jello
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Post by jello on Jun 8, 2016 8:45:58 GMT
I recently sold an ifi ipower PSU on ebay. Had no issues with it myself but it has been mothballed for a few months.
The buyer has mentioned getting a high pitched whining sound from the PSU and has asked if I can suggest anything. Not my area of expertise so thought I'd ask here.
Ideally trying to figure out if it is an issue with the PSU itself or if he simply bought a PSU that is incompatible with his (non-ifi) DAC.
The specs for the PSU are as follows:
Input: 100-240VAC
Output: 9V/1.5A
Output plug: 3.5×1.35mm; 4.0×1.7mm; 4.8x1.7mm; 5.5×2.5mm
But the specs for his DAC are a bit unclear. The instructions he has simply mention using a 9V power supply.
His DAC is an m2tech evo2 which I can find very little on. The closest match I can find on m2tech's site is the evo2 plus which I'm assuming is an updated version. Again it mentions using a bundled 9V power supply.
The specs for the evo2 plus are as follows:
Supply Voltage: 7.5V to 15V, 300mA
Supply Input: 5.5/2.1mm jack, positive on tip
Does the ifi PSU look like it would be suitable assuming the evo2 has similar specs to those above? Assuming it is would that point to a problem with the PSU or could there be something else afoot?
Thanks for any help!
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solderdude
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Post by solderdude on Jun 8, 2016 11:36:40 GMT
Some SMPS do emit whining sounds. Sometimes they just start doing that after a while (inductor or transformer with vibrating windings) Some only do this when having a too high load or when the load is too light. Maybe too much capacitance is loading the ifi ?
9V/1.5A PS should have no trouble feeding something like 7.5V to 15V, 300mA The DAC seems to have a wide range SMPS inside. Perhaps too much or too little input capacitance ?
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jello
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Post by jello on Jun 8, 2016 12:06:52 GMT
Thanks for the reply Frans.
I'm not sure how bad the noise is. He simply mentioned it being high pitched so it may be considered 'normal' for an SMPS. I didn't notice it myself but perhaps it was above my audible hearing range or simply that the ifi amp I had was better 'matched' in terms of the draw it placed on the PSU?
I must admit that capacitance isn't a term I'm familiar with. But if that was the underlying cause (presumably with the DAC being only 300mA the PSU might not get much of a work out?) then would that likely indicate a bad pairing between the DAC and PSU rather than either being faulty?
Cheers and apologies for my ignorance (as always..).
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solderdude
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Post by solderdude on Jun 8, 2016 13:48:57 GMT
Every power supply circuit has 'reservoir' and or 'decoupling' capacitors in its circuit. Not all power supplies (the switching kind but also some 'linear' regulators) get 'improved' by adding more capacitance. Audiophile people always like to see moarrr capacitance over power supply lines believing moarrrr is always better.
In most cases it has a grain of truth in it but in other cases it may work the other way around. Just mentioned it as a possible reason though.
Chances are: a: It functions properly B: It functions outside of an expected (specified) load C: It may be developping/having a fault D: 'Pairing' with the DAC is suboptimal (for whatever reason)
Difficult to tell without having a second (similar) power supply around.
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jello
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Post by jello on Jun 9, 2016 9:06:23 GMT
Fantastic - cheers Frans!
Sounds a lot like PC troubleshooting. The only surefire way is to swap things out or test in isolation (not always practical or cost effective) or you are left with a number of possible causes.
I believe the guy has raised a ticket with ifi too so will see what they say and if they know of similar 'pairing' issues with other non-ifi products.
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jkeny
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Post by jkeny on Jul 14, 2016 19:39:12 GMT
Don't know if this has been solved?
Another suggestion - he may have a ground loop issue which you didn't have? Ask him/her to plug all his audio devices into the same mains outlet.
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jello
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Post by jello on Jul 16, 2016 11:13:09 GMT
Thanks for the reply jkeny.
It was only a few quid so ended up just giving the guy a refund rather than have things drag on. Didn't have any means to test it my end either so seemed the best option but something to keep in mind in future.
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