[Chris J]

So, basically, make sure to replace the fuse and not take shortcuts?

The fuse is for protection.
Protection from fires, at worst!
Think of them as brakes, would you drive around without brakes on your car?
Would you disable other safety features like seat belts?

 

[rgs9200m]

I sure wish Stax would try to work on an upgraded version of their 007 (and 727 I guess) amps.
 
I don't see why it would be so expensive for them to do this, and I bet they would sell a lot of them to the Stax owners out there.
And it seems like there is a lot of low-hanging-fruit as far as improvements go that could provide a lot of bang for the buck.
 
They don't need to do another T2 to make some improvements to what seems to be a fine amp foundation already.
Just do some tweaking. They don't have to start from scratch.

 

[miceblue]

Are there any other really expensive electrostatic headphones in production? The only ones I ever hear about are from STAX, of course (SR-007 and SR-009).

 

[DefQon]

There might be another Jade in the near future, early speculations that Sennheiser had a stat (possibly successor to the Orpheus) in the works but that turned out to be bs.

 

[autoteleology]

I guess Sennheiser doesn't want to make lots of money.

 

[autoteleology]

If I take a picture of my SRM-Xh PCB, can anyone tell me if/where a fuse is located on it?

Also, how does the Lambda (normal) compare to the Lambda Pro?

 

[arnaud]

I sure wish Stax would try to work on an upgraded version of their 007 (and 727 I guess) amps.

I don't see why it would be so expensive for them to do this, and I bet they would sell a lot of them to the Stax owners out there.
And it seems like there is a lot of low-hanging-fruit as far as improvements go that could provide a lot of bang for the buck.

They don't need to do another T2 to make some improvements to what seems to be a fine amp foundation already.
Just do some tweaking. They don't have to start from scratch.

From the interview we had with them last year, and reflecting Birgir's point all along, there's no magic bullet though: the size / weight are bound to go up if you want to increase the drive capability while ensuring stable operation.

I don't know the details on what Birgir plans to do to the 007t, but it seems along the line of pushing it further into class-A by increasing the idle current and the dissipated power at the same time? It may work better but the case wasn't designed to dissipate as much heat.

For Stax, the current amp they're working on does require new sinks / new chassis to fit in properly and dissipate the heat.

The differences in feedback topologies between 717 and 727 are a matter of taste and a designer choice and there does not seem to be one better than the other. When I asked them if they would be keen on providing the user a switch (like was done with the latest kgsshv version), they said no way it would happen.

Arnaud

 

[kevin gilmore]

here is a lousy picture of my shorted out fuse
 
http://gilmore.chem.northwestern.edu/dsc_0423.jpg
 
edit: I found another unit, also a srm-xh with a different board
that does not have the fuse or the protection diode.
(PB201-08438-00210) much older
 
if you have this one, and the led on the front panel lights up
when you turn it on, then you are likely going to have to replace
the ic (SG3524D or equivalent) and the 2 transistors 2sk940
if the 2 led's on the circuit board do not light up.
 
 
Without going into further details what birgir is going to do is remove the resistive plate loads
and replace them with a T2 style current source. The overall power will remain roughly the same.
Where the heat goes will not remain the same. But he is also going to change the power tubes to
6s4's because with 4 tubes, this is an easy upgrade.
 
the local/global feedback thing on the kgsshv is deliberately designed to be something you have to
do with the power off. being able to change the feedback with the power on would be a VERY BAD
thing for the headphones.

 

[autoteleology]

I was wondering why I couldn't find a fuse on the PCB. I thought the board used some kind of special fuse that looked different or something.

Well, if there's no fuse, is it possible to repair my Xh some other way? The thing still turns on, it just won't output anything.

 

[DefQon]

Sounds like a toast diode or transistor.
 
One of the jfet's on my SRM1 was toast on the left side so I had no sound output on the left channel. Good luck with repairing the unit though.

 

[autoteleology]

Well, that really sucks. Geez... I was hoping to be able to fix it up and sell it. Is it worth anything at all in this condition? :/

 

[DefQon]

Quote:

Well, that really sucks. Geez... I was hoping to be able to fix it up and sell it. Is it worth anything at all in this condition? :/

Actually looking at my old Xh pictures, it could possibly be just a shorted jfet (semi round black semiconductors), jfets are more easily prone to shorting out from spikes or dc offsets than transistors itself.
 
Here is a pic of my unit before re-cap (browse through my profile pictures for more pics)
 

 
There are 4 jfets per channel as shown above. 
 
It's worth repairing imo, the parts would be more easier to locate than the parts from my 30 + year old SRM1.

 

[kevin gilmore]

you first have to look at the 2 leds in the middle of the board. if both are off, you have
a power supply problem. which you can fix with the 3524 and the 2 switching fets.
if the led's are on, you have other trouble. (see edited post above)
or (CAREFULLY) measure the voltages on the power supply caps.

 

[autoteleology]

My PCB looks exactly like yours. Assuming the problem is from DC power of incorrect polarity, what would I need to replace on the board?

On a side note, a big thanks to everyone who has been helpful so far. You've already given a whole lot more help than I could have expected.

 

[DefQon]

Quote:

you first have to look at the 2 leds in the middle of the board. if both are off, you have
a power supply problem. which you can fix with the 3524 and the 2 switching fets.
if the led's are on, you have other trouble. (see edited post above)
or (CAREFULLY) measure the voltages on the power supply caps.

Good point on the leds as well, almost forgot about it. 2 red led's for each stage I'm assuming?