KOSS ESP-950 Thread
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doctorjazz

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You're correct, it's been a while since I used the E/90, I've been using a Stax SRM323II with an adapter cable. But I have a vague memory from some maybe a year and a half ago, maybe 2 years ago, when I first got it, tha @crazychile had recommended a power upgrade for the E/90, it did involve a better cable, must have been some other addition (or my incipient Alzheimers :wink: )

(just connected my LTA LPS as power supply, really nice, not sure if it is a good voltage, though).

Yes. I forget the details as well. I am currently using a different amp with my Koss, but the original "upgrade" was to buy an external ps for the Koss ( I think it came from Mouser) and then that psu would also accept a standard power cable . Anyway, the details are in this thread from about a year and a half ago.

And, if I may ask, what amp are you using these days?
 
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doctorjazz

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upgraded power cord on a wall brick?

clearly you have never seen or listened to the koss esp950

You're in the Stax thread quite a bit, do you have both the Koss and the Stax? Which one/ones? Can you compare? Would it be worth driving a good Stax, say 007, with the SRM323II amp, or is it wasting the expense (eventually would likely upgrade, but all this stuff ain't cheap).
 
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Das Mookid

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Picked up a pair of ESP 950 new from Amazon a little over a month ago for $700. Honestly more than I'd thought I'd ever spend on a single pair of headphones  even at this 'budget' entry price (I know, welcome to Head Fi), but Koss have a special fascination for me. In this industry, the irreverence of a company offering a lifetime warranty on its cheapest pair of earbuds, where many other vendors in this esteemed 'High End' forum won't stand by their product for a year - well that's the kind of special I can get behind.
 
I don't have any other experience with Orthodynamic cans, but these have made me a believer - a baptism by electrostatic discharge. I assumed I would be well into dwindling return territory, but these headphones seem like a bargain. The detail and linearity beats out my trusty ER4s, but does so with a soundstage and impact range I have no comparison for. Whereas my many trusted dynamics all had their pros and cons, these mercilessly lay bare everything I throw at them. The build quality is anything but premium feeling, but this honestly appeals to my utilitarian sensibilities. The cans are a vessel to deliver that transducer, the cost is entirely technology focused - this isn't a luxury headphone designed to pamper you with rich mahogany scents or leather bound ear pads, this is a bunker buster of audio technology.
 
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ambchang

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I used the srm-001 mkII with them for a while and it is a clear upgrade over the e90. I don't really have great ears and even I can tell the difference.

You can find that amp her for $350 or so once in a while.

I never tried a different power cord or stuff like that.

The headphones are so good I didn't let them go until i got the 007+KGSS. It's that good.

Btw, the front page reviewer said he got it for $299. That's the best deal in the universe. You can sometimes find them for $450 to $500 used but it takes awhile to see that price. $600 is usually considered a reasonable price
 
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doctorjazz

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I've seen them used occasionally about $300, but that is indeed a great price. And, with the lifetime warranty, you don't have to worry about the condition you get them in.
 
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mrstrangeguy

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Big thanks to pawn shop staff who have no idea what was on their hands, asked me whether I wanted their store warranty or a bigger discount...
 
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crazychile

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You're correct, it's been a while since I used the E/90, I've been using a Stax SRM323II with an adapter cable. But I have a vague memory from some maybe a year and a half ago, maybe 2 years ago, when I first got it, tha @crazychile had recommended a power upgrade for the E/90, it did involve a better cable, must have been some other addition (or my incipient Alzheimers :wink: )

(just connected my LTA LPS as power supply, really nice, not sure if it is a good voltage, though).

Yes. I forget the details as well. I am currently using a different amp with my Koss, but the original "upgrade" was to buy an external ps for the Koss ( I think it came from Mouser) and then that psu would also accept a standard power cable . Anyway, the details are in this thread from about a year and a half ago.

And, if I may ask, what amp are you using these days?

