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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


4 posters

    Volume loss when splitting line out signal

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    breading


    Posts : 45
    Join date : 2010-01-08

    Volume loss when splitting line out signal Empty Volume loss when splitting line out signal

    Post by breading Tue May 24, 2022 1:50 am

    I am attempting to do some A/B testing, comparing audio quality between my VTA SP14 and my newly rebuilt PAS3.  

    I am splitting the line out signal from a Marantz DAC1 using a simply RCA Y cable. One of the Y out legs connects to the line in on my PAS3 while the other Y out leg connects to the SP14 line in.   The line out from each of the preamps is, in turn, run through an A/B switch to my VTA ST70.  The idea is that by switching the A/B back and forth I can compare audio quality of the Marantz signal being sent through the SP14 and PAS3.

    In theory this should be an easy process, however, when I switch to the SP14 side, I have virtually no volume.  I can faintly hear the source with the volume cranked up to max.  On the PAS3 side all is well with volume attenuating properly.  

    I have tested the SP14 side with the PAS3 turned on and off.  No volume on the SP14 either way.  However, if I unplug the Y leg to the PAS3 the SP14 volume operates perfectly.

    It is my understanding that splitting a line level signal does not affect the signal strength or quality.

    The question then becomes why do I get full volume attenuation on the PAS3 and next to no sound on the SP14?  

    Hopefully someone out there can lead me in the right direction toward solving this dilemma.
    peterh
    peterh


    Posts : 1689
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Volume loss when splitting line out signal Empty Re: Volume loss when splitting line out signal

    Post by peterh Tue May 24, 2022 2:52 am

    Dynaco PAS will short unused inputs to suppress unselected sources. Make sure that
    the input used IS selected all the time.
    avatar
    mijohn


    Posts : 111
    Join date : 2013-06-19

    Volume loss when splitting line out signal Empty Re: Volume loss when splitting line out signal

    Post by mijohn Wed May 25, 2022 12:05 am

    I think will need to switch both inputs and outputs on the preamps. ie: Marantz > A/B switch > preamps > another A/B switch > ST-70.
    avatar
    mijohn


    Posts : 111
    Join date : 2013-06-19

    Volume loss when splitting line out signal Empty Re: Volume loss when splitting line out signal

    Post by mijohn Wed May 25, 2022 9:45 am

    Breading, in my last post i wrote that you should put your switch at the inputs of the preamps, but I thought about it some more and I think you also need a switch on the output as well, so I edited my post to reflect that.
    Seamus
    Seamus


    Posts : 32
    Join date : 2020-03-17

    Volume loss when splitting line out signal Empty Re: Volume loss when splitting line out signal

    Post by Seamus Sun Jul 03, 2022 10:51 am

    breading wrote:I am attempting to do some A/B testing, comparing audio quality between my VTA SP14 and my newly rebuilt PAS3.  

    I am splitting the line out signal from a Marantz DAC1 using a simply RCA Y cable. One of the Y out legs connects to the line in on my PAS3 while the other Y out leg connects to the SP14 line in.

    What you are doing is essentially pointless. You have added additional wire and connectors, changed the load and impedances. None will sound like the unit individually.

    Listen to a lot of program with each unit alone in the system and make a decision.

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    Volume loss when splitting line out signal Empty Re: Volume loss when splitting line out signal

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