Dynaco ST-70

13

Comments

  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    So I guess I order some new tubes...

    Post number 1000. :D
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    I'll shut it down, let it cool, then switch the tubes sides. That should indicate a tube problem, right?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • Tour2maTour2ma Old School Posts: 10,176
    edited April 2004
    Congrats on the post milestone...

    Do you have access to a decent, mutual conductance tube tester?

    Remember if the Dynaco/ Mullards test OK, they are worth something on the market...
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
    "Death doesn't come with a Uhaul." - Dennis Gardner
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    No mutual conductance tube tester.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Looks like the tubes. Once I switched them sides the results were the same just on different sides.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • Tour2maTour2ma Old School Posts: 10,176
    edited April 2004
    Do a sequence of swaps and partial swaps to see if one tube is the culprit.

    There's probably a repair shop not too far from you with tube testing capability. Wouldn't charge much of anything I'd imagine. They can quantify the life remaining in the "good" ones.

    If there isn't one, and you're curous, after your get a new matched set, you could send the originals my way. I've a nice old Hickok.
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
    "Death doesn't come with a Uhaul." - Dennis Gardner
  • organorgan Posts: 5,022
    edited April 2004
    Congrats Derick! The biasing problem you're having is most likely due to weak tubes or mixing the Mullards and Sovtek output tubes. You will hear a big difference with fresh new tubes.

    Never heard anything about that rectifier tube but those Sovtek drivers need to go asap. I wasted my money on Sovtek 7199's. Even the guy who's going to do the restoration for me told me to stay away from the Sovtek 7199.

    Are we going to see some pics of the complete system? The sound of the ST-70 can be a little mellow with more hungry speakers but it kicks every SS amp's **** when it comes to high sensitivity speakers IMO. Are you planning on going horns in the future? The sound of my ST-70 and RF-35 is amazing. What is it powering right now?

    So what's the deal with that output transformer? Is it really misaligned or it's the pic?

    Keep us posted

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • gidrahgidrah Posts: 3,031
    edited April 2004
    Congratulations! Stop swapping tubes and just enjoy it. Do some research on some tube choices and then worry about it. I only say this because I've been wanting to retube mine for some time now, but every time I listen to it, I say "Why?".

    I know I'll get a quad of EL-34s or big bottle 6CA7(or whatever)s in the future, but that's more just for a piece-of-mind.
    Make it Funky! :)
  • organorgan Posts: 5,022
    edited April 2004
    Gidrah,
    I was very impressed with the Electro Harmonix 6CA7. Less "personality" and warmth than the Svets but very detailed and rich sounding. Great low end too.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    I going to splurge on new tubes all around. I wasn't planning on adding anything to my system except for a power cord for my CDP. Now this amp's going to cost me, but hey, it's going to be worth it. :)

    I'm running the RT1000i's and although they don't have a great reputation here, they've shown an improvement with every upgrade and still going very strong. At the cost of speakers, I won't be get any new ones unless I can snag a deal on the cheap.

    I'll give you some pics soon, my digicam is at my parent's house.

    All in all, I'm very happy with the results and extremely optimistic for what's going to come with some upgrades. I love the soundstage. The detail is yet to be desired but with new tubes that should change I'm sure.

    The misaligned OT seems to be some paper or something inside. I have no idea. I'll have to take it all apart and clean it up. It needs some work.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    My 800i sounded fantastic with the ST-70. I'm sure your 1000's should be better because they require less power. I agree with you on the soundtage.

    With new tubes, the bass should be much stronger and you should hear more detail, especially the texture. Weak tubes give you less power and resolution.

