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    KT88's in the ST70?

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    MontanaWay

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    KT88's in the ST70?

    Post by MontanaWay on Fri Apr 11, 2014 7:53 pm

    I have a matched quad set of KT88's. Any problems with sticking them on my ST70 (Bob's version)?, and, any benefits at all?, thanks.

    polarflux

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    Join date : 2010-02-12

    Re: KT88's in the ST70?

    Post by polarflux on Fri Apr 11, 2014 8:15 pm

    Bob will advise you to bias them to 500 miliamps, but no. Provides a little more authority on the low end but the effects to the rest of the range will depend on the tubes you are using.

    MontanaWay

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    Re: KT88's in the ST70?

    Post by MontanaWay on Fri Apr 11, 2014 8:48 pm

    interesting, just put them in, now keeping in mind that these are brand new, I am getting quite a bit more at the high frequency, for a given song, had to knock the treble back a bit. Low end seems about the same, maybe a touch more.
    I'll keep them in for a while now and see how the settle in.

    Dave_in_Va

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    Re: KT88's in the ST70?

    Post by Dave_in_Va on Fri Apr 11, 2014 9:28 pm

    I tried two sets of KT 88's (Russian and Chinese) in my VTA ST 70 and ended up preferring EL 34's (new Valve Art, NOS Sieman's and NOS Mullards).

    peterh

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    Re: KT88's in the ST70?

    Post by peterh on Sat Apr 12, 2014 3:42 am

    MontanaWay wrote:I have a matched quad set of KT88's. Any problems with sticking them on my ST70 (Bob's version)?, and, any benefits at all?, thanks.
    It's ok.
    You will see lower impendace that might improve bass control ( depending on speakers)
    I settled for JJ 6550 which was an improvement from valve art el34

    mhardyman

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    Re: KT88's in the ST70?

    Post by mhardyman on Sat Apr 12, 2014 6:27 am

    MontanaWay wrote:I have a matched quad set of KT88's. Any problems with sticking them on my ST70 (Bob's version)?, and, any benefits at all?, thanks.

    Have been using the Genalex KT-88 reissues for several years now.  A very nice sounding tube.  Even, nicely extended highs and very well controlled bass.  Bear in mind that the preamp board will do more for tone control than the power tubes.  My final setup employs an NOS Tungsol 12AU7 in the center position and the sides are new EH 12BH7s.  

    This current set powers a pair of DCM Timewindows that I bought new and are power hungry yet revealing speakers.  They have never sounded so good.  I have tried the SED EL34 and the JJ EL34 in this amp.  They were ok but...  underwhelming in comparison to the KT88.  It feels like the KT88 tube has more range and punch.  I like it.

    Bob Latino
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    Re: KT88's in the ST70?

    Post by Bob Latino on Sat Apr 12, 2014 7:49 am

    In the VTA ST-70 KT88 output tubes do have more output at the frequency extremes - the very bottom and the very top of the frequency range. This may be a benefit IF you have speakers or other associated equipment that are "soft" on the top end. It may, however, be a liability if your speakers are a little "bright" to begin with. KT88's also have the liability of costing twice as much as an EL34. They will, however, last longer than an EL34 in the VTA ST-70 which offsets somewhat their increased cost.

    EL34's are the traditional output tube used in ST-70 type amps. They are cost effective and are really good sounding tubes especially in the mid bass and vocal range.

    In the VTA ST-70 you can use EL34, 6L6, KT66, KT77, KT88 or 6550 output tubes. NOTE - do not use the last two output tubes mentioned in a STOCK ST-70 unless you have an upgraded power transformer. They draw more current and can put an already overworked ST-70's original PA-060 power transformer "over the edge".

    Bob

    MontanaWay

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    Re: KT88's in the ST70?

    Post by MontanaWay on Sat Apr 12, 2014 9:57 am

    well I've been running the KT88's for quite a few hours now since yesterday afternoon and yes, there is a noticeable difference between them and the KT66's.
    I loved the KT66's over the EL34's, I am starting to like the KT88's over the KT66's, they do sound, to my ears, even clearer and crisper again, pretty much on all music I played so far, ranging from classic, jazz, blues to rock, I had to knock the treble and bass back a bit on the preamp.
    Be interesting to see how they settle in over the coming weeks.

    Jim McShane

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    Re: KT88's in the ST70?

    Post by Jim McShane on Sat Apr 12, 2014 1:32 pm

    polarflux wrote:Bob will advise you to bias them to 500 miliamps, but no. Provides a little more authority on the low end but the effects to the rest of the range will depend on the tubes you are using.

    Is that correct?? 500 ma!! Wow, even for four tubes that would be 125 ma. per tube, and with 430 plate volts that's 53 watts dissipation! affraid

    Bob, if you read this - is that correct?

    Bob Latino
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    Re: KT88's in the ST70?

    Post by Bob Latino on Sat Apr 12, 2014 1:48 pm

    Hi Jim,

    I am pretty sure that Polarflux meant 50 milliamps per each output tube - not 500 milliamps ... 500 milliamps is 10 times the recommended bias current ! Some of the confusion probably comes from the fact that the recommended bias VOLTAGE is 500 milliVOLTS or .500 volts (1/2 volt) per each output tube.

    Bob

    Jim McShane

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    Re: KT88's in the ST70?

