2. analog
  3. 147043-80294

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

Showing 4 responses by ct0517

ct0517's avatar
ct0517
2,041 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.  
ct0517's avatar
ct0517
2,041 posts
 
I am not sure if locking of a thread is even an option. If Tammy Audiogon Support sees this maybe she can confirm either way.

Roger - the posters comments were along the lines of connecting the SG Cart up to his own personal preamp, first using the phono input, and then if I recall using the AUX input; with no mention of Peter's preamp. This is an incorrect setup. As I understand, Peter's unique preamp goes hand in hand with the SG Cart, cannot be separated. Based on my limited knowledge of them, his SG Cart and Preamp appear to be - "real thinking/ design out of the box". 
  
As far as how it is eq'ed, maybe you can get Peter to provide his input here since you have talked with him already, so we can have sharing and learning by all of us. That would add a lot of value for me. On a thread like this I am looking to learn. FWIW - I find the available online documentation for RIAA inconsistent, confusing, misleading, incorrect data .. no wonder, imo, it is difficult to grasp when we have experts like yourself contradicting words and terms we have read online..... trying to fill in the blanks. 
 
A definition of terms for important Words would help to fill in some blanks.   

Like for example - Constant Velocity, Constant Amplitude

ct0517's avatar
ct0517
2,041 posts
 
Hi Admin
Thanks for responding. 
Ramtubes (Roger) looks like there might be an option.
Anyway, as you are the OP - its your call. 
I would contact Admin by PM to decide its fate. 

ct0517's avatar
ct0517
2,041 posts
 
Great article imhififan.

Contains an excellent glossary, and what appears to be a complete definition of terms.
For my own benefit as a form of reference, I challenge those in the know, to tell us of any inaccuracies, incorrect data, misleading information, in that article.

*****************
For additional information.
A web page that I was familiar with in the past, from the IASA, these definitions relate to earlier 78’s, and the link contains an interesting table at the bottom. The table shows how varied the EQ’s were between companies, and just how limited in frequency the 78’s were.

A clear case of too many cooks in the kitchen ?

8^0

The control knobs on the preamps that allowed for setup of the different EQ’s must have been interesting.

https://www.iasa-web.org/tc04/mechanical-carriers-replay-equalisation



More to discover