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    Fired up my "new" ST 70 today

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    charlief64

    Posts : 13
    Join date : 2012-12-21

    Fired up my "new" ST 70 today

    Post by charlief64 on Sat Feb 09, 2013 5:44 pm

    I just finished the install of my new VTA driver board for my ST 70. I am so happy with the results. I am thrilled beyond words (and that is saying something for me). It's like hearing stereo for the first time. I'm pulling all of my favorite vinyl and digging in for the rest of the weekend. I'm using a new Denon 103r cartridge with the Denon step up transformer, through a PAS 2 that just had all of the VTA upgrades, into my ST 70, driving Klipsh Tangent 5000s. I'm in music heaven (and all of my tubes are new so they are still burning in). I hope this honeymoon lasts forever.
    BTW Dave Bruebeck is not dead, He's in my living room right now playing for me!
    Another very happy VTA camper
    charlie

    Zimmer64

    Posts : 112
    Join date : 2013-01-29
    Age : 52
    Location : Switzerland

    Re: Fired up my "new" ST 70 today

    Post by Zimmer64 on Sun Feb 10, 2013 5:43 am

    Congratulations! I know how you feel. It's a great amp. Since I finished mine I spend every free minute listening to music. Vinyl, CD or streaming, it is pure joy.

    Enjoy

    Michael

    rickelrod

    Posts : 7
    Join date : 2013-02-05
    Age : 50
    Location : Berryville,VA

    Re: Fired up my "new" ST 70 today

    Post by rickelrod on Sun Feb 10, 2013 10:51 am

    I cant wait to join in the fun! Im due to receive my new to me ST70 tomorrow and a PAS2 later in the week!

    Ed Cheek

    Posts : 6
    Join date : 2013-02-10

    I Just Fired Mine Up Today Also

    Post by Ed Cheek on Sun Feb 10, 2013 5:41 pm

    Hello all,

    I finished wiring my new ST-70 up today and fired it up 2 hours ago. I am listening to some Ambrosia on vinyl now. It sounds wonderful. I would like for someone who knows from experience to answer some questions for me. I have been restoring antique radios for years but have just gotten into tube Hi-Fi. How long will the EL34's last playing them 1 hour a day on the average? How about the GZ34? I would like to know so that when I have to replace my tubes I know whether they are dying early or not.

    Does anyone use anything other than they EL34's as the output tubes? Which ones and why do you like them better?

    I thank anyone who answers me in advance for your time and help. I want to get the best experience possible from my new amp.

    Ed Cheek
    Kannapolis, NC

    Bob Latino
    Admin

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

    Re: Fired up my "new" ST 70 today

    Post by Bob Latino on Sun Feb 10, 2013 10:53 pm

    Hi Ed,

    EL34's should last 2000 to 3000 hours but many of todays EL34 tubes are not made as well as those in the 1950's and 1960's. If they are still working after 2000 hours, I would replace them anyhow and use the original tubes as spares .. The driver tubes should last maybe 5000 hours. GZ34 tubes should last 1000 hours but many don't even make it that long. I have found the generic Chinese GZ34/5AR4 made by Shuguang to last longer than either the JJ or Sovtek version. The Ruby GZ34 tube which is also a selected and tested Chinese tube is also very good.

    My favorite output tube in the VTA ST-70 is the Genalex Gold Lion KT66. The only downside is that a quad of these are fairly expensive at about $160 for a matched quad.

    For driver tubes you can use any 12AU7, 12BH7, 5963, 5814A or 6189 tube in the VTA ST-70/ST-120 amps (shipped after April 1, 2012). I have tried them all and they all work fine. Which one works best is many times system dependent so I don't want to go out on a limb and say one is a lot better than another. I just acquired some real nice USA made GE and Sylvania 5814A driver tubes which I have been shipping with the kit amps for those that want tubes included with their kits. Both the GE and Sylvania 5814A's have a really neutral sound and give a big soundstage. Some people don't realize that many times the driver tubes (especially the center driver tube) can have more influence on the sound of the VTA amps than the output tubes.

    Bob


    Last edited by Bob Latino on Mon Feb 11, 2013 8:39 am; edited 1 time in total

    Ed Cheek

    Posts : 6
    Join date : 2013-02-10

    Re: Fired up my "new" ST 70 today

    Post by Ed Cheek on Sun Feb 10, 2013 11:38 pm

    Thank you Bob. That is exactly what I needed to know. I appreciate the information. It is nice to hear real Hi-Fi again.

    Ed Cheek

    skriefal

    Posts : 116
    Join date : 2011-09-20
    Location : Utah, USA

    Re: Fired up my "new" ST 70 today

    Post by skriefal on Mon Feb 11, 2013 9:33 pm

    Bob Latino wrote:GZ34 tubes should last 1000 hours but many don't even make it that long. I have found the generic Chinese GZ34/5AR4 made by Shuguang to last longer than either the JJ or Sovtek version. The Ruby GZ34 tube which is also a selected and tested Chinese tube is also very good.

