| Peter Daniel |
I'm working on a new project, where GC chip would not be mounted to the heatsink (after reading pads thread I have some reservations about mounting the chip to piece of metal;)) but would be immersed in copper cylinder filled with water or some other fluid. My question is if this will effect the chip in a long run? I would be using an isolated version of a chip.
There are possible advantages to this approach of heat dissipation, mainly better damping and avoiding vibration pick up from the chassis. It is also more original way of building an amp, as I promised the members of AA to come up with something refreshing and original;) |
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| Bricolo |
I think that the chip is water proof. You'll just have to take care about the pins. They musn't touch the water!
Or use a dielectric (like oil) |
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| Peter Daniel |
| So, if using oil, the pins can touch it? |
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| fdegrove |
Hi,
| quote: | | Or use a dielectric (like oil) |
And it has a better damping factor too.;) |
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| analog_sa |
| quote: | | So, if using oil, the pins can touch it? |
Of course not. You trust dielectric absorbtion of oil? Great risk of contamination, especially long term.
cheers
peter |
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| fdegrove |
Hi,
| quote: | | So, if using oil, the pins can touch it? |
Some oils have dielectric properties that isolate upto 23KV/mm...think that should be good 'nuff?
Cheers,;) |
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| Peter Daniel |
| Any fluids that are "pins" friendly? |
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| peranders |
Most parts today can withstand cleaning with water..BUT...they need very often to be dried in a oven for quite some time.
Normal plastic (epoxy) absorb moister (failure eventually) so I unrecommend this! Maybe if you use some insulating fluid, oil but the idea seems not to be very good. :no:
You could make a tin box of copper, brass and then sink box down in the fluid. Make it completely fluid proof.
As answer to your question: NO part is water proof unless the datasheet tells you so. |
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| UrSv |
Peter,
Are you sure that the heat dissipation is better like that? Sounds to me that it would be worse than when mounting with pad on sink. I suspect hotspotting would be way worse. Obviously I don't know for sure, it just seems logical, to me at least, that it would be way worse. |
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| fedde |
Kewl, a gainclone that's running on oil ;-)
Watch out though that certain countries do not get interested in your oil though! Also, watch out for excessive volumes or your amp will explode :devilr:
But now more seriously:
I think that it's risky to use oil or water on the chip. Even if the pins are not in the fluid, they will be during transport of the amp. Though what you COULD do is to make a metal box filled with oil (and closed well!) and mount the chip on top of it. The resonances of the metal will be damped by the oil and the heat of the cheap will be dissipated quick by the fluid. Though maybe the thermodynamic effects of the fluid will also cause resonances...
Fedde |
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| Bricolo |
Peter, you should look at some extreme computer overclocking websites (I'll try to get you some urls)
Some guys completely watercooled theyr computer (except the HD and CDs) by putting them in some kind of dielectric oil
I thinks that this answears your question ;) |
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| fdegrove |
Hi,
| quote: | | As answer to your question: NO part is water proof unless the datasheet tells you so. |
I agree, but it's not that hard to make it waterproof though.
Cheers,;) |
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| fdegrove |
Hi,
| quote: | | by putting them in some kind of dielectric oil |
Yes, that's transformer oil they use...he,he...;) |
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| Peter Daniel |
It is just a wild idea, and I was thinking about isolating the chip completely from external vibrations. Putting it in some sort of fluid might be solution. Of course, I also don't have any idea about heat dissipation efficiency by a fluid, but there should be something out there that works well. As I said before, I would be using isolated version of a chip and I think it is possible to completely immerse it, while still isolating pins.
Would be interested to see those links, Bricolo. |
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| fdegrove |
Hi,
| quote: | | Would be interested to see those links, Bricolo. |
Not being Bricolo but I hope you guys don't mind:
OIL COOLING.
Cheers,;) |
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| Cobra2 |
We have no problems with all sorts of electronics & electric motors up to 3000V submerged in hydraulic oil, not for cooling, but for pressure-compensation in sub-sea equipment (ROV).
Arne K
NORWAY |
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| Bricolo |
| karma is right, that was mineral oil |
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| Alexander Rice |
My two cents is that it is a daft idea, for a start the dielectric contant for mineral oil is much greater then that of air making for a large interlead capacitance, secondly, it is a much poorer conductor of heat than say aluminium which will cause the chip to overheat in a short order, even if it does not overheat you still need to get rid of the heat from the oil somehow so the container neads to be a heatsink, i dont fancy having a container of hot oil near my hi-fi.
My question is... WHY ... what's wrong with a heatsink, and why would you want to vibration isolate a chip - how could it possibly affect the sound???
just my 2c
Alex |
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| fdegrove |
Hi,
| quote: | | and why would you want to vibration isolate a chip - how could it possibly affect the sound??? |
For the same reason you want to isolate everything else from external vibrations???
And he did promise the guys at AA he'd come up with something errr....new?
Cheers,
;) |
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| Peter Daniel |
| quote: | Originally posted by fdegrove
And he did promise the guys at AA he'd come up with something errr....new?
