spritzer

No phase splitter is needed with these amps since the gain is so high. The WES is basically a GES with the front end removed so to run it SE they had to add the front end to the circuit again. The ESX also has gain issues when running in SE mode which are due to the amp not using ECC81's like it should.

Isn't it about equal in Class A?

The different parts are mostly due to the amp being made from 1982 to 1992. The 2SJ109 didn't exist back in 1982 hence the J75 used instead. That layout is indeed the final one as the original Mk2 normal bias amp had only two main PSU caps instead of 3. The first A models used that PCB as well and an off board Pro bias supply.

Marc and Justin pretty much covered this but yeah, even with minimal matching and thermal drift you shouldn't be able to hear the difference between SE and XLR, assuming the outputs of the source are of equal quality which they almost never are. Also to add to what Justin said, there are quite a few sources out there which only have SE output stages but then generate a balanced output from that. There are also plenty of Euro and Japanese gear which simply isn't balanced even though they shipped with balanced outputs.

There is no way to nail down the SRM-1 Mk2 amps in terms of serial number or series. Way too much crossing over and since this is by far the most popular amp Stax ever made, there are a lot of revisions and different parts used. That amp doesn't have the 2SJ109 dual fet but otherwise it is the same circuit. Here is a pic of the PP I'm rebuilding, this is what a late C-type should look like on the inside (minus the balanced pot and my other mods): It would have been nice to have the heatsink as well but one can't be too picky...

I've had something like this happen before so now I triple check every solder joint.

Ok, that is funny...

The voltage swing would naturally only be half of the XLR inputs. In practice this shouldn't make any difference.

The pot is simply added between the input terminals on the chassis and the input terminals on the board, just like it is on the Crack you built. I would recommend a 4 gang pot and XLR inputs even if you are using SE only since these can be a pain to add later on. If you want to have both XLR/RCA inputs then you need to have a switch to ground the - part of the amp when running it SE (XLR/RCA adapters do this already so no need to worry about it). I for one use a 4PDT ON-ON switch on my amps so the two inputs are isolated from one another but you can just use a 2PDT switch if you do not want that. There is also the option of using bridging pins as you can see on many power amps.

Why the fuck are you bumping this old thread for a retarded comment like that?

They are two pieces of neoprene rubber with adhesive backing, one on top of the other use to damp any ringing from the two metal grills. The first units didn't have them so they were a later addition. That hasn't been my experience. I've gone up to 900V and they really couldn't have cared less. What the SR-007 really needs isn't more power, just a very stable amp that doesn't give a damn about the load it sees. It's a bit high since there is nothing special about this amp. The whole C-series stigma only applies to some units which had the same PCB as the rare PP units. They had better wiring (massive solid core PC-OCC wires) and better resistors. I would ask for an internal shot to verify that this isn't just a plain old SRM-1 Mk2.

To be clear, the stock amp didn't use ECC88's but rather E188CC

For me they serve one great purpose, a quick way to see if a new amp is performing ok as they pickup hum and any bias issues other phones don't mind. Being pretty cheap helps when you've destroyed one earpiece like I have...

Nice!!

Tubes = valves to the rest of the English speaking world.

Mkey....

Yeah, I wouldn't even try tuberolling this amp. For instance the ES-1/2 should only be used with ECC81's but Mikhail probably thought they looked odd driving the EL34's so used octals instead...

Yup, the SR-007 drivers made out of stiff PCB material encased in a resin frame. That is in turn bolted to a massive piece of aluminum (for a headphone that is) that sits inside an aluminum ring which forms part of the rather unique headband assembly.

Stax mafia doesn't agree. I think I tried a JH13 at CJ though I'm not sure (fairly certain my good friend Douglas made me do it ) but the DSP unit didn't sound as good as a SR-003. It wasn't bad by any means but the bass was just odd to say the least with a definitive coloration. I've also never heard a headphone that can match the spectacular midrange of a well driven SR-003 (yup that includes the SR-007). Rumor has it that Stax are working on a new version which is about damn time given the Mk1 was from 1995 and the mk2 from 1997. I do hope they will fix the fit though as that's what really lets them down. Couple that to the Gilmore portable amp (which we hope somebody can build the transformer for) and it would be a very interesting shootout.

I do have a bunch of them and I might try it with slightly lower rails just to be on the safe side, +/-380V maybe.... I like crazy ideas like that. I want to do a single ended SS amp with an output transformer for Stax one of these days...

That's enough about those inferior dynamics!!! So I've been working on this SR-Omega that needed some TLC. I don't think I've ever posted pics of an empty SR-Omega shell to show why I sometimes call them the tin cans... As you can see the cups are very thin and it is mostly just plastic in there. Couple that to the huge driver and no wonder they get a bit ill tempered at higher volume levels. Far cry from the SR-007 design where the drivers are securely mounted in a large slab of metal. Another insteresting bit is that Stax grounded the metal enclosure through large resistors to the + and - terminals.

You only need to alter the gap between the diaphragm and the magnets a little bit to loose a lot of sensitivity so there could be tweaks done to the drivers you could never spot unless you opened them up. I don't get the benefits of marketing a headphone like this though where a B22 or a Dynahi/Fet are your only realistic options for driving it.

More voltage swing and higher slew rate and the biggest factors.

I can always supply red vodka if it helps my US legal team. Get better soon Al. Yesterday I had a mini-meet here with Stuart which was basically us talking until midnight with about 10 minutes of listening thrown in. Pretty much the definition of a mini-meet... Today I was busy with cleaning up the house and even attempted to sort out all the DIY related parts cluttering up the place. That pretty much failed...

It would limit the voltage to 400V but I've been using them in the BH PSU's for years now with good results.