spritzer

All the Stax amps have used Jfet inputs since the early 70's. The 313 used the J109 dual fet until it was discontinued and replaced with matched pairs of J74's (which is just what a J109 was, matched J74's) thermally coupled.

There are at least two main versions, the one with the normal bias and the one that is Pro bias only. Both have the side mounted PCB but there were some small changes to the chassis such as went holes on the back. There are also some that look a lot like the 323 inside (pcb sitting on the bottom of the chassis) but I've never seen one up close to know if it's really a 323 in an old style chassis or just the first redesign to get around the discontinued dual jfets at the time. This is Stax though so there could be other revisions that nobody knows about. The SR-2 above doesn't exist officially yet, there is one.

That's pretty much as rare as they come. There is nothing there but a fire hazard. The person doing that has zero clue as can be seen from the axial power caps haphazardly mounted or the local PSU film bypass caps in the amp stage replaced with some audiophile crap.

Did you export the edge?

We need to melt down that silver into something useful..

Here something funny, an upgrade service for Stax tube amps... T1 and variants 007t and variants Not so sure about this clusterfuck...

All of the ground connections are shared so anywhere with GND next to it.

The quad ALPS layout we used on the Megatron works perfectly as a reference.

I've always been meaning to buy a pound or so of 925 sterling silver wire to make some cables. You know me... I buy in bulk!!! We so have to cryo some headphones one of these days. Take a SR-009 down to 4.2K and see if it changes anything. I do wonder how peek will behave after doing that... A specific thread about ripping shit apart and analyzing it would be fun. Cables are extra fun too as it is all BS. Virtual Dynamics was my favorite, garden hose filled with ferrite powder and bog standard inwall wiring (solid core).

The amps do need to be adjusted when swapping tubes but it's pretty easy to do. The adjustment pots are pretty much the hardest part as they are touchy and can break apart. On the last T1 I bought back to life both the offset pots split in two when I tried to adjust them.

The HD580/600 cables are a pain to work on so I'd use a 650 cable. I do like Ari's idea though.

At least they used an Amphenol plug for that cable... Speaking of connectors, I wouldn't use a RJ45 as the conductors are tiny. What about neutricon? http://eu.mouser.com/ProductDetail/Neutrik/OSC8M/?qs=sGAEpiMZZMsBYeZNO4kNBLFlOQUkTYt3

You have it rough my friend. I really should finish the KSA-5 one of these days but 3 complete sets of KGSSHVk boards need to be tested...

You could also just hack off the ends of a HD650 cable.

As Kevin said, while this may look easy enough the parts are a pain to work with. The traces lift off the PCB if you just look at them the wrong way and to make matters worse, the PSU caps aren't proper snap in units but have longer leads. These are bent into place and then flooded in solder so they can be a pain to replace with modern units.

Ain't it grand? There have been some issues here too and they have consumed a lot of my spare time. Simply getting replacement transformers from SumR out of customs was all but impossible and took a month. Ended up paying 150$ in tax for free replacements. Goes to show how stupid the HF lot is to think I do any of this for the money. If I'd ever sell an amp that I broke even on then I'd take it as the first sign of Ragnarök!!! That said, two more HV's under way. There is an output device in current production that might work at +/-450V so that needs to be tested. The Vbr fits but there is no better test than to build a channel or two. The HV's nature to go all arcy sparcy and issues with finding good sand is pushing me to try a +/-400V version. At that level it is no problem to source output devices in current production making things a whole lot easier. We can also increase the current which is always good....

Have a good one Dinny!!!

I must say I've been contemplating picking up one of those for my HE90...

If a project blows up then the first guess wouldn't be fake parts, especially for the noobs.

Can't go wrong with a Dynalo...

Yup, the TKD is just installed as it comes. Shouldn't need any extra resistors. Those on the Khozmos should be Caddocks but those look like Takman's which is an option they offer. Are you referring to the 400$+ monster metal stepped attenuators? If so then I've never tried them as they are stereo only and who needs that... The other simply have steps but are 100% pots based on a resistive track so you don't loose any resolution. Why people use those I truly don't get though...

There are known issues with Khozmo pots so I'd advice against installing another one. No way to fix the pot too as it's just a fucked design/build. I'd replace it with something else, Alps or TKD spring to mind. http://www.partsconnexion.com/controls_pot_tkd.html I think there is a 20% off deal going on now...

No idea who designed the Studio Six but they are right to not advertise it. Transformers wound with silver is a good way to waste money but I'm far more interested in the core shape, material and winding techniques. Now if all of those aspects are already taken care of then why not drop a few thousand on silver transformers. They did it in the Manhattan Project after all...

Looks good Adrian!! Some news on my end as this landed on Thursday: These are all the latest HV boards and hopefully this is the final version of both power supplies. No more issues with the stacked capacitors shorting to ground, about 4 times the ground plane clearance compared to the first version, better instructions on the board and the bias supply now has a fuse when used off the prereg feed. I also ordered some of my power boards which make wiring the multi voltage transformers easier, especially if using more than one transformer. Small problem as the holes intended for the CL60 are too small but they can go in the transformer mountings anyway.

Is it wrong to see so many problems with such simple amps? I really like the second from the top, thinking that adding Muse caps to the DC heater supply will make up for it being unregulated. "Heater supplies for people who like buying new tubes all the time...."