Cheers,
;) |
Exactly;)
Anyway I would be interested how it sounds isolated from all external influences. A small container the size of half pop can is more than enough, as this surface is similar to what I'm using now and the amp rarely gets hot.
I would say, I'm doing that as an experiment, and if it works well I might use it more seriously. |
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| karma |
| we look forward seeing it if it work's;) |
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| JoeBob |
Water conducts heat well and takes alot of energy to heat it up, so it would be perfect for cooling. Now, just submerging the chip in oil or water wouldn't be the best way, you would still be limited by the surface area of the chip dissipating the heat.
What you could do is attach the chip to a relatively small heatsink, and submerge the pins or fins of the heatsink in water, you could isolate the heatsink from whatever will be suporting it anyway you like because it will be the water transfering the heat.
Or if you don't want to mount the chip on metal try putting it on a small (in area, but still high wattage) peltier element, then get rid of the heat any way you'd like. Then the chip won't be mounted on metal, since you seem to think that ain't good (I ain't going to argue about that, but I'll give any ideas Ihave) but instead on ceramic.
Maybe you could make a water block with one side made out of a someodd micron diamond sheet (saw these a while back on some crazy *** overclocking site) and mount the chip on that, again no metal and to boot you've got better heat transfer.
If you think that the pads make a difference, have you ever mounted the chip on a different metal than Al? Cu conducts heat better, radiates it less but most heat will be put off by convection anyways, maybe it resonates differently? |
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| millwood |
along the line proposed by JoeBob, you can also use heatpipes. They can carry incredible amount of heat away in a very small and compact package.
However, they are expensive. an alternative is to salvage one from a notebook computer. |
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| SY |
| quote: | | And he did promise the guys at AA he'd come up with something errr....new? |
Is that the Thirteenth Step? ;)
| quote: | | along the line proposed by JoeBob, you can also use heatpipes. They can carry incredible amount of heat away in a very small and compact package. |
Heat exchange is a useful idea. The nice thing about inert fluids, and the principle use for Fluorinert, is that you can pump them past the heat sink with very little noise compared to air, and run them through a heat exchanger. That strikes me as a great benefit, much more so than any incidental vibrational damping that one can get as a nice byproduct. |
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| Sawzall |
| in a thread with one of the kids, I suggested using one of the heat conductive epoxys to pot the chip and leads. Given you construction skills Peter, I could easily see you building a nice little cube that had 5 wires coming out of it. Place in water. The Artic Silver? guys make it. |
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| Elkaid |
It could be an idea to fix the chip to a very little heatsink and submerge this famous heatsink in oil, water or why not.... liquid nitrogen ?
You would have no problems related to dip your chip in liquid and you would reduce the problems related in fixing your chip to a large heatsink...
Well, it's only an idea
Potting the chip is also an idea but I'm not sure about how well they transfer energy (heat) to their environment...
hmmm it's late
edit :
d/$%m, forget it, looks like it has been already suggested in another post...
As I said previously, it's late... |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
There are possible advantages to this approach of heat dissipation, mainly better damping and avoiding vibration pick up from the chassis. |
How would it avoid picking up vibration from the chassis?
se |
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| DSummer |
| If just avoid from vibration, why don't oil the the transformers instead, like the old British Partridge/Pameko...They are still the best transformers in my opinion.. |
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| Peter Daniel |
| quote: | Originally posted by Steve Eddy
How would it avoid picking up vibration from the chassis?
se |
The coupling between chip module and the cylinder containing the fluid would have to be soft (rubber, foam or something similar). |
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| Peter Daniel |
| quote: | Originally posted by DSummer
If just avoid from vibration, why don't oil the the transformers instead, like the old British Partridge/Pameko...They are still the best transformers in my opinion.. |
I'm not that much concerned with vibrations coming from transformers. My current amp has separate PS. |
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| mbroker |
| quote: | Originally posted by fdegrove
Hi,
Some oils have dielectric properties that isolate upto 23KV/mm...think that should be good 'nuff?
Cheers,;) |
Transformer oil, mineral oil (drug store), lightweight, non-detergent motor oil (the really cheap stuff) all work fine in high voltage transformers, so I don't see why it won't here. A word of caution: oil exposed to the air will hydrate, thereby ruining the insulative properties.
If you clean everything really, *really*, *really* good, you can use laboratory-grade distilled water (pure water is an insulator with a dielectric constant in the high 80s). But the slightest amount of contaminants drastically reduce the resistance, so things have to be extremely clean. And water has a way of "disolving" things, like certain metals, to create conductive water...... I had several discussions about this with a chem prof in college when I considered making a 30kV water pulse cap. :bigeyes: After the discussions I opted to go for a "normal" design instead.
Cheers,
Mark |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
The coupling between chip module and the cylinder containing the fluid would have to be soft (rubber, foam or something similar). |
So you mean the chip amp in fluid in some soft container in some cylinder?
se |
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| Peter Daniel |
Here's some rough idea. The cylinder can be done out of copper tubing used for plumbing (maybe 2" dia). The bottom can be soldered, as there are copper caps available. The lid on top could be machined out of acrylic, with a groove for O-ring. The O-ring both seals the cylinder and isolates the acrylic lid from cylinder, as most vibrations will be picked up here. All I have to figure out, is how to keep the lid attached to the cylinder. The drain plug is there to assure that the cylinder is filled in full. In case better heat transfer from the chip is required, I can always attach to it additional copper plate.
