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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
clio09
3,362 posts
 
@ramtubes, let the other thread stay dead and if this one keeps going the way it is kill it too.

@ramtubes thinks that he discovered the " black thread " with those 12 dbs and said that manufacturers not understand it.

@rauliruegas: I don’t think Roger ever said he discovered the black thread as you say, and it was pretty obvious in the last thread that many disagreed with his theory anyway.

However it does appear that perhaps Roger and Peter Ledermann agree, so there’s that at least. It would be nice if Peter Ledermann joined the conversation as it would be interesting to hear his thoughts and add another expert to the conversation bringing the total to 3 in my opinion.

It’s really hard sifting through some of this stuff (as it was in the last thread) to get to the posts of two (or three) people whose posts you want to read. I wish Audiogon would let me filter out the "noise" so I can just read what I need.
solypsa's avatar
solypsa
462 posts
 
I'm interested in vinyl replay. If this thrread is to be useful, imo, the purpose of the discussion needs to be better defined.

Is it theoretical? A discussion on why what was decided 70 yrs ago was?
Is it to better replay technology and implementation? If so stating some areas of focus will be required (such as cartridge design,  phono eq design etc)
Is it to commiserate on how tricky this all is?
ramtubes's avatar
ramtubes OP
460 posts
 
Here is something to consider. What if we didnt use RIAA or any EQ in making a record. If we recorded a constant voltage sweep from 20 to 20Khz and looked at it under a microscope what might we see? When we played the final product what would a voltmeter connected to the speaker (or elsewhere) indicate from 20 to 20 KHz.

Choose your cutter wisely and state if it is amplitude or Velocity. Even better do both.
uberwaltz's avatar
uberwaltz
13,381 posts
 
Clio
That is somewhat pretentious don't you think?
Who gave you the right to decide there were only 2 or 3 "experts" whose opinions are all that is valid here?
Your opinion maybe but still as has been stated many times this is a free forum and ALL opinions are welcome as long as they remain within the posting guidelines of this forum.
Whether you like them or not or agree with them is completely irrelevant.
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Audiogon Official
@ct0517 The thread was closed by the author. 
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