    1000 hours seems low for a GZ34. Or were you referring only to the new-production stuff? If so then I'll be sure to stay away from those on my ST-120 when it arrives. I have a Weber WZ68 and a Mullard 5AR4/GZ34 that I can use...

    Bob Latino
    Admin

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

    Re: Fired up my "new" ST 70 today

    Post by Bob Latino on Mon Feb 11, 2013 9:52 pm

    skriefal wrote:
    Bob Latino wrote:GZ34 tubes should last 1000 hours but many don't even make it that long. I have found the generic Chinese GZ34/5AR4 made by Shuguang to last longer than either the JJ or Sovtek version. The Ruby GZ34 tube which is also a selected and tested Chinese tube is also very good.

    1000 hours seems low for a GZ34. Or were you referring only to the new-production stuff? If so then I'll be sure to stay away from those on my ST-120 when it arrives. I have a Weber WZ68 and a Mullard 5AR4/GZ34 that I can use...

    Yes - the 1000 hours is just an estimate strictly of the newer production GZ34 rectifier tubes .. The Mullard GZ34 and the Weber WZ68 will last longer ...

    Bob

    skriefal

    Posts : 116
    Join date : 2011-09-20
    Location : Utah, USA

    Re: Fired up my "new" ST 70 today

    Post by skriefal on Mon Feb 11, 2013 10:02 pm

    Thanks Bob. I had briefly considered trying a Shuguang/Ruby 5AR4/GZ34. I'll cancel those plans and use the Weber or Mullard.

    rmyauck

    Posts : 9
    Join date : 2012-02-18

    Re: Fired up my "new" ST 70 today

    Post by rmyauck on Mon Feb 18, 2013 6:19 pm

    How long will the new production GZ34/5AR4 last with the posted SS diode mod?

    Regards!

    Randy

    xlr8

    Posts : 68
    Join date : 2010-02-09

    Re: Fired up my "new" ST 70 today

    Post by xlr8 on Tue Feb 19, 2013 9:05 am

    I have 2 ST 70s and I've been using JJ 5ar4 for nearly 4 years now with the diode mod. Before the mod I had lost 2 rectifier tubes within a year. I have a friend who builds and sells vacuum tube guitar ampllifiers and after seeing how long mine last, he now use this mod on all of his tube rectified amps.

    Zimmer64

    Posts : 112
    Join date : 2013-01-29
    Age : 52
    Location : Switzerland

    Re: Fired up my "new" ST 70 today

    Post by Zimmer64 on Fri Mar 01, 2013 2:25 pm

    Bob Latino wrote:Hi Ed,

    EL34's should last 2000 to 3000 hours but many of todays EL34 tubes are not made as well as those in the 1950's and 1960's. If they are still working after 2000 hours, I would replace them anyhow and use the original tubes as spares .. The driver tubes should last maybe 5000 hours. GZ34 tubes should last 1000 hours but many don't even make it that long. I have found the generic Chinese GZ34/5AR4 made by Shuguang to last longer than either the JJ or Sovtek version. The Ruby GZ34 tube which is also a selected and tested Chinese tube is also very good.

    My favorite output tube in the VTA ST-70 is the Genalex Gold Lion KT66. The only downside is that a quad of these are fairly expensive at about $160 for a matched quad.

    For driver tubes you can use any 12AU7, 12BH7, 5963, 5814A or 6189 tube in the VTA ST-70/ST-120 amps (shipped after April 1, 2012). I have tried them all and they all work fine. Which one works best is many times system dependent so I don't want to go out on a limb and say one is a lot better than another. I just acquired some real nice USA made GE and Sylvania 5814A driver tubes which I have been shipping with the kit amps for those that want tubes included with their kits. Both the GE and Sylvania 5814A's have a really neutral sound and give a big soundstage. Some people don't realize that many times the driver tubes (especially the center driver tube) can have more influence on the sound of the VTA amps than the output tubes.

    Bob

    Hi Bob,

    Maybe a stupid newbie question, but how does one bias the KT66? .400 or .500? I was not aware that one can use them as the manual does not mention them.

    Best

    Michael

    Bob Latino
    Admin

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

    Re: Fired up my "new" ST 70 today

    Post by Bob Latino on Fri Mar 01, 2013 2:41 pm

    Hi Michael,

    You can raise the bias a little on the KT66's to about .450 VDC per tube.

    You are correct in that the 240 volt version of the VTA ST-70 manual made no mention of the use of KT66 output tubes in the VTA ST-70. I just made the change below in the 240 volt manual to read as follows > "Set the bias for .400 volts DC if you are using EL34 output tubes, .450 VDC for KT66 or KT77 output tubes OR .500 VDC if you are using KT88 or 6550 output tubes."

    Bob


    Last edited by Bob Latino on Fri Mar 01, 2013 2:50 pm; edited 2 times in total

    Zimmer64

    Posts : 112
    Join date : 2013-01-29
    Age : 52
    Location : Switzerland

    Re: Fired up my "new" ST 70 today

    Post by Zimmer64 on Fri Mar 01, 2013 2:43 pm

    Thanks for the quick answer!

    Michael

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