spritzer

I've never seen one of the 8CG7 amps but it would be mighty reckless of Stax not to mark them in some way. I'm sure they know the bias procedure for these amps is well known and people are replacing the tubes. Perhaps why Stax is moving to the ECC99 since it is only new stock and the only upgrade would be to the gold pin version.

If it happens more often as you push the amp harder then it may be a thermal issue which would be a component somewhere on its last legs. I'd start off by replacing all electrolytic caps and if that doesn't cure it, it's time for more drastic measures.

Stax were always a bit stingy when it came to the size of coupling/output caps so I'm not surprised you like the effect of having much larger output caps. You should be able to add a variable Pro bias supply pretty easily to your amp. Something like the KG Blue Hawaii supply (which is also used in your KGSS) is very simple to build. The diaphragms in all of the Stax phones are as tight as drums so the bias won't alter their behaviour. Did it make any difference to turn the volume knob or engage/disengage the EQ?

Only some of the II/A units have them. Rumor has it that Stax found a large stash of 8CG7's for virtually nothing...

There were some people whining about burnt fingers on the volume knob but they should have tried the stock Stax unit...

There is a bit more bass but the comfort makes all the difference for me...

There isn't a third flap, the Mk2 fitting is to the inside of the fabric support since the spring is smaller.

Stax are mostly matter of fact but something like the 1968 SR-3 has this lovely musical nature. The Gamma's are also more get up and go than any of the Lambdas. As for the HE-5., truly horrible headphones. Up there with Ultrasone in the "I'd like to smash 'em with a hammer" category...

Can't go wrong with something Rudistor approved. APL is using them too these days...

We will cover most of the common pitfalls but if you can manage to cram the right parts in the right spots then the amp will function. The same holds true for the normal KGSS. As for a chassis, basically anything which will fit the boards/transformer/attenuator works. The Hi-fi2000 cases are cheap and look ok.

I've never had any hum issues with tightly twisted filament wires bundled in with the DC but separating them can't hurt. Just remember to use high voltage wire for the filaments.

There is no fixed date for any of this and we are still working on making this project as idiot proof as is possible for something this nuts.

The Stax mafia approves of this message... Still it would be far easier to sell at 117V...

Break out that DMM and measure the primary....

Very nice read. The Omegas have a similar family sound but even more control and less of a "sound" of their own. Deeper bass, soundstage depth (well as much as a headphone can pull off) plus a much higher level of comfort. Those leather earpads are just beyond comfy. The only "problem" with the Omegas is their demand for better designed amps and insatiable need for more power. Now we never really need all that voltage swing something like the KGSS will give us but it does mean the amp is just idling at normal listening levels. The SRA shouldn't clip at all but I'm not sure how linear it really is once you start pushing it. As for SR-5 earpads, I got a bunch of them from a Japanese source in 2007 but I just checked and it looks like they don't have any left. Now you could try some similar earpads like those designed for the Denon 5000/7000 headphones or even the SR-007 earpads which are roughly the same size.

That one looks like Antonio's unit but I don't think we ever confirmed what the 3 primary wires are. They could be a 0-100-117V taps or one of them could be the ground wire for an internal shield. Only a look under the small PCB and a DCR test of the primaries will tell us what's what...

It's caused by trapped air trying to escape to equalize the pressure. Put the earphones on and with music playing, press them gently towards the head... I don't recommend doing this with the HE90, it's a bit unnerving...

The really odd bit about the Beveridge speakers is their single ended nature.

RIP Fred...

Happy Birthday!!!

Happy Birthday Matt!! I approve of the doughnuts....

Happy Birthday!!!

No, I love my new knob. Tice industries really should branch out into titanium...

Yup, he needs to remove the front panel to secure the screw though. A bit of a pain but the modular construction of Stax gear makes it easier.

Fair point but swapping in another tube type changes a lot of other things besides just the output power. I take it no adjustment is done to the amp besides changing the tubes?