Amp Camp Amp - ACA

music soothes the savage beast
Joined 2004
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Question: I see in the advertisment for this amp in the store that it makes more power because of a better power supply. Would running it off a couple 12v batteries help even further? One of my amps is a Virtue M901 tripath and it made a pretty big difference to run it off batteries instead of the power supply it came with which is similar to the Meanwell on the ACA.

ClassD draws almost no current when idle. ClassA draws full current all the time. Apples to oranges.
 
Hi all,
I hate the idea, but It looks that I have to put a fan in my aca amp box!
Box closed today and after warming up for 1 hour, my heat sinks reaches 64.5c at some spot . Mosfets surprisingly were at about 57c on visible side! Which does not make so much sense even if the heat conductive part is on the heat sink side!
I am using a laser pistol thermometer, I know them to be quite inaccurate on raw aluminum ! And was just now wondering if the measurement is correct on the type of composite used for the mosfets ! I actually notice the same thing on some cl-60 inrush limiter!
What are you guys using to sense temperatures ? Thermocouple ?
Someone’s recommandations , for a quiet case fan of 60mm max ?
Thanks
 
Official Court Jester
Joined 2003
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music soothes the savage beast
Joined 2004
Paid Member
Hi all,
I hate the idea, but It looks that I have to put a fan in my aca amp box!
Box closed today and after warming up for 1 hour, my heat sinks reaches 64.5c at some spot . Mosfets surprisingly were at about 57c on visible side! Which does not make so much sense even if the heat conductive part is on the heat sink side!
I am using a laser pistol thermometer, I know them to be quite inaccurate on raw aluminum ! And was just now wondering if the measurement is correct on the type of composite used for the mosfets ! I actually notice the same thing on some cl-60 inrush limiter!
What are you guys using to sense temperatures ? Thermocouple ?
Someone’s recommandations , for a quiet case fan of 60mm max ?
Thanks
I have recently purchased infrared thermometer. Works fine, very precise, but just like ZM mentioned, laser spot does not agree exactly with measured spot.
They coincide quite far, but in close proximity they are apart. I made small extending tube infront of infrared sensor and I place it close to the part and I get very accurate reading this way.
If your heatsink is 65, output mosfet is close to 100, you are just not measuring correct spot.
 
I have recently purchased infrared thermometer. Works fine, very precise, but just like ZM mentioned, laser spot does not agree exactly with measured spot.
They coincide quite far, but in close proximity they are apart. I made small extending tube infront of infrared sensor and I place it close to the part and I get very accurate reading this way.
If your heatsink is 65, output mosfet is close to 100, you are just not measuring correct spot.

Is this 100c still good for the mosfets? Would you recommend installing a fan? I guess my mosfets also reach such temp since I live in a tropical country
 
You can test with wet finger if mosfet reach 100 C at the surface. Why not just use ACA as is and if ok after 1 or 2 month it will probably survive many years. Problem may be temperature inside the case as E-caps does not like high temperature. It will be good to keep those below 40 C or so. So try also with box closed to measure top cover (after a couple of hours) and see if it stays below 40 C (I assume top cover will have approx. same temp as air inside the box).
 
You can test with wet finger if mosfet reach 100 C at the surface. Why not just use ACA as is and if ok after 1 or 2 month it will probably survive many years. Problem may be temperature inside the case as E-caps does not like high temperature. It will be good to keep those below 40 C or so. So try also with box closed to measure top cover (after a couple of hours) and see if it stays below 40 C (I assume top cover will have approx. same temp as air inside the box).

I read somewhere that I should be able to touch the case for at least 10 seconds. My palms can tolerate the heat less than that with them.flat on top of the case.
 
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Hi Syl20m,
The fins on your heatsink look much shorter than those on the official ACA chassis (if I recall they’re about 50mm). I built an ACA similar to yours (my fins might be taller) with an internal power supply, and my heatsinks run at 60° (25°C ambient) with some internal components approaching 80°C.
Amp Camp Amp - ACA

I’m planning to vent the bottom plate and add a heatspreader (copper bar) before the weather heats up -it runs fine in my poorly heated garage during the winter months .
You could also try running your amp at a lower voltage (say 19V) to help it run cooler.

-Olen
 
Another ACA custom box

Hi all,
I finished my ACA a few weeks ago and thought I'd share it. It's two kits (4 individual amps) with my speakers bi-amped. I'm running the stock external SMPS with each pair of amps completely separated (there's insulation between the heat sinks so they don't touch). There's no extra space inside, and no airflow from bottom to top, so I added two 80mm "Silent" fans. They're turning pretty slowly and are very quiet. I can hear them if I stand right by the amp, but not from where I listen.

The highest ambient temp I've hit so far this year is 22 C. At that temp, the case internal temp is 30 C and the highest temp on the heat sink is 52 C.

You can see in one of the pics below that there are small holes (wire gauge drill, I don't recall which one) drilled around each transistor. That allows a small amount of air to be pushed through to the top of the heat sink which helps the hot air rise off the the top. It helps to over come the inefficient orientation of the heat sinks.

The heat sinks are 40mm Heatsinks - 250 x 210mm 0.19 C/W from the DIY Audio store, here.

The two pre/headphone amps in the pic are an O2 and a LittleDot MK III.

Forgive the abysmal speaker placement. I don't have a lot of options right now.
 

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Thank you for the kind words, RafaPolit, I was quite happy with how it turned out. I'm practicing my wood working skills as I'm learning about amps. Two things I enjoy quite a bit coming together!

For now, they're not PWM controlled. I just used the resister lead they came with to plug them in which slows them down pretty well. In the (not so distant?) future, I'll add an Arduino that controls fan speed based on input from a K-type thermocouple.

For power, I used a 12 volt SMPS that I luckily had laying around. That had the benefit of keeping both halves of the amp completely separated, but at the expense of a third plug. Oh well. I can live with that.
 
That had the benefit of keeping both halves of the amp completely separated, but at the expense of a third plug.

I should clarify... of course there are a hundred other ways to keep the halves separated, but this was the simplest way that was separated, maintained balanced power, and didn't require buying or building anything extra (I already had the power supply).

If anyone has feedback on how much extra power may be on tap from each of my ACA power supplies, I may run each channel's fan off of its own ACA power supply when I get back to the Arduino part of the project. I just don't want the fans to affect the power available to the amps.

Or I may measure that... or I may just stick with 3 plugs... it's not a big deal to me.
 
For now, they're not PWM controlled. I just used the resister lead they came with to plug them in which slows them down pretty well. In the (not so distant?) future, I'll add an Arduino that controls fan speed based on input from a K-type thermocouple.



Unless you want to learn and play with arduino, the eBay pwm controls already come with a thermocouple and cost a few dollars... The meanwell power supply I use already has a +12v output for a fan. Very handy...