    Enjoy

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • Tour2maTour2ma Old School Posts: 10,176
    edited April 2004
    dc,
    Don't forget to have the EL34 Dyn/ Mullards tested. Some potential bucks to be recouped there.

    maurice, you have a tester don't you?
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
    "Death doesn't come with a Uhaul." - Dennis Gardner
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    After the new tubes, I'm going to have to replace the inputs. I have a pair of Kimber Hero's ready to be plugged in only they don't fit right now. :mad:

    I was also thinking of maybe sticking an IEC plug on it to accommodate a swappable power cord.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • gidrahgidrah Posts: 3,031
    edited April 2004
    Heck, I just picked up an Olson from our buddy SGTGTO. If need be I can send it on up. Sell the 2 closest Mullards as a pair and one as a spare and you'll probably clear a Franklin (or is it a Queen:D ). If your money isn't that tight I'd wait and possibly pick up a forth though.
    Make it Funky! :)
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Thanks for the offer. Money's not much of an issue, I'll hold on to them for now. Is a tube tester a must?

    I had no idea who was on a canadian $100 dollar bill. :D I would have guessed the Queen. It turns out it's a former Prime Minister Sir Robert Borden.

    http://www.bank-banque-canada.ca/en/banknotes/general/character/2004_100.htm

    I've just ordered new tubes as per Maurice's recommendations.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    Tour,
    I don't have a tester yet. All the ones I've come across are too expensive. I had the same problem as Derick when I first got my ST-70 with the weak power tubes giving me low bias. Same crap happened to my JJ E34L. Hated the tube anyway, even when it was working fine.

    Derick,
    I replaced the inputs on mine with gold plated female RCA's from rat shack. It was pretty simple but I had to make the holes a little bigger to fit the new RCA's.

    Which tubes did you order?

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Mullard, Jan-Phillips, SED.

    I've looked at the radioshack.ca website but can't find any decent rca's. Which ones did you get?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • Tour2maTour2ma Old School Posts: 10,176
    edited April 2004
    dc,
    Tube tester is not a must have, but they are nice to have. Really depends on how serious you want to get into tubes, if you plan to buy used lots for resale, etc.

    I nailed a very nice Hickok TV-7-D/U on ebay a while back. Was a bit of a crap shoot as it was one of those "working fine when I lasy used it" listings. But seller was an older gent and I got for ~$150 under the going rate for these. Pic attached...

    Here's a good reference link...
    http://www.tubewizard.com/recommended_Hickok_testers.htm

    Hickok also made a line of testers for the Canadian military under the name Stark.
    i-2.jpg 20.8K
    More later,
    Tour...
    Vox Copuli
    Better to remain silent and be thought a fool, than to open your mouth and remove all doubt. - Old English Proverb

    "It's easy to get lost in price vs performance vs ego vs illusion." - doro
    "There is a certain entertainment value in ripping the occaisonal (sic) buttmunch..." - TroyD
    "Death doesn't come with a Uhaul." - Dennis Gardner
  • organorgan Posts: 5,022
    edited April 2004
    Derick,
    Sounds great. That's the tube combo I'll be using when my Dyna is well again. I think you'll really enjoy the texture and warmth of the SED. The Mullard GZ34 added plenty of bass compared to the Sovtek I used before.

    Can't remember the name. I threw out the packaging. I think it was just radio shack brand. I just went into the store and grabbed it along with the binding posts. I'm sure your nearest radio shack should have them.

    Tour,
    That tube tester is a beauty. If I see one that's in good condition and the price is right, I may buy one.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Originally posted by organ
    I replaced the inputs on mine with gold plated female RCA's from rat shack. It was pretty simple but I had to make the holes a little bigger to fit the new RCA's.

    Did you modify the chasis at all?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Maurice, have you tried running your NAD amp for the lows in a biamp configuration?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    Derick,
    No mods to the chassis. If you open up the amp, you'll see a small brown platic material holding the RCA inputs which is screwed on to the chassis. All I did was make the holes on the plastic a little bigger to fit the new RCA's. Actually, there's two pieces of it holding the inputs. Part of the RCA is sandwiched between them.

    I did try bi-amping with the LSi9 because my NAD have a variable input. I didn't like the sound. The higs were very sweet but I was missing the great mids from the Dyna. It just didn't sound right to me.

