spritzer

You know Ari that those are just minor issues that get in the way of the glorious tube sound...

FR4 and 4oz like the original test boards. Only two layers on all of our amps... That's the general idea, fix those small issues such as a proper way to do the test pads, redo the input a bit to suit my particular needs (hello loopouts) and the like.

I solder everything where I can. Can't stand the pluggable stuff. Edit: Ohh and this amp sound fucking fantastic!!!

I will be ordering amp boards soon but I'll need to make a new version first. It needs some changes...

...an hour or so later spent wrangling wires it was alive. I went for orange as the power indicator to try something different... No hum noticeable with the headphones but I'll measure it when I get a chance. Running at 9mA and the sinks get warm but not hot. Next one will be run harder but the really neat part is that aside from the 2SA1968's everything is in current production.

Ehhh... not sure there is anything I have left. I need to fix up my SRA-14S and sell it (need a new transformer like they all will) but nothing else I'd want. If I find a broken T2 I might buy it just for fun.

Said fuck it to other things requiring my attention... It lives but I haven't done any testing except for balance/offset etc. Now for some not so fun wiring...

If I can find the time then I'll start testing it today. That plus another small HV...

The output tubes sit at +600V so it's easy to generate Pro bias. Not that it isn't always easy to generate it...

I'll wash the front panel clean and then have the new graphics laser etched which will not wash off... ever!! I'd just have thrown that SRA-3S in a bucket of water. Been there though as one of my SRA-12S amps was filthy to say the least.

Happy Birthday Doug!!!!

Happy Birthday Douglas!!!

I mean the Stax ones aren't that great but I've never seen a brand new one split into pieces like that.

It really depends on the contacts and their quality. I suspect they are the same as the teflon units so you should be fine. That's assuming you are referring to something like this: http://www.ebay.com/itm/1pc-9pin-Ceramic-Tube-Socket-Machine-Made-Gold-Pin-for-12AX7-EL84-6922-New-/130674502828?pt=Vintage_Electronics_R2&hash=item1e6cceacac

It's some cheap Chinese crap but still better than the "wood" boxes.

I didn't draw it up but I have the full schematic of the amp sitting in Japan. I'll post it when it gets here.

It is a lot of fun to repair/refurbish this old stuff, dirt and grime included. This one was filthy though, here is what the PCB's looked after I had cleaned them twice: Also fun to see how things have changed. All the electrolytics are odd values such as 50uf and the band indicated +, not -. Also all those 10% resistors must make the magic "vintage tone"... Started to repopulate. Was going to go with some fancy caps but I found a bag of these so I didn't bother to wait for new ones. The tube sockets are in amazing condition so no need to tamper with them. One cool thing, the values for the PCB are written by hand on the underside of the PCB with some notes in Japanese. What the chassis looks like now. Might install an IEC input and I also might replace the transformer as it's just 100V-117V and the PSU is actually a voltage doubler off a single 220V winding. One of the Hammond units fits in there and would give me a CT winding so a proper stacked PSU. Would just have to modify one of my old PCB's slightly and it would fit. Cost is raising quickly though and I still have to figure out what to do with the input connectors, volume/balance controls (TKD or ALPS) and the input selector (Grayhill?). Already bought new slide switches but the mono/stereo makes no sense so I'll leave it out. The filter just messes with the earspeaker output so I'll leave it out as well. Here is the current state of the front panel. As I expected the silk screening didn't stand up to my degrease efforts so it's needs to be redone. Only problem is that I have no idea what font that it. Probably something custom but it appears to be as wide as it is tall. A close up... I spent an hour this morning drawing this up. Biggest problem was the Stax logo which had to be redrawn from a picture. So if anybody needs to have the old logo as a PSD file it's available...

No chance on a regulated PSU but I will probably make a small PCB for the PSU as it will be so much neater. This way I can also upgrade to 220uf/350V or something like that and have a bias supply built in. The green thing is SD-1, literally Silicon Diode-1. Half wave rectified as diodes weren't cheap back in the day... Just tried to clean the front panel and some of the lettering came off so I'll have to clone it. Find a suitable font, copy all the markings and make something that looks similar.

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.