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    ST-70 Coupling Cap questions

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    Aljaheejus

    Posts: 27
    Join date: 2010-01-03

    ST-70 Coupling Cap questions

    Post by Aljaheejus on Thu Apr 07, 2011 10:08 pm

    I have a stock-board ST-70 that I have re-built with new resistors and capacitors - except for the coupling capacitors which are silver colored 0.10 uF. Each one has the markings as follows:
    M39022/01.
    1487
    8013 B
    JAN 56289
    .10uF 10% 600V

    Can anyone tell me brand/type etc. about these? For example, how they might compare to the 0.22 uF russian PIO caps recommended by Bob L on this board. The gentleman who sold me the amp said they were oil-filled and audiophile quality. I do not have experience rolling caps, except as described below, and would appreciate advice regarding my particular caps, or more general guidance.

    For kicks I have substituted some Mundorf F MKP M-caps of 1.0 uF value 400v. I have not given them more than 15 hours, and as of yet they seem to lack the bass volume and power of the originals. The treble is more clear and possibly extended however.

    I see that Bob L of this board recommends 600V or higher, so maybe I should abandon this experiment with these inexpensive Mundorfs.

    Are two of the four on the audio path, and the other two are in feedback path? Which ones are "pairs"? Any point in trying both in parallel - bypassing? Where would I find out more about all this?

    Thanks in advance!




    Luddite

    Posts: 235
    Join date: 2009-02-04
    Age: 64
    Location: Texas

    Re: ST-70 Coupling Cap questions

    Post by Luddite on Fri Apr 08, 2011 10:17 am

    Aljaheejus wrote:

    For kicks I have substituted some Mundorf F MKP M-caps of 1.0 uF value 400v. I have not given them more than 15 hours, and as of yet they seem to lack the bass volume and power of the originals. The treble is more clear and possibly extended however.


    It is likely that an increase in capacitance by a factor of ten would noticeably alter the frequency balance. This has probably shifted response away from flat (like using a tone control). I suggest you return to the lower capacitance.

    Charlie

    Aljaheejus

    Posts: 27
    Join date: 2010-01-03

    Re: ST-70 Coupling Cap questions

    Post by Aljaheejus on Fri Apr 08, 2011 12:32 pm

    Thanks, Charlie. That's what I was wondering, since the bass is so weak in comparison.

    I must have made a mistake in using the value of 1.0 uF. Looks like 0.22 uF is recommended as an alternative value, but not 1.0. I know I got the voltage wrong and need to up that to 600v...

    Likely, I will just go back to the ones that came with it and try to find a more appropriate use for the 400v 1.0 uF caps.

      Current date/time is Fri Dec 19, 2014 7:21 pm