    Let me know how the amp sounds when your new tubes arrive.

    Oh yeah, another thing I did was replace the power cord and power switch. Radio Shack had the exact same switch.

    One thing I'm still thinking about with my amp is the 7199 tubes. The guy I talked to said he could mod the circuit board to accept non 7199 tubes. I'm still thinking if I should do this because NOS 7199 is becoming very expensive and there's only one company making them now and their 7199's suck. If it's going to improve the sound, I'll get it done for sure. Need to do more research.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    I went to Radioshack and couldn't find RCA inputs. I may have to order online.

    I did pick up some speaker wire to give biamping a try, if it doesn't work I'll have some decent wire for my camp rig.

    The tubes shipped yesterday, I'm hoping they'll come tomorrow.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    The tubes should arrive tomorrow. I always ordered on Mon and it arrives on Wed every time. Their default setting for shipping is express. So if you didn't change it, it should be there tomorrow.

    Don't forget to lower the bias all the way before turning on the amp with the new tubes. Once it's turned on, wait about a minute and set it to around 1V. Slowly raise it to 1.56 over the next 15-30 mins. As the amp heats up, the bias voltage may increase slightly.

    I'm sure partsexpress.com should have better quality inputs. You might want to check there.

    I was just thinking. I think you will really benifit from bi amping the 1000's because the lower posts are connected to the subs only right? The top posts are connected to the woof and tweet? This should give you the impact of SS and bloom and air of tubes.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Ya, I was just thinking the same thing. hehe. :D

    I just finished hooking up the new wire and noticed a nice little gain in the lows even without the burn in. I now have Kimber 4vs on the mid/highs and some Kimber 8PR on the subs. The 4vs have some banas on them ready to switch to the Dynaco which is currently on my coffee table getting a bit of polish.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    Sounds great. Funny how you can't seem to max out the 1000's:D. There's always something to try out. You should use the better cable for the woof/tweet since that's what you'll be hearing most of the time.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    I think... the 4vs are the better of the 2. I'll have to play around with it once the 8pr is burned in.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    And yeah it's funny the 1000's are still in my rig. They were the first of my purchases a little over 2 years ago. I picked them up on clearance at Futureshop for $899, I missed out on a pair of 800's for $600.
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • dcarlsondcarlson Posts: 1,740
    edited April 2004
    Well, I got the new tubes today. I haven't done a shoot out or anything, I simply dropped the new ones in. I still can't get it to fully bias though. Any thoughts?
    SDA-2a, Anthem Pre-2L, Anthem Amp 1, MF A324 DAC, Rotel RCD1070

    Senn HD650 Cardas, Mapletree Audio Ear+ HD2, Kimber KS1030, Bel Canto DAC2, M-Audio Transit, Laptop.
  • organorgan Posts: 5,022
    edited April 2004
    That's strange. My best guess would be your bias supply caps could be weak or the selineum have build up too much resistance over the years.

    What's your highest bias reading?

    One thing we already know is that your weird left/right bias from before was from the tubes that came with the amp. The bias changed when you moved the tubes around.

    Replacing the bias supply is a very simple procedure. All you have to do is remove 5 parts and solder the replacements. The bias supply kit includes a diode to replace the selineum, 2 bias caps and resistors underneath near the right output transformer. You get a great step by step instructions as well. The kit sells for under $10. I got mine from www.triodeelectronics.com Just type 'dynaco' in the search function.

    Let's wait for Tour and the other ST-70 guys to chime in. I'm sure they know about this problem.

    Did you install all the new tubes?

    I'm sure it won't be long before you find the problem.

    Maurice
    CD Player: Original CD-A8T
    Receiver: Harman/Kardon HK3390
    Speakers: Polk Audio RT1000p
    "I would rather have a cup of tone than an ocean of power" **Dr. Harvey Rosenberg**
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