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    Snubber, B+ ?

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    Dahlberg

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    Snubber, B+ ?

    Post by Dahlberg on Thu Nov 23, 2017 1:40 pm

    I'm wondering if anyone has calculated an R-C snubber for the B+ voltage for the M-125 amplifier ?
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    peterh

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    Re: Snubber, B+ ?

    Post by peterh on Thu Nov 23, 2017 6:21 pm

    Dahlberg wrote:I'm wondering if anyone has calculated an R-C snubber for the B+ voltage for the M-125 amplifier ?
    For what purpose ?
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    Dahlberg

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    Re: Snubber, B+ ?

    Post by Dahlberg on Thu Nov 23, 2017 7:01 pm

    As a precaution for eventual ringing caused by the transformer/rectifier.
    I will be going for solid state rectifiers, without any voltage dropping
    resistors or softstarting devices. As i have been reading up on this evening
    it schouldn't have to be as elaborate as in the drawing, an R-C link between
    the ac sides of the rectifiers would be sufficient.
    The values of the components are possible  to calculate given that you have
    the necessary information, but that's above my level of expertise.
    Ballpark numbers, usually 0,022uf/100ohm or somewhere fairly close to that.

    I belive it's called a "transformer snubber" (?)




    Edit: Right now I'm using byv96e Sounds great.

    I'm waiting for: C4D05120E In transit  Cool

    In my mouser basket right now there is: STTH812

    and: VS-HFA06TB120PBF
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    peterh

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    Re: Snubber, B+ ?

    Post by peterh on Fri Nov 24, 2017 3:07 am

    Dahlberg wrote:As a precaution for eventual ringing caused by the transformer/rectifier.
    I will be going for solid state rectifiers, without any voltage dropping
    resistors or softstarting devices. As i have been reading up on this evening
    it schouldn't have to be as elaborate as in the drawing, an R-C link between
    the ac sides of the rectifiers would be sufficient.
    The values of the components are possible  to calculate given that you have
    the necessary information, but that's above my level of expertise.
    Ballpark numbers, usually 0,022uf/100ohm or somewhere fairly close to that.

    I belive it's called a "transformer snubber" (?)




    Edit: Right now I'm using byv96e Sounds great.

    I'm waiting for: C4D05120E In transit  8)

    In my mouser basket right now there is: STTH812

    and: VS-HFA06TB120PBF
    The transformer is so small and weak that no snubbers are needed.
    A pair of 2n4007 is all that is needed.
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    Dahlberg

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    Re: Snubber, B+ ?

    Post by Dahlberg on Fri Nov 24, 2017 7:41 am

    In my experience there are sonic differences on rectifiers, even if small in my book everything matters.
    A pair of 1n4007 rectifiers will work, no objection there but I will try a number of other rectifiers anyway.

    Rectifiers will be in more or less need of a snubber circuit to get rid of ringing, if it's sonically detectable ?
    Sometimes if you ask me and the cost of finding out is not what's gonna ruin my economy.

    I have been searching for information and came up with this paper.
    Some reading on the subject of snubbers
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    peterh

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    Re: Snubber, B+ ?

    Post by peterh on Fri Nov 24, 2017 10:49 am

    Interesting. Please keep us informed.
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    arledgsc

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    Location : SF Bay CA

    Re: Snubber, B+ ?

    Post by arledgsc on Fri Nov 24, 2017 12:38 pm

    The abrupt shutoff of modern fast switching diodes can cause glitches that could be heard as "frying" or "ticking" as B+ kicks in.  But I have tried all kinds of rectifiers in the ST-120 and never heard any diode switching artifacts where I felt I had to do something about it.  The amp has so much filtering that any power supply noise is nearly non-existent.

    I had lighter filtered guitar amps that chattered readily from diode switching noise.  I tried snubbers with limited effect.  The best solution for these amps was to find standard or soft recovery diodes for rectification as their slower cutoff produces less switching artifacts.  And try to avoid fast or ultra-fast recovery diodes if you can.  Not needed for 50/60Hz. Though the Weber WZ-1 and WZ-68 that I have used successfully both employ fast switching diodes.  And a tube rectifier would be considered soft recovery.  

    Be careful using single pairs of 1N4007 diodes in a B+ circuit that delivers 500Vdc.  The maximum peak inverse voltage of 1000V can briefly be exceeded.  1N4008 is a better choice at 1200V.
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    Dahlberg

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    Re: Snubber, B+ ?

    Post by Dahlberg on Fri Nov 24, 2017 1:05 pm

    The Byv96e rectifiers have a settling time @ 300ns so they wouldn't be considered UF.
    They are described as fast and by some recomended as a possible update to standard
    rectifiers. The amps have no audible noise at all now, it will be interessting to find out if any
    of the rectifiers I have ordered will produce that result.

    Did you do some calculations for the snubber values ?
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    arledgsc

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    Re: Snubber, B+ ?

    Post by arledgsc on Fri Nov 24, 2017 1:26 pm

    Interesting... I used Philips BYM26E in the guitar amps and much less noise that 1N4007. They are considered fast soft-recovery - fast turn on, soft turn off. The BYV96Es are also fast soft-recovery so good choice.

    For snubbers I tried the R-C series circuit across the diode instead of one side connected to ground as in your schematic. I just used some standard suggested values but I had so much noise that they did not help much. Best approach would be connecting an oscilloscope and measuring. You could fine tune the R-C circuit this way.
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    Dahlberg

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    Re: Snubber, B+ ?

    Post by Dahlberg on Mon Dec 11, 2017 7:35 pm

    I went for a version of this since the voltage requirements would be hard to
    meet in a different solution. C6 and C7 are not present. R/C values for a first
    try without any measurements (don't have a scope and I'm not shure what to look for)
    are, 0,01uf and 300ohm. Have to get back to that, for now it's just with or without.

    I'm also trying out a couple of SS rectifiers and it sounds promising.
    The http://www.mouser.com/ds/2/90/4d05120e-838548.pdf
    is in the lead right now. I haven't tried them all yet so...... Cool

    The amps are almost dead silent when they are supposed to.   Smile


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