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Koss ESP/950 electrostat thread


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8 minutes ago, spritzer said:

You can also just use the extension cable that came in the box.  :)  

Also the angled earpads were a custom order from Vesper Audio.  Fong carries the normal flat pads but it is easy enough to order the custom ones from Belarus. 

How much do these angled earpads go for? Now I need to look through all of my cables boxes to see if I still have that koss to stax adapter.

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Now for something pretty rare... the ESP900...  This is the closed back version of the ESP950 made for medical use such as MRI's etc.  Not much is known about these and only a few sets have

So I've had the Massdrop version of the Koss ESP/95X sitting here for probably a month but not spent any time with them.  I know I'm awful...    That changed today so first some pics:  Let's start wit

So yea Angle'd Vesper Pads and the removal of that nasty foam make a difference!  @spritzer , I thank ya for your recommendation and guidance, it makes quite the improvement

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I was comparing Koss to Sony ECR500 and Sony surprisingly still sounds very good. I would say not as good as Koss, but very liquid with lower end authority and good soundstage, and this is with default "sweaty" pads. This makes me think that new pads on Sony will make them sound better and make them that much more comfortable. Anyone know how if someone makes pads for ECR500? Maybe Vesper Audio can do make them? I think SR-007 style pads would work. Spritzer, did you ever swap pads on ECR500? What style worked?

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Now for something pretty rare... the ESP900... 

DSC00115-2.thumb.jpg.2606a8095fa69470d76b16c1d9fe0003.jpg

This is the closed back version of the ESP950 made for medical use such as MRI's etc.  Not much is known about these and only a few sets have ever surfaced.  I'll do a more indepth post about these when I modify them and dig into them a bit.  Stock...well...they don't sound good.  The earpads are unique to these so when you press them to the head...the sound gets better but it is no 4070...that's for sure. 

DSC00116-2.jpg

DSC00114-2.jpg

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I recently impulse bought a set of the 95x on EU blowout ($290 all in, which includes 20% VAT so that's a little ridiculous) - regretted the compete waste of money from the moment they said they wouldn't cancel the order until these things arrived earlier today. I've always been a QUAD fan, but found the STAXs in my budget to be ear-shreddingly shrill so really didn't know what to expect. So far, what a lovely transducer! Now I'll have to go back and read through this whole damn thread before asking annoying questions...☺️

By the way, does anyone remember the dynamic headphone that KOSS sold for a while years ago that used the exact same enclosure? I had a pair briefly in the days where head-fi was part of my life (!) and remember finding it extremely smooth and friendly to my ears. Then in a childish moment of idiocy I 'dismantled' them 'for the benefit of the community' and that was the end of that. But, sonically, goes to show how much of an effect the enclosure has on the sound.

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The specs from Koss are clear plus the bias is directly off the B+ so 600V.  There is a spot there for a voltage divider with infinite value resistor (i.e. open) from the factory which they can then engage if the squeal becomes an issue.  

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Yes but I've never seen them do that.  They usually take it down to 500V or so.

That 300V value does smell a lot of somebody measuring the bias at the output socket...

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On 12/23/2019 at 12:39 PM, spritzer said:

Crap, I missed that sale as I would have bought 10 sets...  :)  

I think the dynamic Koss set was A/250 but I could be wrong

Spritzer, in the Kaldas thread you mentioned removing damping from your ESP95X.  I've removed the foam on the pad side - did you remove any damping on the grill side?  If so, did you notice any improvement?

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I do always remove the damping inside the earpads so that's well worth it.  The older ESP950's (remember they have been in production for 30 years) also had damping on the back of the drivers which has to be removed. 

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I recently removed the damping inside the earpads based on this thread and conversations with PolloLoco, and I'm surprised at how much of a difference it makes. They definitely sound more lively and it's a welcome change. When I first bought these I didn't understand the hype, but now I get it.

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On 6/1/2020 at 4:21 PM, spritzer said:

I do always remove the damping inside the earpads so that's well worth it.  The older ESP950's (remember they have been in production for 30 years) also had damping on the back of the drivers which has to be removed. 

One more Koss question for you if you don't mind.  I read a while back that you modded a Koss E90 to run Stax headphones.

 

Even though I don't think its very good, my E90 is sitting around and I was thinking of making a stax to Koss cable adapter for it.  Did you have to add resistors or something to the energizer to make it safe for Stax headphones?

I know you've expressed concern about Kingsound and Wee energizers.

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The bias in the E90 is run off the HV+ line so 600V.  That is fine for Stax but the issue is that the ballast resistor is not the right value and there is a cap after it.  Now you could just place a 4M7 resistor on the adapter but I prefer to go into the amp and modify it with a voltage divider and moving the cap.  The issue there is opening up the damn thing...

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4 hours ago, spritzer said:

The bias in the E90 is run off the HV+ line so 600V.  That is fine for Stax but the issue is that the ballast resistor is not the right value and there is a cap after it.  Now you could just place a 4M7 resistor on the adapter but I prefer to go into the amp and modify it with a voltage divider and moving the cap.  The issue there is opening up the damn thing...

Thank you, the ballast resistor was what I was thinking of.  I'm terrible at soldering and this would be a fun distraction in lockdown, not an amp I'd really start using.  If I added the resistor to the adapter, it would just go on the bias wire, right?

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