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-   -   Just another RIAA...... (http://www.diyaudio.com/forums/analogue-source/9461-just-another-riaa.html)

Chris 4th January 2003 07:29 PM

Just another RIAA......
 
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Some time ago I posted a thread where I asked if anybody had any opamp based riaa design to recomend. I got a few answers and paulb gave me the following webadress:

http://www.national.com/an/AN/AN-346.pdf

I decided to use the design described in this application note. This design is a two stage riaa phono preamplifier.
Currently I use BB opa 37 in the first gainstge an BB opa 606 in the second gainstage. The result is shown in the following pictures.

Chris 4th January 2003 07:30 PM

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Another picture,.....:)

Chris 4th January 2003 07:31 PM

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Last one .......

mlloyd1 4th January 2003 09:58 PM

Looks nice; great job! How do you like the sound?
mlloyd1

Chris 4th January 2003 11:22 PM

The sound is nice. Good soundstage, relaxed but dynamic..
However it has a somewhat enhanced s-sound. I wonder why ?:confused:

Cobra2 5th January 2003 12:07 AM

RIAA...
 
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Quote:

However it has a somewhat enhanced s-sound. I wonder why ?

Did you try other op-amps? Or (DC-blocking) caps?

I have just finished off another "Bugle", running it in now, and it sounds fine w. RIFA caps & AD825 op-amps in and out, and a "cost-saving" OPA2134 inbetween.

Arne K
NORWAY

Chris 5th January 2003 12:20 AM

Hi Cobra2

I`m not using any DC blocking caps. There is no DC at the outputs.

Could it be the load capacitance ? :rolleyes:

peranders 5th January 2003 08:09 AM

Quote:

Originally posted by Chris
The sound is nice. Good soundstage, relaxed but dynamic..
However it has a somewhat enhanced s-sound. I wonder why ?:confused:

Have you been able to eliminate the vinyl itself? Is it the new amp or is it the LP?

Have you checked the input capacitance? Maybe you need a trim? Some pickups needs up to 400 pF.

Chris 5th January 2003 10:53 AM

Quote:

Originally posted by peranders


Have you been able to eliminate the vinyl itself? Is it the new amp or is it the LP?

Have you checked the input capacitance? Maybe you need a trim? Some pickups needs up to 400 pF.


Hi :)

The pickup i use (ortofon om 10) should be loaded with about 100 - 200pF. I have tried both values with no real improvment IMHO. Currently I have no load capacitance and it`s better I think.
Could it be that the cable I use introduce enough capacitance ?

peranders 5th January 2003 05:27 PM

Normal TT cable has approx. 100 pF per meter and must of course be included.

If you connect the TT to an another RIAA amp, do you get the same S-sounds?

I salute you also to your achievement (I can feel the joy you feel) but unfortunately your wiring doesn't get any high score. NEMKO had :no: their heads. Think tidyness. Separate 230 volts from the rest. NO unisolated parts!

Which circiut have you built? The last one in the application note?


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