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    A question of balance or unbalanced? And Altec Valencia 846A speakers--8/16 ohms.



    Posts : 1
    Join date : 2012-09-27

    A question of balance or unbalanced? And Altec Valencia 846A speakers--8/16 ohms.

    Post by jaxgaryj on Fri Oct 05, 2012 3:09 pm

    Dear Bob and forum folks,

    I got my ST-120 Kit yesterday and I'm really excited to commence with the fun!! Thank you for what should be a great project. My first question revolves around the feasibility of wiring the amp for a balanced input and output. My only experience with a balanced system is with my fantastic headphone set up cheers cheers : ALO's MK3-B balanced amp, Algo Rhythm Solo DAC, Audeze LCD-2 headphones(cabled for balanced input), and 160 gig iPod. The staging, imaging, and overall sound quality is simply amazing. I've read the JENSEN AN-003 paper discussing the "Interconnection of Balanced and Unbalanced Equipment", and also BLUE JEANS CABLE "A Question Of Balance". I am intrigued by the possibility of wiring the ST-120 to incorporate a balanced system. Is this feasible, or not worth the effort?

    My second question is about the output circuit of the amp. I have two different speaker sets that I would like to be able use with the ST-120: my original 1972 AR-3a's (4ohm) and a pair of 1967 Altec Valencia 846A's (8/16 ohms). The AR-3a's are pretty straight forward as far as your instructions about how to wire. The Altec's confuse me as to the spec sheet stating that they are 8/16 ohms. Because I physically don't have the pair of Altec's yet, I can't see what the input connections look like. The high/mid freq. drivers are the 806A listed as 16 ohm. Does the crossover network take care of splitting the different impedances? How does the tube amp. handle this?

    My third question: is it possible to wire the amp. output jacks to be able to switch between using the AR's and Valencia's different impedances?

    Any and all comments and suggestions would be appreciated before I start to wire up Bob's great looking amp!!! I will post some photos during the build.

    Thanks so much,

    Gary M. Jensen

    Bob Latino

    Posts : 2644
    Join date : 2008-11-26
    Location : Massachusetts

    Re: A question of balance or unbalanced? And Altec Valencia 846A speakers--8/16 ohms.

    Post by Bob Latino on Fri Oct 05, 2012 3:34 pm

    Hi Gary,

    Most people who use an amp use it on just one pair of speakers AND probably 90% of all speakers are 8 ohm speakers. If you do have TWO sets of speakers then > On the Tubes4hifi web site Roy offers a 3 post binding post option in which you can set your ST-120 up for 4 and 8 ohm speakers or 8 and 16 ohm speakers. Check about 1/2 way down this web page > Tubes4hifi ST-70 web page for the three post output binding posts.

    As for the balanced inputs ... I don't think that the effort to install them on the ST-120 is really worth it. I have in the past listened to balanced vs. unbalanced (RCA) inputs. I couldn't really hear any difference or "upgraded sound" from the balanced inputs over the unbalanced inputs. Pro audio gear is many times balanced cables only because they have to run long lengths of cable. In a typical home stereo system where RCA interconnects are usually less than 8 feet or so there is no real advantage (IMHO) to using balanced inputs and balanced interconnect cables. Another pain in the butt is that you would have to drill the chassis in two places to install the balanced inputs.


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