Bob Latino ST-70 Kit Project

Discussion in 'Tube Audio' started by 1MOR, Mar 7, 2010.

  1. 1MOR

    1MOR AK Subscriber Subscriber

    Messages:
    466
    After a few Emails with Bob, I ordered one of his ST-70 kits with all the upgrades. About a week later a very heavy box got kicked off the BBT. Opening it up and removing much packing, these kits are very well packed, I got to the good stuff in the box.

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    Laying out the initial assembly, mechanical assembly.
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    Layout and assemble the VTA driver board PCB
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    More to follow
     
    Last edited: Mar 7, 2010
  2. Glassweights

    Glassweights Compulsive about tubes

    Awesome!

    That looks really good.

    Interesting that he likes Xircon caps. In fact, it is always interesting to see what sort of caps people like. I am a Nichicon man myself LoL - That strikes me as funny when I say it.

    Seriously though, I bet that PIO upgrade you paid for is well worth it. I know a lot of our members are really big on matching everything and there has to be a payback.

    Every time I look at those kits I want one. Thanks for showing us as much detail as you can stand. I will enjoy any pics on your build.

    Dan
     
  3. 1MOR

    1MOR AK Subscriber Subscriber

    Messages:
    466
    Mount completed driver board, assemble and mount bias sockets, input jacks and the dummy mono/stereo switch.

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    Ready to do initial tests, trip to RS for extra fuses, ya never know!

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    Installed the three 12AT7 driver tubes, only one had power to the filament. Trouble shoot, correct heater wiring install to the driver board and life is once again good. Time to hook her up and see what happens, some fireworks? Will this become a "burning amp" project? Magic smoke? The excitement builds! I had a fire extinguisher at the ready. Here goes!

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    Got all three driver tubes lit. Insert the 5AR4 and the four EL34Bs. Turn on the juice, no flames, no flashes, no smoke, just a slight hiss from the left channel. Trace wiring, heater supply is way to close to the input terminals, disconnect, reroute, two channel quietness is achieved. Time to set initial bias on the output tubes.

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    Time to make music, the speaks have the Minimus 7 Zilch Lab crossovers installed and sound far better than they should. Cables are stuff from the old cable bag.

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    We got tunes, life is good. I let them cook for 5 hours before the trip to the big rig. Still have two virgin packs of RS 3 amp slow blows. Stay tuned!
     
  4. 1MOR

    1MOR AK Subscriber Subscriber

    Messages:
    466
    Here she is, installed in the big rig.

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    Here she is, all dressed up and looking great at sunset!

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    Fire in the bottles, we have fire in the bottles, and she sounds better than she looks, using the AK DIY Indignias and Wally World's Patio Cord speak cables. The Krell 200 wpc FPB has been replaced. SaaaaaWeeeeet!
    This pic has some blur due to hand held time exposure. :music::music:

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  5. ruffian

    ruffian Super Member

    Messages:
    3,060
    Location:
    Northern NJ
    Looks sharp. I had a lot of fun making mine too. Kind of makes me want to get one of the ST-120 kits.
     
  6. 1MOR

    1MOR AK Subscriber Subscriber

    Messages:
    466
    I want to share some of the experiences I had while doing this project. I got back into DIY last year after a 40 year hiatus, after arriving at no where to go and all day to get there, HA! During that time, I built the AK Indignias, the AK Minimus XO mods and stumbled into a cherry Scott 222C and a Scott 350B tuner. Along the way, UPS has delivered a Hakko 936 soldering station and a Harbor Freight DMM. Listening to the Scott was delicious, after many many many years of very big solid state muscle amps.

    I double checked everything while working through assembly. I measured all the resistors prior to installation and inspected every solder joint with a magnifying glass. I went back and measured every resistor after soldering, to see if any had values changed by the heat. I checked every chassis connection prior to power up.

    Well, I did make a few errors but managed to catch them by double checking each step. Even managed to lop off one of the tranny leads too short after having the church ladies pounding on the front door and refusing to take no for an answer. Fixed with a splice and shrink wrap. You can see it in one of the pics. I mounted V1 with the wrong orientation of the octal groove, easy fix prior to attaching any wires. The right channel filament wiring to the driver board went astray, again, an easy fix. A slight hiss from one of the channels was again an easy fix, rerouting the AC heater wiring. Per Bob Latino, attaching the dummy stereo/mono switch, was tough, due to the lack of space between the driver board and the chassis. Super glue the nuts to the switch prior to attempting the assembly of that part to the front of the chassis.

    The large Russian coupling caps presented some challenges as was expected. I shrunk wrapped the bias wiring and pins on the octal sockets attached to front of the chassis used for bias taps, I also cut off any of the tube pin tabs that were not needed. This was done to eliminate the caps from shorting the bias taps, as the big Russian caps have an exposed steel jacket. If I were to do this again, I would also shrink wrap the caps to insulate them from making any unwanted connections to the circuit board or the bias taps.

    I used 20ga silver coated copper Teflon insulated mil spec wire instead of the supplied wire.

    I want to thank Bob Latino for the great product and for the excellent customer service. I had a lot of questions before and after the purchase, and Bob always responded by Email within minutes, no matter how many times he has answered that same question from other newbees.

