spritzer

Try two months... Not happy about that but it is mostly fixed now. Oscillations and wild drifts are the nature of the beast when you use 1970's era PCB's and cutting all the wrong corners on the design. As for problems, what about unstable PSU's and the need for 50+ jfets to get a good quad which seems a bit silly given that this is supposed to be a budget design. Now all of this is gone once the new PCB's will land as they are probperly designed and no matching is needed. Plus the whole buisness of distortion being a few orders of magnitude lower and all that... Stax bitches!!!!

You would have to do quite a bit of modding to the main board to do the newest upgrades and using the old PSU isn't really an option IMO. Personally I'd just build the KGSS stock and then sell it. It's a great project and going by the exstata thread on HF, a hell of a lot less trouble then building the Exstata. I didn't have them both at the same time sadly. A used 323 would be a good budget option though and the A model I had was easy to change the voltage on...

First off, take the top off the amp. You will notice two PCB's standing upright in the amp, one for each channel. These have pots marked TVR1 and TVR2 which you can adjust via holes in the side of the chassis. Now the TVR1 pot is the balance and the TVR2 pot is the offset. What you have to do is take a voltmeter, set it to about 30VDC range (or if you have an auto-ranging unit, just set it to DC) and measure at the Stax sockets on the front. Use the diaphragm above and put the red and black probes into + and - for one channel and adjust the balance pot (TVR1) for 0VDC. Now remove the probe from the - output and hook the lead to any exposed part of the chassis for a ground connection. Now adjust the offset pot (TVR2) for 0VDC. You will have to go back and forth between the two adjustments a few times and then repeat for the other channel. Normally it is best to do this after the amp has warmed up for a bit (say and hour or two) but you can set it instantly after power on and then readjust later on. Now there is a relay bank on the output of the amp (the soft "tick" sound you hear when powering up the amp) and if they don't engage then you can't measure at the Stax sockets. This makes things just a little bit trickier though...

Could also be the slightly over reactive protection circuit. Listen for the output relays... Yup and I'm guessing Larry didn't bother to check the offset/balance either... There are number of designs cooking, all of which are better then the Exstata. As for being easy to build, I for one think an amp could be made a lot easier then the Exstata but that maybe just me... I had the 323 once and it is indeed great.

How about adding some simple regulator like a 317HV to the stock PSU? One could use shorter caps and place the whole thing above the stock PSU inside the box... Happy to help and I'm pretty sure the SRM-Monitor is a SRM-1 Mk2 with the EQ added. Certainly appears to be the case with the SRA-14S as well but without great pics one can never be too sure.

...and your point is? Does any iron made today match the quality of for instance the old Peerless iron? I certainly don't think so...

SRM-1 Mk2 schematic. This includes the Pro bias supply in case somebody wants to modify a non Pro unit...

You would be correct as the exstata version which measures properly is very similar to the SRM-1Mk2 design. Now the PSU lacks regulation in the Stax amps but with fresh caps and a stable line voltage it shouldn't be a big deal. You certainly will get a lot cleaner, more transparent sound from the Stax amps. Now speaking of the SRM-1Mk2, it appears I've just bought one and the tasty P.P. version at that. I see some mods in its future, adding balanced inputs and I might even try to add some regulation to the PSU...

The only "real" hurdle with any of these amps is getting output transformers good enough. With that sorted you can build almost anything you'd like.

As Kevin has pointed out, we aren't normal but I for one don't get the point of 3rd party amps if aren't getting any real improvements for your money. My SRM-Xh has the same voltage swing and a lot less distortion in a tiny box. The SRM-1 Mk2 (not the Mk1, very different design) is mostly identical to the SRM-313 except different parts used. This isn't a bad amp but comparing a stock unit to anything modern is madness since the PSU caps will be way past their sell by date. As for the SRM-T1, it's a good circuit built on the cheap and with the wrong tubes. The ECC99's should solve some of the compression issues but the real "fix" is the KGST. 6S4A tubes with a 10M90 CCS which I should have up and running as soon as I place a new order with Mouser. I'm as you all know certifiable so I'm running it at +/-400V for added effect...

Your best bet really would be to sell the boards and wait for the next release as it will be far, far better. The short story is that KG and I both built our P-P versions of the amp (not using the stock PSU which is IMO rather terrible but rather a known benchmark which is the BH supply) and we were not happy with the results. Now KG measured the build and it wasn't pretty, distortion many orders of magnitude higher then the KGSS (1%!!!!!) but until an amp had been built using the stock boards we couldn't be sure what was going on. Now fast forward to this weekend and Kevin finishes a bone stock amp exactly like the BOM on the stock boards and exactly the same results. Throw the circuit in a sym and the SRM-212 circuit absolutely thrashes the Exstata let alone the more advanced versions of the same circuit. Now KG gets tinkering and modifies the Exstata circuit so it is far, far better. Alex will then supposedly make those changes to the next board run. In other news, we are also working on quite a few things right now, including a +/-500V capable SS amp which isn't quite as insane as the KGSSHV. Cheap to build too...

