Fans on amps.

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.

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.

Wow, excellent information. I was mistaken, I had 105's installed. Could you clarify your last sentence? Thanks!

@ieales. NEVER BLOW AIR ON / INTO AN AMPLIFIER.  I never knew that ! I thought I was doing something good for the amp. While I was listening to music the other night for a few hours or so I went to feel my amp like I do on many occasions and like always it was so hot u could not touch it for more than a sec. U literally u could of fried an egg on top of if. So I placed a fan right next to the right side of the amp for about a half hour or so and it significantly cooled down the right side of the heat sinks so much that they were only warm now. I didn’t know if that was a good idea or not so I took the fan away and decided to ask you guys for any suggestions about that. I was even tempted to buy another fan and place it on the left side like I did to the right side to have even cooling from both sides of the Krell Fpb 600. Thanks a lot for your advice. 

I run a fan on an amp at such a low rpm and airflow rate, that if it’s power supply is unplugged, it stalls out. It’s a small 12V fan running at approx 4.1V DC. When I plug it in, I have to touch one of the vanes to start it by hand. That is what you call the ’just above stalling’ voltage for the 12VDC fan. Each will be different.

It’s ’just enough’ air flow to move the air away from the heatsinks, and no more. The running temp drops by a good 20-30 degrees.

You can also buy a 12V fan speed controller from a computer shop. One that is all passive, just resistors and a few switches. That would have the least level of interference in your audio equipment.

Do not, I repeat, do not buy a PWM electronic controller of any sort. Buy a small unpowered passive one that uses resistors and is meant to go ’in line’ (in series) with the DC power line for the fan, and uses simple switched resistors to vary the loading or current/voltage that the fan has access to.

The problem is that the passive/resistive/switched fan speed controllers have all died away for the more expensive and ’egotistically more stroking’ expensive electronic ones with switches, big panels, tons of parts, LCD displays, lights, alarms, knobs, etc. This kind of poorly implemented (pulse power supplies, PWM voltage control, and electronic added noise) device is fine for computers (where the entire box is almost pure electrical and RFI noise) but absolutely terrible for high end audio.

You’ll have to search out a simple passive switched fan speed controller, that will have only a few speeds available to you, via the switches, and that’s usually slow, medium, and fast. they are difficult to find as ’passive’ type speed controllers are not cool and complex, and are considered passe and cheap. There is a good amount of them out there, but their specs and build are mostly hidden away from eyes, due to human perceptions about quality.

This kind of simple device:
https://www.newegg.com/p/376-0020-00007

Which is fine, if the cooling considerations you reach for... does not have an electrical system that does not destroy the sonic qualities you are trying to hold on to.

There are some that have simple amplifier circuits and are not PWM modulated, but this will take some discernment on the part of the buyer, to understand which is which.