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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
ramtubes's avatar
ramtubes OP
451 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
451 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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gdnrbob
2,421 posts
 
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.

As others have pointed out, a forum is for discussion.
As for :
behavior was not polite nor was a lot of the information correct
I, for one, found none of the responses to be such-Actually, quite to the contrary.
In fact, the only 'impolite' responses seem to be coming from you.
B
ramtubes's avatar
ramtubes OP
451 posts
 
At this rate I doubt this post will last long. We are already off topic. 

Sorry if you miss the old post. Several members posted such long and confucing replies I could hardly get through them myself. 

I have nothing to gain here. Im not going to win a prize if I am correct. I chose this topic because vinyl is on a comeback, our local club is about 50% vinyl, we have phono preamp "shootouts" which take a great deal of time and effort to set up. We want to know first if we are listening to a preamp with more than a few dB of RIAA error, so I check for that as I am matching levels.

Wouldn't it be nice to know what RIAA is? Is there anyone here who would like to have a go at explaining RIAA to me. I am all ears.

I had a nice half hour conversation with Peter Ledermann of Soundsmith today. We agreed this is a difficult concept to grasp.
ct0517's avatar
ct0517
1,798 posts
 
^^^
Roger
I contacted Peter myself by email, this week,  for clarification on his SG cartridge and unique preamp. I did this because there was incorrect info posted on your other thread about his product. He confirmed some things for me. I was going to publish corrections but your thread was deleted .....not locked. Locked would have allowed viewing without input.  
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