F5m kit

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#721
audiosteve said:
JeyDee (et al) I like what you said about a fan. I have a problem to solve. We just bought new furniture for the living room. My plan is, now was!, to put the new amp under the new credenza. I have been vetoed by my wife on that so I need to put the amp inside the credenza and be sure it is properly cooled.

I would greatly apprciate any suggestions you or anyone has for brands, models, furniture cabinet mountinglocations, etc, that will do the needed cooling for a well biased F5m.​

I think that is the only way I'll ever get one of Papa's amps into my main system. Many thanks in advance,
Click to expand...

I bought my wife a 77" OLED and put it in the den, also the best couch in the house is in the den.

She doesn't much care if I have three racks of equipment in the living room ( and no coffee table ).

Credenza... well... other than buying something made for audio... like a Salamander.. you might end up putting holes in it to exhaust the air. I did that with an old credenza that we have.... redid the floor of one of the sides with a piece of plywood and two holes with fans. In and Out... with a 3" tube to pull the hot air from the top (fan was mounted on the top intake). BUT, this requires either (a) furniture that has removable bottom pieces or (b) willingness to put holes on the cabinet.

Also, putting the vents (holes) in the bottom is the least damage you can do on a nice piece of furniture. Just make sure there is good flow under the cabinet and that the intake and exhaust holes are reasonably far apart. If you have the room, put a 90 degree elbow on the exhaust side. 3" PVC did it for me.

https://www.quietpc.com/casefans

For temp control, they sell cheap temp control AC switches. Nowadays I got one in the "data closet".

https://www.amazon.com/Temperature-Controller-Thermostat-Greenhouse-Homebrewing/dp/B0B5SSVGSL/ref=sr_1_8?crid=1MFAQ6MQOFS7Y&dib=eyJ2IjoiMSJ9.ii3i07j1nG4nIhOgaWJ7LxpubW1OIMe0HQxVUJRMpkV8OHqwmhsoHgFO7E7b2aJbluo2Ui0uRthLyxOl7HKW1By1C0MVjdROAp4djL5K3hloRRecat2DzEJ20ik_nKeF1BBLH8V9pNu6LzB1AbOkVIc8kzk1q1uI-64KwNy-5pTUO3F-mayooA5kT5jkVXaOylwAMBcxF020E-DJZF7ABn2XAOdjznCVNH3d23T7ecg.sXSrdtndHaMhT08D8jXz0JInEodXOmIP0dPU1B31fq4&dib_tag=se&keywords=temp+controlled+ac+switch&qid=1710186412&sprefix=temp+controlled+ac+switch,aps,138&sr=8-8

But an F3 amp is gonna generate a lot of heat. I used to have a Nuforce STA200 amp in the credenza, which is a rather hot running AB SS amp, but the F5 runs hotter.
 
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#723
birdbox said:
@audiosteve

Are you sure having the fan controlled by temp value is helpful? Its a cool project, however, I'd think "always on" when amp is on would result in reaching an equilibrium state, which is what we want to avoid a fluctuating bias current (function of MOSFET temp). By having a fan turn off and on, based on temp, you'll never reach a state of equilibrium, regardless of the delays built into the control code. Maybe I'm misunderstanding how the fan is intended to be used.
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@birdbox, you bring up a very good point. So mainaining a steady heat sink temperature, not enclosure or cabinet temperature, seems to be the viable solution with a class A amp. That can be done with PWM control OR a full on fan but full on will be more subject to ambient temp. So the real question is, what temperature range is desirable? If anyone kn ows please chime in lest we risk overthinking this. But I will play with it. Your point is well taken, birdbox. Thanks.
 
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#725
@audiosteve

I think if you use a variable speed fan, which those CPU fans are, and tune your control loop, the idea actually could result in a very well controlled heat sink temperature, which would be maintained regardless of room temperature (within reason of course).

Don't let the KISS approach of 'always on' change your plans. I, for one, am very interested in what you come up with and would love to learn how to do what you're suggesting.

