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Re: [dallasaudioclub] NON pasive preamp

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  • Blair Chapman
    You can make both RIAA and the preamp on Rat Shack PCBs for about $20 total. Call me or email me. Dave should also have designs. Blair
    Message 1 of 4 , Feb 27, 2011
      You can make both RIAA and the preamp on Rat Shack PCBs for about $20 total. Call me or email me. Dave should also have designs.

      Blair

      On Feb 27, 2011, at 3:53 PM, Paul Stewart <musicman32150@...> wrote:

       

      OK, 0PA2134 is always a good choice. ESP makes some PCBs for a 2134 preamp. Does anyone know of a good design.

      I may need to add an RIAA board.




      Date: Sat, 26 Feb 2011 16:42:06 -0600
      Subject: Re: passive preamp
      From: ryckebusch@...
      To: Dave.Thomas@...
      CC: musicman32150@...; akhilble@...; bill.w.brown@...; dallasaudioclub@yahoogroups.com; danny.thai@...; hileman65@...; lee_roitberg@...; mdchilds@...; texcurrier@...

      I have to agree with Dave. If you use an OPA2134 (dual) and leep the input impedance matched or <2K you will be hard pressed to measure the distortion much less hear it.

      On Sat, Feb 26, 2011 at 2:11 PM, Dave Thomas <Dave.Thomas@...> wrote:
      Passive preamp is an oxymoron it is a passive attenuator. I would build an opamp preamp instead.

      passive stepped attenuators are more likely to increase the noise floor in your system than they are to have any audible reduction in distortion.

      An opamp preamp will have distortion less than .001% and can be considerably less if you are willing to fork over $4 for the a high end chip. Still well below even the most punch drunk audiophile's ability to hear distortion. Plus they can swing sufficient voltage to insure you drive your amp to its full potential and get all the dynamic range it can deliver.

      Passive preamps being better is a myth with zero merit. It is right up there with singing tibetan bowls.

      Saying all this there is nothing wrong with it as long as your source player has really low output impedance and sufficient voltage swing to accomodate any amplifier you hook up to it. Problem is most folks don't have a clue what the voltage swing on their source player is or the output impedance. And most manufacturers don't seem willing to tell you. A preamp will insure you don't have to worry.

      There are several very good Opamps that have very high input impedance and very low output impedance, both are things you want to have when driving your amp.

      If you insist on building a passive attenuator (by the way it is not a passive preamp becuase it can't amplify only attenuate), non-inductive metal film resistors. They have the least effect on the input signal an induce less noise.

      <graycol.gif>Paul Stewart <musicman32150@...>



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      "Bill W (Sarge) Brown" <bill.w.brown@...>, Chris Paulson <akhilble@...>, DAC <dallasaudioclub@yahoogroups.com>, Danny Thia <danny.thai@...>, Dave Thomas <dave.thomas@...>, <hileman65@...>, <lee_roitberg@...>, Mark Childs <mdchilds@...>, "ryckebusch@..." <ryckebusch@...>, "texcurrier@..." <texcurrier@...>
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      Subject
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      passive preamp
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      Today's subject is passive preamp designs. I have a couple of boxes of Dale 1% resistors. Not sure what is best or how many steps in the attinuator. Also, to reduce the noise while adjusting the volume.

      INPUT

      Time to work on the pool.




    • Dave Thomas
      Here you go this has been built several dozen times by more people than I can count. (See attached file: OPAMP preamp.JPG) (See attached file: Opamp power
      Message 2 of 4 , Feb 27, 2011

        Here you go this has been built several dozen times by more people than I can count.

