spritzer

I bet the hum is coming from the transformer. That is literally the worst place possible to put it. As for the bass issue, what PCB is that hiding underneath the volume pot? Not a chance the RK27 is the culprit and I can't even think what could possibly do that to the circuit. Edit: Also the diodes in the power supply could go boom at any moment... They have to be insulated with this PCB layout.

I'd love to hear some of the speakers some day.

Yup, that's it.

Bunnies and cables is a special kind of hell.

You are probably running higher mains than the original design called for which explains the higher voltages. This happens all the time here as the gear was designed for 220V but we are edging closer to 240V. When using contact cleaner on the pot make sure it has some lubrication. Some are just cleaners and they will kill the pot quickly by washing away all of the lubrication. I would use shielded wire due to the small nature of the box. You could just use a super thin microphone cable with two contacts and a shield. Edit: Side mounding the tubes is actually better in many ways. The chassis acts like a cooling tunnel for the tubes.

Who knows why Stax swapped it out. Might be some part issues as the amps are filled with out of production transistors.

Both of those are very obvious...

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"...