Systemic Development > Amplification and Preamplification
RIAA Inaccuracies
steve:
Hi Gents,
I finally found the AES article covering RIAA equalization by Stanley Lipshitz I lost many moons ago. According to the article, there is a problem with correct RIAA equalization design in some/many phono stages. (I am wondering about recording as well.)
No need for math etc, the introduction and references 1-18 at the end of the article give a sense of the scope of the problem. Granted the article is from 1976, but who knows who is really following the true RIAA curve?
https://forums.melaudia.net/attachment.php?aid=1301
Interestingly, the computer program I used for designing the RIAA in my test phono stage was up to 0,7 db off in the highs and 0,3 db off in the bass. After correcting the problem, what a sonic improvement. Of course I had to reset the TT tracking, rake angle, and anti skate.
For those who diy, here is a website whose calculator is based on Stanley's design equations.
http://www.mh-audio.nl/Calculators/CalculateRIAA.html
cheers
steve
P.I.:
--- Quote from: steve on January 21, 2022, 01:31:13 PM ---Hi Gents,
I finally found the AES article covering RIAA equalization by Stanley Lipshitz I lost many moons ago. According to the article, there is a problem with correct RIAA equalization design in some/many phono stages. (I am wondering about recording as well.)
No need for math etc, the introduction and references 1-18 at the end of the article give a sense of the scope of the problem. Granted the article is from 1976, but who knows who is really following the true RIAA curve?
https://forums.melaudia.net/attachment.php?aid=1301
Interestingly, the computer program I used for designing the RIAA in my test phono stage was up to 0,7 db off in the highs and 0,3 db off in the bass. After correcting the problem, what an sonic improvement. Of course I had to reset the TT tracking, rake angle, and anti skate.
For those who diy, here is a website whose calculator is based on Stanley's design equations.
http://www.mh-audio.nl/Calculators/CalculateRIAA.html
cheers
steve
--- End quote ---
The my-audio.nl site is a great resource for all kinds of things audio!
_Scotty_:
Even if the designers math is right when calculating the parts values used in their phono stage,
parts tolerances can ruin the RIAA accuracy. Every single resistor and capacitor used
in the network has to be measured and matched if errors are to be minimized.
How often does anyone think that happens in a phono stage that is not custom made.
Tolerance stacking is a problem in many fields of endeavor including our hobby.
In some cases it can actually lead to products that are unsafe to operate.
Scotty
P.I.:
--- Quote from: _Scotty_ on January 21, 2022, 08:14:30 PM ---Even if the designers math is right when calculating the parts values used in their phono stage,
parts tolerances can ruin the RIAA accuracy. Every single resistor and capacitor used
in the network has to be measured and matched if errors are to be minimized.
How often does anyone think that happens in a phono stage that is not custom made.
Tolerance stacking is a problem in many fields of endeavor including our hobby.
In some cases it can actually lead to products that are unsafe to operate.
Scotty
--- End quote ---
Exactly and precisely (redundant?) said. For critical applications, even when it comes to power amps where tolerances "could be" wider, it is essential to match within at least 1%.
I have found this to be true even with loudspeakers. Details, details, details: the quest for excellence!
HAL:
A straight gain cartridge preamp and DSP RIAA EQ work well here. As accurate as the RIAA math for both channels.
Had my DSA Phono One preamp moded for flat gain to drive the stereo ADC.
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