Just another RIAA......

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Chris

Chris

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Joined 2001
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.
 

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Cobra2

Cobra2

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RIAA...

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


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
 

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Chris

Chris

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peranders said:


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.
Click to expand...


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

peranders

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sjostromaudio.com
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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?
 
peranders

peranders

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:up: Does it work yet?

Arne, do you have DC-servo PLUS capacitor? Either one fat mama or DC-servo. Check carefully how you choose between "Linear Tech original" and "P-A original" feedback network.Check here and the part about DC-servo.

Note also parts for optional compensation.

We had a diy party when we used my monster QSXM2 together with a homemade TT with tangential arm. Look at the painting of the TT! I thought it was plastic imitation. :cannotbe:

We hadn't time to REALLY listen to the amp or TT but it didn't sound bad anyway. The power came from two norwegian Mascot lab PS, not very high tech.

http://www.hififorum.nu/topic.asp?TOPIC_ID=14408
 
EC8010

EC8010

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Joined 2003
Chris said:
The sound is nice. Good soundstage, relaxed but dynamic..
However it has a somewhat enhanced s-sound.
Click to expand...

The Ortofon OM10 is a bit sibilant, that's almost certainly the cause of your "enhanced s-sound." I had an OM10 in an SME3009 S2, and had the same problem, so I changed the stylus for an OM30 stylus (the bodies are identical), and the problem went away.
 
Cobra2

Cobra2

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Re: QSXM3

And it also sounds great ! Now, I need to find a home for it (chassi).
A little gain-adjustment 100ohm -> 75ohm was what I needed.
All components are matched, even had to order another 10 of the RIAA caps for getting a match...

Arne K
 

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