adding Balanced inputs to Mono block kit/DIY

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  • jaakan
    Member
    • Dec 2002
    • 98

    adding Balanced inputs to Mono block kit/DIY

    I have 4x Magnepan MG12s I'm currently running them with a Yamaha DSP-A1.

    the amp x4 at this link is what I want but it does not have Balanced inputs for when I get a pre/pro like the Sunfire TP III or MC12B.



    What would be needed to change the inputs to Balanced ones?

    Are there other kits that look great after they are done with Balanced inputs? (Solid state, Hybrid, Digital amps only)

    Any other Ideas?
  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15261

    #2
    You've raised an interesting question here, but to really discuss it properly I have to raise another one-

    "When do balanced inputs on consumer electronics actually enhance the performance, as opposed to being a "marketing" feature check?

    I raise this question because the majority of consumer market electronics are single ended internally, and then use some extra circuitry to implement a balanced transmitter or balanced receiver. An example would be the Sony SCD-1 SACD player, which uses an extra transmitter stage (opamps) to realize a balanced output, and for which the unbalanced outputs are considered by most to be a skosh more transparent.

    Balanced inputs on most midrange consumer gear are implemented with an opamp differential receiver. These are often referred to as "Transformerless" balanced inputs. These circuits are used to lower costs.

    Good balanced transformers have much better common mode noise rejection than an opamp circuit, but they also cost much more than a two dollar opamp- typcially more like $50 to $75, and up. (the set of very high grade transformers I use in my current experimental DAC design for isolation and filtering between the DAC outputs and the analog buffers cost $400 a pair....)

    My point (and there is one), is that balanced inputs and outputs on lower price point gear may not deliver the expected improvements in performance that they do in gear like Jeff Rowland, Ayre, where either premium transformers and/or true balanced differential amplification is used. Sometimes, you'll find that in most installations, with good power grounding practice and reasonable cable runs, you'll get just as good, or better performance overall using the single ended connections.

    For an introduction to transformer coupling/isolation technology in the signal path, check out Jensen transformers....


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    They supply to a number of audio manufacturers, and also sell direct. In theory, you could retrofit a Velleman multi channel amp kit with Jensen transformers- but the transformers for four inputs would be over half the price of the amplifier itself. Not an attractive economic proposition. But they sure do work nicely....

    Here's the electronic crossover I built for my X1 Klone project- it uses "mid grade" line output transformers from Jensen, and totally eliminates any ground noise issues driving multiple amplifiers from a single source. With the JT11 line output transformer, you can run balanced or convert to single ended at the cable output, and the -3 dB bandwidth of the transformer is 0.1 Hz, and 15 MHz.



    Bottom line? With the gear you're looking at, I wouldn't worry too much about running single ended outputs and inputs- unless you've got long cable runs and/or you're powering your amplifier(s) from a different AC circuit than the preamp, you shouldn't see any performance issues.

    Other opinions and suggestions are welcome...

    Best regards,

    Jon




    Earth First!
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    Comment

    • Brandon B
      Super Senior Member
      • Jun 2001
      • 2193

      #3
      Jon -

      Do you happen to know if Parasounds two new Halo pre/pros use true balanced outputs?

      BB

      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15261

        #4
        No, I don't. I haven't read anything detailed yet about their "guts".

        Now, one of the interesting things is that even for a solid state unit using direct coupled opamps running 180 degrees out of phase to realize a balanced output, you CAN retrofit true balanced isolation transformers. Particularly in areas where EMI might be a problem, due to local RF sources (nearby FM or TV transmitters, for example, or a HAM or CB operator), true transformer outputs might pay for themselves. But in other cases you may not notice much difference.

        In a perfect world, we wouldn't need that kind of CMRR, but in the real world with voltage differences between AC neutral lines on different circuits (when other appliances and lighting are running) and sometimes less than perfect grounding schemes implemented in consumer gear, it can make quite a difference.

        Common problems I hear from people are buzz/hum introduced when a cable TV lead is connected to their AV system, or when a PC is connected, etc. The conventional transformer less balanced inputs and output don't bring a lot of relief, for several reasons owing to typical shortcomings in their design and implementation.

        But then, I even prefer DAC inputs with pulse isolation transformers (Schott is a good brand; you can get pretty good ones for a little under $10 from Digikey). For the same reasons....

        -Jon




        Earth First!
        _______________________________
        We'll screw up the other planets later....
        the AudioWorx
        Natalie P
        M8ta
        Modula Neo DCC
        Modula MT XE
        Modula Xtreme
        Isiris
        Wavecor Ardent

        SMJ
        Minerva Monitor
        Calliope
        Ardent D

        In Development...
        Isiris Mk II updates- in final test stage!
        Obi-Wan
        Saint-Saëns Symphonique/AKA SMJ-40
        Modula PWB
        Calliope CC Supreme
        Natalie P Ultra
        Natalie P Supreme
        Janus BP1 Sub


        Resistance is not futile, it is Volts divided by Amperes...
        Just ask Mr. Ohm....

        Comment

        • jaakan
          Member
          • Dec 2002
          • 98

          #5
          In my perfect dream world Meridian would team up with Magnepan and make DSP Maggies...blah blah blah. Anyway, I have no current problems with buzzs, hums, EMI, RF.

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15261

            #6
            Then you'll probably be fine with just the standard single ended inputs; don't worry about balanced. 8)

            Best regards,

            Jon




            Earth First!
            _______________________________
            We'll screw up the other planets later....
            the AudioWorx
            Natalie P
            M8ta
            Modula Neo DCC
            Modula MT XE
            Modula Xtreme
            Isiris
            Wavecor Ardent

            SMJ
            Minerva Monitor
            Calliope
            Ardent D

            In Development...
            Isiris Mk II updates- in final test stage!
            Obi-Wan
            Saint-Saëns Symphonique/AKA SMJ-40
            Modula PWB
            Calliope CC Supreme
            Natalie P Ultra
            Natalie P Supreme
            Janus BP1 Sub


            Resistance is not futile, it is Volts divided by Amperes...
            Just ask Mr. Ohm....

            Comment

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