spritzer Posted October 18, 2013 Report Posted October 18, 2013 Most excellent. The lower serial does make me wonder what they are up to as all the sets being replaced have to end up somewhere.
spritzer Posted October 18, 2013 Report Posted October 18, 2013 Stax really didn't skimp on the transformers back in the day: Might have something to do with this: Given how rare these are it might be one of the first ever made.
DefQon Posted October 18, 2013 Report Posted October 18, 2013 Are you going to replace those "Silicon Diode - 1's" ? Those are some massive resistors at the back there, 15-25watt rated?
spritzer Posted October 19, 2013 Report Posted October 19, 2013 (edited) Those are C-core transformers btw... same as Lundahl. The resistors are just 5W units but they used to be huge in the 60's. The diodes need to go if I were ever going to use that bias supply. It has no input limiter though so it won't work off anything but 100VAC. Edited October 19, 2013 by spritzer
DefQon Posted October 20, 2013 Report Posted October 20, 2013 5W resistors? Damn I got some similar looking ones with bolt mounts on the sides that are rated at 25watts, I'd hate to see what 15-25W rated resistors looked like in the 60's.
spritzer Posted October 20, 2013 Report Posted October 20, 2013 The 5W resistors used in the SRA-10/12S are larger than the 12W Mills units. The Mills are nowhere near accurate (more like a 7W unit max) but goes to show how things have changed.
jwzhan Posted October 25, 2013 Report Posted October 25, 2013 Not strictly stax, but I guess this is the best place for it. This is the amp made by the guy who made Jade, now called HIFIMAN. There is rumor that he is going to be producing electrostatics again very soon. This is the amp he made for the headphone. I assume this is the prototype...
spritzer Posted October 25, 2013 Report Posted October 25, 2013 Very similar to the GES but 7 pin output tubes? None spring to mind that can handle 600V... He did build some amps back in the day, the SS one was a bastard version of the SRM-001 and the tube amp was a GES clone.
Jon L Posted October 25, 2013 Report Posted October 25, 2013 This is the amp made by the guy who made Jade, now called HIFIMAN.There is rumor that he is going to be producing electrostatics again very soon. This is the amp he made for the headphone. I assume this is the prototype...Hey, I still have one of those HE Audio electrostats, which looks somewhat dated sitting next to my SR009. Do you have a link for the company or dealer?
jwzhan Posted October 25, 2013 Report Posted October 25, 2013 It's just Hifiman. It's nothing but a rumor that they have been working on an electrostatic for a while now.. That amp is also done by an engineer at Hifiman a while back.
spritzer Posted October 25, 2013 Report Posted October 25, 2013 Here are the old ones, SS first: Notice the output caps and a Stax clone all the way Looks familiar? Same circuit but different output tubes.
kevin gilmore Posted October 25, 2013 Report Posted October 25, 2013 Both of them seem to be GES clones. The second one is 6fq7 as the output tubes. Not sure what the 7 pin output tubes are.
spritzer Posted October 25, 2013 Report Posted October 25, 2013 EL95? http://www.hebertech.com/view/1287-philips-el95.pdf That anode resistance isn't high enough, 20K won't cut it.
DefQon Posted October 26, 2013 Report Posted October 26, 2013 (edited) Size, mica structure and (if 0 getter) looks awfully similar to a 6005/6aq5, though only pushed to max about 280-350vdc. Unless it's the Chinese/Russian version similar to how they made 6p1's to handle up to 350vdc easily from a bog standard el84/6bq5/6p14. Edited October 26, 2013 by DefQon
spritzer Posted October 26, 2013 Report Posted October 26, 2013 They could be pulling a KingSound M-20 on this and running a 300V max tube at 600V. What I don't get is why would anybody use these tubes when there are still dirt cheap TV tubes out there that will do the trick.
spritzer Posted October 26, 2013 Report Posted October 26, 2013 Could very well be. Well either that or they just don't know any better. The M-20 would certainly point in that direction...
spritzer Posted November 4, 2013 Report Posted November 4, 2013 Just picked up my super rare Stax SR-2 (aka the set that doesn't officially exist) and they are even more a conundrum in person. I got these from the UK and what makes them truly odd is the yellow baffle and odd earpads. The baffle is off a PWB headphone so these were modified by the importer or PWB at some point. I haven't cracked therm open yet as I was eager to try them first. The earpads look a bit like the AKG 240 series but were utterly shot so I put on the first earpads I found A-T W3000ANV. To call this headphone rare would be an understatement though as according to Stax it never existed. No mention of it on the official product page and the unofficial Stax site (which is now defunct) didn't list it until one popped up on ebay. I've seen exactly two of these for sale in the last 10 years and this is one of them. I've found one review from 1968 of these and that's it. Stax have never explained why it was so short lived as the SR-3 was released in 1968. I plugged the set into my SRM-007tA and both channels came up to song in an instant. Always a good sign from vintage sets that the drivers are in perfect condition. The sound is typical of vintage Stax, midrange, midrange and a bit more midrange which is heavily damped. There is some top end and there is "enough" bass for most music but nothing like the modern sets. Still a far cry from something like the Koss ESP6 which is from the same time.
Ali-Pacha Posted November 4, 2013 Report Posted November 4, 2013 The sound is typical of vintage Stax, midrange, midrange and a bit more midrange which is heavily damped. Best vintage Stax description ever Ali
spritzer Posted November 5, 2013 Report Posted November 5, 2013 I opened them up last night so some pics will be coming when I have time. Identical build to a late SR-1 but I'm sure they did some internal changes to the drivers. Aside from the PWB baffle (same one as found on the yellow model here) the rest is 100% Stax so I might try to change to a SR-3 baffle.
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