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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    Few Questions on ST120

    Rbertalotto
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    Rbertalotto


    Posts : 98
    Join date : 2021-02-25
    • Post n°1

    Few Questions on ST120 Empty Few Questions on ST120

    Post by Rbertalotto Fri Feb 26, 2021 11:53 pm

    Can the power switch be moved to the front where the non functioning Stereo Mono switch is located?

    Is there any way to move RCA jacks to the rear?

    What is the advantage of the gain control option?

    Is there a ground wire on the AC plug?

    Can what appears to be lampcord wire for the AC line be replaced with something more substantial?

    Are the two sockets on the front only used for bias connection?

    Thank you!
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°2

    Few Questions on ST120 Empty Re: Few Questions on ST120

    Post by Bob Latino Sat Feb 27, 2021 12:11 pm

    Rbertalotto wrote:Can the power switch be moved to the front where the non functioning Stereo Mono switch is located?

    Is there any way to move RCA jacks to the rear?

    What is the advantage of the gain control option?

    Is there a ground wire on the AC plug?

    Can what appears to be lampcord wire for the AC line be replaced with something more substantial?

    Are the two sockets on the front only used for bias connection?

    Thank you!

    The original concept of the VTA ST-70 and VTA ST-120 amps was to make these amps LOOK LIKE an original Dynaco ST-70 amp of the 1960's yet take advantage of 50 years of advances in electronics and produce a better sounding amp.

    1. Move the input jacks to the rear > You can do that BUT now you will have two pairs of 16 inch twisted wires running around the sides of the chassis to the rear. This sets up a situation where increased wire length exposes those two sets of wires to pick up hum from the power transformer. With the input jacks on the front, there are four short 1 1/2 inch that run directly to the driver board. They are so short, there is no need to twist the wires. What I recommend is to plug your interconnects into the two front input jacks and then run the wires UNDER the amp to the rear and plug the other ends into your preamp.

    2. The gain control (stepped attenuator) on the amp allows you to plug in any high level signal source directly into the amp (CD player, output from a computer, music server, DAC) and then use the stepped attenuator to control volume. If you have just a single high level input, this works well. If you have multiple input sources, then get a preamp. You don't need the stepped attenuator.

    3. Yes - You can use a 3 wire cord of your choosing in place of the 2 wire cord and ground the 3rd wire to the chassis if you want.

    4. The supplied power cord is not a "lamp cord". It is a 16 gauge power cord that is rated at 13 amps. On the ST-70 the fuse blows at 3 amps and on the ST-120, the fuse blows at 5 amps. The supplied power cord can carry far more current than either amp could ever use.

    5. Yes - Those front power sockets are only used for bias. Sure, you can remove them and use some bias test pins (like on the VTA M-125 amps) in their place BUT > Without the front tube sockets then the amp won't look like an original Dynaco ST-70 anymore ?

    Bob

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    Rbertalotto
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    Rbertalotto


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    Few Questions on ST120 Empty Re: Few Questions on ST120

    Post by Rbertalotto Sat Feb 27, 2021 12:57 pm

    Thank you Bob......All makes sense.
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