The chip goes from the bottom through the lid, so I could even use a small PCB on top to hold few parts and 2 filter capacitors. The size of a cylinder has to be large enough to dissipate enough heat from the oil.
Actually, if I use wooden block to hold 2 pairs of caps (like my polycarbonate block in Amp-1) on one side and something to hold the cylinders on the other side and common platform for everything, I have a self supporting assembly, which also takes care of the lids attachment to the cylinders.
If I put all this together in a nice package, it may be the L'AMP;) |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
Here's some rough idea. The cylinder can be done out of copper tubing used for plumbing (maybe 2" dia). The bottom can be soldered, as there are copper caps available. The lid on top could be machined out of acrylic, with a groove for O-ring. The O-ring both seals the cylinder and isolates the acrylic lid from cylinder, as most vibrations will be picked up here. All I have to figure out, is how to keep the lid attached to the cylinder. The drain plug is there to assure that the cylinder is filled in full. In case better heat transfer from the chip is required, I can always attach to it additional copper plate.
The chip goes from the bottom through the lid, so I could even use a small PCB on top to hold few parts and 2 filter capacitors. The size of a cylinder has to be large enough to dissipate enough heat from the oil.
Actually, if I use wooden block to hold 2 pairs of caps (like my polycarbonate block in Amp-1) on one side and something to hold the cylinders on the other side and common platform for everything, I have a self supporting assembly, which also takes care of the lids attachment to the cylinders. |
Mmmm. Still don't see a whole lot of isolation there. At least not any more than if you'd mounted the chip to a heatsink and simply isolated the heatsink from the chassis.
| quote: | | If I put all this together in a nice package, it may be the L'AMP;) |
Hehehe.
se |
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| SY |
| If you want to do something a little wilder (OK, a lot wilder), consider bonding a piezo film to the chip and using it actively to cancel out vibration. This can be combined with the fluid immersion idea, since piezo film couples very, very well to fluids with specific gravity near one. |
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| Peter Daniel |
| quote: | Originally posted by Steve Eddy
Mmmm. Still don't see a whole lot of isolation there. At least not any more than if you'd mounted the chip to a heatsink and simply isolated the heatsink from the chassis.
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The heatsink actually is a chassis in my amp. I can only isolate it from the supporting platform, and I hear a difference when I'm using spikes or rubber pucks. The platform itself affects the sound. So with this design I'm aiming at something that is not placement dependant.
I'm not sure myself how this would work out, but in my proposal the heatsink is actually in a liquid state (oil). The regular heatsing is a piece of metal. I imagine that the sound from a chip might be different in both instances. I'm only afraid, if the oil version wouldn't be sounding too slow and damped, without enough top end extension. OTOH, I shouldn't worry about "liquidity" of the sound;) |
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| JOE DIRT® |
| a sarcastic thread ....shame on you all |
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| Variac |
Realistically, why not pot the whole circuit in some propriatary mixture.
epoxy, marble chips, sand, carbon fiber, etc. Leave the heatsink attachment surface protruding 1/32" at the surface of the block. Make a heatsink out of a 1/2" thick plate minimum. Bond this to the potted blockwith epoxy with the plate in contact with the chip , filling in the gap around the chip at the same time. Of course the chip and heatsink need grease between them. Now you have bonded disimilar materials together- even better damping
Then suspend the block inside the cabinet using lengths of monofiliment fishing line under tension. You can adjust the tension using a guitar string tuner knob.
Make sure the solid core wire going in and out has a loop in it to
allow movement and avoid (unlikely) fatigue breakage. Stranded wire might add noise when it flexes?
Another idea is just trim cut the epoxy/aluminum and buff so it is a clean solid polished block. Don't even put it in a case The only trick is how to embed the in/out connecters into the block. How
about blocks soldered to each wire and when you embed the circuit leave the blocks partially protruding. Then they get cut off flush with the surface during the trimming/polishing operation. Now drill and tap the block for a screw to secure the outputs, power, etc.
Wait..... instead of a potting mixture, use the clear resin that they use for those paperweights with bugs in them. (available at hobby shops) Then you end up with the visible circuit bonded to the aluminum plate, all polished up. OK I feel better now, thanks........
Or don't do all this- it's just what I plan to do.... |
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| theChris |
| gainclones in cans, what's next? a six pack? |
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| jh6you |
Post#36.
When the cylinder is under the steady-state vibration, how does the oil isolate the chip from the vibration? I do not even imagine that. I do not think that the oil will absorb the vibration energy and swallow it.
:yinyang: |
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| phase_accurate |
Peter
You might also use natural oil for insulation and thermal transport (instead of all those poisonous xformer oils). I once heard that some natural oil (I vaguely remember it was peanut oil) was used during WWII for high-voltage capacitors in RADAR devices. So its dielectrical properties shouldn't be that bad at all !