        (See attached file: OPAMP preamp.JPG)(See attached file: Opamp power supply.JPG)(See attached file: OPAMP Phono Preamp.JPG)

        Inactive hide details for Paul Stewart <musicman32150@...>Paul Stewart <musicman32150@...>


                Paul Stewart <musicman32150@...>

                02/27/2011 03:53 PM


        To

        "ryckebusch@..." <ryckebusch@...>, Dave Thomas <dave.thomas@...>

        cc

        Chris Paulson <akhilble@...>, "Bill W (Sarge) Brown" <bill.w.brown@...>, DAC <dallasaudioclub@yahoogroups.com>, Danny Thia <danny.thai@...>, <hileman65@...>, <lee_roitberg@...>, Mark Childs <mdchilds@...>, "texcurrier@..." <texcurrier@...>

        Subject

        NON pasive preamp

        OK, 0PA2134 is always a good choice. ESP makes some PCBs for a 2134 preamp. Does anyone know of a good design.

        I may need to add an RIAA board.




        Date: Sat, 26 Feb 2011 16:42:06 -0600
        Subject: Re: passive preamp
        From: ryckebusch@...
        To: Dave.Thomas@...
        CC: musicman32150@...; akhilble@...; bill.w.brown@...; dallasaudioclub@yahoogroups.com; danny.thai@...; hileman65@...; lee_roitberg@...; mdchilds@...; texcurrier@...

        I have to agree with Dave. If you use an OPA2134 (dual) and leep the input impedance matched or <2K you will be hard pressed to measure the distortion much less hear it.

        On Sat, Feb 26, 2011 at 2:11 PM, Dave Thomas <Dave.Thomas@...> wrote:
            Passive preamp is an oxymoron it is a passive attenuator. I would build an opamp preamp instead.

            passive stepped attenuators are more likely to increase the noise floor in your system than they are to have any audible reduction in distortion.

            An opamp preamp will have distortion less than .001% and can be considerably less if you are willing to fork over $4 for the a high end chip. Still well below even the most punch drunk audiophile's ability to hear distortion. Plus they can swing sufficient voltage to insure you drive your amp to its full potential and get all the dynamic range it can deliver.

            Passive preamps being better is a myth with zero merit. It is right up there with singing tibetan bowls.

            Saying all this there is nothing wrong with it as long as your source player has really low output impedance and sufficient voltage swing to accomodate any amplifier you hook up to it. Problem is most folks don't have a clue what the voltage swing on their source player is or the output impedance. And most manufacturers don't seem willing to tell you. A preamp will insure you don't have to worry.

            There are several very good Opamps that have very high input impedance and very low output impedance, both are things you want to have when driving your amp.

            If you insist on building a passive attenuator (by the way it is not a passive preamp becuase it can't amplify only attenuate), non-inductive metal film resistors. They have the least effect on the input signal an induce less noise.

            Inactive hide details for Paul Stewart <musicman32150@...>Paul Stewart <musicman32150@...>


            To

            "Bill W (Sarge) Brown" <
            bill.w.brown@...>, Chris Paulson <akhilble@...>, DAC <dallasaudioclub@yahoogroups.com>, Danny Thia <danny.thai@...>, Dave Thomas <dave.thomas@...>, <hileman65@...>, <lee_roitberg@...>, Mark Childs <mdchilds@...>, "ryckebusch@..." <ryckebusch@...>, "texcurrier@..." <texcurrier@...>
            cc
            Subject

            passive preamp

            Today's subject is passive preamp designs. I have a couple of boxes of Dale 1% resistors. Not sure what is best or how many steps in the attinuator. Also, to reduce the noise while adjusting the volume.

            INPUT

            Time to work on the pool.



      • Paul Stewart
        Dam, it s in three different languages. Time to get in the parts box. Thanks Dave To: musicman32150@hotmail.com CC: akhilble@hotmail.com;
        Message 3 of 4 , Feb 27, 2011
          Dam, it's in three different languages. Time to get in the parts box.

          Thanks Dave



          To: musicman32150@...
          CC: akhilble@...; bill.w.brown@...; dallasaudioclub@yahoogroups.com; danny.thai@...; hileman65@...; lee_roitberg@...; mdchilds@...; ryckebusch@...; texcurrier@...
          From: dave.thomas@...
          Date: Sun, 27 Feb 2011 17:55:14 -0600
          Subject: [dallasaudioclub] Re: NON pasive preamp

          Here you go this has been built several dozen times by more people than I can count.

