Another Super High End Phono Stage! No expense spared...

Discussion in 'Turntables' started by Fasterdamnit, May 25, 2011.

  1. Fasterdamnit

    Fasterdamnit AK Subscriber

    We needed a nice, modern phono pre-amp for the shop- One that was not expensive but would really give high end performance. I like the KISS principle and picked the recommended circuit from the National Semiconductor datasheet using two LME49720 op amps.

    Two sockets, two chips, two 9V batteries, a switch, two 100uf power supply caps and a handful of .1% and 1% resistors with Panasonic poly caps on a ratshack board and this little preamp sounds VERY good! :music: Big Bill did most of the assembly. As with most bread board projects, it took a little troubleshooting to find the cause of one dead channel. But perseverance paid off!

    Just started listening and the acoustic performance is open, airy and very detailed. No heavy bass on this recording, so that will be checked later.

    For a total outlay under $40, I am quite pleased.

    Two more batteries and it can run at +18V/-18V.



    Build of materials link:


    Original schema/breadboard.…......01/010........Fasterdamnit
    Original Layout......….....03/033........HypnoToad
    Layout #2...............…..08/106........HypnoToad
    1st PCB......................12/174.........HypnoToad
    Tips #1................…....12/180.........HypnoToad
    Tips #2...............….....13/189.........HypnoToad
    CNC BOM.............….....13/193.........HypnoToad
    List of opamps........…...32/471.........shelly_d
    CNC schematic .jpg…....39/572.........ghazzer
    SSP BOM................…..51/762.........HypnoToad
    Omshira’s PCB layout.....52/775........Sachu888
    Last edited: Dec 27, 2011
  2. Big Bill

    Big Bill Summertime Rolls.....

    I cant wait to hear it for myself!
  3. shelly_d

    shelly_d Not An Audiophool

    I've seen that circuit in the App Note and wondered about it's performance. Thanks for sharing.

  4. HypnoToad

    HypnoToad Ms Puss Puss

    That's fantastic, I often wondered how that would sound as they have the same circuit for LM4562's.

    Oh and I just noticed you have a switch and proper battery connectors, that is indeed high end.

    Just a quick question, when the circuit says: 22nf//4.7nf//500pf is that all three in parallel?
  5. Fasterdamnit

    Fasterdamnit AK Subscriber

    Thanks HT!

    We will be running the 4562's and see what sounds best. While I was at the shack picking up the board I splurged on the connectors and switch. Pretty much broke the budget. ;)

    Yes, the caps go in parallel to arrive at the correct value. I had to ask that question, myself. Resistors with "+" in series.
  6. HypnoToad

    HypnoToad Ms Puss Puss

    Although a bit pricey, the AD823 is very nice and works well in battery powered circuits.

    I might even go all out and make a PCB of this circuit.
    Last edited: May 26, 2011
  7. Pio1980

    Pio1980 AK Member

    Passive RIAA and no coupling/blocking caps, this is an interesting mag phono stage.
  8. Fasterdamnit

    Fasterdamnit AK Subscriber

    Now that would be cool! I will post my fancy, shmancy, layout drawing once I get to the shop and snap a pic. Tip: use paper bigger than a small notepad...
  9. Fasterdamnit

    Fasterdamnit AK Subscriber

    That's what I thought, Steve. It is about as simple a circuit as I have seen for a phono pre amp. It will get some serious listening an we will report our findings.
  10. Fasterdamnit

    Fasterdamnit AK Subscriber

    OK- straight off the high resolution digital plotter...

    Note: It should say use a DPST or DPDT switch for power.

  11. kotofei

    kotofei permanent gear evolution

    Could we expect a Moving Coil version of this pre?
  12. quadtech

    quadtech New Member

  13. Fasterdamnit

    Fasterdamnit AK Subscriber

    If anyone has any idea I would be glad to try. :scratch2:

    I can assure you they are not. Put three LM4562's in a Hagerman Bugle and it is sharp, detailed and in your face. Fatiguing after a few songs. Put three LME49720's and the edginess and "in you face" presentation are gone. Same great detail and strong, crisp bass. Not fatiguing.

  14. HypnoToad

    HypnoToad Ms Puss Puss

    For a MC version you would have to add another gain stage at the start, using something like AD797's. Which are low noise at low impedance op amps, the only catch is you need two of them as they are single circuit.
  15. Pio1980

    Pio1980 AK Member

    I suggest avoiding ceramic caps altogether if possible unless they are audio grade, use polyprops or polystyrene instead.
  16. catman

    catman Banned

    G'day all, an interesting design. The general circuit looks rather similar to the 'two stage phono preamplifier' in the AN-346 application note for the LM833 dual op amp. Regards, Felix aka catman.
    Last edited: May 26, 2011
  17. Fasterdamnit

    Fasterdamnit AK Subscriber

    Good point. I had a hard time finding one in 500pf and 10pf values.

    Pic of a Sansui XR-Q9 awaiting repair of the auto functions being tested thru the pre. Uses a Sansui branded Ortofon FF15 cart with conical stylus.

    Last edited: May 26, 2011
  18. Fasterdamnit

    Fasterdamnit AK Subscriber

    Thanks, Felix. With the above mentioned Ortofon FF15 MM cart, it sounds quite good. Next week I hope we can do some critical listening and compare to a a couple of different Bugle pre amps and my modded AT PEQ3. I believe right now, it has better definition and clarity than the AT. Bass attack is better. For the cost, I highly recommend it as a first, budget conscious, phono pre amp. :music:
  19. ecluser

    ecluser New Member

    You can replace the 150 Ohms resistor on the (-) input of the first stage by a 15 Ohms resistor, this would give 20dB more gain on the first stage. You can adjust this resistor to the output of your MC cartridge.

    Replace the 47k resistor on the (+) input of the first stage by an appropriate loading resistor for the MC cartridge, say 100 Ohms to 1kOhms.
  20. catman

    catman Banned

    G'day all, this circuit is is interesting as I'm not sure where the bass eq network is :scratch2: Ok I see it now but my feeling is that it may need tweaking a little perhaps.

    My beloved ESP P06 also has no coupling capacitors directly between the two op amp stages, but the bass eq is done actively in the first op amp stage and the treble eq passively through the RC network off the output. This circuit is very interesting though. Regards, Felix aka catman.
    Last edited: May 26, 2011

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