spritzer

Yeah, small size does add a lot of issues if you scale up power just a little bit.

Interesting input fets....

They are silistors actually and yeah, overload protection, and I remove them as they serve little to no purpose these days.

You can still get kits from Stax with the foam liner and the wool at least a couple of years ago. As always though, getting any parts from Stax is a pain....

The foam has no impact on the sound at all but the wool makes a lot of difference. I prefer to keep the wool in place as it makes them sound more balanced.

The 507 is the top tier Lambda in terms of build quality and comfort (though some don't like the new 009 style headband) but the sound is just so bloody thin. Compare them to the SR-404LE and the difference is startling, no substance to the sound.

Yup, the 507's are the biggest turd Stax have ever made. I don't think there is any other set which has just been truly bad like that. I'd take the 207's over them any day let alone the 307/407 which were the best from that generation.

Pure quality right there. Who needs full frequency response anyway...

The SRM-353X certainly superior to the SRM-1 Mk2 but it all comes down to value. The cost in parts of refurbishing the SRM-1 Mk2 is far lower and the difference between the two isn't all that big. I personally prefer the direct drive amps and with a transformer the cost is really high too due to the stepped attenuator.

A refurbished SRM-1 Mk2 does stand well up against the transformers. For me it is a toss up between the detail and accuracy of the amp vs. the raw power and voltage swing of the transformers.

A perfect transformer doesn't exist and they usually have a lot of capacitance which adds to the load and thus...loss. Bunch of other issues as well but for a budget setup, transformers work well and are easier than ever to use with all the excellent chip amps out there. Well not the Wee...all the ones I've seen have a shared negative which will blow up the amps...

It's the EIZZ 24 step attenuator.

https://www.head-fi.org/threads/the-stax-thread-iii.677809/page-1198#post-15108864 Ok, it's not often we see this level of shit... but holy fuck on a stick. So this is claimed to be an "improved Carbon" but the only improvement I can see is an added chance to burn your house down or give you a nasty shock. Seriously, this is apex level shit and how anybody would ship something like this out...is just beyond me. Also, gotta love "thinker" who consistently shows any possibility to do just that....

I've only talked to him once but he seemed like the nicest guy. Makes sense to do both panels at the same time. Might also be time for the bias supplies too.

I doubt anybody has a spare panel for these but Kent is at Electrostatic Solutions

The price of these has shot up recently so this will probably just get worse... As for the T8000, just get a 727 instead.

The balance and offset adjustments are the same as the for the Stax SRM-T1 so all the same applies. The pots are marked on the PCB so its easy to spot which is which.

On the ones I build that is not possible. Those dual split shaft pots are impossible to get outside of ordering thousands of them at a time.

Great write-up but one note, that is a regular KGSSHV and not a Carbon.

I like that one a lot!!

Let's just say I have a personal museum...

Yes, dual concentric volume control on this one and I'm pretty sure this was the first balanced Stax amp.

Now for something pretty rare... the ESP900... This is the closed back version of the ESP950 made for medical use such as MRI's etc. Not much is known about these and only a few sets have ever surfaced. I'll do a more indepth post about these when I modify them and dig into them a bit. Stock...well...they don't sound good. The earpads are unique to these so when you press them to the head...the sound gets better but it is no 4070...that's for sure.

Now time for something super rare... a balanced SRM-1 Mk2 PP. I didn't think any of these existed as there was the ATR version for studio use which had a stepped attenuator and balanced inputs but in almost 20 years of searching...none have turned up. Then I came across this one last year in Japan in pretty rough shape with tape all over it. I naturally over payed as usual but then again, how often does one find something like this: So years ago I did this and nice to see Stax did the exact same mod as me. Remove the 100R resistor to ground on the other side of the fet and put two resistors off the board in its place. The amp also arrived with one channel dead, shorted transistors and almost open resistors in the front end. Now for the money shot... This is clearly stock from Stax as all the screws match what they used at the time but one odd thing is that the markings are actually engraved into the back and not simply silk screened.

They are quite a bit better than my Massdrop unit sitting here. It's not stock though so angled leather earpads and a Stax Wide PC-OCC cable plus most of the damping in the earcups has been removed. The whole sound from the RR1 is tighter and more focused while the ESP is warmer and slightly softer. It does remind me that I need to post about something in the ESP thread... They do share one thing in common though, squealing. Now the RR1 has dust covers but the left driver on this set has been noisy from the start. It comes and goes and right now it is absolutely silent. The right one has always been silent though.