          (See attached file: OPAMP preamp.JPG)(See attached file: Opamp power supply.JPG)(See attached file: OPAMP Phono Preamp.JPG)

          Inactive hide details for Paul Stewart <musicman32150@...>Paul Stewart <musicman32150@...>


                  Paul Stewart <musicman32150@...>

                  02/27/2011 03:53 PM


          To

          "ryckebusch@..." <ryckebusch@...>, Dave Thomas <dave.thomas@...>

          cc

          Chris Paulson <akhilble@...>, "Bill W (Sarge) Brown" <bill.w.brown@...>, DAC <dallasaudioclub@yahoogroups.com>, Danny Thia <danny.thai@...>, <hileman65@...>, <lee_roitberg@...>, Mark Childs <mdchilds@...>, "texcurrier@..." <texcurrier@...>

          Subject

          NON pasive preamp

          OK, 0PA2134 is always a good choice. ESP makes some PCBs for a 2134 preamp. Does anyone know of a good design.

          I may need to add an RIAA board.




          Date: Sat, 26 Feb 2011 16:42:06 -0600
          Subject: Re: passive preamp
          From: ryckebusch@...
          To: Dave.Thomas@...
          CC: musicman32150@...; akhilble@...; bill.w.brown@...; dallasaudioclub@yahoogroups.com; danny.thai@...; hileman65@...; lee_roitberg@...; mdchilds@...; texcurrier@...

          I have to agree with Dave. If you use an OPA2134 (dual) and leep the input impedance matched or <2K you will be hard pressed to measure the distortion much less hear it.

          On Sat, Feb 26, 2011 at 2:11 PM, Dave Thomas <Dave.Thomas@...> wrote:
              Passive preamp is an oxymoron it is a passive attenuator. I would build an opamp preamp instead.

              passive stepped attenuators are more likely to increase the noise floor in your system than they are to have any audible reduction in distortion.

              An opamp preamp will have distortion less than .001% and can be considerably less if you are willing to fork over $4 for the a high end chip. Still well below even the most punch drunk audiophile's ability to hear distortion. Plus they can swing sufficient voltage to insure you drive your amp to its full potential and get all the dynamic range it can deliver.

              Passive preamps being better is a myth with zero merit. It is right up there with singing tibetan bowls.

              Saying all this there is nothing wrong with it as long as your source player has really low output impedance and sufficient voltage swing to accomodate any amplifier you hook up to it. Problem is most folks don't have a clue what the voltage swing on their source player is or the output impedance. And most manufacturers don't seem willing to tell you. A preamp will insure you don't have to worry.

              There are several very good Opamps that have very high input impedance and very low output impedance, both are things you want to have when driving your amp.

              If you insist on building a passive attenuator (by the way it is not a passive preamp becuase it can't amplify only attenuate), non-inductive metal film resistors. They have the least effect on the input signal an induce less noise.

              Inactive hide details for Paul Stewart <musicman32150@...>Paul Stewart <musicman32150@...>


              To

              "Bill W (Sarge) Brown" <
              bill.w.brown@...>, Chris Paulson <akhilble@...>, DAC <dallasaudioclub@yahoogroups.com>, Danny Thia <danny.thai@...>, Dave Thomas <dave.thomas@...>, <hileman65@...>, <lee_roitberg@...>, Mark Childs <mdchilds@...>, "ryckebusch@..." <ryckebusch@...>, "texcurrier@..." <texcurrier@...>
              cc
              Subject

              passive preamp

              Today's subject is passive preamp designs. I have a couple of boxes of Dale 1% resistors. Not sure what is best or how many steps in the attinuator. Also, to reduce the noise while adjusting the volume.

              INPUT

              Time to work on the pool.



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