The Dynaco Tube Audio Forum

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


    VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Share

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by Bob Latino on Mon Jun 30, 2014 3:48 pm

    Mike in California Emailed me with some photos of the new Tung-Sol KT150 output tubes in his VTA M-125 amps. He said that the tubes biased up fine and sounded "great". I have not tried these myself as yet because of the expense involved. The KT150's are about $100 apiece and eight output tubes for two amps would be $800. The power transformers on the all the VTA amps are "overbuilt" and can handle more current draw than the normally specified output tubes for the amp. So - I guess if you want to try the Tung-Sol KT150's in your VTA ST-120 or M-125's and have a fat wallet, give them a try. Do NOT, by the way, use these tubes in any ST-70 type amp.

    Note also > Below the table one of Roy's VTA SP preamps and phono preamps being used to drive the M-125's ..

    Bob





    Last edited by Bob Latino on Wed Jul 02, 2014 9:01 am; edited 1 time in total

    corndog71

    Posts : 451
    Join date : 2013-03-19
    Location : It can get windy here

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by corndog71 on Tue Jul 01, 2014 11:00 am

    Well, now those are sexy.  Cool 

    arledgsc

    Posts : 340
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by arledgsc on Tue Jul 01, 2014 11:07 am

    How about a pair of KT-150s replacing a quad of KT-88s? Could you only get about half power with this dual setup?

    deepee99

    Posts : 1333
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by deepee99 on Tue Jul 01, 2014 11:44 am

    Very nice layout. I too would be curious as to how a pair of the 150s in each M-125 would measure up to a quad of KT-88s.

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by sKiZo on Tue Jul 01, 2014 1:23 pm

    Seems to me it'd take some fairly serious engineering to make a single tube replace a push/pull bank, and there'd be no going back ...

    Maybe do something like with the T/P switches where you could change mode on the fly I expect.

    If you remember right, I had some issues with floating tubes when designing the meter circuit for my build, and it tweren't nuttin purty ...

    PS ... if it's all about tone and the KT150's show enough of an improvement to compensate for the price without any appreciable output gain ... and you're rich ... I can maybe see it. I'd be concerned about the tubes even getting up into their working range or anywhere near their sweet spot as well.

    It would be interesting to meter a set for actual output. I've been meaning to do that with the KT120's, but the consensus is that they show around a 10% gain at best over KT88's (in an ST120 anyway). I wouldn't expect anything different in the monoblocks. I do know the KT120's benefit from higher bias - I run mine at 60mV (thanx, kward!) and that adds a bunch of punch over the usual 55mV. Wondering what the pic'd setup is running?

    corndog71 wrote:Well, now those are sexy.  Cool 

    Be much sexier without the silly little stickers ...  rabbit 

    deepee99

    Posts : 1333
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by deepee99 on Tue Jul 01, 2014 1:47 pm

    sKiZo wrote:Seems to me it'd take some fairly serious engineering to make a single tube replace a push/pull bank, and there'd be no going back ...

    Maybe do something like with the T/P switches where you could change mode on the fly I expect.

    If you remember right, I had some issues with floating tubes when designing the meter circuit for my build, and it tweren't nuttin purty ...

    PS ... if it's all about tone and the KT150's show enough of an improvement to compensate for the price without any appreciable output gain ... and you're rich ... I can maybe see it. I'd be concerned about the tubes even getting up into their working range or anywhere near their sweet spot as well.

    It would be interesting to meter a set for actual output. I've been meaning to do that with the KT120's, but the consensus is that they show around a 10% gain at best over KT88's (in an ST120 anyway). I wouldn't expect anything different in the monoblocks. I do know the KT120's benefit from higher bias - I run mine at 60mV (thanx, kward!) and that adds a bunch of punch over the usual 55mV. Wondering what the pic'd setup is running?

    corndog71 wrote:Well, now those are sexy.  Cool 

    Be much sexier without the silly little stickers ...  rabbit 

    Yeah, I never cared for them Tube Despot stickers either.
    Skiz, the 125s can run with a single-pair bank of tubes. That's what he was asking about. In summer I often run just a single pair in each amp, re-biased to 6 mv. Since our summers are only about a week long, nothing untoward ever happens.

    sKiZo

    Posts : 1310
    Join date : 2013-04-01
    Location : Michigan USA

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by sKiZo on Tue Jul 01, 2014 2:49 pm

    Ah ... my fun fact for the day ... in that case, I imagine you could get the full rated power out of the single KT150? If that's true, might be fun to still add switches so you could flip between those and a pair of KT88's for late night listening ...

    ~~~~

    I had some fun with the stickers when I got mine. Tried peeling one and it was shredding bad. eMailed support, and asked ...

    "How do I get those silly stickers off your tubes?"
    They wrote back, "They're not silly stickers."
    To which my reply was "OK then ... how do I get your silly tubes off the stickers??"

    Anyway ... a hair dryer or heat gun takes them right off. I imagine a couple hours of Porcupine Tree at 11 would soften them up pretty decent also. The match number is on the box also, so you're covered if you need to replace one down the road.


