[Mach3]

Hello
I hope someone can help. I was reading the STAX II thread and it had some instructions and photos for converting a 100V SRM717 to a 117V unit. I opened it up and I think even though it is marked as 100V in the back, that someone has already converted it.

Can someone comment on these photos? I think it is already set up but I don't want to plug it in until I know for sure. The board looks good, but am I supposed to move any other wires or check other wires? I didn't follow that part all too well and I am going to go back and try and re-read it. Also, am I supposed to change out the fuse? What should the value be for 117V usage?

Thanks!

Posted by saoudad
Regarding Voltage input to a 717 and 007t I can clarify that:

The power supply transformer has 7 tap on the input side which are
Yellow= common (winding 1)
(1)White=same as yellow (winding 1)
(2)Green=100v tap (winding 1)
(3)Purple=120v tap (winding 1)
(4)Black=common (winding 2)
(5)Brown=100v (winding 2)
(6)Blue=120v (winding 2)

Six jumper bar for voltage change number 1 thru 6
1 thru 4 are to select:1=100v 2=120v 3=100v 4=120v 5=220/240 6=100v/120v
So for 100v you install one bar each for 1,3,6.
For 120v you install one bar each for 2,4,6.
For 220v/240v you install on bar each 3,5.

 

[jsts]

Posted by saoudad
Regarding Voltage input to a 717 and 007t I can clarify that:

The power supply transformer has 7 tap on the input side which are
Yellow= common (winding 1)
(1)White=same as yellow (winding 1)
(2)Green=100v tap (winding 1)
(3)Purple=120v tap (winding 1)
(4)Black=common (winding 2)
(5)Brown=100v (winding 2)
(6)Blue=120v (winding 2)

Six jumper bar for voltage change number 1 thru 6
1 thru 4 are to select:1=100v 2=120v 3=100v 4=120v 5=220/240 6=100v/120v
So for 100v you install one bar each for 1,3,6.
For 120v you install one bar each for 2,4,6.
For 220v/240v you install on bar each 3,5.

 

[kevin gilmore]

there is a thermal fuse between yellow and white.

 

[vitop]

Saoudad

thanks for your resonse
It looks like this is how this is set up already.
Is that all that needs to be dome? Does the fuse need to be changed from the one used for 100V?
Thanks!

Posted by saoudad
Regarding Voltage input to a 717 and 007t I can clarify that:

The power supply transformer has 7 tap on the input side which are
Yellow= common (winding 1)
(1)White=same as yellow (winding 1)
(2)Green=100v tap (winding 1)
(3)Purple=120v tap (winding 1)
(4)Black=common (winding 2)
(5)Brown=100v (winding 2)
(6)Blue=120v (winding 2)

Six jumper bar for voltage change number 1 thru 6
1 thru 4 are to select:1=100v 2=120v 3=100v 4=120v 5=220/240 6=100v/120v
So for 100v you install one bar each for 1,3,6.
For 120v you install one bar each for 2,4,6.
For 220v/240v you install on bar each 3,5.

there is a thermal fuse between yellow and white.

Kevin
Do you have any idea if the value of that fuse needs to be different between a 100V and a 117V?

I'm going to try and follow that circuit tonight. It's simple enough that even I can do it

 

[playmusic]

For high frequencies, this swapping back and forth of charge happens really quickly, which means it requires more current to move the charge fast enough. Stax amps apparently can't manage a full +/- swing above 10 kHz when the amplitude is high. At least, that's how Kevin Gilmore explained it.

Simply put, in higher frequencies, the amp has much less time to fill the stators with enough statical charge.(the louder you listen the harder it gets) at 20hz, it has 1/20 second to fill the stators with statical charge but at 20khz, it has only 1/20.000 seconds to do that(things are not that simple of course) So the current must be high enough to deliver enough charges in time. If it can't, the voltage sags. As the voltage sags, the signal integrity starts failing.

Thank you for your feedback. These two explanations look consistent in themselves.
Still, I am not convinced that they actually match with reality.

The part that is hard for me to grasp is that if these above problems occured in reality then they would show up in a massive deterioration of the frequency response of the combination SR-009s + Stax amp at higher volumes at frequencies > 10 kHz.
But I have not found any measurements on the internet that substantiate such a deterioration of the frequency response.
This might have two reasons:

1. There is no deterioration of the frequency response > 10 kHz at high volumes.
2. Measurements > 10 kHz at high volumes have not been made or published.

