spritzer

I figured something this rare deserved a thread of its own. Let me introduce the Stax SRA-7S, integrated amp for earspeakers. This was introduced in 1966 for the SR-1 and remained in production into the 70's. With Stax we never really know when they stopped making something but given it's all tube design, it was dead by the mid 70's. This one was missing just one knob but amazingly they are still in current production. A full set has already been sourced... Those RCA's really need to go but pretty clean over all. Pretty much unmolested but somebody decided to remove the fuse holder. Not a good sign... Amp and phono stage on separate PCB's. All original parts and all the tubes are original. Hell the entire amp is a Matsushita advert on the inside... All of this will be stripped though. Not a chance components nearly 50 years old are even close to spec. Interesting tube choice though, ECC83 for the phono stage but the Stax amp uses a pair of 6AU6's, an 12AT7 and 12BH7's for the output. Power supply is as simple as it can be, two diodes feeding stacked caps to give +300/+600V. The two chassis mounted resistors are 100R so probably there to generate a center tap for the heater but I haven't retraced it yet. Finally the back of the front panel. Not sure how many of the features I'm going to recreate as pretty much all of this will be scrapped. I know I'm the collectors worst nightmare but I'm far more interested in making something better than it ever was than keeping broken parts and useless features in there.

Small is good but it isn't easy...

Well this does seem to fit, if a bit cramped...

There is nothing to be gained from running the front end at 400V, well nothing but bad things that is. There is already a dropping resistor on the board for just this setup. Those adapters are cool but there seems to be very little in the way of heatsinking. Shouldn't be a problem but something to look out for...

Just say you have super high res, anything below 384khz/32bit is just not worth your time.

The TKD's have their own quirks...

Anything on ebay would be fake too. Hell most of them have sanding marks and with 2SA1968 laser etched afterwards, not even close to how the original looks. After helping some users with their Megatron I have some ideas on how to improve the PCB and make it more user friendly. Swapping to the STN9360 for the CCS would make sense.

The amp ships with the new Mullard's and they are dependable even though they "sing" way too much for my tastes. One of my other Blue Hawaii's that's been on loan for well over a year has the new Mullard's and with zero issues despite heavy use. As for the XF2's, any tube can prematurely fail but the set in my BHSE has been in some Blue Hawaii here for almost 10 years and I bought it slightly used. These are pretty much bullet proof... I'm talking about the bog standard EL34 from JJ too. The blue (and red glass) version is supposed to be identical.

In a "normal" tube amp you have the signal entering on the grid with the cathode and anode loaded with resistors or chokes. If the tube shorts then too much current is passed and the resistors burn up. None of that applies here... Personally I'd never use a Shuguang tube in any of my gear. Hell I'd rather use my "made in USSR" tubes instead... Good question. Not sure what happened to this one but the heater died so I'm guessing it shorted to the cathode as the mosfets all lost their magic smoke.

Same problem here but add on far higher taxes.

I never had any problems with my 10+ year old SED's but something might be off with the more recent production. The JJ's are excellent and the new production Mullard's seem to be solid as well. The real "problem" with the BH circuit is that tube failure can be very bad news indeed.

Bingo

Me like shiny!!!

Happy Birthday Al!!!

Metcal has something similar in the newer stations, sort of a stand-by feature when the wand sits in the stand. I simply removed the magnets so it doesn't do that any more.

In the KGSSHV then, not the Dynahi? They are functionally identical, the STN9360 is just easier to source.

Nope, Yamas are just greedy bastards.

Never tried that Weller so I can't comment on that.

Yes and it is not subtle. One cool thing, when you solder LED's they light up... The difference in power is not something I've ever noticed, even with them side by side.

Just washed mine while it was snowing, though only slightly.

Anything from the PS900 should be interchangeable as they are pretty much the same device, albeit the 900 has a much nice chassis (die cast). The chisel tips are what I use most of the time though I have pretty much every one they make. SFV-CH25AR is what I've been using for the last few months....

Anybody can do a board run but don't expect one from Kevin and I.

Look closer....

200mb's+ I can get those plans too but this one is about 50$ a month for 200GB of foreign download so why spend more.

That also isn't the KGSSHV front end. It's similar but not the same. If we had any new parts that we could use then an updated BH would be possible.