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

[Fasterdamnit]

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! 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:

http://www.audiokarma.org/forums/sho...&postcount=193

Credits:

..........Item.................pg./.post.........member

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

[Big Bill]

I cant wait to hear it for myself!

[shelly_d]

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

Shelly_D

[HypnoToad]

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?

[Fasterdamnit]

Originally Posted by HypnoToad

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?

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.

[HypnoToad]

Originally Posted by Fasterdamnit

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.

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.

[Pio1980]

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

[Fasterdamnit]

Originally Posted by HypnoToad

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.

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...

[Fasterdamnit]

Originally Posted by Pio1980

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

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.

[Fasterdamnit]

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

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

[kotofei]

Could we expect a Moving Coil version of this pre?

[quadtech]

Originally Posted by HypnoToad

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

There has always been speculation that the LM4562 and the LME49720 are
the same chip.

http://www.diyaudio.com/forums/chip-...vs-lm4562.html

[Fasterdamnit]

Originally Posted by kotofei

Could we expect a Moving Coil version of this pre?

Well,
If anyone has any idea I would be glad to try.

Originally Posted by quadtech

There has always been speculation that the LM4562 and the LME49720 are
the same chip.

http://www.diyaudio.com/forums/chip-...vs-lm4562.html

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.

[HypnoToad]

Originally Posted by kotofei

Could we expect a Moving Coil version of this pre?

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.

[Pio1980]

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