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st-70

  1. ADClosson

    Bringing a flood-damaged ST-70 back to life

    Hi all. I've got a previously restored ST-70 that I want to resurrect after a flood a few years back. As you can see, the output transformers and power transformer have some surface rust. The interior, to my eye, looks remarkably well preserved. My question: what are essentials steps to take...
  2. brizey

    Upgrading speaker posts on VTA ST70

    Hi everybody. I picked up a beautiful VTA ST-70 that was assembled by a lady named Sue in 2013 (signed in the chassis). It is set up to accommodate 8ohm speakers only. I want to hook it up to a pair of Klipsch Fortes which are 4ohm. Anybody know what I'd have to do to upgrade this on the amp...
    • brizey
    • Thread
    • ohm st-70 terminal upgrade vta
    • Replies: 12
    • Forum: Tube Audio
  3. DaveStra

    Speakers with ST-70, Pat-5

    I am wondering which of the two sets of speakers that I currently own would sound best with an original, unmodified Dynakit ST-70 amp and a Pat-5 preamp - EPI 100's or Jensen Model 4's? I know that my ears will be the final judge but I would like to find out what others have found in their...
    • DaveStra
    • Thread
    • epi 100 jensen model 4 pat-5 st-70
    • Replies: 6
    • Forum: Tube Audio
  4. TubesGlo

    Warming Up The Tubes

    Friday night jazz session with the warm glow of old Mullard's. Always a front row seat and the drinks are cheap.
  5. T

    Dynaco ST-70 with Lovan modifications

    Hi to you Dynaco owners. A few years ago I purchased a ST-70 which has been highly modified by "Lovan". I have used it intermittently but it has been idle for a few months while I listened to my MC-40's. Today, I thought I would put it back "on line" and try it with a recently acquired Van...
  6. ADClosson

    ST-70 on the fritz

    I recently had trouble getting my fully restored ST-70 to bias properly. The left channel didn't have enough range to bring the bias within spec. It kept reading high, around 2.5 volts. This issue spontaneously resolved and I enjoyed the amp for a few weeks. Then today the left channel fizzled...
  7. ADClosson

    ST-70 low bias after blown fuse

    I recently noticed a hum in the left channel of my completely refurbished ST-70. I read a thread suggesting to swap the pairs of EL34s to see if the hum moved channels. I did this without re-biasing (perhaps foolishly?) and upon powering up the fuse blew. When I replaced the fuse, I could not...
  8. zastin17

    Dynaco ST-70, 1959, Freshly Drawn Hafler Schematic :)

    https://www.dropbox.com/s/k8bo95iab6bc9vu/Schematic_Dynaco St70 Final_2021-09-28.pdf?dl=0 I like to make older Schematic nice a "pretty" for my own archiving, but I rather share it, as maybe its still helpful today High quality PDF available above. Prints out very nice! This does not take me...
    • zastin17
    • Thread
    • 1959 amp dynaco halfer schematic st-70 tube
    • Replies: 4
    • Forum: Tube Audio
  9. zastin17

    Dynaco St-70 Running On a 83 Murcury Vapor Recitifer!!

    Now why did I do this? Is it for better sound? No absolutely not. Is it because i'ts beautiful and dangerous and wacky? Yea, probably!!! I made an adapter with a socket saver and 4Pin socket just soldering through the pins. 3A filament, very close to 5U4, but far better in voltage drop. If I...
    • zastin17
    • Thread
    • 83 adapter dynaco murcury rectifier st-70
    • Replies: 49
    • Forum: Tube Audio
  10. johnnytheg

    A question about biasing new tubes

    Hi all, I just replaced seven year old Svetlana EL34 tubes (one of the tubes shorted) with Mullard re-issues. When I hooked up the new tubes and let the amp warm up (twenty minutes) I hooked up my multi-meter. The previous older tubes had the bias set to 1.56 (dynaco specifications) but when I...
  11. David_NC

    Dynaco ST-70 - Upgrade Time?

    I bought this ST-70 about 2 years from a local GW. It came with good T-S 7199's and Philips EL34 / 6CA7's. It's in great shape and worked well, but I replaced the selenium rectifier, multi can cap, caps and resistors underneath, and the six caps on the driver board before putting it into use...
  12. goldswimmerb

    Struggling with an ST-70

    Hey, looking for some help here as this thing is whooping my butt... I have an ST-70 I am trying to get up and running properly, from what I've been told it worked just fine for a while then one day started "flashing then popping a fuse".... I've been going through and checking everything but I...
  13. HowlerMonkey

    dynaco ST-70 w/ou bias sets

    I have this great ST-70 that i bought from a fellow Ak'er. It is a very clean kit with the only "non standard" difference that the front sockets to check the bias have not been wired. I am debating if i have the skills to wire them myself (i might need step by step instructions like the ones you...
  14. J RR