But I fear that its heat transfer properties will be much much worse than those of aluminium for instance.
Regards
Charles |
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| AuroraB |
| quote: | | gainclones in cans, what's next? a six pack? |
Something for HT..???:goodbad: |
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| Raka |
I work for a motor manufacturer and I know that there are submerged motors (pods) that are oil filled, and that are higher voltage fed that an amp, with inverters that have a dv/dt in the order of infinity and beyond, so the dielectric capability is proven. Unfortunately, we don't build them and can't help you with a reference for the oil.:(
What I can suggest you is to use an internal blower to toss the oil bath. Don't laugh, please. The micro turbulences and waves can act like a resonance barrier with very good results. You only have to tune it to the desired Fs and Q, (I think the speed &power control of the motorfan will do) that is the one that causes less problems to the chip. This concept is studied by me in another field (nothing to do with electronics) and maybe has some use for you. I hope so. |
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| Lisandro_P |
I once found a couple of dielectric properties tables while i was playing with high voltage; and it's true; some oils are quite good isolators (with dielectric constants comparable to porcelain, 5-10). Water (distilled, deionized one of coz) is a one of the best known electrical insulator, with a dielectric constant of 75-80.
Whatever you choose to use, i'd make sure to have a *tight* seal on the can, so not only it doesn't leak at all but also it doesn't get dirty. |
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| phase_accurate |
Hi Peter
I had a look into an older ARRL handbook. There you could find the construction of an RF dummy load. There is also a discussion about availability/properties of xformer oils and mineral oil.
They claim that the product "Regal Oil R&O No.46" by TEXACO (sold in 5 gallon cans as "turbine oil" for servicing purposes) was in fact a relabelled heat transfer oil as it is used in some xformers. It seems to be the only heat transfer oil available in "small" quantities.
Regards
Charles
BTW: I have seen huge inverters in a lab intended for railway locomotives, using oil cooling. I have seen some electronic containers that were ripped open by boiling oil when "things got interesting"*.
*copyright by NP |
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| rikkitikkitavi |
Peter ,
Water has about 25 times higher thermal conductivity than air, but in autoconvective cooling as in this case we can expect the thermal resistance junction-ambient to decrease maybe a factor 10. (a engineers guestimate)
Take the Rtja value for LM3875 is 43 C/W, we land on about 4,3 C/W. With a powerloss of 15 W => delta T = 65 C. Add this to the thermal resistance of the rest of the equipment where heat is dissipated.
As for oils, forget it. They usually have a much higher viscosity so the Rtja will not decrease 10 times, and if it only decreases 5 times you land on a temperature rise of about 130 C from chip junction to liquid. Perhaps the 3-M stuff could do it, Fluoriert.
Anyway, you could probably coat the whole smackarang in epoxy, or even mold it into expoxy to protect it. What you lose in form of higher Rtja by more material, you probably gain by increasing surface in contact with cooling liquid. plus you can use deionized water, whcih perhaps has to be replaced from time to time because it dissolves impurities .
BTW , water hardly stops vibrations.
/rickard |
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| Raka |
Quote:
"BTW , water hardly stops vibrations. "
I was talking about oil, and water stop vibrations. Not all kind of waves, not in standstill condition and not all frequencies, but does something useful to stop vibrations. |
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| rikkitikkitavi |
water dampens vibrations better than metall, yes, but hardly stops them.
Immersion an object in water is a very very bad way of damping vibrations. Compare it to an ultrasonic bath, or an "utltrasonic agitator , a rod vibrating with ultrasonic frequencey.
It is partly affected by different temperatures , since the speed of sound alters with water temperature, thus "bending" the sound waves , and make it possible to reflect the sound.
The point is that you should put different layers of substance , which all have a very wide dispersion of speed on sound.
This leads to that instead of transfering sound (vibrations) between the different layers , it is reflected out.
And oil is such a lousy heat transfer media without agitation, i e natural convection that I hardly thinkt that it will work. The dampening factor is probably higher, due to higher viscosity and lower speed of sound, but this also means that the convective heat transfer factor is reduced dramatically.
/rickard |
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| crown300 |
I think that by the time you get through, you can achieve the same results by vibration isolating a normal heatsink. That methoid (sp) would allow one to easly tune the isolators for a specific frequency.
PS: I spent many years working with motors used in underwater remote operated vehicles and we used Floronert.
PPS: Oil cooled amp would be BIG marketing idea though - especially using oil with specific gravity to cancel out negative gravity waves. |
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| mikelm |
Hi peter,
I recently contacted electrolube here to find the best resin for my resin & small stones chip mounting idea. They came back to me today and in the course of the conversation It came out that either of the resins that they recommend - both of which are heat conductive compounds - have heat transfir properties of about 100 times less than aluminium. that's what they said
That got me thinking a bit...:scratch:
can anyone out there confirm that these are good ballpark figures
do you have similar data for any of your proposed fluids ?
mike |
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| millwood |
for those who think so hard about resistor/capacitor/heatsink sound because of the additional capacitance (change) caused by insulation pads, aren't you going to be concerned about now massive (relatively speaking) amount of capacitance between the leads, the container, and the wires because of the dielectric liquid?
