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I own a Musical Fidelity A1-2008 version class a amp.
The sound is gorgeous, liquid, sweet, smooth, extended highs, tight bass, midrange is a bit forward and clear as a bell. Not much sybilance and overall I can listen for hours with no listening fatigue. One of my favorite amps...HOWEVER, it runs quite hot and since it is now unobtanium (long out of production and they only made a few thousand units from what I have heard) I am worried the heat will take it's toll on the life of the unit.
The case has a "ridged" aluminum top (depth of ridges looks to be only 3 - 5 mm).
I would like to find a fanless solution to supplement the heat sink function of the case.
Currently I do have a "side-blowing" (sounds a little pornographic) muffin fan sitting on the top of the case with air flow directed towards the hottest quadrant of the case top.
But I fear it is not adequate, the top plate is still hot although with the fan operating I can leave my palm on it for 20 seconds or so with minimal discomfort. Without the fan I could not do that.
Any ideas for a supplemental heat sink that could sit on the ridge top plate of the case and provide supplemental heat dissappation?
I thought about those aluminum bricks that are avaailable on the bay for a reasonable price, but sitting on a ridged top plate I doubt there would be much heat transfer, and running the amp for hours at time might even heat up the block to the point where it would not absorb more heat.
I suppose a really strong fan would work but they are all noisy!
I will be a bit heartbroken if this amp dies up before I do :(
thanks for any ideas!
[[edit]]
Maybe a Peltier cooling device? But how loud is the fan? And sitting on a ridged case, the heat transfer would be poor?
sex after 70 is like trying to play pool with a rope
Edits: 09/13/20 09/13/20 09/13/20 09/13/20 09/13/20Follow Ups:
I'm not familiar with this piece of equipment but I am familiar with a couple ways of reducing operating temperatures.
You could remove the cover and have it sandblasted with a fairly coarse grit top and bottom. This will increase the surface area allowing for better hear transfer. Use relatively low air pressure, no "industrial" blasting.
The surface is most likely simply painted. There are "heat transfer coatings" that are more efficient than paint. Always apply a thin coating.
Most coating shops will do blasting before coating anyway. Cheap hobby store Badger spray guns work well for the coatings I have used. Tech-Line and Cerakoat have them in small quantities.
John
Per Dr. Who: "Run!"
NOCTUA fans are perhaps the quietest available.
Cooling can have an adverse effect so do not over do.
Also? Chances of proprietary parts are very low. All parts should be available with the exception of chassis parts and circuit boards.
I'd immediately send off for a SCHEMATIC of the amp if they haven't locked it in a safe and thrown away the combo. Some companies are funny that way.....
Too much is never enough
I used to have the A100 version from the 1990's.
I bought it second hand, kept it a week: it was so hot to the touch (including the potentiometers) that it was barely useable.
Then some day while I had my back turned my stupid flatmate put a newspaper on it and I thought the thing was about to melt... fortunately nothing bad happened but that incident made me return the amp and get something less dangerous.
I've had some other classA amps since, but none that would get as silly hot as this MF amp. Far from it. The way they conceived it is flawed for long term reliability IMHO... so yes, you might want to add some heat sinking if you plan on keeping the amp!
There are some interesting threads out there on the A1 2008 design.
The DIYers have the parts list and those power transistors are well known for being very musical but very difficult to control thermally.
The DIYers were burning up the transistors right and left trying to make them work biased in class A, without success.
So no one has been able to repeat what MF did with them AFAIK.
sex after 70 is like trying to play pool with a rope
I think you have little to be concerned about since the heat being transferred to the top of the enclosure is a sign that it is an effective heatsink. If the top panel was not hot, that would be a bad sign, since the heat would pose a real problem for the transistors. I expect the Zippi fan will do what you wish by providing cooling of the top panel which is acting like a proper heatsink.
I have a Newmar marine power supply that runs hot enough to burn my fingers when I touch the massive aluminum heatsink, and as a result I'm sure the PSU is not being stressed by the load.
First thing you want to do is have the amp serviced by a competant technician. Have him clean out the old silicon grease (thermal paste) from the output transistors and the mating site on the inside of the heatsink. Reinstall with plenty of new silicon grease. Then check the bias and adjust to spec. Bring it home and run it for an hour and then measure the temp with a digital thermometer. Install your chosen supplimental heat sinking device and measure again after an hour to see if you have a lower overall temp. If you can reduce the temp by 10-15 degrees thats plenty. I have serviced lots of those amps over the years and they do run hot. A complete service every couple of years as above will extend the life. Consider changing the output transistors as they are certainly stressed by now if they are the originals. Should not be too expensive but pay a little more to a real pro over a bargain fix by a cowboy. Nick Gowan at True Sound in Campbell California is highly thought of.
Edits: 09/14/20
Agreed 100%. I recall working on an old Krell KSA 100. The thermal paste had essentially turned to dust and as such lost its heat transfer characteristics.
If you replace the output devices you may wish to purchase some spares should they be discontinued in the future.
"Plenty" of silicon grease will only make the heating problem worse. Grease should be applied only at the very minimum to ensure intimate contact between the active device and the heatsink. Excess reduces conduction of heat.
berate is 8 and benign is 9
I don't know how it applies, but when I installed a new copper / aluminum 'mushroom' heatsink on the CPU of my computer, I put on a layer of Arctic Silver and scraped it flat with a razor blade. The I installed and secured the heatsink, I got a VERY tiny 'squeeze' of compound around the edge. I never looked back OR had to touch it again. Ran quite a bit cooler than stock, especially when doing intense tasks like processing images in Photoshop.
