[bmichels]

Don't fix it if ain't broken

+1

 

[Ali-Pacha]

I think i read somewhere that Kingsound M-03 is recommended for other electrostatic headphones such as Stax. Why not you guys email them first and ask? They are quite responsive.
Don't fix it if ain't broken

Mmmh...do you know whom you're talking to ?

Ali

 

[Whitigir]

Mmmh...do you know whom you're talking to ?

Ali

I don't think they do , just pure innocence hehehe

 

[musicday]

Mmmh...do you know whom you're talking to ?

Ali

Thrilla in Manilla ?

 

[JimL11]

Well, I admit some of what I've posted is guessing, since I've never looked inside an M-03. However, it is specified for 300 VRMS into electrostatics, and also 3 VRMS into a 1 kHz load via a 3.5 mm jack, which tells me it has to have some kind of amp inside, presumably going directly into the 3.5 mm jack, and using a transformer step-up for the electrostatic load, and also a bias supply for the electrostatic. The SRD7 was a transformer and bias supply, but no amp, so a somewhat different animal. If the bias supply has a 1 megohm resistor out, as Soren says, then it would be reasonable to replace it with a 5 megohm resistor for Stax headphones. The transformer outputs, which I didn't know about when I first posted, but should have guessed given the specifications for both regular and electrostatic headphones - my bad, makes the 5.1 kilohm resistor for the electrostatic headphone outputs unnecessary.

BTW, the SRD-7 has been long obsolete. The last version of the SRD7 used 2.2 megohm resistors from the bias supply, but all the current Stax amps use a 5 megohm resistor, which is why I recommended that value.

 

[soren_brix]

If the bias supply has a 1 megohm resistor out, as Soren says, then it would be reasonable to replace it with a 5 megohm resistor for Stax headphones

looks like (not saying that it is so, Jim) ...and it looks like there are a voltage multiplier before the 1Meg resistor ... the voltage will drop pretty fast when you plugin the headphone, until it is fully charged ... I assume the 1Meg is probably a compromise for charging time ... anyways, if it is 1Meg rather than 5Meg, does it still constitute a "dangerous" amp? ...

 

[JimL11]

looks like (not saying that it is so, Jim) ...and it looks like there are a voltage multiplier before the 1Meg resistor ... the voltage will drop pretty fast when you plugin the headphone, until it is fully charged ... I assume the 1Meg is probably a compromise for charging time ... anyways, if it is 1Meg rather than 5Meg, does it still constitute a "dangerous" amp? ...

I don't know if it is dangerous. I just figure Stax knew what it was doing when they specified a 5 megohm resistor (either 4.7 or 5.1 megohms is close enough). Sennheiser, for example, apparently specified a 10 megohm resistor for their bias supply for the HE90, so people who build amps for the Sennheiser use 10 megohm bias resistors for them. Most Stax headphones (aside from the SR002/3) have a capacitance of approximately 100 pf stator-to-stator, so since the membrane is half-way between stators, figure 200 pf capacitance stator-to-membrane (think of the stator-membrane-stator as two capacitors in series). With a 5 megohm resistor, the RC time constant is approximately 1/1000 of a second - close enough for government work, as the saying goes. Actual charging time is probably slower than that as the membrane should have a high resistivity so the charge won't migrate when the membrane vibrates - you want the charge to remain "fixed" on the membrane for good linearity. In any case, the 5 megohm resistor is probably not the limiting factor in how fast the membrane charges, but since the preceding capacitor in the bias supply is usually 0.1 uf, which is 500-1000x higher than the capacitance of the headphones, the resistor helps prevent that bias cap from dumping too much charge too quickly onto the diaphragm should the worst happen.

 

[soren_brix]

I don't know if it is dangerous. ....

OK.

 

[musicday]

" M-03 is compatible with other electrostatic headphones provided they are using the same connector as STAX used. Of courier, to have a perfect matching, using electrostatic headphone & amplifier from the same factory is preferred. "

 

[ChaseM]

Tried to search for this but can't find the info. Does anyone have any info on changing the pads on a 007MK1? I'm getting a new set in Monday. Thanks for any help!

 

[statfi]

By popular demand, here is the process I used to reduce the length of my Stax009 cable from 2,5 meter down to 1,1 meter.
...
Also note that the operation have been made easier thanks to the other mod that I have done that allows the SR009 to lay flat (to be transportable in a slim case)
....

Nice job and write-up! Is "the other mod" written up as well? If so, where?

 

[georgep]

Pad replacement instructions from Stax provided by spritzer

Tried to search for this but can't find the info. Does anyone have any info on changing the pads on a 007MK1? I'm getting a new set in Monday. Thanks for any help!

Searching "stax sr007 pad change" in google images led me to the post above...

 

[ChaseM]

Thanks! I looked on google and YouTube and could t come up with anything.

 

[arnaud]

@bmichels , that was courageous . I would have placed a sheet on top of the earcup in case some flux jumped around but perhaps the solder used did not have such coating?

 

[bmichels]

Nice job and write-up! Is "the other mod" written up as well? If so, where?

the other mod was to have the Stax earcups being able to lay flat so that I can carry them in a slim case.

I just removed the 1 milimeter of plastic that is bellow the STAX aluminium plate, so that the earcup can rotate free