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RIAA, Questions only please

I have closed the previous thread on RIAA and concluded that very few indeed understand the curves or the purpose. Here is my closing statement from that thread. For those who want to understand and have valid well stated questions I am happy to answer. 

Not wanting to leave the party without a clear and accurate statement I will say the following:

The answer to the question concerning noise reduction is that the simple filter that RIAA decided upon was to raise the high frequencies gradually by about 12 dB starting below 500 Hz, being up 3 dB at the 500 Hz pole. The circuit then cancells the pole with a zero at 2,200 Hz and there is then 3 dB of boosting left as one goes to 20 Khz. It is all done very gently with just two resistors and two capacitors.

By reversing this process on playback we get to enjoy 12 dB less noise above 500 Hz.

The RIAA part of things is the same for all cartridges. However we are accustomed to seeing RIAA combined with the 6 dB/octave compensation for a velocity cartridge. That takes off 12 dB, and along with two things that happen at the very ends of the response, brings the total EQ for a velocity cartridge to 40 dB. Next time you look at an RIAA curve ask yourself why there is that flat bench between 500 and 2,200 Hz.

An amplitude cartridge needs only the RIAA EQ of 12 dB. Which also speaks to the fact that the majority of the spectrum of a record is cut at constant amplitude. When you put a sewing needle in a paper cup and play the record you are getting amplitude playback not velocity.

I study these things because they interest me. Anyone can look up the parts values to make an RIAA filter or inverse RIAA. What interests me is that some manufacturers still get it wrong.

128x128ramtubes
uberwaltz's avatar
uberwaltz
13,381 posts
 
I do hate to say so but I tend to agree with Mental and Almarg.
You truly cannot create a thread that has an obviously contentious topic and then get upset because there are a lot of opposing views and posts.
I am still not sure how much I actually learned from the last go round ( bar the fact that put 10 audiophiles in the same room and you are likely to get 10 different opinions!).
However it did contain some potential useful knowledge but deletion was not the answer imho.
Post removed 
atmasphere's avatar
atmasphere
11,577 posts
 
Actually it wasn’t Roger who asserted that. I stated that based on what was said in the following writeup:
@almarg@ramtubes

Thanks Al for that correction. My apologies Roger on this mistake.
ramtubes's avatar
ramtubes OP
460 posts
 
@test It's too bad that the previous thread is now locked as it contained a lot of insightful and useful information. I personally get more from a discussion than I do from a lecture.  

The problem with the previous thread is that is that the behavior was not polite nor was a lot of the information correct. Many of the responses were unclear as to what the participant wanted to know.

Did you learn that RIAA EQ is a 12 db boost on recording and a complementary cut on playback?

Did you learn that the 40 dB curve we are accustomed to seeing is RIAA plus magnetic cartridge EQ?
ramtubes's avatar
ramtubes OP
460 posts
 
@cleeds  I agree. I followed the thread closely, even though I never commented in it. It's unfortunate that now no one can follow that discussion.

I am glad you were following the thread. I am happy to keep it going here if we can get on track and stay there. I would like to see more participation from those who agree with my assessment of RIAA. All I was getting is unsupported disagreement no matter what references I cited, graphs I linked or logic I employed.

I decided that if Ralph wanted to have his own discussion about RIAA he could most easily start his own post. It is clear we will not agree anytime soon.
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