    Yet another St70 issue

    Hey all tubers! Background: ST-70 with new board, can cap, bias circuit, selenium replaced diode, new Power transformer (about a year old, all of it). Started a low buzz a few days ago. Replaced all tubes: no go. Measurements: Can cap: A (Square): 227VDC B (triangle): 282VDC C (blank): 324VDC...
    • J RR
    • Thread
    • dynakit st-70 st70
    • Replies: 26
    • Forum: Tube Audio
  15. H

    Dual ST-70s dilemma

    Hey all, looking for some ideas from the braintrust here. I’ve recently acquired two, original, factory-wired Dynaco ST-70s. I have an Acoustat preamp with dual stereo outs that I originally thought I would just run to each ST-70. Now I’m thinking that I might need something in between that...
  16. jonperry

    C8 power from ST70?

    Hello Folks, I’m looking at a set of C8/C8s preamps and would like to know if I can power these using the octal cables to my Dynaco ST-70? I’m aware the plugs can power a set of PAM-1 Preamps but am not sure if the Macs would be compatible. Although I love the look and sound of the C8s, I’m not...
  17. HowlerMonkey

    Eico HF-85 for Dynaco ST-70, can they be a match?

    I have been looking for a tube preamplifer for a while but there is rarely anything below $500 in my area. And when there is one, I don't have the cash on hand and miss the opportunities lol (like the Audio Illusions 2A for $450) Anyways, I am ready to shoot above $500 now and I am going to...
  18. G

    Driving AR3a’s With Dynaco ST-70

    Hey. Just wanted to get some insight on driving my AR3a’s with my Dynaco ST-70. I looked up specs on AR3a’s and saw that they are rated at 4ohms, but my repair guy says he always runs them at 8ohms. Can the speakers handle an 8ohm current? Is there a benefit to using the 8ohm tap with 4ohm...
    • GR3GRS
    • Thread
    • acoustic research ar3a dynaco ohms speakers st-70
    • Replies: 7
    • Forum: Speakers
  19. Strgazr1967

    Welborne Labs ST70 bias, caps and tube questions

    I picked up this ST-70 a few weeks ago and have been cleaning it, going over it and deciding on tube choice for when I set it up after Christmas. The wife's decorations require I take my system out for the holidays. I have a few questions. While going over the amp I noticed that whoever did the...
    • Strgazr1967
    • Thread
    • bias adjustement capacitors dynaco gold lion st-70 tube amp bias issues tubes
    • Replies: 1
    • Forum: Tube Audio
  20. David_NC

    My Dynaco ST-70 Has Ruined My Other Amps

    My Dynaco ST-70 has ruined my other amps... at least in terms of my listening enjoyment. I've used a QSC USA 900 and later a Parasound HCA-1000A as my main amps with a pair of ADS M12 towers. I've enjoyed these speakers, and the rest of my setup, quite a bit. Recently, I put my refurbed ST-70...
  21. David_NC

    Name That Tube!

    I've been running my Dynaco ST-70 on some cheap JJ EL34's while I was getting it sorted out, tested, etc. Last night, I traded them out for the ones that came with it. It looks like much of the printing on the tubes has been removed. The 7199's are Tung-Sol, and the GZ34 is labeled Dynaco, so...
  22. David_NC

    It Lives!

    Last week, I finally got to test out my Dynaco ST-70. I 'refurbed' it a couple months ago but never got a round to finishing a few things and getting some somewhat disposable tubes to test it with. Last week, the tubes arrived, so I finally got to hook it up. The left channel sounded OK, not...
  23. David_NC

    ST-70 Restore... And What Next?

    I finally finished replacing caps, resistors, and selenium rectifier on my ST-70. I've got four inexpensive matched EL34's and an equally inexpensive 5AR4 sitting here in a box. I assembled a DBT today in case oe is needed and have a 60 watt bulb in it (I assume that's a good wattage to use)...
  24. David_NC

    Dynaco ST-70 Startup

    I finally finished 'restoring' my ST-70 last night. I replaced all the caps, most resistors, and the selenium rectifier. All that's left is to replace the rusty hardware (aka screws) on the chassis, which I'll do tonight. This is leading up to the scary part - powering it on for the first...
  25. Johnny_Law

    Dynaco (kit?) ST-70 - hmm, someone's been in here before ...

    Very excited to buy this ST-70 a while ago, but it's been waiting for me to verify that everything looks good before I plug it in. From the caps up top, I could tell that someone had done some work before, but now I've opened it up and see that someone did much more work than I assumed. I...
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