See signature. The Exstata is entry level for a non-stax amp but I wanted something that would work if I jumped into some Stax hadphones as an upgrade. It's a little better than the E90, but I haven't fully utilized the balanced inputs yet. I'm hoping to get a Yggdrasil this summer and change that.
 
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Ojsinnerz

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You can certainly start out with the amp Koss includes...most people sick with it, though an upgraded power cord does help (Audio Advisors Pangea cords are relatively low cost upgraded to the generic power cord...I see Amazon had them as well). I'd also recommend an external DA converter...I use a Geek Out, but there are quite a few low cost options out there (and higher cost, better options as well, but one has to stay somewhere). Audioquest and Meridian are other not you expensive usb DA converters, CEntrance makes some that are a bit more, and so on. I'm sure you'll get more out of the 950 with a little upgrade to the system (I also use a lot of portable great...my Pono dap does line out...I often use it as a source into an amp).

Much appreciated! I'll be on the look out for a sale.
 
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doctorjazz

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Again, I misspoke to some extent, you need not just a power cord to upgrade, but a better power supply, which can be inexpensive, or more expensive than the 950.
 
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ericj

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Yeah the E/90 is not bad. It's not fantastic, but it's not bad at all. My exstata prototypes are better, but they cost me hundreds of dollars to build, each, using recycled enclosures. The E/90 may actually have an edge where metal and hard rock are concerned. 
 
I haven't tried it with a linear regulated supply. The original supply is just a transformer, rectifier, and capacitor. Since it's an EI core transformer it does a very good job of removing common-mode RFI and EMI but it's conceivable that a better power supply could improve the sound a touch. The E/90 has an internal voltage multiplier but I'm not clear on whether it is regulated. Better smoothing could be good. More capacitance could be good. The original wart is nominally 9v but i haven't checked to see what it's actual voltage is under load - it could be up to 12 volts. But don't go playing with higher voltage supplies until you've checked. 
 
I'm working on a lithium power supply for my e/90 - off and on. four 18650 cells and a high speed dc-dc converter. The protection board for the lithium cells has a built in balance charger. I'm'a throw a 5v supply into the same box. The general idea is to power the e/90 along with a y2 dac and rockboxed iriver h120. I can tell you for sure that the e/90 does not like a 2-cell lithium pack. A 3-cell may put out too much voltage. Eventually I'll measure what the actual operating voltage the thing is getting from the original wart, and set the dc converter right about there. 
 
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kevin gilmore

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The high voltage switcher in the e90 is regulated, +600,-600,+15 and -15 all come from the switcher.
Designed to run on D cell batteries.
 
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ericj

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  The high voltage switcher in the e90 is regulated, +600,-600,+15 and -15 all come from the switcher.
Designed to run on D cell batteries.
 
Right. So, that would suggest that using an external regulated supply would be superfluous, unless that supply has significantly less noise in addition to being regulated. 
 
The 2-cell lithium pack i tried would be nominally 8.4v and the e/90 wasn't happy about it. 3 lithium cells would be 11.1v and maybe too much. Good quality 18650 cells can deliver 3A of current and have pretty impressive energy density. 
 
I'm not sure it's "worth it" vs. the battery box that comes with the kit, but, it's what i decided to build. 
 
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timb5881

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So why not just use 6 rechargeable C cells in the battery pack? I have used 6 alkaline batteries, but the play time is not very long, maybe 3-4 hours at best. Has anyone tried using rechargeable c cells with it? If so how well are they working?
 
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thefitz

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So why not just use 6 rechargeable C cells in the battery pack? I have used 6 alkaline batteries, but the play time is not very long, maybe 3-4 hours at best. Has anyone tried using rechargeable c cells with it? If so how well are they working?

I thought rechargeable batteries are bad for audio - something about a non-constant voltage that would affect sound. At least that's how it works for guitar effects pedals.
 
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timb5881

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I have not heard that before. There are a lot of headphone amps out there that are battery powered, as well as other audio devices.
 
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