    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by Bob Latino on Tue Jul 01, 2014 3:21 pm

    If you use the KT150's in the M-125's, you will probably get about 8-10% more power over a set of KT88's. If you use KT120 or KT150 output tubes in the M-125's, the KT120 and the KT150's will be "used as KT88's". In order to get 125 watts or so out of just TWO KT150's you need a B+ of 600 - 650 volts and then bias each tube of the pair at about 100 milliamps per tube. You can't do that with the present setup of the M-125's which gives a B+ of about 500 VDC. You would need a power transformer with a 500-0-500 VAC secondary and power supply caps that could handle up to 650 VDC. The caps now in the M-125's are good for up to 550 VDC.

    Bob

    deepee99

    Posts : 1333
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by deepee99 on Tue Jul 01, 2014 4:08 pm

    Bob Latino wrote:If you use the KT150's in the M-125's, you will probably get about 8-10% more power over a set of KT88's. If you use KT120 or KT150 output tubes in the M-125's, the KT120 and the KT150's will be "used as KT88's". In order to get 125 watts or so out of just TWO KT150's you need a B+ of 600 - 650 volts and then bias each tube of the pair at about 100 milliamps per tube. You can't do that with the present setup of the M-125's which gives a B+ of about 500 VDC. You would need a power transformer with a 500-0-500 VAC secondary and power supply caps that could handle up to 650 VDC. The caps now in the M-125's are good for up to 550 VDC.

    Bob

    So ain't no point, really, in the 150s if you don't want to modify the pwr supply.
    Will the fact that the 150s are loafing at KT-120 levels, would that project greater longevity?

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by Bob Latino on Tue Jul 01, 2014 4:18 pm

    deepee99 wrote:
    Bob Latino wrote:If you use the KT150's in the M-125's, you will probably get about 8-10% more power over a set of KT88's. If you use KT120 or KT150 output tubes in the M-125's, the KT120 and the KT150's will be "used as KT88's". In order to get 125 watts or so out of just TWO KT150's you need a B+ of 600 - 650 volts and then bias each tube of the pair at about 100 milliamps per tube. You can't do that with the present setup of the M-125's which gives a B+ of about 500 VDC. You would need a power transformer with a 500-0-500 VAC secondary and power supply caps that could handle up to 650 VDC. The caps now in the M-125's are good for up to 550 VDC.

    Bob

    So ain't no point, really, in the 150s if you don't want to modify the pwr supply.
    Will the fact that the 150s are loafing at KT-120 levels, would that project greater longevity?

    Hi David,

    My answer to your question about longevity is most probably > YES - the Tung-Sol KT120 or KT150 should last longer than any KT88 in either the VTA ST-120 or VTA M-125. Yes - These tubes would be loafing at KT88 voltages and bias points.

    Bob

    ths61

    Posts : 4
    Join date : 2014-12-02

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by ths61 on Tue Dec 02, 2014 6:34 pm

    Bob Latino wrote:If you use the KT150's in the M-125's, you will probably get about 8-10% more power over a set of KT88's. If you use KT120 or KT150 output tubes in the M-125's, the KT120 and the KT150's will be "used as KT88's". In order to get 125 watts or so out of just TWO KT150's you need a B+ of 600 - 650 volts and then bias each tube of the pair at about 100 milliamps per tube. You can't do that with the present setup of the M-125's which gives a B+ of about 500 VDC. You would need a power transformer with a 500-0-500 VAC secondary and power supply caps that could handle up to 650 VDC. The caps now in the M-125's are good for up to 550 VDC.

    Bob

    Is a KT150 upgrade kit a possible option for the M-125's (are parts available)?

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by Bob Latino on Tue Dec 02, 2014 7:28 pm

    No .. there is no upgraded power transformer and/or no upgraded output transformer available from me for upgrading the M-125's to use the KT150 output tubes at the higher voltages and higher bias points needed. I am sure some transformer company could wind some transformers that could take advantage of this tube's full potential.

    Bob

    ths61

    Posts : 4
    Join date : 2014-12-02

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by ths61 on Tue Dec 02, 2014 7:39 pm

    Bob Latino wrote:No .. there is no upgraded power transformer and/or no upgraded output transformer available from me for upgrading the M-125's to use the KT150 output tubes at the higher voltages and higher bias points needed. I am sure some transformer company could wind some transformers that could take advantage of this tube's full potential.

    Bob

    Thanks for the quick response.

    tubes4hifi
    Admin

    Posts : 1291
    Join date : 2008-11-30

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by tubes4hifi on Tue Dec 02, 2014 7:49 pm

    I hope that's not a center channel speaker sitting directly on top of the preamp . .. .  . Shocked
    Could give you some interesting feedback if you turn the volume way up and it vibrates the preamp!!
    Super nice photos and nice system !!!
    Is that a mural or an 80" flat screen TV ??

    Sponsored content

    Re: VTA M-125's using the new Tung-Sol KT150 output tubes - photos

    Post by Sponsored content Today at 10:02 pm


      Current date/time is Wed Dec 07, 2016 10:02 pm