    Post by Jim McShane on Sat Apr 12, 2014 2:14 pm

    Bob Latino wrote:Hi Jim,

    I am pretty sure that Polarflux meant 50 milliamps per each output tube - not 500 milliamps ... 500 milliamps is 10 times the recommended bias current ! Some of the confusion probably comes from the fact that the recommended bias VOLTAGE is 500 milliVOLTS or .500 volts (1/2 volt) per each output tube.

    That's more like it!  Very Happy

    MontanaWay

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    Re: KT88's in the ST70?

    Post by MontanaWay on Sat Apr 12, 2014 2:37 pm

    so thats why my ST70 burned a hole through the floor..........

    sKiZo

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    Re: KT88's in the ST70?

    Post by sKiZo on Sat Apr 12, 2014 5:01 pm

    Smokin!  rabbit 

    On a totally unrelated note ... board running slow the last couple days? Only way I can get a page to load is if I tell it to stop loading ... Seems like it's hanging up loading ads or some such. This is the only site giving me problems ... Anyone else?

    PS ... that's using Chrome ... I can't even get it to load in Firefox ...


    pmarcin

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    Re: KT88's in the ST70?

    Post by pmarcin on Sun Apr 13, 2014 8:02 am

    I'm using Firefox on a MacBook. It loads full page ads, which you have to page out.Ugh. It just started doing this.

    peterh

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    Re: KT88's in the ST70?

    Post by peterh on Sun Apr 13, 2014 9:00 am

    pmarcin wrote:I'm using Firefox on a MacBook. It loads full page ads, which you have to page out.Ugh. It just started doing this.
    I have flashblock installed as add-on in firefox. Takes care of many annoying ads.

    deepee99

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    Re: KT88's in the ST70?

    Post by deepee99 on Sun Apr 13, 2014 11:41 am

    No issues here with Chromium on Linux. There was that chocolate bar ad that ate up half the screen but it was fixed a coupla weeks ago.
    If you'e on Verizon DSL they've been doing upgrades up and down the line from Coos Bay Oregon to Libby, Mont., maybe in your neck of the woods, too. We were down completely for 28 hours. Actually had to make conversation with my wife. Turns out she's a nice person.

    MontanaWay

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    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: KT88's in the ST70?

    Post by MontanaWay on Sun Apr 13, 2014 11:59 am

    deepee99 wrote:No issues here with Chromium on Linux. There was that chocolate bar ad that ate up half the screen but it was fixed a coupla weeks ago.
    If you'e on Verizon DSL they've been doing upgrades up and down the line from Coos Bay Oregon to Libby, Mont., maybe in your neck of the woods, too. We were down completely for 28 hours. Actually had to make conversation with my wife. Turns out she's a nice person.

     lol! 

    MontanaWay

    Posts : 767
    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: KT88's in the ST70?

    Post by MontanaWay on Sun Apr 13, 2014 12:03 pm

    I use Safari, no problems here. We don't have the best ADSL2+ speeds here, since we're so far from the distribution hut, we're actually a 'special' customer of 3 Rivers because of our distance, they've been trying out new gear with us. Hopefully fiber optics are not that long away to get here, they have it on HWY287 and the distribution hut, but thats 4.2 miles away!....hence our 'special' status......

    corndog71

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    Re: KT88's in the ST70?

    Post by corndog71 on Sun Apr 13, 2014 12:20 pm

    Ghostery is another good add-on ad-blocker.

    deepee99

    Posts : 1260
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: KT88's in the ST70?

    Post by deepee99 on Sun Apr 13, 2014 12:25 pm

    corndog71 wrote:Ghostery is another good add-on ad-blocker.

    I'll see if I can hack that in to Chromium, and let you know. We're less than a half-mile from the main Verizon FIOS line, but still running coax to the house.
    Back on topic, the Gold Lion KT-88s are incredible tubes, if properly matched. Just don't grab the glass end first when you're pulling them out of the box. They don't work very well after that even when reassembled with Super-Glue.

    pmarcin

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    Re: KT88's in the ST70?

    Post by pmarcin on Sun Apr 13, 2014 1:13 pm

    I installed the add-ons. They appear to work, but now I have other issues.

    pmarcin

    Posts : 131
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    Re: KT88's in the ST70?

    Post by pmarcin on Sun Apr 13, 2014 1:35 pm

    One of the extensions blocked the Javascript for the 'edit' window at bottom of the page. I disabled it.

    pmarcin

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    Re: KT88's in the ST70?

    Post by pmarcin on Sun Apr 13, 2014 1:44 pm

    OT: Two extensions block this window. Nuts, they add security. Just overzealous.

    MontanaWay

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    Age : 58
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    Re: KT88's in the ST70?

    Post by MontanaWay on Tue Apr 15, 2014 12:34 am

    MontanaWay wrote:I use Safari, no problems here. We don't have the best ADSL2+ speeds here, since we're so far from the distribution hut, we're actually a 'special' customer of 3 Rivers because of our distance, they've been trying out new gear with us. Hopefully fiber optics are not that long away to get here, they have it on HWY287 and the distribution hut, but thats 4.2 miles away!....hence our 'special' status......

    I spoke too soon. Getting to load the forum pages has become painfully sloooooooooooooow.....started yesterday......every other web site loads just fine...

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