    As you can tell, I like this amp a bunch. She has 50 hours to date. I expect that I would need at least 100 hours burn in time for the Russian coupling caps. Then the tube rolling begins. Siemens, Mullard, GE, RCA black plates, Telefunken, Sylvania, and Raytheon 12AT7s stand at the ready. A quad of new production Gold Lion KT-66s is next on the list. Thanks to AK for this excellent forum! :rockon:
     
  7. Glassweights

    Glassweights Compulsive about tubes

    great pics!

    I finally got some shrink wrap big enough to go around those Russian PIO caps.

    I picked a light color so I can write the values on them with a sharpie.

    I kinda make it a point to make values easily readable for some future tech, it helps out so much if you don't have a schematic.

    I plan to get my hands on or build some sort of big tube amp like the 120 some day.

    Great work on the assembly and documenting the voyage.
    Dan
     
  8. bobrown14

    bobrown14 Super Member

    Messages:
    2,611
    Location:
    Philadelphia, PA
    Nice - very good job. BTW - where did you get that rack you have your gear in?

    Thanks for sharing.

    Bob
     
  9. Valve-Tech

    Valve-Tech New Member

    Messages:
    41
    Bob Latino ST-120

    I also finished a Bob Latino amp this week-end. It is an ST-120 that went together perfectly. Mr. Latino surely has done a great job with these amps and gives us a product that is worth much more than we have to pay.

    I have about 20 hours on mine and the sound is just fabulous. I am used to listening to my restored Fisher 800-c and KX-200 and this one is much more powerful in the bass register and retains all of the good sound that I am used to.

    I am currently driving mine with an Adcom SS preamp but a Fisher 400-c preamp is in the works.

    I didn't use the triode/pentode switches which cleaned up the wiring a bit. I did that because I don't intend to run it in triode mode. Also, I will eventually move the inputs to the rear and the on/off switch to the front.

    Altogether, I can't image a better amplifier than the ST-120. Thanks bob.

    John
     

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  10. thevic24

    thevic24 deep in sound thought

    Messages:
    653
    Location:
    Columbus Ga
    I have the ST120 and its all that and then some. I am willing to bet it puts out more than 60wpc. I highly recommend it to anyone, outstanding amp!!

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    -Vic
     
  11. 1MOR

    1MOR AK Subscriber Subscriber

    Messages:
    466
    Its a Sanus Euro.
     
  12. sanford12

    sanford12 Vintage ear-Vintage gear Subscriber

    Messages:
    2,770
    Location:
    Central Illinois
    That's it. I going to start stuffing money in the savings jar and get me one O" them purty amps.

    They really do look sweet and I'm really am going to get a ST70 with the upgrades. Now to fill the money jar.
     
  13. RickB

    RickB On the Road to Find Out

    Messages:
    2,252
    Location:
    San Antonio, Texas
    Yeah, those are nice, I just wish that there were other chassis options besides the original...I hate the power switch on the back and the inputs on the front, plus the big octal sockets that were meant to drive a preamp setup gaping at you from the front....nope...don't like that at all...

    Which is why my two original ST-70's sit in a closet...at least my VTA-70i has the inputs on the proper side, the back...too bad the power switch on it isn't in the front...it's no fun reaching across a hot amplifier in the stand and fumbling to get to the power switch....I've scorched my arms more than a few times doing just that...

    If I were to rebuild my ST-70's I would also go with the Tube4HiFi VTA board, I have heard what a fresh front end and 7199's sound like compared to even my VTA-70i's 6GH8A and it's improved over ST-70 power supply, the stock ST-70 is just not in the same league as the 70i or the better boards....which is another reason why my ST-70's sit in a closet....

    You did a nice job, and I'm sure you'll enjoy the heck out of them!

    .
     
  14. bobrown14

    bobrown14 Super Member

    Messages:
    2,611
    Location:
    Philadelphia, PA
    Easy fix for the switch on the back - plug it into a power conditioner and use the conditioner switch. I've been doing that for years... better for the tubes as well.

    Cheers,

    Bob
     
  15. JHoman

    JHoman Tubes & Klipsch!

    Messages:
    331
    Location:
    Meridian, MS
    Nice job!:thmbsp:
     
  16. Dmannnnn

    Dmannnnn Up Late

    Messages:
    1,775
    Location:
    Denver, Colorado
    I have been eyeing the ST120 for some time now. I am very curious how it might compare to the Bottlehead 300B's, if anyone out there has heard both.
     
  17. JHoman

    JHoman Tubes & Klipsch!

    Messages:
    331
    Location:
    Meridian, MS
    I have not heard the bottlehead, but I'm very satisfied with my ST120. I keep mine in triode mode most of the time. I don't notice any loss in power with my cornwalls. I love this amp, it's sweet tube sound is a delight to listen to. My cornwalls pair with it very well.

    I don't believe there is anything out there that can compete with it for the money, just my $.02. :thmbsp:
    Jeff
     
  18. idonthave1

    idonthave1 New Member

    Messages:
    11
    Wow. very nice. Wish i could hear it.
     
  19. Dmannnnn

    Dmannnnn Up Late

    Messages:
    1,775
    Location:
    Denver, Colorado
    The pricing is very attractive.
     
  20. shelly_d

    shelly_d Not An Audiophool

    Messages:
    5,698
    Location:
    Alameda CA
    With the cornwalls sensitivity (102 dB/watt/meter) I can't imagine you would run out of power:D. At 30 watts (the reduced power level in triode mode) you get about 14 dB of power with respect to one watt. That means your system is capable of 102 + 14 = 116 dB of volume.

    I think that's a little loud.
     

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