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    Alternative triode/pentode switch

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    Tubesound

    Posts : 3
    Join date : 2017-01-30

    Alternative triode/pentode switch

    Post by Tubesound on Mon Jan 30, 2017 8:18 pm

    Hello,

    This is my first post on the forum. I have been sourcing parts for m125 build. I was hoping someone could tell me if the dpdt switch is on-off-on. I wasn't sure if completely disconnecting between modes would be detrimental or if this is normal. I'm not even sure if there's such a thing as a 2 position dpdt switch.

    Thanks in advance.
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    arledgsc

    Posts : 454
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Alternative triode/pentode switch

    Post by arledgsc on Mon Jan 30, 2017 8:38 pm

    Tubesound wrote:Hello,

    This is my first post on the forum. I have been sourcing parts for m125 build. I was hoping someone could tell me if the dpdt switch is on-off-on. I wasn't sure if completely disconnecting between modes would be detrimental or if this is normal. I'm not even sure if there's such a thing as a 2 position dpdt switch.

    Thanks in advance.
    It's DPDT no center off postion.  The output tubes need one or the other in circuit at all times.

    Here's a listing from Digikey where I pre-selected "On - On" switch configuration.   Comes back with 3,500 listings.

    http://www.digikey.com/products/en/switches/toggle-switches/201?k=DPDT&k=&pkeyword=DPDT&pv235=1&FV=fff40011%2Cfff80064&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25

    Dogstar

    Posts : 244
    Join date : 2014-06-23

    Re: Alternative triode/pentode switch

    Post by Dogstar on Mon Jan 30, 2017 8:50 pm

    Just as a reminder....should the mode be changed while the amp is off or is switching modes while powered up ok?

    Also...on a VTA ST-120 or VTS ST-70 is it ok the have one channel in triode mode while the other us in pentode mode?

    And lastly ...is it pentode mode or ultra-linear mode?

    Tubesound

    Posts : 3
    Join date : 2017-01-30

    Re: Alternative triode/pentode switch

    Post by Tubesound on Mon Jan 30, 2017 9:42 pm

    Thanks for the quick response.
    I had a feeling that center position was wrong. I found a pairing for my NKK s series power switch. They have a real solid feel and nice thunk when you snap them into position.

    Thanks again.

    Hope this reply works, keep getting a server error.
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    Kentley

    Posts : 428
    Join date : 2015-03-06
    Age : 64
    Location : Worcester, MA

    Re: Alternative triode/pentode switch

    Post by Kentley on Mon Jan 30, 2017 9:54 pm

    It is ultralinear, not pentode.
    Switching may be done while driving, as long as levels are sane and it's not Heavy Metal in full death mode. Evil or Very Mad
    As far as one channel in triode and the other in ultralinear, I've often wondered as well. Might be useful in certain bi-amp situations. But it doesn't seem logically to be a very, er, sound idea. Care to weigh in, Bob L.?

    Tubesound

    Posts : 3
    Join date : 2017-01-30

    Re: Alternative triode/pentode switch

    Post by Tubesound on Mon Jan 30, 2017 10:40 pm

    The amp has a switch which allows operation in pentode/ultralinear mode (125 watts) or triode mode (65 watts). The triode/ultralinear switch may be used while the amp is running.

    From the m-125 page on e-bay.
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    sKiZo

    Posts : 1385
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Alternative triode/pentode switch

    Post by sKiZo on Tue Jan 31, 2017 6:43 pm

    Never tore one apart to see if the ones supplied are make before break or not ... best I can say is they look to be pretty much a stock item, an Bob assures us that hot switching isn't a problem.
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    Bob Latino
    Admin

    Posts : 2542
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Alternative triode/pentode switch

    Post by Bob Latino on Tue Jan 31, 2017 8:11 pm

    Tubesound wrote:Hello,

    This is my first post on the forum. I have been sourcing parts for m125 build. I was hoping someone could tell me if the dpdt switch is on-off-on. I wasn't sure if completely disconnecting between modes would be detrimental or if this is normal. I'm not even sure if there's such a thing as a 2 position dpdt switch.

    Thanks in advance.

    You can use either an ON/ON switch or an ON/OFF/ON switch.

    Bob
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    Bob Latino
    Admin

    Posts : 2542
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Alternative triode/pentode switch

    Post by Bob Latino on Tue Jan 31, 2017 8:18 pm

    Dogstar wrote:Just as a reminder....should the mode be changed while the amp is off or is switching modes while powered up ok?

    Also...on a VTA ST-120 or VTS ST-70 is it ok the have one channel in triode mode while the other us in pentode mode?

    And lastly ...is it pentode mode or ultra-linear mode?

    The VTA amps are actually triode/ultralinear according to the setting of the switch. It is not triode/pentode.

    Yes - You can run one channel in triode and the other in ultralinear. I know someone who actually does this in a vertical biamp situation. He knows that triode puts out only about 60% the amount of power of ultralinear but he likes the way his two VTA ST-70's sound with the woofer section set on ultralinear and the tweeter section set to triode. He probably has a situation in which his room is too "bright" with a lot of reflective surfaces and is using his two amps as sort of a "tone control" to tame the high end a bit.

    @ sKiZo > you can hot switch between the two modes and all you will hear is a little "blip". It doesn't hurt the amp because on the VTA amps the plate and the screen tap are at almost the exactly the same voltage. The only caveat I would mention is to do the switch while the amp is at idle and not playing any music.

    Bob

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