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Angst

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  1. They don't do a lot of repair work in the back. The Apple store will try really hard to convince you that it's too expensive to repair when you could get a new MacBook for a few more dollars. And if you don't go for that, they are paid by the hour. Products are designed for compact dimensions and economical manufacturing, not serviceability. More fun to be a stockholder than a customer.
  2. In decreasing order of use, more or less Koss Esp-950 - effortless & forgiving, mid-range to die for, not as resolving as Stax Spiral ear SE5-way U - nearly perfect for portable use Stax SR-007A - can't listen to poorly recorded albums. but so resolving with the right material Beyerdynamic DT-990 (600 ohm) - for a change of pace, were my primary phones for years. sparkling top end Beyerdynamic DT-1350 - HD25 killer that now gets abused, worn in the rain, around the garage Etymotic ER4 - superb isolation, uncomfortable for extended use but ideal on airplanes
  3. Yup, got tired of the illuminated anti-vandal switches that we usually use. Those look like the type of switch I had in mind. Can I ask where you found them? edit: Looks like Mouser and probably others have them. I didn't recognize the switches without the buttons (caps sold separately). How smooth does the model in your photo feel when you press the button?
  4. Anyone know of a supplier for old school push button power switches? I'm looking for something like the one below. They were everywhere on 70's Japanese consumer electronics. Sansui, Marantz, Kenwood. These latched on-off. Press to turn on. Press again to turn off. You pressed them in about 5 - 10 mm (half-inch) and usually had round aluminum buttons. I still see these used in some new (typically high end) audio gear. But can't find anything at Mouser, Digikey, Arrow, etc.
  5. Wondering what type of plastic Stax uses for the (black) jacks on their amps. Or if anyone knows of a black plastic or material that is machinable and plays nice with high voltage. I don't know what Stax uses, thought it might be bakelite as it is hard and brittle but it fails the "409" test for bakelite and a sliver that I cut from one floats as well (bakelite is heavier than water). You can sometimes identify plastics by the way they burn. Couldn't ignite the (tiny) slivers that I had. Possibly a phenolic smell after heating, might be a lower density resin related to bakelite. DIY jacks are usually made from white teflon (or delrin). Black coloured materials typically have carbon black in them which is conductive (bad for HV). A few people have made black jacks which are usually described as "black teflon" (could also be black delrin). I believe @kevin gilmore mentioned a while back that he tested black delrin and it began conducting at 200 volts. Natural, white teflon and delrin are both rated around 500V/mil, presumably less for the black versions. The only datasheets that I could find for black delrin left the voltage rating spec blank.. Digging around a bit, I found three machinable plastics that might work. Ultem, Noryl and Stycast 2651-40/11. Ultem (polyetherimide /PEI) might be a good choice. It's similar to PEEK, is used to manufacture high voltage circuit breakers and is said to be machinable. There are separate data sheets for the black and natural material which is good. However the voltage rating given is identical on both datasheets which is a little suspect. Anyway the black Ultem is said to have a dielectric strength of 830V/mil which is promising if that is accurate for the black version. Appears to cost two or three times what teflon does, but that would only impact the final part cost by a few dollars. Machining costs dominate and would ostensibly be similar. Any thoughts on Ultem, alternate plastics or the best way to test (hipot)?
  6. You can find a SRD-7 schematic here. More than anything they are isolation transformers because the energizer needs to have a 230 volt DC bias on the headphone side. Your driving amp modulates the audio signal on top of this. The transformer is likely fairly high impedance, and unity gain. You can see in the schematic that Stax put a 27 ohm power resistor load across each primary for amplifier compatibility. Beware of the high voltages, you play with this at your own risk and the voltages are potentially lethal.
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