Popular Post mansr Posted January 19, 2020 Popular Post Share Posted January 19, 2020 I was goofing around with a PCM1794A chip when the idea occurred to me to see what happened if I hit it with some freezer spray. Monitoring with the REW real-time analyser, I gave it a quick blast. The reported THD dropped a little. Another blast lowered it some more. I kept going. The chip got covered in ice crystals. At a temperature of about -25 °C (according to thermal camera), the THD was some 5 dB lower than the starting point. The lesson here is clear. We need silent-running audiophile freezers with stylish looks and convenient cable inlets. MikeyFresh, marce and lucretius 1 1 1 Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 30 minutes ago, esldude said: I ran across this somewhere else at one time. My suggestion was to put a peltier like people use on overclocked CPU's onto the DAC chip. Should do the trick silently if not in an energy efficient manner. I tried that, but I couldn't easily cool the hot side sufficiently. esldude 1 Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 3 minutes ago, PeterSt said: Heat-up: not measurable by thermal measurement (unless by means of whatever behind the decimal point). Huh? Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 10 hours ago, pkane2001 said: run a water cooler to remove the heat, then run the water through a bucket full of water and ice add some alcohol to the water to stop it from freezing. Believe it or not, that works for quite a while. I have a boxful of PC water cooling stuff. The hard part is mounting the water block on the 10x6 mm chip. Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 10 hours ago, PeterSt said: Try it. With really low TDP (like measuring 25C or so at the chip's surface) continuous operation on any of the chips, no continuous use would show a higher temperature. Still, running that for 24/7 will degrade THD by the ever so slightest means (like 0.002dB or so). This is audible like crazy (perhaps because of means beyond my knowledge). You should team up with Rob Watts who "can" hear noise modulation at -300 dB. esldude 1 Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 7 hours ago, gmgraves said: I don’t doubt it, as a former semiconductor engineer, I have seen experiments where microprocessors were subjected to cryogenic temperatures. They always ran faster, and more efficiently, the colder the chips became. In all the experiments to which I was savvy, the cold was applied to the bare die, not to the encapsulated IC. While a cooling system using a refrigerant is somewhat impractical, we could use one of those semiconductor “heat pumps”, the kind used in portable electric coolers, and which are cold on one side and hot on the other. I don’t believe that it would work unless the cold side of the semiconductor heat pump were in direct contact with the DAC die. This case is a bit different since the chip is only producing a small amount of heat, less than 0.5 W. The problem is that to cool it below ambient temperature, you're fighting against inflow of heat from the PCB, which is made of copper and readily conducts heat from the air around it. In the end, you're just cycling a bunch of heat through the DAC chip without actually making anything much colder. Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 39 minutes ago, Ralf11 said: So, SQ on Pluto will be better than here on Earth? Mercury will have worse SQ... Mercury is pretty cold on the dark side. The lack of atmosphere might make listening a challenge, though. Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 26 minutes ago, gmgraves said: But you are cooling the die below ambient and certainly below it’s normal operating temperature. So we’re still, essentially talking about the same phenomenon. Yes, there will be an area of lower temperature by the cold side of the Peltier element. How much lower and how far it extends depends on the thermal resistance of the various parts. To achieve any significant effect, you need to have high thermal resistance between the die and everything other than the cooling element. That isn't the case here, so cooling the chip is a bit like trying to create a vacuum in a leaky container. Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 59 minutes ago, gmgraves said: Processor water cooling will not be cold enough to make any appreciable change in the distortion of a DAC chip I’m afraid. In the case of the water-cooled microprocessor, the cooling is used to keep an over-clocked chip from self destructing due to self-generated heat. It would work to cool the hot side of the Peltier element. Alternatively, it could be attached to the backside of the PCB, giving the Peltier cooler a better starting point. Link to comment
mansr Posted January 20, 2020 Author Share Posted January 20, 2020 Just now, fas42 said: You got impressive results when all you did was "hit it with some freezer spray" - so all you need to do is replicate that physical process by some means which can maintain it indefinitely. The freezer spray also cooled a large area of the PCB considerably. Link to comment
mansr Posted January 21, 2020 Author Share Posted January 21, 2020 1 minute ago, marce said: This works best with bottom terminated components or components with a heat pad, that the die is on. Yes, cooling works best on parts designed to be cooled. What a surprise. Link to comment
mansr Posted January 21, 2020 Author Share Posted January 21, 2020 21 minutes ago, marce said: Yes it is a surprise but how many are conversant with the various packages available one wonders I'm sure there are some I haven't heard of. Link to comment
mansr Posted January 23, 2020 Author Share Posted January 23, 2020 1 hour ago, Jud said: Depending on whom the "one" is, one wonders whether one actually wonders. That depends on what the meaning of the word is is. Link to comment
mansr Posted January 23, 2020 Author Share Posted January 23, 2020 5 minutes ago, marce said: I should have added a question mark, would the noise reduction be noticeable after gain stages. The figures were arbitrary, but would cooling your device down to -25 be beneficial in regards to noise, or would the extra issues created by the cooling mechanisms not be beneficial. One knows its counting how many angels on a pin head, but it is also informative. I sort of play about with cooling devices, these days due to size reduction power density has increased and heat is always an issues, smaller packaging, plastic cases, vacuum all create issues for heat removal. Cooling down to the level Mansr got to is a bit extreme, Jneutron on DIY Audio would be able to help here, It's all rather pointless since we're talking about values around -110 dB (including output stages and ADC) anyway. 5 minutes ago, marce said: or get the wife to stand there with a few cans of freezer spray during critical listening😁. That won't do. Bad things happened during the actual spraying. Link to comment
mansr Posted January 23, 2020 Author Share Posted January 23, 2020 Just now, lucretius said: Freezer burn? Noise went way up. I don't know why. Maybe the the freezer droplets are electrically charged or something. Link to comment
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