Reply #16 on:** 27 Mar 2003, 09:06 pm »

Hello Raj I never measured the dB noise, it the 989 is in a customer's home, but from 2 m distance you can hear at medium volume level how the fan switched between low and high speed modes. Maybe it wasn't so bad but it depends on what are your personal liking and hearing sensibility.

Also I do not know if all of this products have the same noise level.

avahifi · « **Reply #17 on:** 28 Mar 2003, 03:50 pm »

Hi:

Hopefully I can clear up a few things regarding the fans in the Hafler DH-500 chassis. Hafler used an internal heatsink that has a three speed fan located toward the front of the chassis. The fan draws air in from the sides of the chassis and blows the air through a channel (tunnel) of internal fins in the heatsink and out the back of the chassis. Hafler claims that the fan when running on low speed "is so quiet that your ear must be close to the vent to hear it." See the following link for the manual on the original DH-500: http://www.hafler.com/techsupport/pdf/DH-500_amp_man.pdf

When we modify the original DH-500 chassis we use the existing heatsink assembly and power supply parts needed to run the fan. If may be possible to install a different fan, but there are a few things that must be considered.

First, the Hafler fan is a three speed AC line voltage fan. The fan speed is controlled with a series of heat sensors on the bottom of the heatsink and a set of power resistors that controls the voltage to the fan and thus the speed. Because the fan run on AC there is no low voltage DC source for a typical PC fan that runs on 12 volts. If you wanted to install a DC fan you would need to add a DC power supply, most likely a small transformer and associated circuitry.

Second, the Hafler fan "pushes" air through the heatsink. If you install a new fan you need to make sure it can deal with the air pressures needed to push air through the heatsink channel.

Third, electromechanical (EM) radiation from the fan needs to be considered. We have dressed the wires throughout the chassis to deal with the fan's EM and make the audio as quiet as possible. If you replace the fan you would need to examine the EM characteristics of the fan to make sure it's very low, and you would need to carefully examine wire routing. Overall care would be needed to make sure you don't end up with a mechanically quiet amp, but an electrically noisy amp.

One other interesting point regarding the DH-500 chassis -- there is a protection circuit in the power supply feed that cuts off the power to the amp if the heatsink assembly gets too hot. I would guess that Hafler added the circuitry in case the fan failed.

In our amp chassis we don't use fans; rather, we use some pretty heavy heatsinks that do a great job of dissipating the heat generated at loud levels (I know they do because I have tried myself, much to my neighbors dislike). Our heatsinks are custom designed so that there is a lot of surface area for air to flow. We have done many thermal tests in house running the amps at maximum heat generation for extended periods of time just to make sure they don't fail. Naturally you need to have some space around the amp to allow for some air flow, however.

The result of our power amp chassis is that they are quiet both mechanically and electrically.

Hope the information helps!

Larry Jenkins

Raj · « **Reply #18 on:** 28 Mar 2003, 06:10 pm »

Hi,

I suppose were talking about 2 different situations here. I do my stuff diy, I have a kit amp, I can just work round these problems and use the quietest fan I can find. Although my amp doesn't specifically need the fan, I wanted to turn the quiescent current up, so instead of going for massive heatsinking I decided to go for fan cooling (actually this was suggested by Hugh Dean aka AKSA). My point is that almost inaudible fans are now available, which is fine for someone like me. But for someone pruchasing a commercial component obviously you're left at the manufacturers mercy with regards to their choice of fan. One may crack jokes about needing massive heatsinking etc, but like I said earlier, when playing music at low level, you shouldn't really be annoyed by with a low noise 12db fan. I suppose the negative views on this topic are mostly cause the fans you have heard used in amps produce a lot more than 12db in operation.

Thanks
Raj

CE · « **Reply #19 on:** 30 Mar 2003, 11:45 pm »

Quote from: Mathew_M

No I'm not talking about taking sides on either the AVA or Odyssey battle but those who have experience with an amp that has a built in fan to cool. The AVA modded Hafler 500 amp I'm looking at buying has such. The seller says it is about as loud as a computer fan when idle. This seems too loud to me though he says that he doesn't notice. My setup is in a small room and I do listen to a lot of subtle stuff.
They are QUIET on low speed (inaudible), I have 2 in the same system, i Bi-amp my Legacys. If I really CRANK it they will switch up to high speed, but since the music is so loud how can you hear a fan on an amp, sounds like a non issue? Even at normal levels the music is louder than the fans
thanks