I am inclined towards 1. But my following argumentation is not very strong.
The only measurement I found that seems to suggest that option 1 is true is the IM distortion measured by Steve Temme, Sean Olive et al. in "The Correlation Between Distortion Audibility and Listener Preference in Headphones". A Stax SR-009 + SRM-007tII is measured in the following way:
"The test procedure fixed one tone at 43.1Hz @ 94dB SPL and swept the other tone from 190 to 20k Hz at 94dB SPL."
Distortion was below 1% throughout the range up to 20 kHz. (Actually, there was in the beginning some equalization applied to the system to match it to some target.)
Ok, 94 dBSPL is not a very high volume and IM is not the frequency response measurement. I wish they had made the measurement at, say, 108 dBSPL.

Are you aware of any measurements that show a massive deterioration of frequency response of SR-009(s) + Stax amp above 10 kHz at hight volumes?

A little thing that can be interesting is to check is Bob Katz measurements of the KGSSHV Carbon doing square waves at different frequencies

The link to this measurement seems to be https://www.innerfidelity.com/content/katzs-corner-episode-18-icelandic-wonder but it does not work anymore.
Do you know where this article can be found?

 

[tumpux]

Stereophile should revive the Inner Fidelity articles soon.

 

[Eich1eeF]

The link to this measurement seems to be https://www.innerfidelity.com/content/katzs-corner-episode-18-icelandic-wonder but it does not work anymore.
Do you know where this article can be found?

The answer is always the same: The wayback machine has a copy:
https://web.archive.org/web/2019051...tent/katzs-corner-episode-18-icelandic-wonder

If you ever suspect that a page might disappear or change, you can also use the wayback machine to archive pages.

 

[BowWazoo]

Let's play

 

[T3RIAD]

The part that is hard for me to grasp is that if these above problems occured in reality then they would show up in a massive deterioration of the frequency response of the combination SR-009s + Stax amp at higher volumes at frequencies > 10 kHz.
But I have not found any measurements on the internet that substantiate such a deterioration of the frequency response.

Well, with some quick calculations we can see that the Stax SRM-353x, for example, can provide 400 V RMS of maximum output. The sensitivity of the SR-007, the most difficult of the current Stax lineup to drive, is 100 dB / 100 V at 1 kHz. That means the 400 V output of the SRM-353x can drive to SR-007 to around 112 dB SPL.

However, according to KG, the amp becomes current limited at high frequencies around 150 V. That means it's maximum volume in the 10 kHz to 20 kHz range will be limited to around 104 dB.

Whether that's noticeable or not would depend on how loudly you listen. It would not be visible in a 94 dB measurement. Considering most songs have less energy than average at such high frequencies, you would have to have the volume dial quite high to notice it.

 

[RKarim]

Anybody know what the effect (if any) burn-in has on Stax? Usually, I don't believe in burn-in, but Stax are complex and I don't understand them.

 

[Tugbars]

Stax makes their headphones play pink noise for 1 week before they ship. So we don't have to worry about it. During transportation due to cold, earpads might get stiff and it can take time for them to get back to their natural softness again. That's all.

 

[RKarim]

Stax makes their headphones play pink noise for 1 week before they ship. So we don't have to worry about it.

Ah I seem. Thank you for this information.

 

[BowWazoo]

Well, the Topping E30 inspires me.
The 16x oversampling, done by the Neutron Player and transmitted to the E30 with 32bit and 705.6Khz, does the sound really good.
So it really sounds more "analog"

 

[RKarim]

Well, the Topping E30 inspires me.
The 16x oversampling, done by the Neutron Player and transmitted to the E30 with 32bit and 705.6Mhz, does the sound really good.
So it really sounds more "analog"

How did you get your E30 to accept a 705.6kHz signal? The AKM chip only supports natively 384kHz.

 

[The Jester]

First visit to this thread, would anyone know the model of Stax headphones I have ...
seems an odd question but they were bought back in 1990 bundled with an SRM -Xh energiser ..
wondering if one or both is worth keeping or do the newer headphones and energisers sound way better ?