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thrice

The Headcase Stax thread

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The saga continues...

All seemed fine today until I turned off the amp & pulled the plug from the jack. The hum rose quickly in level & changed in timbre. It then disappeared as the plug left the jack. I could not hear any residual hum in the earspeakers after that. It seems to be an amp issue, for sure. Is it failing?

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Yup, sounds like it.  Could me a marginal part like a cap or something like that.  Well either that or the PSU is failing.  It's not the 100V unit, right? 

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The wall wart says 120V.

I presume the screws are beneath the rubber feet. They are stuck-on with tough adhesive.

That SRM-1/Mk-2 is again looking attractive.

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I opened it up, and everything looked clean. I was hoping to see something obviously wrong, but there wasn’t anything that looked scorched or singed. I lack the expertise to go probing. I’m a kit builder & modder, not a troubleshooter.

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Hello, i am new here and since the Mafia reside here... i'm gonna ask for a help to the Padrino or some of his associates....

I recently bought a sra-12s that needs some love (a recap, a pot cleaning and an adding of a pro bias out), i got a discount on the original asking price and i got gifted a pair of stax sigma Normal bias ("because i don't know what to do with them if i sell the amplifier").

The Sigma are really ok, the drivers are ok, they simply need a cleaning AND a new damping because the original glass wool dampening have been removed.

My question is:

What can i use for remake the dampening? (I llan to use quilt batting, is that ok?)

What shape the dampening should have? (Should i cover all the planes except the driver one, am i right?)

And there seems to be a pair of resistor attached to the cable connecting the driver, are they normal?

Thank you very much.

IMG_20190210_094620.jpg

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Those are actually silistors and I'd remove them at this point.  They don't age well and at 30+ years old... jut them off. 

The damping is on all sides of the housing and needs to be very dense or it won't work at all. 

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44 minutes ago, spritzer said:

Those are actually silistors and I'd remove them at this point.  They don't age well and at 30+ years old... jut them off. 

The damping is on all sides of the housing and needs to be very dense or it won't work at all. 

Thank you very much, i'll remove them and try with something dense.

 

By the way in my sra12s i have a +640V rail on the PS that feeds the amplifer board. Using that 640v point and a 2 resistors voltage divider to create the pro bias voltage is the normal way to do that? Ir therebis a better way?

Thank you very much and sorry for the newbie requests...

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That is the best way.  You could do something fancy and regulate the bias but I wouldn't bother. 

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What are the sonic differences between the 007A 2.9 and the SR-007 mk1 (I know there is multiple versions, one of the better ones please). Sorry to intrude, thanks for help!

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Hello, while i wait for some parts for restoring my sra12s i made some new earpads for my sigmas.

I also made the internal dampening. Following the advice of Spritzer i used the most dense material i could find.

By pure luck the material and quantities i used seems to be ok. The soundstage seems here, definitely the best of the headphones i own. The bass is present and clear so i am pretty happy of the final result.

I decided to substitute the earpads because i don't feel comfortable  using earpads that have been used by someone else for 30 years...

I decided to not use a spare pair of lambda earpads because of the different shape of the lower back part.

I made them in leather following the procedure Stax (or their supplier) probably used.

I used an embroidery machine to sew the ear oval on the reverse side of fabrics, then i reversed the fabrics.

With the fabrics now on the right side i added some low heigh memory foam cutted a couple of mm smaller than the finished earpad.

Now i used the embroidery machine to close the earpads. Cutted the excess leather and here they are.

They are a bit bigger than the original ones and are less stuffed, nothing dramatical but i will remade them the next time i have time to use the embroidery machine.

The same method can be used to make them with a sewing machine for the oval and an overlock machine using 3 threads and a short lenght stitch.

 

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