That thing itself is a giant capacitor. |
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| fedde |
You want something new !?
What about soldering a LM3875 to a heatsink ? :bigeyes:
Take a heavy soldering iron and first heat up the solder on a heatsink (takes some time). Then push the LM3875 on the heatsink. Don't know if it works. It should work, I guess. The advantage is a good coupling of heat and a reduction of resonances...
If the heatsink can not be soldered, you could try a thin metal plate (5x5 cm or so). Then attach the plate to the heatsink!
Fedde |
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| carlosfm |
Guys, you're burning your fuses with a simple thing.
I would do it this way:
1. Mount everithing (chips, components, etc), be it P-P or in a circuit. Circuit is better for this.
2. Connect all the wires and TEST everything.:devily:
3. After tested, drawn everything, holding by the wires, in a can of VARNISH.
4. Let it dry holding by the wires and do it again two more times.
5. Attach a very small heatsink to each chip.
6. Put everything inside the box and THROW THE WATER IN.:eek:
That's it.
Well... you have to see if the box doesn't leak.:devily: |
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| millwood |
the chip is available in either unpackaged die or wafer form. So get one of those (one wafer could be too much), use the minimal configuration (two resistors plus wire out for two by-passing caps. solder those two smd resistors on, and seal the whole thing with one drop of epoxy.
now, that will get any "shortest signal path" freak to smile, :)
you may be able to pack a 4-channel gaincloen in a Timex. |
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| DRC |
Murcury ?
Woods metal (Bi50/Pb25/Cd12.5/Sn12.5 liquid at 70C) ?
Toxicity would be a problem though !!
Dave |
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| carlosfm |
| quote: | Originally posted by millwood
you may be able to pack a 4-channel gaincloen in a Timex. |
:eek: :bigeyes: :bawling:
This chip deserves a Rolex.:devily: :nod: |
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| Peter Daniel |
| quote: | Originally posted by carlosfm
:eek: :bigeyes: :bawling:
This chip deserves a Rolex.:devily: :nod: |
Somebody actually suggested to me a Patek.;)
Thanks everybody for the ideas. Of course I want to make it as simple as possible and I will definitely try it. One reason for me to pursue that type of approach is building active speaker system, where drivers are mounted in a wall (as it's made of 2x4s, I will have resonances to deal with). The amps, I want to be mounted as close to the drivers as possible (so the speaker wires effect is also eliminated) and that's why the demand for more isolation. |
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| fedde |
I see. You could use a jam pot. Try one with a plastic lid that can be closed very well (peanut butter pots will do I guess). Then mount the chip under the lid and make the lid heavier with glue. Ensure the wires are glued in. And you can try to solder a thin metal plate to the chip. Fill the thingie with oil and throw it in your speak's...
Fedde |
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| Peter Daniel |
| quote: | Originally posted by jh6you
Post#36.
When the cylinder is under the steady-state vibration, how does the oil isolate the chip from the vibration? I do not even imagine that. I do not think that the oil will absorb the vibration energy and swallow it.
:yinyang: |
I'm not that familiar with physical aspects of it all, but are you trying to say that the oil can transfer the vibration from a cylinder to the chip, without any loss of those vibrations? |
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| Elkaid |
Well it's a fact,
Liquids are EXCELLENT in transmitting vibrations. That's why a sound travels much farther in water than in air by example.
So, if you plan to use liquids to damp vibrations, then your solution don't seems to fit your needs :( |
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| millwood |
| quote: | Originally posted by Elkaid
Well it's a fact,
Liquids are EXCELLENT in transmitting vibrations. That's why a sound travels much farther in water than in air by example.
So, if you plan to use liquids to damp vibrations, then your solution don't seems to fit your needs :( |
that's absolutely correct. Because liquids tend to be non-compressable. and sound travels much faster in liquid than in air.
so sinking your amp into a liquid is no different than perfectly surrounding your amp with steel, from the damping perspective. |
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| fedde |
True, you can hear an outboard motor in water from a very large distance, especially if you're under water!!!
Fedde |
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| millwood |
| quote: | Originally posted by fedde
True, you can hear an outboard motor in water from a very large distance, especially if you're under water!!!
Fedde |
when I was a child, I used to put my ears to the rail road tracks to hear trains coming from miles away - don't do that at home, :)
for the same reason, or I was told, dogs sleep with their ears to the ground: to hear further and quicker.
I would be interested in finding out how this liquid "damping" will do to the sound, :) |
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| fdegrove |
Hi,
| quote: | | when I was a child, I used to put my ears to the rail road tracks to hear trains coming from miles away - don't do that at home, |
I think what you mean is that you feel the train coming...
So, what's against oil as a damping material all of a sudden?
With tonearms often oil is used to damp vibrations coming from the cartridge/arm.
Some shock absorbers use oil, etc,etc.
Cheers,;) |
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| Peter Daniel |
OK, here's another approach. The chip has attached small copper plate to help heat transfer. It is also not in the oil, only the copper plate. There is a small PCB and 2 PS caps are used to suspend everything, by using some sort of a frame.
