The Stax Thread III
Apr 13, 2024 at 3:34 AM Post #25,397 of 25,622
I need to buy a pair of wireless phones ( noise reduction not needed ) that do not sound too different from
my Staxes (Lambda Sig, 404 Sig and L700 mkII). The Edifier “Stax” do not qualify mainly due to mechanical noises from
headband/earcubs,

Any suggestions based on experience ?
I enjoy listening to the new Dali IO-12. Of course it has less detail and separation than my SR-X9000, but it does not sound too different in my view. Soundstage is somewhat comparable. I mostly listen with noise reduction switched on, but others prefer it with ANC switched off (see https://www.head-fi.org/threads/new...nes-–-impressions-thread.970380/post-17997906).
 
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Apr 13, 2024 at 7:56 AM Post #25,398 of 25,622
I have a High-Amp Alpha Centauri and wrote a review about it in a German forum (here). This is an English translation (via Google translate):

After I've been using my Alpha Centauri (AC) for a few days now (with Stax X9000), here's a first report.

Andreas Rauenbühler sent me the AC to Switzerland straight away so that I could test the amplifier for a few days. After just a short listen it was clear to me that I would keep the AC. The sound is absolutely great, especially considering the price.

So far so good. It is well known that the high-amp devices are basically self-made devices by Andreas Rauenbühler. In particular, his website is explicitly aimed at the DIY community. Accordingly, I didn't expect outstanding workmanship and feel, and that's exactly how the device comes across. The case looks a bit rickety and the front panel has a small dent. But that doesn't affect the function or the sound, and I didn't buy the device to climb the Olympus of fine craftsmanship.

However, two points irritated me a bit:

(1) The device does not have a CE marking. I'm not a lawyer, but as I understand it, every device with a "socket connection" must have such a marking when it is placed on the market. When I asked him, Mr. Rauenbühler said that he builds his devices to the best of his knowledge and belief and therefore has no safety concerns. Oh well.

(2) The XLR input has the so-called "Pin 1" problem. Pin 1 must be connected directly to the housing. Unfortunately, pin 1 on my AC is connected to the audio GND, which in turn is decoupled from the housing via a 100 ohm resistor. This can lead to humming and disturbing noises (see e.g. https://www.ranecommercial.com/legacy/note165.html). On this point, Mr. Rauenbühler said succinctly that there was no clear rule as to how pin 1 should be connected. That's really not the case. Well, for the second one.

I will use the device as a basis for my DIY modifications and builds. Accordingly, I can safely overlook these technical inconsistencies. In particular, I have already started experimenting with CCS loads in one channel (it has great advantages in terms of measurements, listening test is still pending). However, Mr. Rauenbühler simply ignored my questions on this topic despite asking him several times. If it were a "normal" manufacturer I would understand this, but High-Amp is explicitly aimed at the DIY community, where such secrecy is rather unusual. Well, for the third one.

Overall:
If you are only interested in very good sound at a very reasonable price, the AC is a great choice (and probably the same with the other high-amp devices).
Technically, in my opinion, the AC offers a good DIY basis, unfortunately with a little less enthusiasm on the part of the developer.
 
Apr 13, 2024 at 8:04 AM Post #25,399 of 25,622
Hi All! I've got the SRM-313 and the first thing I did - i listened to it. Completely fantastic with the Lambda Pro!

But the second thing was - I opened it up and checked for the internals. This is the version with the vertically placed board and what surprised me a lot - there are no adjustable pots there for balance and offset. How can it be?

I measured the balance and it's fine. About 250 mV on the Right and around 1.2 V on the Left channel. But the offset is higher, abound 6 Volts on both channels.

Does anyone know why is there no pots to regulate the balance and offset? What for a version is it?

Thank you!
Going to add some photos for more context.

Maybe someone is familiar with this SRM-313 version and knows if the balance and offset adjustments are even possible here.
 

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Apr 13, 2024 at 9:37 AM Post #25,400 of 25,622
Going to add some photos for more context.

Maybe someone is familiar with this SRM-313 version and knows if the balance and offset adjustments are even possible here.
This thread "might" help???
https://www.head-fi.org/threads/sta...f-need-some-help-find-the-broken-part.964718/
This post in particular (but I would look at eh whole thread to make sure it is referring to your same version?)
https://www.head-fi.org/threads/sta...d-the-broken-part.964718/page-3#post-17174994

Looks like yours is an earlier version though... so may not help.
 
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Apr 13, 2024 at 10:10 AM Post #25,401 of 25,622
This thread "might" help???
https://www.head-fi.org/threads/sta...f-need-some-help-find-the-broken-part.964718/
This post in particular (but I would look at eh whole thread to make sure it is referring to your same version?)
https://www.head-fi.org/threads/sta...d-the-broken-part.964718/page-3#post-17174994

Looks like yours is an earlier version though... so may not help.
Hi bearFNF,

Thank you for your reply!

I saw this thread while doing my initial research, but the board version is definitely different.

I haven't found any information about the board I own, that's why I decided to ask here.

You can find the pots adjustment method in this thread, which is very similar to all the STAX amplifiers. The same was in the SRM-1 mk1 and SRM-717 I owned, but on my 313 board there are no pots at all. I assume that maybe some fixed value resistors are used instead.

Wonder if someone is familiar with this layout. Nothing critical to adjust, but very curious about the completely different approach.
 
Apr 14, 2024 at 3:37 AM Post #25,403 of 25,622
"OUTPUT VOLTAGE 1600V peak-to-peak"
how much in BH BJT - I have not yet found out

@Svperstar by the way, I completely forgot

found some interesting information

https://web.archive.org/web/20130115042635/http://headwize.com/?page_id=751

very cool resource, but doesn’t work anymore(

it is written there

"BH - can output 1500 V p-p measured stator to stator"

thus the BJT should be similar in output swing to the BH and BHSE (SE is 100 volts more)

As for the output current - I haven’t found accurate information yet - in SE it seems like 15mA in the original BH - from 12 and above, I think BJT should have similar
 
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Apr 14, 2024 at 4:23 AM Post #25,406 of 25,622
Hey guys which one has the bigger soundstage? The SR-007 or the L700? I find conflicting results on the internet
Have to hear it your self
Just remember sr007 needs serious juice otherwise its dull like f
 
Apr 14, 2024 at 11:08 AM Post #25,407 of 25,622
Have to hear it your self
Just remember sr007 needs serious juice otherwise its dull like f
Quite busy of late but I will try to get some comparative listening in the next day or two between them.
 

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Apr 14, 2024 at 11:20 AM Post #25,408 of 25,622
Quite busy of late but I will try to get some comparative listening in the next day or two between them.
Yeah i'd love to see a comparison between the two.
Sr007 can't do well with STAX amps , i remember the disappointment i had when pairing it with SRM 727 many years back. That's part of the reason why i moved to SR009S.
 
Apr 14, 2024 at 4:27 PM Post #25,410 of 25,622
Holy crow! 1694 posts and this is Stax thread III. I hope that by replying "to the thread" my question will get noticed :wink:

My question is simple: I'm getting back to building a Stax amp with a stepup transformer. Is it necessary or useful to have buildout resistors (say, 5.1k) on each leg to the phones? And if so, what wattage would you recommend? Thanks.

I've also seen protective Zener diodes across the output of the transformer in some schematics. Can anyone recommend a value if these are recommended in lieu of the resistors? Thanks.
 
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