Ok, lets try THIS fan question

[daz]

I decided to go with a 115v fan and turns out it causes no noise at all, so it's all good. However, i'm not sure what the best way is to implement it. I can set it so it's blowing directly on the CPU heat sink, away from it, or on the chassis to suck hot air out of the chassis, or into the chassis. I already determined it is a heat related issue because it goes away when i keep the chassis cool with a house fan. And I'm not 100% sure but it's possibly and most likely the CPU. But the house fan is a hurricane compared to a little cooling fan so it must be implemented the best way possible to insure it will cool well enough. So of those 4 methods which would you use? I hooked it up temporarily to a cord and plugged it in and stuck it where it would be right in front of the CPU very close to the main board and theres no noise, so thats not an issue. And the way things are laid out it will be easy to logistically implement it in any of the ways i mentioned.

[g1]

On CPU's that have fans attached, I'm pretty sure they blow air towards the CPU.
That being said, the fan is not going to cure what ever fault is making the amp overheat. The underlying cause will remain.

[daz]

There is no fault as in defect, etc. It's a design flaw that most with this amp have. I'm the second person whos discovered a house fan on the chassis stops the issue. But my reason for this post is to ask those who understand cooling what the best way to implement it would probably be. I'm not sure if sucking the air in or out would be the best way, but then i;'m not sure what past is truly causing the issue so maybe that IS the best way since it would cool the entire chassis albeit less cooling to the culprit. In any case i'm just asking to see if anyone has anything to say that i may not have thought of before i go ahead and do it the way i think is the most likely best way, pointed directly on the CPU board.

[TomCarlos]

I checked the amps I have. The fans are mounted on the case, they pull air from the outside and towards the heat sinks. The hot air then escapes somehow. So that seems to be the trick; having an easy path for cooler air to come in, glide over the heat sink, and then escape.

And I was thinking about the fan mounted my car's engine. "The fan must move the air in the same direction that the air moves when the vehicle is traveling forward." Air comes in through the grill, passes through the radiator, and then is blow towards the hot engine. That air flow then escapes from the sides and towards the bottom of the engine.

[Enzo]

MAkeup air is as important as source air. The fan blows in on the heat sink, but needs an exit. If you cover the exits, all it does is pressurize the chassis.

I had a customer once with a rack full of Yamaha power amps. They had front vents to draw air in. He decided he needed more cooling and so mounted three fans on a rack panel and mounted it in the rack too. Unfortunately he had the fans blowing in. SO instead of adding air flow, his three fans were fighting the fans in the Yamahas. Everything started overheating.

[daz]

there are vents, both on the rear panel and below

[tubeswell]

Sucking air in and blowing it at the CPU will be best (assuming its cool air)

[daz]

Sucking air in and blowing it at the CPU will be best (assuming its cool air)

I just installed it. I don't wanna put a second one in because they are kinda loud and i don't want to cut it up to add a bottom one to suck air in. It's not an issue of anything getting way too hot, just something that happens on occasion so i think think one fan placed right will keep it under the point where it causes the issue. It has a vent on the bottom and at the top rear so i think air with circulate with hot air rising out the top. I just pointed it at the CPU and at an angle so it also catches the PSU for good measure. If i could have used DC PC type fans i could have use several much easier but i got no answers concerning implementing DC fans with respect to potential circuit noise. So i just went with AC but they are much larger and louder and harder to implement. Had i used DC fans i could have easily used 2 and put one on the lower vent to suck cool air in. But i think the one AC fan i put in should keep the issue at bay. I also put a switch in too so i can leave it off and wait till the issue again presents itself then turn the fan on and see if the issue stops which will tell me i did it right. The issue never stops on it's own till i pointed a house fan at the chassis. So hopefully this should be even more efficient and switching the fan on when the issue begins will tell me 100% whether it does the job or not. It can be very intermittent tho sometimes happening weeks apart so time will tell. Great video by the way !!!

[Jazz P Bass]

As to the issue of pulling Vdc to power the fan, it really does depend on the power supply.
I had a PRO Audio power amp (2 in fact) in that had a 7mv hum on the outputs.
It went away when I disconnected the fans.
It had a linear power supply.

[daz]

Here's another question. At first it seemed there as no fan induced noise but now i am noticing there is. It's slight so i am not real concerned, but is there something i can do to reduce/stop it?

[nevetslab]

Here's another question. At first it seemed there as no fan induced noise but now i am noticing there is. It's slight so i am not real concerned, but is there something i can do to reduce/stop it?

