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    New member with ST-120 questions

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    wgallupe

    Posts : 84
    Join date : 2014-05-18
    Age : 62
    Location : Central Mass.

    New member with ST-120 questions

    Post by wgallupe on Sun Jun 01, 2014 11:25 am

    Hi, I'm newly registered here so I thought I would introduce myself. I'm Wayne from central Massachusetts. A long time audiophile (just turned 60!). Kit building experiences include a few GR speaker models as well as a few Bottlehead amps and preamps. My current system includes a Threshold SL-10 preamp and McCormack DNA .5 power amp. Sources are Thorens TD126 with SME 309 arm and Ortofon MC cartridge and an Oppo BDP-95 universal player. Speakers are GR Research OB-5.

    So, now I'm thinking about a tube amp and research led me here. You all seem like a friendly bunch. Still reading lots of posts. I'm looking forward to participating!

    A question for the group: my speakers are rated at 91db with an average impudence of 6 ohms and a minimum of 4 ohms. Do you think the ST-120 is powerful enough? Also looking at the Rogue Atlas Magnum. Any thoughts or comments on this amp?

    Best regards,Wayne

    corndog71

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

    Re: New member with ST-120 questions

    Post by corndog71 on Sun Jun 01, 2014 12:05 pm

    wgallupe wrote:Hi, I'm newly registered here so I thought I would introduce myself. I'm Wayne from central Massachusetts. A long time audiophile (just turned 60!). Kit building experiences include a few GR speaker models as well as a few Bottlehead amps and preamps. My current system includes a Threshold SL-10 preamp and McCormack DNA .5 power amp. Sources are Thorens TD126 with SME 309 arm and Ortofon MC cartridge and an Oppo BDP-95 universal player. Speakers are GR Research OB-5.

    So, now I'm thinking about a tube amp and research led me here. You all seem like a friendly bunch. Still reading lots of posts.  I'm looking forward to participating!

    A question for the group: my speakers are rated at 91db with an average impudence of  6 ohms and a minimum of 4 ohms. Do you think the ST-120 is powerful enough? Also looking at the Rogue Atlas Magnum. Any thoughts or comments on this amp?

    Best regards,Wayne

    As a fan and owner of many of those same manufacturer's products/designs I can heartily recommend the ST120. I have the X-Statiks which are very similar to the OB-5 and my ST120 drives them very well. Of course if you want/crave more power then go for the M125s. I would love a pair myself but have other projects in mind first.

    The VTA amps in my opinion have one of the best driver circuits out there (not that I've tried them all). For the money they are tough to beat.

    wgallupe

    Posts : 84
    Join date : 2014-05-18
    Age : 62
    Location : Central Mass.

    Re: New member with ST-120 questions

    Post by wgallupe on Sun Jun 01, 2014 12:38 pm

    Thanks for the reply corndog. I don't necessarily 'crave' power just want to make sure I don't end up in an under powered situation. What kind of music do you listen to and at what volume level. I mostly listen to classic rock at fairly loud but not floor shaking levels. I forgot to mention I also have two subwoofers to supplement the lowest frequencies where the OB-5s can't reach. (But the OB-5s are running full range).

    BTW, now I recognize your user name from the gr research forum!

    zx

    Posts : 194
    Join date : 2011-08-05

    Re: New member with ST-120 questions

    Post by zx on Sun Jun 01, 2014 12:46 pm

    Vary cool looking speakers.........Wellcome



    Thanks for the site Bob....

    sKiZo

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

    Re: New member with ST-120 questions

    Post by sKiZo on Sun Jun 01, 2014 3:48 pm

    The ST120 is very conservatively rated. It drives my 89db 8 ohm McIntosh XR16 big boxes comfortably to uncomfortable levels ... just the way I like it!   What a Face  

    I added attenuators to mine - Those are set to around 2 o'clock. I also turn the DAC down three clicks and run the output from my music server about 3db down. That matches the input levels through the signal chain nicely. Short version ... I have more than enough reserve for anything I want to throw at it.

    I'd go with the tube set Bob sells to get started. He's pretty picky about what he offers. You can also kick up the output around 10% by going with KT120 tubes. The big iron in the ST120 has no issues driving those at 60mA bias. The KT120s also got some tremendous kick and depth to them, and all at a really decent price. Wait till it's broken in until you start experimenting with drivers and tube rolling. If you decide to try something else later, it's good to have spares ...

    Something else you'll want to consider is either a GZ33 or GZ37 bottle rectifier - hard to find AND pricey - OR a solid state WZ68 copper cap. The 5AR4 varieties are good with a moderate load but do tend to wimp out some if you drive them too hard.

    Oh. Don't forget the special deal ... mention my name, and Bob will only charge you twice the price ...  lol!

    Bob Latino
    Admin

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

    Re: New member with ST-120 questions

    Post by Bob Latino on Sun Jun 01, 2014 7:16 pm

    Hi Wayne,

    I use my own VTA ST-120 with 89 dB speakers in a 14 X 26 foot listening room. I have plenty of power to drive these speakers to pretty loud volume levels in this room. As sKiZo has said below, the VTA ST-120 amps are conservatively rated at 60 WPC. You will also gain about 5 watts if you use the Tung-Sol KT120 output tubes in place of any KT88 output tube.

