DefQon Posted January 22, 2015 Report Share Posted January 22, 2015 (edited) I've got a ECR-500 adaptor box with the electret headset. Thing thing distorts on high volume with bassy tracks and the volume drops down if I turn the volume up to high which ends up kicking in the over-spec protection relay circuit in my integrated amp to prevent clipping and damage to the speaker terminal outputs. It sounds quite nice on moderate volume with normal not so bassy music but as soon as ample amount of bass kicks in, volume drops and distortion occurs. I've cracked open the ECR-500 and the adaptor, reflowed solder connections, by the looks of the adaptor innards I think the two step up transformers are not original, according to the service manual the trafos are provided for low-frequency. There is also a PTH 465 rated thermistor pair connected to speaker terminals in the adaptor and the line out to speaker terminals, once I play bassy music on high volume, the thermistor gets really hot to touch and the volume drops and distortion occurs with the ECR-500's. They are parralled with a 3watter 27ohm resistor for each channel which I've replaced with two 15ohm 3watt Panny ERG resistors in series for 30ohms as I was thinking the resistors were losing there resistance and to be blamed. Afraid not. Any insights on what is happening? I don't think its the ECR-500 itself but the adaptor, if somebody could post some pics that'd be great. Re-wiring my chopped up ECR-400 and going to see if I get the same problem with that one. Ok tried my ECR-400 besides one massive channel imbalance (I opened up one driver), same problem as the ECR-500. Me thinks the adaptor is at fault, so after some quick searches on the google.jp, it appears the transformers in my ECR-500 are original but some soldering marks are present (aside from my own) on the wiring to the terminal strips. Here's a stock unit: http://zigsow.jp/portal/own_item_detail/242527/ On that one the negative phase (black wires) that connect up to an integrated amp is soldered to the terminal strip on both ends of the 27ohm resistors. On my one both transformer black wires and the terminal out are connected to adaptor speaker out and then a black wire is bridged to the 27ohm terminal strip, could this make a difference? Maybe I'll play with it some other day. For now there is definitely some magical leprechauns pulling tricks within the adaptor. Anyway attached a picture I made in Paint as of use for anybody wanting to re-wire or knowing the pinout for the ECR-500 4P pin, DMM'd all the leads so could be of great use. Edited January 22, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
padam Posted January 22, 2015 Report Share Posted January 22, 2015 I have an SRA-3S on the way, and from the description it will probably needs a bit of refurbishment. And since it is a 100V unit, I would like to ask if there is a transformer that might work instead of the factory one. Or if that does not exist, what kind of 230-100V voltage converter should I buy? Thank you in advance. Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 22, 2015 Report Share Posted January 22, 2015 With the ECR-400 I'd just wire the transformers directly to the input and see what happens. Thermistors don't last for long , let alone 40 years. No transformer I can think of fits the SRA-3S but most of the stock units can be rewired to at least 117V. Some even for 230V... Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 22, 2015 Report Share Posted January 22, 2015 Can i remove the thermistors completely? What's the purpose of them being there? Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 23, 2015 Report Share Posted January 23, 2015 They are there to protect the transformers from overload situations so they can be removed. Just don't do anything stupid with the volume... Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 23, 2015 Report Share Posted January 23, 2015 (edited) Thanks going to try without em. EDIT: Confirmed, thermistors were to blame when I de-soldered them the opposite side of the ceramic coating was bit bubbly looking on both, bypassed the selector switch completely from the secondary windings of the trafo's directly to the output line-out to speaker terminals and I can finally listen to music with bass, there is still a bit of distortion in the lower registers if I have the volume past 90db's or so which is about my listening level when I'm in the mood, but I think that's more to do with the nature of the fixed bias in the electret transducer rather then the adaptor or something else at fault. Looking back at the service manual for the ECR-500 makes more sense given that the primary windings from both trafos are connected to the stator -/+ and the secondary windings through the earspeaker-out/speaker selector switch and the speaker line-out are for low-frequency control, which explains why there was severe volume collapse and distortion in the lower registers when I bumped up the volume on bass heavy tracks, the faulty thermistor (voltage/thermal sensor) acts as a bridge for the secondary windings for output and would drastically heat up and cut off as if it was detecting too much current from my integrated amp. I still want to replace the thermistors with a direct replacement to safeguard over load situations, it says PTH 465 Kurata on the ceramic thermistor, what's a replacement for it? Thanks again. Edited January 23, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 26, 2015 Report Share Posted January 26, 2015 This one of your builds spritzer? http://www.ebay.de/itm/ROHRENVERSTARKER-Vollrohre-fur-elektrostatische-STAX-Kopfhorer-PRO-ONLY-Omega-/141550425325?pt=Kopfh%C3%B6rer&hash=item20f51014ed Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 26, 2015 Report Share Posted January 26, 2015 That's not one of mine. Looks ok though and is probably the Stax "circuit A" from 1968 modified a bit. As for the thermistor, it could be 465ohm so a 470ohm replacement. The higher value makes sense on the secondary but not the primary. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted January 28, 2015 Report Share Posted January 28, 2015 The ECR500 has absolutely no problems being driven from a SRM212 without clipping. I would just ditch the transformer box and plug into your favorite Stax/stat amp. Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 28, 2015 Report Share Posted January 28, 2015 Didn't work for me nor did the ECR 400's on any of my Stax amps, I don't get much sound out of em. Do you have the adaptor for your ECR 500? Quote Link to comment Share on other sites More sharing options...
