spritzer

Here I was thinking I was going to have a productive day... I didn't take any pics of the wooden boxes but they are very nice though my EX-1a box was branded as ES-2a... no matter. First off is the ES-2a and I went for the "Omega look" in terms of color. My ES-1a is all black so made sense to separate them in the collection. I like the color a lot, the finish isn't quite perfect but having been through the hell of trying to get perfect anodizing... yeah I understand that. I'm happy the outer screen has mesh in it now as that's a large part of why the Omegas sound the way they do, not that this is a copy of the Omega. I mean not really... The earpads are very nice and supple, concave similar to the newer Audeze LCD pads. A closer look at the driver face and those lover copper stators. The dust covers come with the set and I did install them as I like to keep dust out of all of my headphones. Might have some slight impact on the sound but who cares. I ordered the set with the regular cable but Benson upgraded me to the Stax Wide PC-OCC cable free of charge so thanks for that. The fit and finish of these is excellent, better than the ES-1a and that was no slouch. My main issue with them was the lack of strain relief on the headphones for the cable but that has been fixed here. EX-1a: I was pleasantly surprised when Benson told me that there would also be a cheaper version coming in the form of the EX-1a as ~1k$ headphones are sorely needed. Clearly been in the works long before Stax introduced the X1 but a take on the same Stax SR-1/2/3/3N/5/5N and X design but with much better build quality than the X1. The earcups are actually fixed to the headband and made of aluminum, not needing the new Stax mod of placing some tape over the X1 forks on new units as they won't stay in place. Very nice, all leather, earpads and it looks like leather on the headband as well. Very nice cable entry, made of soft "rubber like" material. Same plug on both sets (this has the basic 6core cable which seems to be perfectly serviceable but more on that when I get some time with them) and it is a mixture of the same rubber-like material and 3D printed end piece. Works perfectly. Now for some impressions. I've just about had an hour since I got them and spent it on the ES-2a and all I can say is... I've very, very impressed. Very neutral sound signature, a bit laid back (as if you are a couple of rows back from the performance) with a large and expansive soundstage. No lack of focus here though, they conjure a very solid stage but it's just a step back from say a 007. Very Omega like really... Treble is nice and extended, not the mess of the Stax 009 and X9000, just as detailed though . Midrange is excellent, voices have the right presence without being too forward. The bass is tight and deep, only small issue I've found would be a bit of a lack of extreme deep bass and some slight resonance in the bass on certain tracks. Nothing I worry about and I'd take these over the Stax 009's or X9000 any day of the week. I'll try the EX-1a when I can take these off my head dig my only working X1 out of storage to compare against it.

Looks like Koss ESP/6's in the last pick

Yes, they did. No idea why as it makes no sense but is a trend with recent Stax designs.

Thanks for the post and lots to unpack here. The issue with using lower bias is less potential on the diaphragm and it has to be compensated to a degree with the drive voltages. That really doesn't work so it opens up a can of worms with regards to peaks and spikes making it onto the drivers, causing damage. It's all about balance. For me, 1uf caps are also way too big for what is supposed to be a high impedance circuit. I'd then put a large value resistor between them and a much smaller cap before the ballast to limit energy transfer. The choice of a Villard voltage doubler puzzles me as it is a terrible circuit with no real redeeming factors while it would cost next to nothing (even less) to use a far better circuit. I'd be less worried about switching noise in the diodes etc. over what it is a bad circuit. Smaller caps with cheaper diodes would work much better. The bias is also summed so any benefits from channel seperation are along gone. One the Stax SB units they took took one AC line from each of the channels to grab the highest potential as the impedance of the transformer would minimize any channel cross talk. Thanks for the offer but I don't need anymore stuff. I like the price and some of the ideas here but I'd switch to a better bias supply, maybe even a voltage tripler, with smaller caps and say a 200V limit on the input.

I have so many questions... why is the max bias 240V and why is there a separate 1uf cap for each channel? The bias on Pro headphones is shared for both channels... so is this a normal bias only unit? The specs list a 303 though so I'm confused.

All of that circuit is wrong so use that transformer and use the Stax circuit as found in the 007t or 717. The schematic for the 007t is certainly out there. Also, don't use caps larger than 100nf as that is plenty of storage for a bias circuit. Stax use 10nf so that works just fine. 1uf or higher is utter madness.

This bias supply will blow up your headphones very quickly so don't use it. Everything is wrong with it so I'd completely scrap it

You think those are output protection resistors... on half of the signal? Yup, makes sense. Notice the cap there, with the resistor? Might that be a fucking RC network?

You said they would serve no purpose, that is clearly wrong. Stax never put any protection resistors in any SRD unit (or anything else for that matter) as they weren't introduced until 1994 with the T2. I don't need to enlighten you about shit but I will call out stupidity when I see it.

The 5k1 output resistors are very much necessary, you clearly have no idea why they are there.

What are the offset voltages? That's when you measure between each of the 4 outputs and ground. In theory you can have the balance at 0VDC but one output is stuck at HV+ or HV- It is also a good idea to measure the rail voltages as the resistors in the power supplies in these love to fail. Also... is the last cap of the main reservoir caps, closest to the tubes bulging a bit? Might just be the reflection.

I would always recommend swapping out the card slots on these as they all fall apart. Also, watch out for the transformers leaking... I found that out the hard way as they aren't grounded. Wasn't there just one pot per channel on these? Should be the balance so go to each tube anode and adjust for 0VDC.

I would just leave them in if they work fine

Yeah and it is 2SA... that is always a PNP.

It's an NPN so no... not a replacement. There are no PNP parts that are past 600V these days.