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STAX SR-M323A transformer re-wiring and balanced input

Marin M

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Hello to all forum users! :)


My name is Martin and this is my first ever post, so please bear with me if I would make any kind of mistake.

I would really appreciate if I could get some help please.

I need to convert 100v Japanese amp to be working with UK power supply.

I believe it could be re-wired; i am just not sure what wires and what pins on PCB needs to be changed.


Also, I am looking to install XLR balanced inputs, is there any simple schematic how to do it? My DAC has an pre amp so the volume control on the 323A is not necessary.


thank you for your time and help


best regards





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Take pics of the transformer primaries and we can see if this one can be converted.  Some can, some can't. 

As for the balanced input, just copy what is already on the board.  From memory there might be spots on the PCB for this as some versions had them.  Also from memory these were a series resistors on the input (2K?), a cap to ground and a shunt resistor as well (probably 500K). 

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Hello Spritzer

Thank you for quick reply! 

Sorry for not replying earlier but just brought the amp home and first thing I did was unpacking it,  removing the cover and taking some photos for you. 

So 2 wires seem cut,  after removing the glue they can be seen better.  


Ooops! Please bear with me,  I can't upload them right now,  it seems I can only upload photo of 0.57MB :D



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meanwhile, I will describe the cable colours

from the right to the eft -  transformer: blue (cut), brown, grey, orange (cut), green, white, yellow.

from the right to the left -  PCB:  GRN, COM, BLU, BRN, PPL, GRY, WHT, YEL. The numbers from 1 to 6 are going from the right to the left

At the back side of the PCB it seem to be 6 possible jumper connections. Numbers 1, 3 and 6 are connected together.

Sorry that I was unable to load the pics, not sure how to make them 0.49 MB size, will try again, otherwise if you'd like me to send them to a email address of your choice I would be more than happy do it.


Many thanks




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Hello Kevin

As per checking some previous posts I have found a similar one with pictures, just not sure exactly how to proceed with the jumpers.

Literally, just now, finished soldering them back; the orange and the blue one to the correct places on PCB.

How should I re connect the jumpers for 240V please?


thank you for reply

best regards




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Must have done something wrong because I did not get any reply apart from the initial response from Spritzer and Kevin Gilmour.

Maybe I don't know how to use this forum correctly, sorry.

Thanks again for the responses, I managed to do it following some of the pics from older posts.

Was very nervous, wasn't sure if this will apply to my amp but decided to go for it.

IT WORKS!!! :)

Very happy now.

I opened another topic for the balanced mod.

This topic can be closed now.


Thanks guys




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Maybe posting pics as was requested would have helped?

Hint: For anything other than small pics, a free photo hosting site such as Photobucket, etc. makes this much easier and allows larger pics to be posted.

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Thank you for your handy suggestion. 

Just created a photo bucket account so will use it for my other post about the balanced mod. 





Apologies for misspeling your last name in my previous post. 

Somehow memorised it as David's from Pink Floyd

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The most important thing is that, thanks to this forum, I could convert the voltage on my amp so I could finally switch it on and really enjoy it!

So big thanks to you for the posts which helped me to make it happen.

I envy you the knowledge and experience you have, maybe one day I will have a small bit of it.


best regards,



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