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ChrisX

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  1. The PCBs look great. From my point of view you should calculate with the original price. In case we really need the spares there will be no $ left over. In case we don't need the spares take the set as a bonus for your efforts.
  2. If I counted correctly I'm already on the waiting list. So I'm in with one set pending.
  3. So the plan is to convert the 900s into DIY-950s. Probably the best use for them.
  4. Interestingly Stax emphasized these resistors in their advertising: "a straight uncolored dynamic sound has been realized by using non-magnetic audio-grade carbon film resistors for load resistance". Probably a good example how marketing works, every trifle can and will be bloated. Exactly these I had also in mind. Unfortunately my last Mouser order just arrived this week (with KGST parts - to return to the original topic ), so it will take some time for the next one, but obviously there is no hurry - after all the years the amp won't blow up next week.
  5. This is reason enough to do some maintanance better sooner than later. This value should be easy to get, not sure if I find the recommended TKDs. But if not it would be still better to use some proven industry grade stuff (Vishay, Panasonic, ...) than risk to keep the unreliable parts I assume.
  6. So the question remains which is the usual failure mode. Maybe I should at least open the amp and check the necessary values soon, just to be prepared.
  7. Coming back to this topic. I own a SRM-600, so this sentence makes me slightly nervous. Should I exchange anything as a precaution, or do these parts fail without entraining other parts so that it would be safe to wait until they fail (if ever)?
  8. I have received the replacement for the bent headband of the Koss ESP900 and also finished building the Stax2Koss adapter, so it's time for some impressions. First the adapter: I don't have access to a 3D printer and any friends who can machine plastic, so I decided to try to use hot-melt glue. The result is not really nice, more like a hot-melt glue mess. But with the heat shrink tube attached the mess is perfectly hidden and the adapter works like a charm. Let's hope it will survive the next summer. To the headphones: The first impression points to the ear cushions, they are made of a hard plastic with a smooth surface. So they are not very comfortable and you sweat easily under them. I assume easy cleaning and disinfection was a requirement for the medical use. I assume that the cushions of the ESP950 will fit, so I probably will buy a pair as an upgrade (When doing so I can maybe open the cans as DefQon requested ). Second impression: I know now what the "Koss squeal" is. It's not permanent, it was very annoying when I first tested the adapter before I closed it with the heat shrink tube, but it disappeared after that. During todays session they were quiet at first, but the squeal came back after some minutes of listening. Since it already happens with CD off and volume set to zero it only seems to be related to the bias and possibly some static charge. Listening session: So today I quickly arranged some stuff in the kitchen for a small comparison session, involved were a Cambridge Audio CD player, the Stax SRM323 amp, a Violectric V200 amp, a Stax 404LE as electrostatic headphone, a Beyerdynamic DT770 (600 Ohm) as closed headphone and of course the Koss ESP900. When I knew how the result would be I wouldn't have moved all the stuff, since the differences are anything but subtle. The Koss has a very thin sound with nearly no noticeable bass. It may work for some vocal music but a CD like Dire Straits' Brothers in Arms is a pain to hear with the Koss. In the mids they have the speed (don't know better how I should call it in English) why we love the electrostats and in this and only this point they outperform the Beyers. There is nothing to compare with the 404LE, worlds are between it and the ESP900. The damping of the closed construction is not very high, much less than the Beyers even less than the Ultrasone HFI-780. But at least the damping seems to be similar over the frequency range which is an advantage over the HFIs which seem to favor some frequencies. Possibly some softer ear cushions could improve the damping since the hard cushions don't seal very well (I should say that i have a small head, so the pressure with which the cans are pressed to the ears is also small). So as a short summary I wouldn't really recommend them. I expected to have some inferior sound compared to the Stax but hoped I could use them due to their closed construction when (mostly TV-) noise is present in the same room, but in this case I will have to continue using dynamic cans.
  9. Hammer worked well. Thanks! Obviously I don't want to risk to destroy my new headphones on the very first day. Maybe you can point me to some pictures/instructions (possibly of the 950) which show how the parts are mounted, so I can judge if I dare to dismantle them.
  10. I contacted the seller today and will get a replacement, so everything will be fine. In the meantime the Koss extension cable and the Neutrik XLR plugs arrived. I remember a posting from Kevin on the other forum where he describes how to get the pins out of the Neutrik plug pressing them with a vise. Is this a proved method or should I better break the plastic insert?
  11. I have also placed my first offer on Friday and it timed out. So I assumed (as it turned out correctly) that the seller only looked into ebay during office hours. Therefore I contacted him on Monday morning and placed a second offer after his reply. The cans arrived today. I received exactly the box that was visible on the second photo, it was sealed so the headphone on the picture must have been another one. It was sent without further packaging, just the address sticker glued on this box, not very careful . Anyway the box looked good on arrival. But when I opened it now it seems that the headband is bend at the right side. Since the box looked ok this could have already been happened before shipping to me, in any case I don't think that this is Koss standard and that they have left the factory in this state. What's you experience? Is the headbamd easily bendable back into shape or is this a case for a replcement? In any case I will contact the seller about this tomorrow.
  12. That was me. Of course only one of them. As spritzer mentioned only one set was on offer yet. Not sure if the other 11 will appear on ebay bit by bit. Mine are on the way and should arrive tomorrow. Also on their way is a Koss extension cable and some Neutrik plugs. But I'm still not sure how to get the plates for the pins made. I have to look for a turning shop or a 3D printing service nearby, or maybe I spend the weekend with drills and files (... for a less than pleasant result). So the report with the first impressions has to wait some more days. I hope they have some good degree of damping and don't compromise too much on the sound. Currently my electrostatic gear is used way too rare, because usually in the evening my wife watches TV in the same room so I have to go for closed cans.
  13. Thanks in advance for your efforts. I just didn't get which version of the boards you plan to order? Kerry's SMD version or Kevin's/Birgir's through hole version? (Personally I would prefer the latter)
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