Amen brother... The stators are pretty fragile too as they are fixed to the molded plastic frame via tiny plastic pieces which could melt pretty easily. Shouldn't happen but then again nobody should be able to melt an XLR plug while trying to solder to it but it happens all the time...

Yeah, the cable certainly is damaged and knowing this fucknut soldered directly to the drivers doesn't inspire me with confidence...

There is a metal grille on all the Lambda/Sigma drivers and I've seen dust covers tear over the years even with the grille in place. As for the arc's, just sitting on them is enough to break them.

Mmmm tasty... I just love vintage Japanese gear.

Stay far away from those. First off, the cable entry has been hacked, the arc is a joke and just look at the corrosion on the drivers. I wouldn't pay 5$ for those...

Very purdy but show us the real porn, i.e. the inside.

There are direct flights from Orlando...

Any notion that caps need to charge for 250hours, drivers need to flex or some such can be filed away with people claiming Stax phones can be damaged by playing them while not on the head i.e. complete lack of understanding of what is truly going on inside the gear. As for the link you posted, there was probably a good reason why the amp was chewing and spitting out tubes. Same deal with the SP ES amps. Now I for one don't doubt that there is a perceived difference but there can be a range of causes. Fluctuating line voltages, different operational temperatures (warmup is a very real phenomenon) or just simply a better understanding of how the system sounds. Another option would be the multitude of crap designs out there which drift like mad or show some other non linear traits which are hard to account for. There is also the whole issue of wanting to believe it is better due to cost, peer pressure etc. which would translate into wishful thinking.

I'd say Rudi finally figured out how bad the Egmont of Circlefuck really are, not that they aren't the exact same amp. I've built a couple of these Egmont type amps and how Rudi builds them they are worth about 250$. The parts quality is a joke and performance wise they are far behind the Stax tube amps. Now you can modify the circuit and put in a proper PSU but Rudi could never figure out how to do so. Add some feedback and throw out the crappy 6SN7's and it isn't a bad little amp, in fact that's what I initially wanted to use for the Poorman amp project. There is also one fun fact about the Rudistor amps, they will destroy your headphones as an added bonus on top of the retarded asking price. Bias supplies should be low impedance which is why Stax always used a voltage divider when they fed them off the B+ just to make sure no current could get trhough. That's also why you never see caps much larger then 0.1uf in any bias supply (the Beyer ET1000 has 1uf but that one is special) but Rudi uses 32uf. It's stupid beyond comprehension...

What indeed are you talking about? I said burnin is crap but different cable designs have different electrical properties which you can clearly measure. That can't be said about burn-in effects after 250 hours in any piece of gear... Again WTF are you talking about? I was speaking about the fucknuts on HF banging about burn-in as if it was some set in stone fact.

I could rant all day about that but instead I just make a killer loaf which people come from all over Reykjavik to buy. Hell people come from NJ to buy my pastries...

I for know cables matter but we too can measure that. Talk to any layman about the myth of electrical components some how changing after 200-800 hours of use and they think you are retarded. Dig a little deeper and why would caps somehow start to change after 200 hours after what, a few million charge cycles? Also, why is burnin always good, why does it never make anything sound bad? Now I for one know it takes a while to know any piece of gear. This time gets shorter with experience much the same way any professional who has to use his subjective skills does. I could really hold a lecture about bread and cake tasting and just how wrong and fucking clueless most people are. That said, the people who bang on the most about burn-in are the least experienced and have never held a soldering iron in their life. HAve no clue what makes the equipment tick nor how these supposed changes would come about.

SR-Lambda (6-pin) is 230V but 250 is close enough. You can also shave off a few volts since the danger of arcing with this beast can't be underestimated.

The normal bias is actually 200V for the 1967-1975 models (the SR-1 is also 200V but the very first units were 150V). The 1977 and onwards models all used 230V bias but many models still used pre-1977 drivers and worked just fine off the higher bias voltage. A simple voltage divider off any of the PSU lines would work for a normal bias supply or any of the other bias voltages we are using (180, 360, 500 and 540V). Mine is sitting here right now. 16kg of aircraft grade aluminum just for the BH amp boards. I'll post pics when I have some time...