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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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    VTA ST-120 and ohms

    coolhandjjl
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    coolhandjjl


    Posts : 5
    Join date : 2012-12-28
    • Post n°1

    VTA ST-120 and ohms Empty VTA ST-120 and ohms

    Post by coolhandjjl Thu Feb 28, 2013 6:02 pm

    I was looking at the pics of the VTA ST-120, and it has just one pair binding posts per channel instead of the usual multiple output terminals where you attach your leads to the impedance of your actual speakers. Can the VTA ST-120 be configured with multiple impedance outputs, or do you have to internally wire it to handle 4 ohm speakers? Oh yeah, can it handle 4 ohm speakers?

    Thanks in advance!
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    peterh
    peterh
    peterh


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    Join date : 2012-12-25
    Location : gothenburg, sweden
    • Post n°2

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by peterh Thu Feb 28, 2013 6:15 pm

    coolhandjjl wrote:I was looking at the pics of the VTA ST-120, and it has just one pair binding posts per channel instead of the usual multiple output terminals where you attach your leads to the impedance of your actual speakers. Can the VTA ST-120 be configured with multiple impedance outputs, or do you have to internally wire it to handle 4 ohm speakers? Oh yeah, can it handle 4 ohm speakers?

    Thanks in advance!
    The classical 4 terminal posts will fit. I think you may order your vta-120 with them too.

    http://www.triodeelectronics.com/dyna-termstrip.html

    There is also industry "barrier-strip" one example :
    http://www.te.com/catalog/bin/TE.Connect?C=16676&M=PPROP&P=2323&BML=10576,17560,17844&LG=1&PG=1&IDS=232201,232309,145511,146804,145672,145788,145791,144379,144608,144609,144728,144823,144853,144932,147907,147916,146315,146353,146733,146772&N=1

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    Bob Latino
    Bob Latino
    Bob Latino
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    Location : Massachusetts
    • Post n°3

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Bob Latino Thu Feb 28, 2013 7:30 pm

    coolhandjjl wrote:I was looking at the pics of the VTA ST-120, and it has just one pair binding posts per channel instead of the usual multiple output terminals where you attach your leads to the impedance of your actual speakers. Can the VTA ST-120 be configured with multiple impedance outputs, or do you have to internally wire it to handle 4 ohm speakers? Oh yeah, can it handle 4 ohm speakers?

    Thanks in advance!

    The VTA ST-70 and VTA ST-120 may be set up for either 4, 8 or 16 ohm speakers. Both output transformers have a separate tap for each of the three impedances. You just connect the one that you want to the red binding post inside the amp. If you have TWO sets of speakers and one is say 4 and the other 8 ohm, we do have the the optional (at extra cost) VTA 3 post binding posts, which may be set up for any combination of TWO of the impedances like 4 and 8 ohms or 8 and 16 ohms or 4 and 16 ohms.

    Bob
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    coolhandjjl
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    coolhandjjl


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    • Post n°4

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by coolhandjjl Thu Feb 28, 2013 8:52 pm

    Thanks Bob. The 3-way (8 & 4) seems ideal to make the amp flexible for future use.

    On another issue, (aside from drilling holes, adding wiring, et.) can the rca inputs be moved to the rear, and the power switch be moved to the front without affecting performance?
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    Bob Latino
    Bob Latino
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    • Post n°5

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Bob Latino Thu Feb 28, 2013 9:01 pm

    I suppose you could do what you propose by altering the chassis and drilling holes in the rear face for two input jacks. Running two input lines to the back of the amp should be done using shielded cable so that input wiring does not pick up noise from the power transformer.

    Bob
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    coolhandjjl
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    coolhandjjl


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    • Post n°6

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by coolhandjjl Thu Feb 28, 2013 11:50 pm

    So I could use shielded cable with two conductors. Would I connect the shield at each end to the chassis?

    Regarding the switch for power cord, would that create any noise by passing so close to the underside of the main board up front?
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    peterh
    peterh
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    • Post n°7

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by peterh Fri Mar 01, 2013 3:14 am

    Regarding power switch;
    i installed an SSR(solid state relay) at the back, and a connector for DC . To power on
    i tap my preamp for control voltage.( anywhere from 3 to 32V, one mA will do)

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    Bob Latino
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    • Post n°8

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Bob Latino Fri Mar 01, 2013 9:05 am

    coolhandjjl wrote:So I could use shielded cable with two conductors. Would I connect the shield at each end to the chassis?

    Yes ...

    Regarding the switch for power cord, would that create any noise by passing so close to the underside of the main board up front?

    It is best to run the power cord wiring around the side of the amp so it does not pass over the driver board.

    Bob
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    Donspokane
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    Donspokane


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    • Post n°9

    VTA ST-120 and ohms Empty Add another speaker binding post

    Post by Donspokane Sun Mar 03, 2019 1:46 pm

    Hi Bob,
    I have the VTA 3 binding posts on my 120 now configured for 4 and 8.   I would like the ability to have all three impedances available for use with banana plugs.  I've just ordered the auto bias board and will be doing surgery for that this week.  So while it's open, I'd like to tap the 16 ohm to test with some 12 ohm speakers.  Could I just drill out two holes in the back, and add two more posts to use with the 16's?  I know it's stainless and will be hard, I assume, but I have cobalt bits.  If I can, are there certain locations that are better than others?  Do I need to keep them away from the transformer?  There seems to be most space right under the transformer....but then, maybe there's room right under the existing 3 binding posts.   I just want to make sure I don't pick up any noise.  Thanks.
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    Bob Latino
    Bob Latino
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    • Post n°10

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Bob Latino Sun Mar 03, 2019 1:58 pm

    Donspokane wrote:Hi Bob,
    I have the VTA 3 binding posts on my 120 now configured for 4 and 8.   I would like the ability to have all three impedances available for use with banana plugs.  I've just ordered the auto bias board and will be doing surgery for that this week.  So while it's open, I'd like to tap the 16 ohm to test with some 12 ohm speakers.  Could I just drill out two holes in the back, and add two more posts to use with the 16's?  I know it's stainless and will be hard, I assume, but I have cobalt bits.  If I can, are there certain locations that are better than others?  Do I need to keep them away from the transformer?  There seems to be most space right under the transformer....but then, maybe there's room right under the existing 3 binding posts.   I just want to make sure I don't pick up any noise.  Thanks.

    You could drill a hole for each channel on the rear face of the amp and add an extra RED output binding post for 16 ohms if you want ? Just make sure that the metal of the post does not short to the chassis. You would then remove the YELLOW (16 ohm) wire on each channel that now goes to the NFB eyelet on the driver board and solder it to the new red post. You would also have to run a wire from the new red post to the NFB eyelet to reconnect the feedback line for each channel.

    Bob
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    Donspokane
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    Donspokane


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    • Post n°11

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Donspokane Sun Mar 03, 2019 2:43 pm

    Thanks! No problem with the transformer? Can I put them right under it?
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    Bob Latino
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    • Post n°12

    VTA ST-120 and ohms Empty Re: VTA ST-120 and ohms

    Post by Bob Latino Sun Mar 03, 2019 3:39 pm

    Donspokane wrote:Thanks!   No problem with the transformer?  Can I put them right under it?

    Any place you have a space on the rear face of the amp would be OK.
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