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Fans on amps.

Ive been checking out some posts about fans by amps but cannot find anything about them being good or bad for the amps. This is what I would like to know. Ok. I have a Krell Fpb 600 and I listen to my music about a 28-30 volume on my ARC Ref 6 which is pretty loud most of the time depending on recordings. Tonight I felt my amp like a lot of times and felt very hot like u could fry an egg on top. This is the normal with a few hrs of listening. Anyway I put a fan on the right side of amp and about a half hour later I checked the right side and was significantly cooler I mean like a night and day difference between the right and left top and heat sinks. I was wondering if adding 2 fans one on each side to cool the amp down would do more harm than good. Would I get more life out of the amp with fans ? Or are amps designed like that without using fans and just heat sinks to get rid of the heat. Btw my amp has plenty of ventilation as it is on the floor. Thanks. 
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ieales's avatar
ieales
1,201 posts
 
  1. fans should pull air AWAY from the amp
  2. use inherently low noise fans with sub 30db ratings
  3. use 12v DC fans on a variable AC/DC adapter
  4. adjust the DC level so the fans run slightly above the stall point

Each installation requires its own design.

On a tube amp with cage, fans mounted atop the cage will keep the whole amp comfortable. For a PrimaLuna with 4 power tubes in line, two fans. http://ielogical.com/assets/Audio/PrimaLunaAmpFans.jpg These fans have been running for about 3 years and have zero dust build up.

For a SS amp with external heatsinks either use a rack and mount fans to pull heat away from the amp or fabricate a stand to draw air away from the amp.

!!! NEVER BLOW AIR ON/INTO AN AMPLIFIER !!!

Keeping the amps at more constant operating temperature makes them sonically more consistent and prolongs their life. HEAT KILLS

I’ve been doing this for more than 40 years.

Power supply example: https://www.amazon.com/AUTOTOOLHOME-Adapter-Adjustable-Supply-Controller/dp/B01M3NL3NV
evelyn1
51 posts
 
I see anotherbob already mentioned the AC Infinity fan unit. Must've been still asleep earlier this morning. I checked the Audio Advisor site and they are still selling them. T9 is the top mount version.
ieales's avatar
ieales
1,201 posts
 
AC Infinity fan unit
One purchaser mentioned it is quite audible at anything above a 1.

This device will pull air through the amp and likely build up dust in the bottom vents.

What is desired is to pull a small amount of air around and away from the amp. The airflow should be incapable of moving dust or holding a piece of cellophane against a vent.

Avoid any unit that cycles and does not provide CONSTANT air flow. Inconsistent airflow over grilles can be distracting.

Size fans for the device so they can run at minimum speed.
captaindidactic
79 posts
 
I have the AC T9, seems very quiet to me. I have 80's NAD amps and never ran any cooling on them and they lasted quite well. But I did notice that I was losing some bass. I took it in and had all new capacitors and learned that there are two types of temperature ratings for capacitors. 85 degrees and 110. On my amps, it had all 85 degree caps. They are rated to work at that temp for x amount of hours. Then they start to deteriorate. Anyway, putting in all new caps Really increased the bass and the overall sound. It did however take a full month of 24/7 playing to burn in the new components. Every service person I spoke with said "keep them cool!" Now, running the amps with the fan, the temp never exceeds 82 degrees. 

Just my two cents.
ieales's avatar
ieales
1,201 posts
 
I have 80's NAD amps
Electrolytic capacitors have an industry rated life of about 15 years. Anything beyond that is borrowed time, running or not.

Capacitor temperature ratings are 65°C, 85°C, 105°C & 125°C

Caps are rated for about x000 hours @ the rating temperature. They start deteriorating from the instant they are made. For each 10°C decrease in temperature, double the life.

85°C caps rated for 2000h in an amp running @ 35°C [95°F] have an rated life of 8000h. Run a couple of hours a day, that's 4000d or more than 10 years. In well designed devices like NAD, caps a rarely likely to be much over warm.

Old electrolytic caps increase ESR and decrease in capacitance. Loss of bass indicates capacitor coupled [boohoo] stages.
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