Foreplay pre amp?

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  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    Foreplay pre amp?

    Whats everyone's oppinion on the foreplay pre amp kit? Sounds like a fun project...






  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10934

    #2
    I'm not a fan of tube generated euphonics.




    theAudioWorx
    Klone-Audio

    IB subwoofer FAQ page


    "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

    Comment

    • Andrew Pratt
      Moderator Emeritus
      • Aug 2000
      • 16507

      #3
      Thomas I know you're not a fan of tube amps due to the added distortion...is that the same reason you're against the tube pre amps as well?




      Comment

      • JonMarsh
        Mad Max Moderator
        • Aug 2000
        • 15259

        #4
        Tube based equipment tends to have a characteristics sound, just as solid state does. This is typically a result of either deliberate design choices, or inability to overcome the inherent characteristics of the components.

        Some very good, neutral and open tube preamps have been designed. The same is true for solid state.

        They tend to be the exception, rather than the rule, unfortunately.

        And there are those that like very specific colorations inherent in simple, single ended tube designes which are replete with even order harmonics- and intermodulation distortion and impedance related frequency response variations. Many listeners nonetheless enjoy this kind of equipment for specific listening experiences in synergistically assembled systems. But, they tend not to be my cup of tea. Nonetheless, I would prefer a system like that to one with colored "solid state" gear, as the latter tends to *not* have any euphonic characteristics, other than a deep, extended bass. (Nothing wrong with that, but if the mids and high end aren't very natural, it's not nearly enough to float my boat.

        It's not a bad idea to listen to a lot of different things with an open mind- including live music! Then, your ultimate choices will be more informed, and more satisfying in the long run.

        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-Saƫns 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

        • ThomasW
          Moderator Emeritus
          • Aug 2000
          • 10934

          #5
          Andrew

          What jon said........

          And I'm cheap and lazy Tubes wear out and must be replaced.




          theAudioWorx
          Klone-Audio

          IB subwoofer FAQ page


          "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

          Comment

          • Andrew Pratt
            Moderator Emeritus
            • Aug 2000
            • 16507

            #6
            Thomas you built/use a passive pre amp don't you in your system? whats the deal with that one? Basically I'm fairly happy with mt HT performace but as always 2 channel could be improved...I figrue the two weak points for me at the moment gear wise are the transport (Sony mega changer) and the pre amp in the Denon 3300. If I replaced the Denon it would likely be with the outlaw HT pre amp or some other such beast and in all likelyhood I doubt its pre amp section will be that spectacular either...so I am starting to think about integrating a better pre amp for the 2 channel side of the system. This kit interested me b/c it seemed easy to build and would get me started in DIY electronics...though I'm not fond of the box the foreplay uses but thats part of the charm of DIY right suggestions?




            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15259

              #7
              Here's a challenge for you, Andrew-

              Integrate the pasive Shallco attenuator volume control of the Marchand PR41 Preamp (ThomawW and I both use one of these) with the active gain stage of the Foreplay- get rid of the pots and stuff they use.

              Repeat after me: Pots are bad, switched attenuators are good. Pots are bad, switched attenuators are good. or God.

              Seriously, the Shallco attenuator uses heavy coin silver contacts and metal film resistors, which you can upgrade to Vishay's.

              A first question I have for all tube preamps, is how low an ouptut impedance can it drive without significant distortion? This is a limitation of the Marchand vacuum tube crossover, also.

              Passive preamps require some system planning because the impedance of the attenuator network interacts with the cable capacitance to change the HF performance. Vacuum tube preamps, unless they're using a cathode follwer output with a current source load, suffer the same problem.

              BTW, if you're thinking about the Foreplay, you should plan on the upgrade kit with the active current source loads for plate and cathod circuit. That does linearize things a bit, particularly for greater output swings.

              For good tube gear on a budget, the Anthem gear from Sonic Frontiers is pretty nice.

              I've been pondering modifying or creating a modified Marchan PR41 with an active gain stage (taken from my electronic crossover output buffer, which uses OPA627 in conjunction with AD615 video driver as a buffer), but it's so I can use it with Jensen output transformers, like my active crossover, and drive the active inputs on my Aragon and Ayre amps, plus cut out some of the RFI and ground loop issues.

              My experience has been that even good line level solid state gear is pretty tolerable; (for example, Marchand electronic crossovers with Op Amp upgrades); where it makes the most difference to upgrade is in the power amp. Give a listen sometime to a high end vacuum tube or zero feedback solid state design (Ayre, Theta Digital, BAT) to see what I'm talking about.

              Happy hunting....

              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-Saƫns 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

              • ThomasW
                Moderator Emeritus
                • Aug 2000
                • 10934

                #8
                Andrew

                Jon forgot to mention a few things.......

                Preamps were developed primarily to amplify the signal coming from records. The output from the cartridge isn't 'high' enough to work with a power amp.

                Current sources CD, DVD, tuner, tape, etc., have a fairly standard 2volts output. Most power amplifiers can be driven to their full output with 2 volts in.

                So the only thing needed is to attenuate (decrease) that voltage to control the volume. Passive attenuators are nothing but volume controls that lower the voltage coming from the source. The reason they sound better a standard preamp is because there is no active circuitry in the signal path (remember in audio less is frequently better)

                The attenuators in the Marchand PR 41 has tons of individual resistors. They are wired in steps. And the volume goes up or down by clicks/steps, 46 of them to be exact. The cool thing about the Marchand is that the cost of the Shallco attenuators if purchased individually is more than Marchand charges for the kit. The balance control is 23 step Shallco attenuator. Now the kit isn't cheap $495, below is the reason why....

                Shallco 46 step attenuator. Solid silver contacts, 1% metal film resistors, military spec construction






                theAudioWorx
                Klone-Audio

                IB subwoofer FAQ page


                "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

                Comment

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