    For 6 ohm speakers I would use the 4 ohm taps because, as you mentioned, most speakers have a dip in their impedance at some (or multiple) frequencies.

    Since you and I are both from central Massachusetts, if you ever want to audition an ST-120, PM me directly and I can set up an appointment here in my home for you to stop over and listen to my ST-120.

    Bob

    wgallupe

    Posts : 84
    Join date : 2014-05-18
    Age : 62
    Location : Central Mass.

    Re: New member with ST-120 questions

    Post by wgallupe on Mon Jun 02, 2014 9:08 am

    Hi Bob,

    Thanks for the comments. It sounds like I don't have to worry about not having enough power. I will definitely take you up on your kind offer for an audition. I'm on a business trip this week but will contact you when I get back.

    SkiZo and Montana,

    Thanks for your input also. As for drinks on me, no problem!

    This could be dangerous if you guys try to offset your travel expenses....  Wink 

    Wayne

    deepee99

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

    Re: New member with ST-120 questions

    Post by deepee99 on Mon Jun 02, 2014 12:39 pm

    I would echo sKiZo's advice on rectifiers, esp. with a 4-ohm load. The Weber WZ-68s work fine in my M-125s with an 89 dB speaker pair, and I keep a pair of NOS Mullard GZ-33s on hand for cold weather or when royalty visits. Ditto on the KT-120s. In triode mode they're about as sweet as you can get.
    So when's the party? This could be a pre-function for MontanaWay's planned Tubefest in September, to see if we play well with others before tearing his ranch apart.

    wgallupe

    Posts : 84
    Join date : 2014-05-18
    Age : 62
    Location : Central Mass.

    Re: New member with ST-120 questions

    Post by wgallupe on Sat Sep 20, 2014 9:17 am

    Just a quick update for anyone interested, I did audition the ST-120 at Bob's place (several weeks ago) and liked it so much I walked out with a kit in hand. I started the build but business travel and vacation has slowed my progress Sad

    Anyway, It's about 2/3 complete. Will post comments and pics when finished. Thanks again to all for the help.

    Wayne

    MarcVBelgium

    Posts : 83
    Join date : 2013-12-06
    Age : 63
    Location : Antwerp, BELGIUM

    st-120

    Post by MarcVBelgium on Sat Sep 20, 2014 1:46 pm


    A question for the group: my speakers are rated at 91db with an average impudence of  6 ohms and a minimum of 4 ohms. Do you think the ST-120 is powerful enough? Also looking at the Rogue Atlas Magnum. Any thoughts or comments on this amp?

    Hi Wayne,

    Welcome to this forum. People here are saints ! (at least to my experience :-)))

    I happen to have 91 db/W 6 ohms speakers (Tannoy Glenair 10) and I can assure you the ST-120 has plenty of power. Unless you have a very, very, very large listening room.......
    Originally I wired the amp for 8 ohms output and it sounded very well... later I rewired it for 4 ohms output and that definately sounded better.

    The ST-120 can be recommended and sounds magnificent!

    Good luck with your search.
    Marc

    deepee99

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

    Re: New member with ST-120 questions

    Post by deepee99 on Sat Sep 20, 2014 2:07 pm

    MarcVBelgium wrote:
    A question for the group: my speakers are rated at 91db with an average impudence of  6 ohms and a minimum of 4 ohms. Do you think the ST-120 is powerful enough? Also looking at the Rogue Atlas Magnum. Any thoughts or comments on this amp?

    Hi Wayne,

    Welcome to this forum. People here are saints ! (at least to my experience :-)))

    I happen to have 91 db/W 6 ohms speakers (Tannoy Glenair 10) and I can assure you the ST-120 has plenty of power. Unless you have a very, very, very large listening room.......
    Originally I wired the amp for 8 ohms output and it sounded very well... later I rewired it for 4 ohms output and that definately sounded better.

    The ST-120 can be recommended and sounds magnificent!

    Good luck with your search.
    Marc

    Wayne, I think your switch to the 4-ohm tap is wise. I have 87 db/watt speakers nominally rated at 8 ohms, but the dips can get much, much lower, down to 4 or lower. I too got much better sound off the 4-ohm winding. Switching to the 4-ohm tap took a lot of stress out of the power supply, too.
    Marc, I can't speak to the ST-120; I have a pair of M-125s and they just loaf breaking my neighbours' windows out.

    wgallupe

    Posts : 84
    Join date : 2014-05-18
    Age : 62
    Location : Central Mass.

    Re: New member with ST-120 questions

    Post by wgallupe on Sat Sep 20, 2014 2:48 pm

    Hi Marc, Thanks for the welcome and yes I have already figured out that the people here are indeed saints. Very different in a good way from some of the other forums I frequent Rolling Eyes Thanks for the info about your speakers. That makes me feel confident that I made the right choice with the ST-120.

    Hi Deepee, Good to know that the 4 ohm taps are probably the best way to go. I have wired mine up that way. Thanks.

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