Too much is never enough
Perhaps removing the top cover would also be helpful.
Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed. - Albert Einstein
possibly OK to try only if you are replacing it with another heatsink.
The cover IS the heatsink. Amp should never be on without the cover.
Apologies in advance if you already knew this and I just misread your post!
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Even if the top cover is the heat sink, does it not also act to keep
heat inside the case? And if this is the situation, would not removing the
top cover/heat sink allow more heat to escape, thus obviating the need
for additional cooling? Or am I missing something?
Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed. - Albert Einstein
Air alone would not dissipate the high heat from the output transistors in this class "A" design. You need heatsinks.
The transistors are mounted on a (aluminum?) bar. The bar is coupled to the cover with thermal paste. The cover is ribbed to work as a large heatsink.
If the cover is hot it is working properly.
Remove the cover, the transistors will overheat.
Musical Fidelity did this interesting design to maintain a modern slim look.The alternative would be to have a taller cover drilled for ventilation. And then large internal heatsinks for the transistors.
Hope this makes sense.
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
for using the top cover as a heat sink. I think.
I'm not an engineer, and my understanding of physics is rather limited
(to say the least!), so I defer to those who are more knowledgeable in
these matters, such as yourself.
Whether or not you can observe a thing depends upon the theory you use. It is the theory which decides what can be observed. - Albert Einstein
I'm no technical expert either. Sometimes I feel comfortable commenting only because of trial and error experiences.
In this instance, besides my own experiences with heat sinks, I related to the many super (gaming) computers my two sons have built over the years with heatsinks, fans, and water cooling systems. In their case it was for processor chips vs output transistors.
So much crossover technology out there!
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
I have the 2008 A1 version anyway, I understand it is quite different eletrically than the original A1.
this is a good photo (not mine)
sex after 70 is like trying to play pool with a rope
My understanding is that all the A1 models use the ribbed cover as a heat sink. It is coupled with thermal paste to a metal (aluminum?) bar inside. The output transitors are mounted on the bar.
The heatsink cover is working properly when running hot. It is drawing heat away from the bar/output transistors.
The fact that the temperature has remained consistent all these years is a good sign that the integrity of the thermal coupling is intact. In fact a "cold" cover would indicate an internal issue.
The fan you bought will help the cover dissipate the heat faster and allow the temp to drop to the touch and internally.
Excellent fan suggestion by Duster in that it can work vertically.
Overall good idea to cool things down to prolong the life of your amp.
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
That is a great idea and is now on my official todo list.
Maybe this winter since I can use my OTL tube amp once the temps drop below 100f here in Vegas.
I have only actually used the amp for maybe 24 months total on and off over the years switching with my other amps.
sex after 70 is like trying to play pool with a rope
A couple of replies in this thread suggest to add a 'coat' or 'plenty' of thermal grease. The thermal resistance is not that low but it is better than air so the role of the grease is to fill any tiny voids in the mating surfaces, so, should be applied sparingly. You don't want a coating of grease keeping the mating surfaces further apart than they need to be.
13DoW
my Kinergetics Class A has a built in fan and is very quiet. That's what you want, silent running like a Red October.
Maybe a used Rotron Whisper Fan. I don't know if they are available new because I've had several for 30 years and they still work nice. A variac will control the speed to very quiet levels if necessary.
"Bass is the place..the rest is filigree and lace" Doug Sax
A fan is only bandage and doesn't fix the cause. If the amp hasn't run that hot in the past then a fan will only treat the symptom and hasten its demise. If running hot is a recent issue then I'd find out what is causing it to run hot and address that.
Thanks!
The amp has always run as hot as it is running now. This is a known characteristic of these class A musical fidelity amps.
I am just trying to "baby" the amp as I am retired now, these are no longer being manufactured, and would not be able to easily replace it with similiar quality.
sex after 70 is like trying to play pool with a rope
Image: Vornado Zippi
Your muffin fan should be sufficient if you place an aluminum heat sink coated with thermal paste on top of the enclosure, with the fan blowing down into the heat sink fins.
Folks often use a 12V fan with a 6V power supply to keep the fan noise very quiet.
Another option could be to use the very quiet, compact Vornado Zippi soft blade table fan. The metal stand allows the airflow to be aimed down onto the top of the enclosure. It pushes a lot of air with no noise, whatsoever.
I can easily hear mine across the room at low speed so, in my opinion, it's not suitable for audio systems. It's now on my bench blowing solder fumes away from my face.
Maybe you got a bad unit, or you have super ears :)
sex after 70 is like trying to play pool with a rope
I've used these for years and they're dead quiet.
It's not motor noise. It's the noise of a fan blowing air.
I use a Zippi blowing right in front of me while using a computer.
While on the low speed it's dead quiet. On the high speed only a slight whirling sound can be heard.
Nothing that even low-volume music levels are affected by, IME.
The zippi fan is working great, very very quiet, I would even say silent at the low speed, and at low speed it has reduced the top plate temp of the case very significantly. Can't say it is even hot now, just warm.
I don't have a non contact thermometer handy but the temp is certainly safe now from premature failure.
Don't know how long the fan will last running 5-10 hours per day but it is very solidly built and only cost $15 delivered from Amazon. And of course I will organize things better (moving this month anyway into a new home)
sex after 70 is like trying to play pool with a rope
thanks Duster, I have one arriving today from Amazon.
And if I don't like it for the amp I can always use it somewhere in the house here in Las Vegas...
sex after 70 is like trying to play pool with a rope
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