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whodiini
25
Feb 24, 2021
I received my unit today - ordered a 220V version because the 120V was out. This info may be helpful for those in the same bind. The 220V power supply was NOT a switching supply. It is a class 2 transformer with an unregulated 9V 1A output (transformer + diode bridge + 2 caps). Translated - it will NOT work at 120V. At 120V, it will supply 5V. If someone has the 120V power supply, please respond to this and comment if it also is a class 2 transformer 9V 1A output printed on the wall wart. Next piece of important info - the output of the power supply is a 5.5mmx2.5mm male plug. So, if you want a power supply, here are a few possibiilties in my opinion: 1) Buy a iFi iPower 9V for $49. It has an included 5.5mmx2.5mm adapter (white) . I know it works because that is what I am using. 2). Buy a switching DC power supply. I looked at ebay tonight and looked at ones with the right specs and ones that there are a bunch of. This one is $9. https://www.ebay.com/itm/AC-120V-100-240V-DC-9V-1A-power-adapter-supply-9V-1A/202919278892?hash=item2f3eee792c:g:qlEAAOSwqG1eXVZk It even has the right plug. It should be plug and play, but since I havent tried it, I dont know if it will work. Switching power supplies tend to be a bit noisy normally, so this one may affect the sound with higher noise. Koss clearly didnt use a switching power supply, even though it is cheaper, so I would be wary of this choice. (IFi Ipower is a switching power supply with added noise suppression circuits. I didnt hear any issue.) 3) Buy a class 2 transformer 9V 1A wall wart 120V. I looked on ebay and this one seems to have close to the right specs: https://www.ebay.com/itm/AC-Adapter-Plug-In-Class-2-Transformer-9V-DC-1A/264559873999?hash=item3d98ff4fcf:g:js4AAOSw4pJd7FmW But they only have 2. Someone else sells a bunch of 1.2A 9V class 2 : https://www.ebay.com/itm/Jaguar-9V-DC-1-2-Amp-Atari-Power-Adapter-1200-mA-120-V-Input-5-5mm-Plug/280907991055?epid=1500251864&hash=item41676bc80f:g:nKcAAOxye5BREO3H The problem with this one at 1,2A is that the open circuit voltage may be higher and there is a power input capacitor on board that is only rated at 10V. So while it will work initially, you may get premature failure down the road in a year or 2, so I would look for a 9V 1A Class 2 transformer wall wart. If it doesnt say class 2, then it is a switching power supply and you might as well get the one in 2). The final issue is that the output for these class 2 transformers is 5.5mmx2.1mm male, so you need to buy an adapter like this one to go from 5.5x2.1 male to 5.5x2.5male for $3. https://www.ebay.com/itm/5-5x2-1mm-Female-to-5-5x2-5mm-Male-DC-Power-Plug-Connector-Adapter-QP-US-Seller/312836733513?hash=item48d685ba49:g:MiEAAOSw64ZdxN21 Out of curiosity, I purchased a 9V 1A 120V class 2 transformer on ebay for $16. It measured 12.3V open circuit output (no load), which is typical for an unregulated supply no load. I connected it with the $3 adapter also from ebay above, which looks near identical to the one that came with the iFi. Worked just fine. I cannot tell (with my ears) any difference with confidence. It may be a bit cleaner in the highs (cymbals) than the iFi switching supply, or it may be my imagination. I will be using this one to power the Koss a while. Hope this is helpful. You may just decide to pay a little more and get the iFi power supply on Amazon for $49, or if you want to experiment, try the other options. Disclaimer: Note that I hold no responsibility for any of this info nor any damage to your equipment or yourself. This is simply some personal opinions.
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