I'm still influenced by the idea of using oild to damp vibrations, as it was used on certain TT, where there was a bolt attached to the arm, dipped in oil. |
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| millwood |
| quote: | Originally posted by fdegrove
I think what you mean is that you feel the train coming... |
no, you hear it coming - well, hearing is feeling of vibration by your ears so you are right too.
| quote: | Originally posted by fdegrove
So, what's against oil as a damping material all of a sudden?
With tonearms often oil is used to damp vibrations coming from the cartridge/arm.
Some shock absorbers use oil, etc,etc.
Cheers,;) |
those oil damping devices work different than what is proposed here: they have an outlet for the oil. Damping is achieved as oil, specifically high viscosity oil, flows from one part of the device to the other part of the device through a very small hole. By controling the size (and shape) of the hole, you can control the speed of the flow thus the degree of damping - variable damping shocks. |
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| millwood |
| another way to look at this is to check out those ultrasonic welding devices and cleaning machines at a dentist's office. They use liquid to transmit, not damp, high speed vibrations whereever the liquid is. So using oil does nothing to damping but helping vibration getting where it could not have otherwise gone. |
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| Peter Daniel |
| quote: | Originally posted by millwood
those oil damping devices work different than what is proposed here: they have an outlet for the oil. Damping is achieved as oil, specifically high viscosity oil, flows from one part of the device to the other part of the device through a very small hole. By controling the size (and shape) of the hole, you can control the speed of the flow thus the degree of damping - variable damping shocks.
another way to look at this is to check out those ultrasonic welding devices and cleaning machines at a dentist's office. They use liquid to transmit, not damp, high speed vibrations whereever the liquid is. So using oil does nothing to damping but helping vibration getting where it could not have otherwise gone. |
It doesn't seem to be a case in that design. |
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| moamps |
| quote: | Originally posted by millwood
when I was a child, I used to put my ears to the rail road tracks to hear trains coming from miles away - don't do that at home, :)
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Hi,
Yes, that's true.
Also, speed of sound in iron is almost 6000m/s !!! (343m/s in air)
Regards |
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| fdegrove |
Hi,
Ah, the famous Elite Rock.
There at least a few dozen of tonearms that use viscous damping in similar ways.
Regarding the speed of sound:
The higher speed of sound in liquids and solids, compared with gases, is also partly the result of the fact that liquids and solids are usually more dense than gases. Traveling-wave speed generally increases with increasing density and hardness of the medium.
From which I think it's safe to conclude that the use of oil will transmit vibration slowlier than a solid such as aluminium.
Cheers,;) |
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| Peter Daniel |
| Here's a similar approch to damping arm vibrations in my TT. |
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| millwood |
| quote: | Originally posted by fdegrove
From which I think it's safe to conclude that the use of oil will transmit vibration slowier than a solid such as aluminium.
Cheers,;) |
but that's not the point of damping, right?
Otherwise, we would all be buildinging amps in vaccum boxes, or suspending them in thin air - some of them do look like that anyway, :) |
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| fdegrove |
Hi,
| quote: | | but that's not the point of damping, right? |
Not sure what you mean here...
Let's just say that the time delay allows for energy to be converted to heat.
Within the context of Peter's application I think that the combination of a copper sheet and the viscosity of the oil would render that part of the amp well isolated from external vibrations.
Maybe too much so... ;) |
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| Steve Eddy |
| quote: | Originally posted by fdegrove
Within the context of Peter's application I think that the combination of a copper sheet and the viscosity of the oil would render that part of the amp well isolated from external vibrations. |
Not as well isolated as if the cylinder were simply filled with air. The denser liquid would provide much more efficient coupling to the vibrating cylinder allowing more vibrational energy to be transmitted to the chip.
Think about it. How many molecules of liquid are there per unit volume versus molecules of air per unit volume?
se |
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| Peter Daniel |
| That may be true, but also there is a reason for a small heatsink plate, much smaller than regular heatsink, and use of oil to dissipate more heat from the plate. There are tradoffs here and only building a prototype can show the effect of it all. |
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| Tensop |
Peter, as you may be aware water cooling is used extensively with computer hobbyiests, and to an even further degree, some go as far as refridgerants to freeze the cpu well below 0.
Many also use a TEC(Thermoelectric coupler) - a device that creates a thermal difference between its 2 sides by being a transducer(this is what i recall, might be slightly off), but can yeild temperature differences of 60c easily(imagine a thermocooled lm38xx with watercooling against the TEC(aka peltier)?
MWP, who is also a member of this forum and also built an 8 channel, 220wrms lm3886 amp built this:http://pcdb.overclockers.com.au/vie...e=MWP&page=pics
That would be mostly homebrew,
If you search for computer watercooling of forums such as www.overclockers.com.au
www.overclockers.com
www.hardocp.com
or www.dansdata.com (highly recommended - this guy has alot of technical knowledge which extends WAY beyond plugging up cables inside his computer
as you are in Canada, computer watercooling parts will be very easy. i beleive a company makes a 'spiral' waterblock in toronto canada, and can be picked up cheap cheap.
