spritzer

Stax never bothered with that...

It has nothing to do with the build, it's built in into the circuit. Any peaks that are double the bias voltage will run a high risk of damaging the drivers. That's why the old transformers were fitted with clamp circuits. Run an active preamp into the KGSSHV and you can have enough gain for this to happen...

If you do something stupid then the KGSSHV has more than enough potential to fry any Pro bias headphones.

It's always fun to see how badly this shit is made so I bought one. As for the pads, the SR-1 was never supposed to have flat pads. See this original instructions booklet: They are a tall ring of neoprene so I've been experimenting with various pads to try and find a modern equivalent.

Maybe in some rare cases that might be the case but I've never run into that even with my super cramped PCB's. Filaments being the most obvious example. That's clearly not the case here as we could do this layout in our sleep with a complete ground plane.

Hmm why on earth are they using jumpers on a double sided board? Seriously!! The feedback is still identical though. Two 150K resistors in series so just remove the bottom one and connect the new resistor between the top pad and the empty socket connection.

I didn't know there was a new version of the amp boards so can you post some pics?

I don't remember anything like that but it's been some years since I last had a SRA-3S here... Been working on the SRA-7S complete rebuild. It was in horrible shape when it came here so it was full restoration time. No original components left...

How about reading the post above...

Not sure what those two arrows mean but I'd guess the text in Japanese has something to do with it. Those resistors will see some load especially if their values have drifted over the years. 3W units will be overkill but why not.

Just google fuses with a T rating so 3AT and the like. I'm sure they have some slow blow fuses in Japan.

It's just to enable or disable the servo. Even with the opamp not installed and all the other parts populated it will have an effect on the circuit with the jumper engaged.

That would be perfect. CCF60 series?

I can't see it as it needs a login. Koa, Xicon, Vishay etc. will all be fine.

These are sad days indeed. We should all be using opamps for everything... I'm sure somebody will make high performance parts for us but they won't be as cheap as the K389/J109 were back in the day.

I'd use 1/2W units but quality 1/4W units should work. That is non Chinese crap... I just did the mod recently and it was fun to have a proper SMD heat gun for it. Removing the stock resistors was easy as pie.

The glue that either holds the drivers to the baffle or the protective mesh to the drivers has failed. Only way to fix that is to take it all apart very gently, clean off the nasty glue and reglue it all. The glue they used back in those days is just horrible so the baffle is just stuck to the case due to that. Use some force and they will break apart. I did this exact thing last week when I fixed a really old SR-404.

Just ebay 600V teflon wire and you should find plenty. 1/2W 500V 5K1 resistors will work perfectly. ooops that was supposed to say "mint"...

I had the same issue and I'm pretty sure it was simply leaking to ground somewhere. At these voltage levels it is to be expected.

600V is a must for the HV stuff, bias and output wiring. I would also add 5K1 resistors to the output per the modern way to do things Bias is easy, you could just take a 4M7 resistor off the B+ but I'd put something in there that limits the possible current. A high impedance voltage divider that shaves off just a few volts in normal operation but comes in handy if there is a short. In other news, I just bought a mini SRA-3S so there will be a reforestation project soon. I might just go crazy with this one though...

I'll manage...

I use Bostik branded but that close to the sensitive electrostatic drivers isn't the best idea.

This new glue Stax is using is nasty, nasty shit. Some form of neoprene...

I'll probably just add them to my rather large stock of spare parts.

That's what I was going for. Good news on the 4070 front, I scored a SR-303 so I can bring them back to their proper state. Also made a new baffle so I can easily swap in the new drivers. It does help that quite a few Lambdas have met their end here...