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Threshold S 300/II Main Caps Replace
Threshold S 300/II Main Caps Replace
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Old 2nd April 2010, 04:24 PM   #1
jpetek is offline jpetek  Germany
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Default Threshold S 300/II Main Caps Replace


I want to replace my Mallory 29.000y / 100V with other Caps.

What is the best choice? Do you heard any difference if you use a different type of Caps?

Thanks for help.

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Old 2nd April 2010, 04:54 PM   #2
analog_sa is offline analog_sa  Europe
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Location: Cascais
No idea what is the best choice but i used Rifa PEH169 33mF/100v. At the same time also replaced the 10uF nfb decoupling polyester with a polyprop, the input jacks and binding posts with Vampire and shorted all the fuses apart from the mains fuse. Did not expect much but the improvement really startled me. It is just an amazingly good amp now. Future upgrades include a separate, possibly shunt regulated PS for the input. And of course not using a heatsink as a ground bus.

The Stasis circuit is so simple and easy that i wonder why are there no diy designs around it. As the output is a completely separate entity it will be easy to use any type of voltage amplification and also easily build a tube hybrid. Even if one retains the original input circuit there must be some possibilities to enhance its performance. Higher quality CCS are one option and probably replacing the VAS transistor with something better is another.

Sorry if this appears as threadjacking, i'll probably start a new thread devoted to improvements of the Stasis amps.
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Old 12th April 2010, 04:01 PM   #3
jpetek is offline jpetek  Germany
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Thanks for the Message. Do you know if I can change the Voltage from 100 V to 63V without any Problem?


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Old 12th April 2010, 10:03 PM   #4
RobertS61 is offline RobertS61  Netherlands
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Join Date: Jul 2007
The railvoltage of the S/300 is 63 Volt. So I would take at least the next voltage range 75 or 100 Volts and buy the same casedimension. You will probably get a much higher uF value as a bonus.
Try Cornell Dubilier (They also market Mallory as a brand name) and see at resellers what's in stock. If they don't have stock in your value you have to buy at least 24 to place an order. If you buy NOS (much cheaper) you have to reform them first.
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Old 22nd November 2015, 05:46 PM   #5
kosscher is offline kosscher
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Join Date: Dec 2014
Hello, can someone advice exact size of the original PS caps?
As I want of order a pair for replacement.
What other caps need to be refreshed (???47uF Electrolytic and 0,15uF Tantalum???), please advice voltage and capacitance value. Someone also talking about some mylar caps to be replaced!?

I also would like to ask for the rating of the bridge rectifier or p/n for the IXYS HEXFRD rectifier, which is highly advised.

I am talking about S/300 Series II w/o optic bais
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