Dealing with Fan noise is a multi-faceted issue. Before getting into the loading issue on how the fan interacts with the chassis, and whether in such designs, it's pulling air in from the outside, or forcing the air inside to exhaust to the outside, there is the CFM Rating of the fan itself, the bearing types, as well as how a given fan, say 33 CFM, behaves with the load on the fan. Mounting of the fan is also an issue. I recently had to deal with the rear panel 120mm size AC fan for an Ampeg SVT-VR, whose fan had been in service for several years, and, finding a new fan that would be an improvement required purchasing several fans...three of the same/similar CFM rating, as well as a couple with lower CFM rating (Cubic Feet per Minute).

In general, lower CFM rating will yield lower overall acoustic noise. Those of same/similar CFM rating had a different acoustical noise signature, found using a laboratory microphone feeding a spectrum analyzer, as well as my ears for the subjective impression. In this particular instance, I also installed shock mounting made from surgical tubing, to lift the fan slightly off the full perforated grille, though still having mechanical contact thru the four mounting screws. I ended up using one of the similar CFM rated fans, and got an average 5dB improvement overall.

Often, it's just a matter of replacing an aged fan whose bearing noise has become beyond effective service where it's acoustical noise is too great. When just replacing a noisy fan, I'm usually reluctant to use the same make/model, unless I'm real familiar with that mfgr and am sure what I'm replacing is at the end of it's tolerable noise life. Expensive adventure unless you're a manufacturer, where sampling new fans for existing or new products is supported by the fan mfgr representatives who are looking for that yearly quantity order.

Below was an exercise in both reducing and changing an 80mm 120V cooling fan mounted to the wooden front panel in an Ampeg SVT-CL, where I had cut a shock mount pad from white packing foam, increased the mtg hole diameter to use shock mounting of some #8-15 x 3/4" Truss Head screws, plus showing the B & K 1/2" measurement mic and the B & K 2035 Spectrum Analyzer, first showing the room's residual acoustical noise without the amp/fan noise running, then the noisy fan, and finally a new quieter fan.

[Helmholtz]

CFM rating (Cubic Feet per Minute).

Thanks for this!

[daz]

I should clarify it's not the acoustic noise i'm talking about but electronic. The AC fan is somehow injecting noise into the circuit.

Dealing with Fan noise is a multi-faceted issue. Before getting into the loading issue on how the fan interacts with the chassis, and whether in such designs, it's pulling air in from the outside, or forcing the air inside to exhaust to the outside, there is the CFM Rating of the fan itself, the bearing types, as well as how a given fan, say 33 CFM, behaves with the load on the fan. Mounting of the fan is also an issue. I recently had to deal with the rear panel 120mm size AC fan for an Ampeg SVT-VR, whose fan had been in service for several years, and, finding a new fan that would be an improvement required purchasing several fans...three of the same/similar CFM rating, as well as a couple with lower CFM rating (Cubic Feet per Minute).

In general, lower CFM rating will yield lower overall acoustic noise. Those of same/similar CFM rating had a different acoustical noise signature, found using a laboratory microphone feeding a spectrum analyzer, as well as my ears for the subjective impression. In this particular instance, I also installed shock mounting made from surgical tubing, to lift the fan slightly off the full perforated grille, though still having mechanical contact thru the four mounting screws. I ended up using one of the similar CFM rated fans, and got an average 5dB improvement overall.

Often, it's just a matter of replacing an aged fan whose bearing noise has become beyond effective service where it's acoustical noise is too great. When just replacing a noisy fan, I'm usually reluctant to use the same make/model, unless I'm real familiar with that mfgr and am sure what I'm replacing is at the end of it's tolerable noise life. Expensive adventure unless you're a manufacturer, where sampling new fans for existing or new products is supported by the fan mfgr representatives who are looking for that yearly quantity order.

Below was an exercise in both reducing and changing an 80mm 120V cooling fan mounted to the wooden front panel in an Ampeg SVT-CL, where I had cut a shock mount pad from white packing foam, increased the mtg hole diameter to use shock mounting of some #8-15 x 3/4" Truss Head screws, plus showing the B & K 1/2" measurement mic and the B & K 2035 Spectrum Analyzer, first showing the room's residual acoustical noise without the amp/fan noise running, then the noisy fan, and finally a new quieter fan.

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[g1]

You used AC fan? 120V? Where did you connect for power? Where did you route the wires?
Pictures would help.

[daz]

You used AC fan? 120V? Where did you connect for power? Where did you route the wires?
Pictures would help.

I took the power from the switched side of the power switch and routed the wire as away from all boards as much as possible. Would twisting the wires help ?