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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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GreggW
Roy Mottram
LeGrace
peterh
buchela
9 posters

    M-125 triode/pentode switch elimination

    buchela
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    buchela


    Posts : 79
    Join date : 2011-03-09
    • Post n°1

    M-125 triode/pentode switch elimination Empty M-125 triode/pentode switch elimination

    Post by buchela Fri Sep 27, 2019 1:22 am

    I would like to eliminate the triode/pentode switch and triode mode capability, on  my M-125 monoblocks, pentode mode is good enough for me, Does anybody know how to do this ?. I suspect I have to remove all the wires going to the switch, and then ?..........
    Any help will be very much appreciated.
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    peterh
    peterh
    peterh


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    • Post n°2

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by peterh Fri Sep 27, 2019 6:29 pm

    buchela wrote:I would like to eliminate the triode/pentode switch and triode mode capability, on  my M-125 monoblocks, pentode mode is good enough for me, Does anybody know how to do this ?. I suspect I have to remove all the wires going to the switch, and then ?..........
    Any help will be very much appreciated.
    Ain't it enough to leave the switch in UL position ?
    ( the available choices are UL and triode, pentode is not offered in M-125)

    Of course it's possible to remove the switch and permanently wire it as
    UL ( ultralinear )just connect the plates to the outer pair and the screens to
    the inner pair. By examine the connections across the switch it should be
    self-evident.

    If you feel uncertain about this i would recommend to leave the switch in place until you find a technician for the task.
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    buchela
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    buchela


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    • Post n°3

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by buchela Thu Oct 03, 2019 3:01 pm

    Thanks, peterh, I decided the switch has to go, since triode mode does not mean anything to me, and having parts for ornamental purposes is not something that I enjoy.  I like the simplicity of these monsters, and wiring them as only  Pentode Ultralinear ( as it is described in the tubes4hifi website ), is very much in tune with that principle; I am not trying to reinvent anything.
    I'm sure you can do this with your eyes closed, I don't, that's why I asked for help to the brilliant minds ( like yours ) in this list. Thank you for taking the time to reply to my post.


    Last edited by buchela on Thu Oct 03, 2019 3:05 pm; edited 1 time in total (Reason for editing : spelling)
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    LeGrace
    LeGrace
    LeGrace


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    Location : Ontario, Canada
    • Post n°4

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by LeGrace Thu Oct 03, 2019 3:42 pm

    If it were me I would permanently wire triode mode. Nice thing about the M125 is the headroom they provide.
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    buchela
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    buchela


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    • Post n°5

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by buchela Thu Oct 03, 2019 9:51 pm

    I thought about that, but I can barely hear any difference between the two, and according to what I hear, I can not say that I like triode mode better than Pentode ultralinear. My ears perceive them as equally pleasing, but I prefer the one with the better tush, and window rattling capability.
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    Roy Mottram
    Roy Mottram
    Roy Mottram
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    • Post n°6

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by Roy Mottram Thu Oct 10, 2019 12:44 pm

    the topic of triode VS pentode (actually ultra-linear) has been covered quad-zillion times in this forum and all over every tube audio forum in the universe.
    Triode mod will enhance the sound of midrange, and give you less highs and less bass.
    Pentode mode will give you flat frequency response. Ultra-Linear mode (which is what all VTA amps are) gives you the best of both, and more power with less distortion.
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    GreggW
    GreggW
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    Join date : 2015-07-15
    • Post n°7

    M-125 triode/pentode switch elimination Empty Took 'em out

    Post by GreggW Sat Oct 26, 2019 10:13 pm

    Last week, flipped the switches to triode and got a slight pop from the left speaker on my ST-120. Since I can't hear the difference between ultralinear and triode (probably due to 7-decade old ears), the switches were removed from the ST-120 and my son's ST-70 during yearly maintenance. The wiring looks a little cleaner and both amps work great. Simpler is better.....
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    HarryY
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    Location : NY
    • Post n°8

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by HarryY Sun Oct 27, 2019 12:20 am

    I also removed them from my ST-120 since I prefer the Ultralinear sound.

    I nearly didn't install them if the first place since I have
    a small 6L6GC amp that I also prefer in ultralinear mode.

    I filled the switch holes in with a couple of pan head hex drive bolts.


    .
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    Bob Latino
    Bob Latino
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    Location : Massachusetts
    • Post n°9

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by Bob Latino Sun Oct 27, 2019 9:29 am

    GreggW wrote:Last week, flipped the switches to triode and got a slight pop from the left speaker on my ST-120. Since I can't hear the difference between ultralinear and triode (probably due to 7-decade old ears), the switches were removed from the ST-120 and my son's ST-70 during yearly maintenance. The wiring looks a little cleaner and both amps work great. Simpler is better.....

    First of all it mentions in the manual of all the VTA amps that you will get a "blip" or a slight "pop" sound when you switch from triode to pentode ultralinear mode or vice versa. That little noise is normal and does not hurt the amp. It's your amp and if you want to remove the switches and run the amp in straight pentode ultralinear mode, then do so. Think about these things however.

    1. The amp will sound EXACTLY the same whether it is in pentode ultralinear mode selected by the switch OR hot wired directly into pentode ultralinear mode - so - why remove the switch ? Just leave the switch in pentode ultralinear mode ?

    2. If you remove the switch completely (M-125), then you have an empty hole in the chassis. With the VTA ST-70/ST-120, you would have two empty holes.

    3. If you ever decide to sell the amp, my feeling is that the amp would be devalued if it does not have two modes of operation and devalued even more with empty holes in the chassis if you remove completely the switches. You may not like triode mode but the person you sell the amp to may want to TRY triode mode ?

    Bob
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    rjpjnk
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    rjpjnk


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    • Post n°10

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by rjpjnk Sun Oct 27, 2019 3:55 pm

    I feel similarly. If the switches are working might as well leave them. However, I think it would be nice to have a lable indicating the positions triode/UL. Just a thought.
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    Hops
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    Hops


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    Join date : 2019-09-21
    Location : South Detroit, Michigan
    • Post n°11

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

    Post by Hops Sun Oct 27, 2019 5:39 pm

    A label indicating the positions would be great. Since the switch works and causes no damage, I am leaving mine in - I tend not to want to touch un-broken things that are working well. Unless I come into gobs of time, space and money and decide to build some M125s, I can't imagine wanting to sell the Amp I built, so why would I care about resale value? Even if I built M125s, either my daughter or myself would certainly find a use for it.
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    • Post n°12

    M-125 triode/pentode switch elimination Empty Re: M-125 triode/pentode switch elimination

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