Dynaco ST-70

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  • organ
    organ Posts: 4,969
    edited April 2004
    What number did you get on the matched output tubes? The sticker is on the box and tube. All mine is 30.

    Maurice
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    Damn... gotta think on this some. Doesn't make sense given what happened with the tube swap moving the bias problem.

    Derric,
    Were you able to pinponit one original tube that was the culprit?
    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

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "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
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    I'm pretty sure it was the oddball one. The original Dynaco's all seemed to bias the same when I swapped them one by one.
    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.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    Originally posted by dcarlson
    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?
    Are you just saying the adjustments are still different, or one channel still will not reach bias setting?
    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

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "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
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Both channels aren't fully biasing but they do bias at pretty much the same somewhat weak level. I'm going to grab my fathers meter later tonight and give that a shot.
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    Is it possible that dirty pots could be causing this?

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    OK.... It seems to be just fine. New multimeter, new results. Sorry guys.

    I'll give it a new test later with the Mullard/Dynaco's in there.
    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.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    Good to know. Suspecting the test equipment is often the last thing.

    Maybe your VOM needs its battery replaced...
    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

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "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
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  • organ
    organ Posts: 4,969
    edited April 2004
    Some multimeters, especially the cheap ones aren't very accurate. Best way to test it is on a single or pair of AA batteries put in series. A single one is 1.5V and in series should give a reading of 3V. My cheap meter was slightly off and after doing some calculations, I had to get a reading of 1.67 from the Dyna which is actually 1.56V. The meter was reading everything a little high.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    My question now is.... There's a slight hum coming from both speakers equally. It was there with old tubes as well. Is it reasonable to assume that this is normal or does something need to be replaced?
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    How loud is the hum? With mine I get a very low buzz that I can't hear unless my ears are right up to the drivers and that's on really efficient speakers. It's normal for tube equipments to have a low thermal noise but if it's loud, something is wrong.

    A few days after getting my ST-70, I got a loud hum. I was able to hear it from my listening position. I had to change the quad cap (the one that looks like a tall metal can). Then the noise was almost gone. http://store.yahoo.com/triodeel/40ufat52twis.html

    The bias supply replacement kit can be found here. http://store.yahoo.com/triodeel/otparfordyn.html They're also selling the good quality RCA inputs. The bias kit is $3.95 and the RCA's are $2.95ea. These items are something which you can use in the future if you plan to do a full restoration.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    The hum is audible from my listening position. When music is playing I can't hear it but when it stops it's there.
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    Your quad cap could be weak. You can take it to an electronic reapir shop and have them test the cap to see if it's still strong. For now, as long as it's not bothering you, leave it and enjoy the amp until you figure out the problem. You can also ask the folks over at the forum on www.dynaco-doctor.com It seems like Tour and Gidrah got healthy ST-70's and we got the ones that haven't been powered up in a long time.

    Tour??? Do you think it's the quad cap? That's what mine was when it hummed.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    I'm on crack. :o

    Last night, it seemed like the hum was loud enough to hear from my listening position. It's not, really, not today anyway. It is there though, more so when closer to the speakers. Nothing to really be concerned about, although I would like it to be dead quiet. After the inputs and power cord, I'll try few other small mods and we'll see what happens.
    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.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    LOL...

    I would think Quad Cap , too, but if it's varying it might be noise in the AC line supply.
    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

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "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
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    LOL... Could a dying fridge be the cuprit? Cause mine's literaly about to blow.

    I'm diggin the tubes. :)

    I looked all over town for some new rca's and no luck. I'm going to take the good old lazy way out and order online.
    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.
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  • gidrah
    gidrah Posts: 3,049
    edited April 2004
    If you look at RS you usually have to look in the drawers.
    Make it Funky! :)
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  • Brianomatic
    Brianomatic Posts: 58
    edited April 2004
    Here is a good site for troubleshooting your ST-70.

    http://www.triodeel.com/trouble.html

    You may have a ground loop in your amp caused by a poor solder connection. Solder joints degrade after many years thereby creating two grounds at different potentials, e.g, the joint is at a higher resistance thus a uniform grounding isn't available.

    Another possible cause could be your ICs. Use only balanced, shielded interconnects.

