Stax SRM-T1 Repair, Re-Cap, Mod

[Krassi]

Yeah i already gotn an answer and now i am doomed to make this
I got the Kaldas RR1 with a custom original stax cable from spritzer, did some haptic and comfort modding and this could really improve the experience.
Since i am done and happy with what i have in headphones the amp could need some love since i cant say how exhausted all the parts are on a 30-40 year old device.

 

[armani006]

I got the Kaldas RR1 with a custom original stax cable from spritzer, did some haptic and comfort modding and this could really improve the experience

Ooo.. indian headphines for 500 euros here, I remember reviews about them, seems like they have a huge bass response and detachable cable, with modded T1 they will play more deep bass as with standard T1. It's good possibility to try custom cables on it )). I thought to try custom cable on my L500 mkII and I found 5 pins Stax socket but didn't find jack for headphones...

 

[Krassi]

Well i cant compare them with anything since those where my first real eletrostats. But i really like the comfort and sound of them. Aumkar has really built an amazing Headphone.

I got a original flat stax cable with nice connectors from Mjölnir.. I am glad he made them and with my modding the usual super sharp edges of the aluminium headband are now perfectly product shot polished and with a new leather strap ( https://media.discordapp.net/attach...2/Kaldas_RR1_pimped.jpg?width=1248&height=832 )..

So i dondt want to hear anything else! staying happy with what i have is my motto now and that T1 can now get some hifi steroids ... As soon as you hear something way better you get sad with what you have in the blink of an eye..

 

[armani006]

As soon as you hear something way better you get sad with what you have in the blink of an eye..

right, Best is the enemy for Good. Like you enjoy your phones. What about left-right balance? are they symmetric in volume?

 

[Krassi]

Seems like rev2 or at least a good working pair. I never had any kind of trouble, always touch the pins after listening sessions and have the Headphones in a stax dustcover.
Totally symmetric and great.. this would have instantly ruined the listening experience if that would have happened.

 

[armani006]

never had any kind of trouble, always touch the pins after listening sessions and have the Headphones in a stax dustcover.
Totally symmetric and great..

I do the same )

 

[JimL11]

Jim. any ideas how to improve power section of amp? I mean power transformer, is it any better variants on market?

No idea, sorry. The best improvement for the power section would be a regulated power supply, but there really isn't room. The best you can do is increase the capacitance of the power caps a bit.

 

[armani006]

The best improvement for the power section would be a regulated power supply, but there really isn't room. The best you can do is increase the capacitance of the power caps a bit.

I have one starter option Adam Hall AHPCS10 power conditioner, cheap and minimum stabilization but anyway gives effect. Increasing the capacitance is good idea, can work on it..

 

[AudioCats]

T1 and 007t use 100v zeners in the 2nd stage, directly in the signal path. Zeners are said to be noisy, has anybody tried using a LED string to replace the zener? It will take a lof of LED's to do 100v, but the current will be very low, small/tiny packages can be used, the final "zener replacement module" can still be rather small.

Z1 and Z2 in the picture below. 1z100 voltage spec is 90-110v, power rating is 1w.

 

[Pokemonn]

according to my very old knowledge of electronics..."blue" LED is least noisy(better)
is this my knowledge(few decade olds) is still right?(in 2020 standard.)

 

[AudioCats]

LED forward voltage drop increases when current goes up, supposedly IR changes the least, and UV changes the most.

but IR LED's only drop 1~1.2v ==> lots and lots of IR led's to get to 100v

 

[JimL11]

Don't forget that even if an individual LED is quiet, lots of LEDs in series will have their noise add up.

 

[AudioCats]

maybe, but more noisy than a zener which operates in avalanche mode?

 

[JimL11]

No idea, if we are talking 2V for the LED and 100V zener, that's 50 LEDs give or take, which is a pretty long chain. That will generate 50 times the noise of a single LED, or sqrt 50 = a bit more than 7 times the noise voltage assuming they are uncorrelated. You would probably have to measure to see which is quieter. Not to mention the fun of soldering 50 LEDs and the amount of space that would take up. Also if one of those solder joints is bad that could cause additional noise.

 

[AudioCats]

after reading the schematic a little closer, the 100v zeners appear to serve some kind of protection function for the 2sa1156 above them.
2sa1156 is rated to 400v, T1 use +48v top and -350v bottom and these voltages are not regulated. Without the zener holding off 100v the voltages might get a little too close to sa1156's limit.

So I guess a better way to do this is to change the 2sa1156 to stn9360 (which is used in the kgss Carbon). stn9360 is rated to 600v. Then you can remove the 1z100, replace it with a piece of wire.

This might take care of T1's "upper-mids glare" issue.