spritzer

I have those universal pads (EP-007) on my Mk1 and they are identical to the ones on this SR-007A AFAIK. Btw. I just got a SRM-727 to mod and holy hell the 007A/727 combo is bad. Two components with exaggerated bass response don't mix well...

The aim with bending the arcs is to make the headphone disappear really. Most of the time it presses a bit to hard somewhere around the ear so you need to give it some slack and/or adjust how the arc is, as in its height.

Have to tried to bend the arcs to get a better fit? A stock SR-007 will never fit me correctly and the same goes for most people, even those not cursed with "gigantic head syndrome"... The ports are indeed still there on the SZ3 models as well but I guess Stax are using the pads to close them when the headphone is worn. Same thing as I'm hearing but since we have confirmation that the SZ3's are indeed a new version (supposed to have new drivers as well) the whole thing didn't work properly. It's clearly one of the 4 best headphones in the world, there is no denying that fact. The whole problem was that the Mk1 is so astonishingly good that even the SR-Omega has serious flaws in comparison.

Happy Birthday Milos!!!

Could very well be the same as such is so often the case. This is the best internal pic I could find of the Evo...

Ok, here is a bit of a conundrum. I got a SR-007A last night and as expected it didn't fart and sounded sub par like all the other Mk2/A's I've tried. Now today came time to try it with the BHSE so I wanted to fix the fit to have it on a level playing ground with my old Mk1. Now the strange part, with a good fit they do fart a bit and the bass is almost as controlled as the Mk1... Now this is one of the first units made (SZ2-1040) so it's not a mk2.5 (SZ3-XXXX) which makes this all a bit odd.

The Stax that made the T2 is long gone and we won't see such insanity again. I would aim a bit lower and perhaps a SRM-007t with ECC99's and a simple CCS for the output plus a nice PSU could be done at the limited price. Bring back the SRM-T1W wide chassis (which uses all the same basic parts as the slim boxes) to save money. It's a shame though that there isn't a good single triode in production that fits an amp like this...

Indeed. One has to wonder if this is also true for the Evo...

SR-007A. I did buy it a few months back but KuboTen just got them to me now. One of the first ones made (nr. 40) and yup, the bass and midrange are annoying even off the SRM-Xh. Now I'll have to see if I can hold off modding them until I get the SR-009...

I have some extras...

Yeah, that cap is a very bad idea.

Happy Birthday!!!

What I truly don't understand is this reluctance to just fucking accept that there is a point to amps like the BHSE and the T2. It may be the eternal search for giant killers but once you've been exposed to the SOTA stuff there is no way to go back.

Just came across this. See there were crazy Stax people here in Iceland when I was just 10 years old...

It certainly won't hurt.

The voltage will overcome the natural insulation of the air inside the driver and burn up the diaphragm. I've seen this way too often on the normal bias sets which were used with transformer boxes. The later SRD boxes used 450V zeners to clamp the output plus the protection in the earcups but it just didn't always work. The phones will continue to work but it is a vicious cycle since the charred remains of the diaphragm shorten the D/S gap so the driver is even more sensitive to arcing so it happens again and again. For the HE90, Sennheiser clearly states in the specs that they should never see anything in excess of 1000V P-P. That would be double the bias voltage (so 460V P-P for the normal bias Stax sets) but I think the SR-007 can take a bit more than that. They aren't really bothered by 900V bias and the driver construction sure points to that. On this subject, it is amazing just how messed up ESP drivers can be yet still produce sound. The first Micro-Seiki MS-1 I received produced sound but it was very faint. When I opened them up there wasn't any diaphragm left, just small crumbles scatted all over the driver yet it made sound... Two things you can do, add a servo with the output running through relays which shuts off if the offset goes too high. The Stax SRM-717/727 and the T2 use this setup with the threshold at around 20V. Another Stax trick, feed the output through 5k1 resistors to protect the headphones and the listener. In reality this isn't much of an issue since the distances inside the headphones are so great that insulation breakdown should never be a factor. Stax did ground the SR-Omega chassis just to be sure but I doubt it was ever really needed.

Nothing yet. I'm spending 12+ hours a day at work so this is on hold until things cool down a bit. I'll probably get the M2Tech Evo and build some nice PSU for it.

Nothing wrong with setting 0V as something else until somebody plugs in an Orpheus or a normal bias Stax. Bye, bye 5000$ drivers...

But the USB allows me to use any software I want and feed 4 dacs at the same time. Who said it was easy being a gear whore...

Yup R7 and R8 form the adjustable cathode resistor which is used to zero out the DC offset. Same setup as is used in the Stax SRM-T1 and SRM-007t amps amongst others. DC offset is the great enemy here as while the drivers are fine with it in theory, it kills the voltage swing. Single Power ES-1/2's had an offset of 100+V and the difference is quite startling once you get rid of it.

Extra load on the system would cause the voltage to sag a bit so that could be the issue.

Overheating isn't the issue here but rather the DC offset rising too much. That is naturally tied to the temperature of the amp but the wall voltage is a much bigger factor.

There should be two zeners in the input stage per phase.

I think my F5 is in a 3U box from Modushop...

I don't really see any need to swap out the 2SC5466's. Their only "problems" are the low operating voltage and that they are pretty hard to find. I used them in my SRM-1 Mk2 rebuild just because I had them at hand and none of the what Stax did use back in the day. You should use metal films for the mod, 1/4W and rated at 350V is more than enough. I used Vishay RN60's because that's what I had at hand and they are hard to top.