The Headcase Stax thread

[Ledzepp]

Did he mean a small DAC card to be inserted in slot 4?  Aren't they also working on a separate DAC product. 

[kevin gilmore]

T2 was the only stax with a servo. both common mode and differential mode.

717 had protection relay circuit if dc was out of spec

 

[arnaud]

There you go, I stand corrected. Now, if I only knew what this servo regulates actually ;-). 

[spritzer]

9 hours ago, Ledzepp said:

Did he mean a small DAC card to be inserted in slot 4?  Aren't they also working on a separate DAC product. 

It's for a dac but why anybody would buy one now is beyond me.  DAC's are moving so quickly these days that nobody can keep up. 

[kevin gilmore]

looking at the pictures, small surface mount transistors on a board that is insulated from the heatsink.

so pretty much the couple of pnp and npn surface mount parts that are available plus a tube front end that emulates the t2 with a lot less parts

price seems grossly high for that

[The Monkey]

1 hour ago, spritzer said:

It's for a dac but why anybody would buy one now is beyond me.  DAC's are moving so quickly these days that nobody can keep up. 

VINTAGE DACKS FTW

[Ali-Pacha]

Just tried Vali2 as a preamp, first with SRM-1/mk2 then with BHSE. It adds a bit of pleasant mellownes with the first one, but it kills dynamics / details / soundstage / impact with BHSE. I've to try further.

Ali

[sorenb]

1 hour ago, kevin gilmore said:

a tube front end that emulates the t2 with a lot less parts

how do you figur that from the pics in this thread?

[kevin gilmore]

my guess is a single dual triode as the differential amplifier, probably a pnp cascode, pnp current source driving a npn

only way to keep it all dc and still get the plate voltage down to something manageable

[JimL]

One correction.  I thought that they would be running more power since the consumption was listed as 95 watts, but I see that that spec includes the "optional slot", without it the power consumption is listed as 58 watts.  The 727 consumes 46 watts, figure 2-3 watts for the 6922 tube heaters, so another couple watts per side for the output stage.

Edited April 28, 2017 by JimL

[kevin gilmore]

also notice the same rms voltage as 727 which means +/-350 power supplies

[spritzer]

Definitely the same heatsinks as the 727 too. 

[2slow4u]

Hi guys, this is my first post!
I ask you a question.
I just bought a Lambda NB, the headphone works but is not in excellent condition.
In particular, the metal grille that protects the left channel driver is deformed, and touches the dust cover.
I believe that the only way to straighten it, involves removing the driver.
This is an operation I've done many years ago on other lambda, but I do not remember in detail now.
If I pull the driver out of the baffle, does the dust cover break?

I do not remember exactly where the dust cover is glued!

Thanks!

 

[spritzer]

You can separate the grill from the driver but yeah, odds are that you will destroy the dust cover as well.  It is attached to the thin aluminum ring that is between the grill and the front stator mounting plate. 

[2slow4u]

Thank you!
I just realized that the grill was glued to the driver, I was convinced it was fixed on the baffle, damn it!
This makes the situation much more complicated ...
Any ideas on what to do without breaking everything?

[mypasswordis]

Maybe just be very careful with a little hook to pull the metal out a bit?  Obviously don't do it where it's touching the cover

[spritzer]

That might work as the mesh is super soft.  That said, it isn't all that hard to just swap out the dust cover for some scrap plastic.  It's just pvc so the small bags you get at the grocery store should work just fine. 

[wink]

.... as long as you don't use the whole bag.........    

[2slow4u]

Ok, job done!

I used a sewing needle to lift the grill, and now is flat.

Now I need to clean the incredible quantity of dirt and foam debris trapped in the "grill/dust cover" gap...

[Earspeakers]

On 4/27/2017 at 3:57 PM, arnaud said:

From the little I understood in the video, slot 4 is for addon that are still in developments. Suzuki-san (chief designer) specifically mentioned about DAC or equalizer (phono that is?).

He also mentioned this line 4 slot has its own transformer / supply, independent from the rest of the circuit.

Maybe a diffuse field equalizer like the ED-1, but tailored for the 009? I believe the later headphones strived to build the equalization into the headphone, but at that point you're fighting physics so I wonder how much can be accomplished. 

Anyhow it looks like a 20 pin connector from the back, and since it has it's own power supply, I'd guess DAC and possibly eq. I love the ED-1/Pawel/Monitor eq personally, would love to see that option. 

[arnaud]

Suzuki-san confirmed this was for dac or phono board when I talked to him at the show. You should have asked me that before, I would have brought it up! Also he confirmed the dedicated low voltage supply for the addon board.

Jude got other things confirmed when he visited Stax office on Friday (such as power supply regulation), I hope to see some news posted in the HF thread at some point.

I liked what I heard on brief listen when compared to stock 727 amp, it felt more significant than differences between other stax amps. Of course, this is to be taken with a pinch of salt given the short audition / show conditions etc...

Oh, and it does look very nice in person, sand blast finish on the aluminum panels, reminiscent of the SR009. It's bigger than other stax amps but nothing compared to my BHSE, I can see people wanting this.

Arnaud

Edited May 1, 2017 by arnaud

[spritzer]

So Stax claimed that the HV supplies are regulated?  I will have to call bullshit on that as the HV supplies have two 220uf/400V caps in them (clearly seen in the Japanese video) so no headroom to regulate a +/-350V supply.  Now there is a single heatsink in there so they might be regulating something for the tube front end, who knows but the main rails are not regulated.  Could be the DC heater supply for the front end...

As for the rest of it, to me it looks like a 727 with a new tube based front end and all the NPN HV resistors swapped out for parallel run SMD devices, probably 2SC6127.  Aluminum backed PCB and then three or so used instead of the single TO220 devices. 

As for the size, looks a bit deeper than than the T1W but same width. 

Edited May 2, 2017 by spritzer

[Earspeakers]

I also heard from another friend in the business that they're using 2sc6127 on the output. The electro harmonix input tubes have me interested. I love the 600LE with it's 6922, maybe this'll sound similar - very energetic. 

Yeah DAC or phono makes sense, the industry has abandoned diffuse field I think. If the DAC wasn't just another delta-sigma clone I'd be thrilled, maybe a R2R.

Heresy but personally I don't mind the lack of regulation in Stax power supplies, curious to hear from Jude what the story is here. It's less accurate but does give a nice looser character which I appreciate for a lot of music. But for a amp of this class I'd expect regulation. 

Spendy, but I'm a stupid sucker for Stax, will surely pop for one. I'll post a write up in that case. 

[spritzer]

I've already put in an order for one so a full dissection is coming as soon as I can have one shipped to Kevin. 

The 600LE used ECC99's... only the T2 has the 6922's in the input section. 

[Whitigir]

31 minutes ago, spritzer said:

I've already put in an order for one so a full dissection is coming as soon as I can have one shipped to Kevin. 

The 600LE used ECC99's... only the T2 has the 6922's in the input section. 

W0000, that would be nice.  Can't wait to see The result