All you need is the waterblock,radiator,hosing, waterpump and a decent thickness copper sheet to attach to the waterblock. |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
That may be true, but also there is a reason for a small heatsink plate, much smaller than regular heatsink, and use of oil to dissipate more heat from the plate. There are tradoffs here and only building a prototype can show the effect of it all. |
But it seems to me that using a larger heatsink in air and isolating the heatsink from the chassis would result in the least amount of vibrational energy reaching the chip.
se |
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| rikkitikkitavi |
waht about attaching the LM3875 to a plate, and let the plate float on a air cusion(or what you call it) , just like a tonearm for a TT?
And if the plate/heatsink is properly designed the air flow beneath it can improve cooling dramatically.
Actually it can look pretty cool done properly with a 40 *40 cm aluminium sheet with a few wires going in and out.
Due to the flexible nature of the cables coming in and out from the amplifier these will dampen out most of the vibrations to.
FloatAmp (yes you may use the name Peter :)
/rickard |
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| millwood |
| quote: | Originally posted by Peter Daniel
That may be true, but also there is a reason for a small heatsink plate, much smaller than regular heatsink, and use of oil to dissipate more heat from the plate. There are tradoffs here and only building a prototype can show the effect of it all. |
I just think the whole thing is foundamentally flawed. Putting aside the doubious sonic benefits of a "well damped" chip, I would have thought that one has to identify the source of the vibration, and figure out which part of it one wants to damp before going about doing something - hi, if a stupid banker can figure that out, a competent engineer should have done at least 100x better, :).
I never understood why you wanted damp anything but that's another topic.
I would suggest that you first figure out your primary objectives in this whole project: damping or heat transfer, or something else. and then we can go from there. For heat transfer, I would suggest watercooling or heatpipes. Water (more accurately liquid) cooling is pretty mature and they are lots of cheap consumer products out there so it can be easily done. heatpipes are a lot more expensive but it is unique - I haven't heard of any amps using heatpipes.
for damping? I would suggest thick gel pads (those those gel mouse of insol). they are cheap but effective. I would use them to damp the who circuitry / heatsink so the whole thing is mechanically damped or isolated fromt he chassis. |
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| millwood |
| quote: | Originally posted by rikkitikkitavi
waht about attaching the LM3875 to a plate, and let the plate float on a air cusion(or what you call it) , just like a tonearm for a TT?
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or hang it from a ballon?
how about using the concept of air bearing? if it works for gyros, it should work here as well. |
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| grataku |
| quote: | Originally posted by Steve Eddy
Think about it. How many molecules of liquid are there per unit volume versus molecules of air per unit volume?
se |
Off the top of my head.
SY will correct me since my freshmen chem is rusty but I think is
only between 55 times for water and maybe 5 times more molecules for greasy liquids than in gases. If it matters.
Liquids are still much better at subsonic damping than solids but air is used in optical tables which is clearly superior.
Peter I thought you had an optical table which was giving you enormous satisfaction. |
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| Variac |
I believe that air bearings are actually pretty stiff and don't isolate that well.
If you want to test your liquid damping idea, put your head in a metal bucket filled with water and have someone hit it with a stick.
The tonearms have a paddle that moves relative to the trough.
That's differnt then just popping a chip into a vial. IMHO
Heck, just put your circuit into cool monoblock towers so they look different |
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| millwood |
| quote: | Originally posted by Variac
If you want to test your liquid damping idea, put your head in a metal bucket filled with water and have someone hit it with a stick. |
ouch! that must hurt, :) |
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| Peter Daniel |
| quote: | Originally posted by grataku
Peter I thought you had an optical table which was giving you enormous satisfaction. |
I have the table, but there's only enough space for CD player. |
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| Peter Daniel |
I could use silicone instead of oil for both damping and heat transfer. How good is silicone with heat transfering?
As to water cooling, I don't want to use any mechanical moving parts, like pumps or complicated piping and heat exchangers. The GC doesn't generate that much heat, to be really concerned with it. |
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| Peter Daniel |
| quote: | Originally posted by millwood
or hang it from a ballon?
how about using the concept of air bearing? if it works for gyros, it should work here as well. |
Let's keep it simple and let's keep an open mind. I think we are quite close to figuring it out;) |
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| Tensop |
| quote: | Originally posted by Peter Daniel
I could use silicone instead of oil for both damping and heat transfer. How good is silicone with heat transfering?
As to water cooling, I don't want to use any mechanical moving parts, like pumps or complicated piping and heat exchangers. The GC doesn't generate that much heat, to be really concerned with it. |
i assume you're talking about silicone thermal material(thermal paste eg?) if so... its performance over distances(think 1mm) is pathetic, as is water and oil without aggetation |
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| Steve Eddy |
| quote: | Originally posted by grataku
Liquids are still much better at subsonic damping than solids but air is used in optical tables which is clearly superior. |
I don't think "damping" is the right word here. We're talking about propagation through a medium, not a resonant system. So we're basically talking about absorption. And in any medium as far as I'm aware, absorption is frequency dependent, with the absorption increasing with frequency. And I'm not sure that low frequencies suffer more absorption loss in liquids than in solids. In fact, I'd hazard that it's just the opposite.
se |
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| Steve Eddy |
| quote: | Originally posted by Peter Daniel
I could use silicone instead of oil for both damping and heat transfer. How good is silicone with heat transfering? |
Ok, let's back up.