cetoole Posted January 28, 2015 Report Share Posted January 28, 2015 Weren't the ECR known for having a magic disintegrating cable? Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 28, 2015 Report Share Posted January 28, 2015 Only the 600 and 800 had that pile of fail. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted January 28, 2015 Report Share Posted January 28, 2015 Didn't work for me nor did the ECR 400's on any of my Stax amps, I don't get much sound out of em. Do you have the adaptor for your ECR 500? No, the ECR500 I bought did not come with an adaptor. Recabled with a Stax Lambda signature cable and it works fine for me. Weren't the ECR known for having a magic disintegrating cable? What Birgir said, but I also replaced the cable because I had to (see above). Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 28, 2015 Report Share Posted January 28, 2015 Does your ECR 500's distort on very low-end frequency with bass heavy passages? Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 29, 2015 Report Share Posted January 29, 2015 Anyway: http://www.buyee.jp/item/yahoo/auction/h197454976 Looks like a 3S circuit converted to half of an SR-X circuit. Quote Link to comment Share on other sites More sharing options...
mypasswordis Posted January 29, 2015 Report Share Posted January 29, 2015 No bass distortion at all. Confirmed with such future classics as Rae Sremmurd's No Type and Tyga Ft. Young Thug's Hookah. These are bassy cans, no doubt, and are very clean and euphonic in the low end. The treble is kind of disjointed but I'm thinking there might be a comb filter effect or something going on. At least it isn't piercing in any way. Will investigate at some point in the distant future. Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 29, 2015 Report Share Posted January 29, 2015 Think my pair is botched then. I've got shit loads of mylar now since I need to keep some spares to repair my Final and Quad's in case things go south, have everything except the epoxy maybe I'll convert them to full blown e-stats. Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 30, 2015 Report Share Posted January 30, 2015 Just updating this thread a little as I've found a piece to the missing puzzle. Many e-stats from the late 60-70's were cloned after the Stax SR-3 lineup. Stax was actually not the first to do electret headphones. Fujiki Electronics also functioned under the brand Elega from the 60's experimented with electret transducers for headphone use in the mid to late 60's, they were also the OEM supplier for the early Sony ECR models released in the early 70's abd approx 1974 for the 500 model. Elega also had there own e-stats and electrets but are just as rare as the Stax SR-2 and were made in limited quantities and absolutely unobtanium. Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 30, 2015 Report Share Posted January 30, 2015 Most of the Stax sets used A-T drivers so this was never really their "thing". Quote Link to comment Share on other sites More sharing options...
DefQon Posted January 31, 2015 Report Share Posted January 31, 2015 (edited) Yeh its fascinating really, Elega even had it's own limited edition flagship dynamic in the 70's dubbed the XO-1 at around 75,000 yen which was incredibly expensive for its time later the record was broken by Sony's R10. What else I want to know is there another OEM or manufacturer we are missing that were first to do electret headphones or even electostats, maybe Stax was the first for esl stats? Who knows. Btw spritzer how was the Toshiba HR1000 electret headphone when you owned them years ago? Edited January 31, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
spritzer Posted January 31, 2015 Report Share Posted January 31, 2015 Stax were the first to make commercial electrostatic headphones, no doubt about that. There were a few designs that came in the late 60's but most are all but forgotten about now. The old Stax unofficial site was a treasure trove of these but they did also miss a few. The HR-1000 was ok but nothing special. Quote Link to comment Share on other sites More sharing options...
DefQon Posted February 4, 2015 Report Share Posted February 4, 2015 Sig Pro's would never reach to this level of wtf over past few years, usually ending around 650-800 usd after conversion This is a new level of http://www.buyee.jp/item/yahoo/auction/m129984042 Was the highest bidder yesterday at 60k yen till somebody bumped it to 161k. Quote Link to comment Share on other sites More sharing options...
nopants Posted February 4, 2015 Report Share Posted February 4, 2015 stateside they are going for 1200 to 1500 so Quote Link to comment Share on other sites More sharing options...
DefQon Posted February 4, 2015 Report Share Posted February 4, 2015 (edited) Yeah but those are still on the very high side from sellers who have no clue what they are selling only because they see the word Stax and vintage. Anyway going to upload some pictures of a rare pair of PWB electrostat's I received few days ago. Interesting drivers for sure, Peter W Belt obviously had no clue what he was doing as there was alot of fuckery going on with the e-stats he offered in the late 60's to early 70's. So many variations. Uploading pics when I get the time. Edited February 4, 2015 by DefQon Quote Link to comment Share on other sites More sharing options...
spritzer Posted February 4, 2015 Report Share Posted February 4, 2015 The prices are getting out of hand but they will come crashing down again. This has happened before... Quote Link to comment Share on other sites More sharing options...
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