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  #1  
Old 05-25-2011, 10:03 PM
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Fasterdamnit Fasterdamnit is offline
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Wink Another Super High End Phono Stage! No expense spared...

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

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..........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
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Last edited by Fasterdamnit; 12-27-2011 at 08:56 PM. Reason: LINKS
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Old 05-25-2011, 10:07 PM
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I cant wait to hear it for myself!
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Old 05-25-2011, 10:15 PM
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I've seen that circuit in the App Note and wondered about it's performance. Thanks for sharing.

Shelly_D
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Old 05-26-2011, 06:45 AM
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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?
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Old 05-26-2011, 07:24 AM
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Quote:
Originally Posted by HypnoToad View Post
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.
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Old 05-26-2011, 07:58 AM
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Quote:
Originally Posted by Fasterdamnit View Post
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.
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Last edited by HypnoToad; 05-26-2011 at 08:01 AM.
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Old 05-26-2011, 08:29 AM
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Passive RIAA and no coupling/blocking caps, this is an interesting mag phono stage.
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Old 05-26-2011, 08:36 AM
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Quote:
Originally Posted by HypnoToad View Post
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...
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Old 05-26-2011, 08:40 AM
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Quote:
Originally Posted by Pio1980 View Post
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.
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  #10  
Old 05-26-2011, 09:54 AM
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OK- straight off the high resolution digital plotter...

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

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Old 05-26-2011, 01:55 PM
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Could we expect a Moving Coil version of this pre?
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  #12  
Old 05-26-2011, 02:39 PM
quadtech quadtech is offline
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Quote:
Originally Posted by HypnoToad View Post
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
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  #13  
Old 05-26-2011, 03:17 PM
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Quote:
Originally Posted by kotofei View Post
Could we expect a Moving Coil version of this pre?
Well,
If anyone has any idea I would be glad to try.

Quote:
Originally Posted by quadtech View Post
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.

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Rek-O-'Crylic, Twin Akito's, Ortofon MC20 Super, Artemis PH-1
Nakamichi RX-202 & CD Player2
Otari MX-5050
Pioneer Elite VSX-39TX, Martin Logan Aerius
Denon DP59L, DL-304
Super Cheap CNC Phono preamp- Build your own!
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  #14  
Old 05-26-2011, 04:17 PM
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Quote:
Originally Posted by kotofei View Post
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.
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  #15  
Old 05-26-2011, 07:06 PM
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I suggest avoiding ceramic caps altogether if possible unless they are audio grade, use polyprops or polystyrene instead.
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