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    Triode/Pentode Switch

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    heyraz

    Posts : 58
    Join date : 2011-10-26

    Triode/Pentode Switch

    Post by heyraz on Thu Nov 10, 2011 11:13 am

    Regarding the 2 DPDT switches, to use them on the fly, are they "make before break" or "break before make"?

    Jim McShane

    Posts : 154
    Join date : 2011-10-19
    Location : South Suburban Chicago

    Re: Triode/Pentode Switch

    Post by Jim McShane on Thu Nov 10, 2011 4:12 pm

    heyraz wrote:Regarding the 2 DPDT switches, to use them on the fly, are they "make before break" or "break before make"?

    The switches I use are non-shorting (break before make). I don't want any spurious connections.

    And I do not recommend switching "on the fly". I do tend to be conservative, so I'm not saying people who do are wrong - I just prefer not to for a variety of reasons.

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Triode/Pentode Switch

    Post by Bob Latino on Thu Nov 10, 2011 8:23 pm

    The triode/pentode (ultralinear) switches on the VTA amp kits are all make before break. The switches may be used while the amp is running but it is not recommended that the switches be switched at higher volume levels. I have also use break before make switches and they seem to work just as well. The reason that you can use them while the amps are running (at least on stock Dynaco and VTA amp kits) is that the voltage gradient between triode and pentode ultralinear is very small. On the stock Dynaco amps and the VTA amps the ultralinear screen tap is not padded down with a resistor and, as such, the voltages are from plate to screen are almost identical. When you make the switch on a VTA ST-70 you will switch from maybe 429 volts to 430 volts and because the difference is so small, there is no voltage spike. When making the switch you may hear a very small "blip" noise (switching noise) through the speakers but there is no voltage spike.

    On McIntosh, Harmon Kardon, Marantz etc. tube amps the plates and screens are probably run at different voltages ? (I am not sure?) and probably a break before make would be best. I once had a pair of Antique Sound Labs monoblocks that you had to turn the amp off when making the switch from triode to pentode (ultralinear?) If you didn't - and I only did it once without thinking - the amp made a God awful noise and scared the crap out of me ! Nothing happened to the amp but I never did that again - lol ..

    Bob

    Bigron865

    Posts : 45
    Join date : 2013-03-15
    Age : 48
    Location : Birmingham Alabama

    Re: Triode/Pentode Switch

    Post by Bigron865 on Mon Apr 15, 2013 10:29 am

    I'm a little confused about the switch position. I wired mine like Bobs picture but on the website it shows the switch flipped toward the transformers for pentode. But looking at the diagram drawing, wouldn't Triode be towards the trannies? If the resistors are closest to the trannies, wouldn't that be triode? My meter showed continuity on the middle pins and the pins closest to the trannies with the resistors? Just confused.

    Ron

    Bob Latino
    Admin

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    Join date : 2008-11-26
    Location : Massachusetts

    Re: Triode/Pentode Switch

    Post by Bob Latino on Mon Apr 15, 2013 10:55 am

    When you move the switch towards the power transformer the switch makes its contacts on the other side of the switch. (the side towards the front of the amp) It is like an oar on a row boat - when you pull the oar back - the the side of the oar that touches the water goes forward.

    Bob

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Triode/Pentode Switch

    Post by sKiZo on Mon Apr 15, 2013 7:22 pm

    Bob Latino wrote: It is like an oar on a row boat

    Bob

    So ... you're saying, they work better if you dip them in water first?

    .

    .

    drunken

    terry37932

    Posts : 22
    Join date : 2011-05-18
    Location : Knoxville

    Re: Triode/Pentode Switch

    Post by terry37932 on Tue Apr 16, 2013 12:07 pm

    OK, I must have gone to a diffrent school than you gentlemen. Make Before Break/Break Before Make? Are these the same as NO Normally Open. NC Normally Closed? Seriously.

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: Triode/Pentode Switch

    Post by Luddite on Tue Apr 16, 2013 12:25 pm

    terry37932 wrote:OK, I must have gone to a diffrent school than you gentlemen. Make Before Break/Break Before Make? Are these the same as NO Normally Open. NC Normally Closed? Seriously.

    Well sort of, but not exactly...Here's an example assuming a SPDT switch:

    Make before break means that when switching, contact A is momentarily shorted together with contact B before contact A is disconnected

    Break before Make means that contact A is disconnected before connection is made with contact B

    Hope that helps.

    Best Regards,
    Charlie


    Last edited by Luddite on Tue Apr 16, 2013 12:34 pm; edited 1 time in total (Reason for editing : Clarity)

    sKiZo

    Posts : 1287
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Triode/Pentode Switch

    Post by sKiZo on Tue Apr 16, 2013 2:12 pm

    The wiper never goes open, having contact with either one or both of the available connections without at all times. No burps or backups in the power chain that way.

    Speaking of different schools ... wouldn't normally open, normally closed denote a momentary contact type switch? Either they're on until you actuate the switch, or off, depending on the circuit requirements. Release the toggle, button, whatever, and they revert back to their original state. Like a horn button, or a load test.

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