Dynaco St70 Series II+

Libertyc
Libertyc Posts: 915
edited April 2004 in 2 Channel Audio
I received my Dynaco St70 SeriesII+ today and fired her up. Everything powered uo OK and both left and rifgt bias leds are light. The amp has a slight hum with the volume control on my preamp turned all the way down. I know the hum is comming from the new Dynaco and think it may be a cap. The hum is heard through both right and left speakers. My old original Dynaco St70 ran dead quiet until it died (will repair soon). Anyone with any suggestions about this problem are welcome. I posting a pic of the amp and I hope it goes through. Thanks,
Bill
Post edited by Libertyc on
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  • Libertyc
    Libertyc Posts: 915
    edited April 2004
    Sorry pic is so large. Will try it smaller. :D Notice the 1.2tl over to the right
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  • Libertyc
    Libertyc Posts: 915
    edited April 2004
    Here is what feeding the Dynaco:
    Preamp - Audio Experience Tube preamp.
    CD Player - ShengYa Tube cd player.
    Sounds real nice except for the 60hz hum.
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  • Libertyc
    Libertyc Posts: 915
    edited April 2004
    Hello....Is there anybody out there?:confused:
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited April 2004
    Well you could be right about the AMP making the hum. And right I could be a Cap.

    Q's are this is this hum 60hz or not ?

    I do think your right about the AMP but I like to be 100% sure before you tear something apart. I think you should pull all inputs to AMP to recheck where this hum is coming from.

    Other then that sorry little help I can give. I never really got into Tubes so I never fixed an tube AMP. I don't know if a hum would be a large filter cap, or a pre driver area cap. But then again a 60hz hum must be in the power supply area, anything else is must likely in the amp circuit itself.

    Just my $.02 hope it offers something to you.

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  • Tour2ma
    Tour2ma Posts: 10,177
    edited April 2004
    Yes, smaller pics please. Got tired just scrolling over.

    Sometimes a poor Amp/ Pre-amp ground connection will induce a hum, but this is not necessarily equal in both channels.

    Possible ground loop issue...
    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

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  • F1nut
    F1nut Posts: 50,654
    edited April 2004
    Agree with the ground loop issue.

    I do have one question, how did you manage to post those LARGE pics?
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Libertyc
    Libertyc Posts: 915
    edited April 2004
    I don't know why the pic size is so large...I'm kinda new at this. I reduced the size and resoultion in Photoshop but they still are very large. I used my new Canon G5 with a tripod and no flash to shoot the pics. Thanks for the help with the amp.
    - Bill
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited April 2004
    Are you running Windows XP?

    Speakers
    Carver Amazing Fronts
    CS400i Center
    RT800i's Rears
    Sub Paradigm Servo 15

    Electronics
    Conrad Johnson PV-5 pre-amp
    Parasound Halo A23
    Pioneer 84TXSi AVR
    Pioneer 79Avi DVD
    Sony CX400 CD changer
    Panasonic 42-PX60U Plasma
    WMC Win7 32bit HD DVR


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  • organ
    organ Posts: 4,969
    edited April 2004
    "The amp has a slight hum with the volume control on my preamp turned all the way down."

    Do you only get the hum when the pre is turned all the way down? If so, I doubt it's the amp. If the filter caps in the amp are bad, you'll hear a hum at any volume. Have you tried hooking up the pre to another amp or the amp to another pre?

    Maurice
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  • disneyjoe7
    disneyjoe7 Posts: 11,435
    edited April 2004
    Excellent point, your right a filter caps will cause a hum all the time.



    Originally posted by organ
    "The amp has a slight hum with the volume control on my preamp turned all the way down."

    Do you only get the hum when the pre is turned all the way down? If so, I doubt it's the amp. If the filter caps in the amp are bad, you'll hear a hum at any volume. Have you tried hooking up the pre to another amp or the amp to another pre?

    Maurice

    Speakers
    Carver Amazing Fronts
    CS400i Center
    RT800i's Rears
    Sub Paradigm Servo 15

    Electronics
    Conrad Johnson PV-5 pre-amp
    Parasound Halo A23
    Pioneer 84TXSi AVR
    Pioneer 79Avi DVD
    Sony CX400 CD changer
    Panasonic 42-PX60U Plasma
    WMC Win7 32bit HD DVR


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  • Shizelbs
    Shizelbs Posts: 7,433
    edited April 2004
    How do you like that Sheng Ya CD player? I almost bought one of their tube headphone amps, but got a little weary since I've never heard of them before.
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