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Improving a Pro-Ject Phono Box SE

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  • Improving a Pro-Ject Phono Box SE


    not quite satisfied with the sound of my Pro-Ject Phono Box SE preamp, I started to improve it and would like to have your opinion about what I have done and what can still be improved.

    This preamp is dual mono with 3 op amps per channel. It works between a Pro-Ject 1-Xpression turntable (with 2M blue cartridge) and a Nad C326BEE amp.

    I started by replacing some PSU capacitors.
    Then I swaped the four NJM 4580 op amps for dual OPA 627, and the two TL071 for AD797 (replacing these two was a HUGE improvement).

    I don't have the doc, so I tried to draw it but as I am not very experimented with electronics I coudn't quite understand the circuit. Here it is anyway, I'm very sorry if it is badly drawn and incomplet, this is all I managed to track with my eyes and my multimeter...

    Power Supply stage :

    RIAA Preamp stage :

    Is there anything obvious you see that could be done to improve it further?
    Or is it a bad architecture and I should directly buy something more serious?
    I'm thinking maybe going to a tube preamp like the Yaqin MS-23B or the Douk audio Little Bear.

    Thanks anyway for your help.

  • #2

    Welcome to the Haven! That is quite an ambitious project you have taken on. Not an electronics expert so I don't have any technical advice. However, I would suggest trying a phono stage with an all tube audio path. You will typically pay more for a unit with no opamps but to my ears, it's worth it. Good Luck!


    • #3
      ... or a good solid state phono preamp.
      I use one (JLTI) and I am pretty darned happy with it.
      The tube preamps I have here (i.e., the ones I can afford) are all a little sub-optimal) for one reason or another.


      • #4
        You could replace the wallwart power supply. I recently did that with an iFi iPhono2, with an sBooster linear power supply, and the difference was not subtle. But the price was not subtle, either...and would likely cost as much as the pre itself. It quickly becomes a "just start with more potential" situation, but I've not heard this phono stage in a long time.


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