For folks like me with, let's say... "novice" microcontroller skills, putting fans that just always run seems like relatively easy solution. I'm pretty sure some Nocturas will just take a DC voltage and fan RPM will be a function of voltage level. No special controller boards needed.
 
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#726
audiosteve said:
So mainaining a steady heat sink temperature, not enclosure or cabinet temperature, seems to be the viable solution with a class A amp. That can be done with PWM control OR a full on fan but full on will be more subject to ambient temp. So the real question is, what temperature range is desirable?
Click to expand...

The steady state heat sink temperature will depend on the bias current setting desired.
 
#727
@rayma

I think the question is "what's an optimal temperature for the MOSFETs to operate at?" Using a well controlled active cooling system means he can target a heat sink temperature to maintain, regardless of bias current (within reason of course). Basically, a highly tuned active cooling system changes the power dissapation coefficient of the cooling system as a whole to maintain a desired heat sink temperature (or MOSFET temp if you measured there) My guess is 55°C heat sink temp is a good target to start with that should be achievable as long as you have enough capability in the cooling system you design. However, I'm still a noob at this F.A.B. stuff, so take my thoughts here with a grain of salt.
 
#729
birdbox said:
For folks like me with, let's say... "novice" microcontroller skills, putting fans that just always run seems like relatively easy solution. I'm pretty sure some Nocturas will just take a DC voltage and fan RPM will be a function of voltage level. No special controller boards needed.
Click to expand...
If you get a 3 pin PC fan, the 3 pins are ground, power (+12V) and RPMs (yellow wire)
Ignore the yellow wire, and provide a voltage of 12VDC or less, fan speed will be proportional to voltage.
Stay away from the 4 pin PWM fans, they are more complicated, unless you get a fan controller for it.

It will take some minimum voltage to startup the fan, so if your voltage is too low the fan will do nothing.
 
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#730
@Holzarbeiter

Affordable fan controller. Will this work?

Screenshot_20240311_134226_Chrome.jpg
 
#732
Holzarbeiter said:
'm using the same fan but in 120mm. I can't find anything to control it.

Forced to think of buying a 5V transformer or so and run it all the time as you have.
Click to expand...

https://noctua.at/en/nf-p12-redux-900/specification

Specs say 11mA current draw. Perhaps you can steal the 11mA from the amplifier power supply. Put the fan in series with a resistor that will drop the voltage to 12V or less based on the 11mA current.

Edit: Just thinking, perhaps that is not such a good idea. It could put noise into the power supply. But it would be easy to try and find out.
 
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#733
birdbox said:
I think the question is "what's an optimal temperature for the MOSFETs to operate at?" Using a well controlled active cooling system means he can target a heat sink temperature to maintain, regardless of bias current (within reason of course). Basically, a highly tuned active cooling system changes the power dissapation coefficient of the cooling system as a whole to maintain a desired heat sink temperature (or MOSFET temp if you measured there)
Click to expand...

The circuit design and performance dictate the setting of the bias current. Then the implementation will dictate
the operating heat sink temperature at that particular power dissipation level. Class A amplifiers have a constant
power dissipation, independent of signal level.
 
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#739
rayma said:
The circuit design and performance dictate the setting of the bias current. Then the implementation will dictate
the operating heat sink temperature at that particular power dissipation level. Class A amplifiers have a constant
power dissipation, independent of signal level.
Click to expand...

Thank you, that makes sense. The question I was trying to help understand was about a good/safe heat sink temp target for an active cooling system. If we adjust the bias higher, then heat sinks will have dissapate more power, which means they will get hotter. Unless, that is, if we have a fan based cooling system that increases convective cooling flow to try and maintain a specific heat sink temperature (within reason of course). At or below 55°C seemed like a good spot to start based on passive cooling targets folks have mentioned, but again, I'm noob here. I'm interested in this as I'm considering a 3U chassis for my F5m. I grabbed a 140mm Noctura fan and that cheapo 4-pin controller board from Amazon to play around with. There's always the liquid nitrogen option 🙂
 
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