    If you need a good look over, I would be more than happy to correct any poor solder joints and check all your components for you. I am an electrical engineer with all the necessary test equipment. Actually, I enjoy modding stereo equipment and have modded my Dynaco 400, 416 and my CD player.
    Music:
    Polk SDA SRS
    Dynaco 416 (2)
    Dynaco Energy Storage System
    Van Alstine Transendence Pat 5
    Van Alstine Transendence CD
    Marantz 2270 Receiver

    Home Theater:
    Onix Rocket 750 (4)
    Onic Rocket RSC200
    Onix Rocket RSS300 (2)
    Denon 3803 Receiver
    Denon 1600 DVD player
    Infocus X1 Projector
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Thanks for the offer. I'm sure it was my fridge. It's in the next room and buzzes right through the wall. I was just a little paranoid with the age of the Dynaco and assumed it was at fault. The hum isn't bad at all.

    *Edit*
    I have some Cardas RCA's on the way.
    http://www.takefiveaudio.com/cardas_ctfa.htm
    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.
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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    dc,
    May want to spread those RCA's a bit wider since you are replacing them. As you may have noted they are pinched together pretty close on the 70. Won't accomodate some of the fatter IC's...
    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

    "Death doesn't come with a Uhaul." - Dennis Gardner
    "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
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Yea, I'm still not too sure how I'm going to go about it. I don't want to start cutting any holes in the chasis.
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    Glad to hear you found the source of the hum. It's normal for tube equipments to generate a little bit of thermal noise. So I guess you're diggin the new tubes? Did you get a big improvement over the ones that came with the amp? I'm thinking about ordering more 7199's because supply for NOS is getting dry and price is going up.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    I haven't bothered with the old tubes just yet. I'll have a better idea once I have the new RCA's installed.

    And yeah, I'm waaaaay liking tubes. :D I now have myself contemplating new speakers.
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    That's cool. Are you planning to change the power cord? I've always wanted to try a good cord on mine but ended up with a generic cord. I was too lazy to look around at the time.

    I guess you already know what speakers I'm going to tell you to audition;). The thing with tube amps is you get more tube sound the higher you go up in efficiency on your speakers. The hardcore tube guys use super efficient horns powered by a 2w/ch SET tube amp. If you can find a dealer that will let you do an in-store demo or home trial of the RF-35, you should give them a listen. Sounds awesome with my ST-70.

    Another option is to look at tube pre amps before speakers. The ST-70 is also amplifying the SS characteristics of your pre. But eventually you'll go tube crazy and end up with a tube pre anyway;).

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    I haven't replaced the power cord yet. I'll probably go the generic route to begin with as well. I'm contemplating installing an IEC inlet on the Dynaco. The problem is always modifying the chasis and I don't know how much of difference a power cord will make on tube gear.

    I find for certain CDs (Radiohead, Flaming Lips) the change is incredible and I find myself thinking "I never heard that before. Is that sound supposed to be there???". The sound is just so much more natural. For some other CDs I just can't listen to them because the magic isn't there at all. It may be the recording.

    I love having the option of SS and tubes. I was thinking of maybe picking up a tube pre but the MF does a great job and can't see myself parting with it. Eventually, I will pick a tube pre down the road.

    I think the B&W CM4 may be a candidate speaker. They're not a horn but they get good reviews, look fantastic and are 8ohm, 90db efficient. They run roughly $2000CDN. I have a very good rapor with my local audiophile store. They're analog freaks and are very knowledgable and accomodating. If I went Klipsch, I think it'd be on the used market.

    Anyway, damn you guys... :p
    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.
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  • organ
    organ Posts: 4,969
    edited April 2004
    Sounds like a good plan. If you have the proper drill, an inlet should be a great thing.

    Do the B&W's have low impedance dips? I've never seen a tube system with Beemers before. The RF-35 retails for $1700CDN which is cheaper than the Beemers. I got mine for $1450 which came up to $1700 flat after tax.

    Maurice
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  • dcarlson
    dcarlson Posts: 1,740
    edited April 2004
    Last week when I went into the store they had a Cayin Tube integrated pushing some B&W 705 bookshelves. It sounded pretty nice for the short period of time I listened.

    This is all talk right now anyway, I'm just weighing my options.
    With the new tubes, the Dynaco has cost me enough for now.
    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.
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