What exactly is it you want to do? Do you want to isolate the chip from external vibration so that the chip doesn't vibrate (or vibrates as little as possible) or do you want to damp the resonance of some existing vibration that is already affecting the chip?
What it is you're trying to do will determine how best to go about it. And damping and isolation are not one and the same.
se |
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| fdegrove |
Hi Steve San,
It's usually not a bad idea to read the first post of the thread.
;)
Cheers, |
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| millwood |
| quote: | Originally posted by Peter Daniel
I could use silicone instead of oil for both damping and heat transfer. How good is silicone with heat transfering?
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the reason silicone is used is that it will form a think layer that touches both the device and heatsink. If you simply mount the heatsink and device together, there will be a thin layer of "air" together - and we all know that air is a pretty bad conductor of heat. |
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| rikkitikkitavi |
thermal conductivty
air 0,024 W/mC
water 0,6 W/mC
silicone 0,5-1 W/CK
thermal silicone paste 0,5-1
granite 2,5
solder 30
Al2O3 27
aluminium 120-220 (dural- pure 99,99 food grade)
copper 395 (OFC)
just a few examples, you can find most materials on google. |
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| Peter Daniel |
| quote: | Originally posted by Steve Eddy
Ok, let's back up.
What exactly is it you want to do? Do you want to isolate the chip from external vibration so that the chip doesn't vibrate (or vibrates as little as possible) or do you want to damp the resonance of some existing vibration that is already affecting the chip?
What it is you're trying to do will determine how best to go about it. And damping and isolation are not one and the same.
se |
I guess I want both. The external vibrations (mostly from sound waves) are picked up by the chassis, both from the air and from supporting platform. So I want make the heatsink as small as possible to dissipate only enough heat. I would prefer to not mount the chip directly to heatsink as this increases the vibrations transfered to the chip. So I need some medium to transfer the heat from the chip to the heatsink. I already decided that heatsink area will be formed by a copper cylinder. It's easy to get from building suppliers. I believe that 1 1/4" tubing, 6" long will be enough to dissipate all the generated heat. |
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| grataku |
| quote: | Originally posted by Variac
I believe that air bearings are actually pretty stiff and don't isolate that well. |
Optical table and other vibration damping systems are all based on air suspensions and they elimitate all subsonic vibrations quite well.
| quote: | | If you want to test your liquid damping idea, put your head in a metal bucket filled with water and have someone hit it with a stick. |
I can use your idea to prove my point too, remove the head from the bucket and have someone hitting it with a stick. You can probably walk away if your head is inside the bucket. That proves the great damping ability of water ;)
You are assuming that the transistor is as good a transducer as your ear.
It is actually a complicated problem, you need to distinguish between subsonic and ultrasound, audiofrequencies happen to be in between which is probably the worst case.
If you want to eliminate the subsonic vibrations or low audio freq vibrations that make your tone arm pickup jump or your cd skip or jitter any liquid will probably do well enough.
You can play with the inertias of the various components to be isolated and that helps. |
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| grataku |
| quote: | Originally posted by Steve Eddy
I don't think "damping" is the right word here. We're talking about propagation through a medium, not a resonant system. So we're basically talking about absorption. And in any medium as far as I'm aware, absorption is frequency dependent, with the absorption increasing with frequency. And I'm not sure that low frequencies suffer more absorption loss in liquids than in solids. In fact, I'd hazard that it's just the opposite.
se |
Interesting discussion.
Maybe we should compile a table of frequencies and the common forms of matter and fill in the blanks as to what propagates and to what extent so we are all on the same page ;)
solid
liquid
gas
in order of decreasing energy
light
IR
phonons
microwaves
RF
ultrasound
audio
subsonic
DC |
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| Peter Daniel |
| quote: | Originally posted by grataku
Peter I thought you had an optical table which was giving you enormous satisfaction. |
Talking about optical table, it is true that it isolates the audio unit on top of it from vibrations. It can be both heard and felt. For instance when I place my hand on the top panel of a CD player, which is on a table, I can't feel any vibrations. Another unit, which is one shelf below, vibrates like crazy (top panel).
But given that, there is still a difference, depending what I use between my stereo unit (CD player in this case) and the table. I made some experiments with acryilic plates and foam pieces, and the sound was greatly dependant on the combination I did choose. IIRC, foam, acrylic, foam was best sounding setup. This makes me very confused as the whole issue. You just cannot say that this and that is the beast, because it simply has to be tried out. |
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| millwood |
| quote: | Originally posted by grataku
I can use your idea to prove my point too, remove the head from the bucket and have someone hitting it with a stick. You can probably walk away if your head is inside the bucket. That proves the great damping ability of water ;)
You are assuming that the transistor is as good a transducer as your ear.
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a fair comparison is to
1) hit the bucket filled with water while your head is in it.
2) hit the bucket filled with air while your head is in it.
which one would you rather it be? |
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