Author Topic: RIAA Inaccuracies  (Read 1216 times)

Offline steve

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RIAA Inaccuracies
« 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 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
« Last Edit: January 23, 2022, 10:23:16 PM by steve »
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Offline P.I.

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Re: RIAA Accuracy
« Reply #1 on: January 21, 2022, 06:50:41 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
The my-audio.nl site is a great resource for all kinds of things audio!
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Offline _Scotty_

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Re: RIAA Accuracy
« Reply #2 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

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Re: RIAA Accuracy
« Reply #3 on: January 21, 2022, 10:37:04 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
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!
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Offline HAL

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Re: RIAA Accuracy
« Reply #4 on: January 22, 2022, 09:03:29 AM »
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. 

Offline tmazz

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Re: RIAA Accuracy
« Reply #5 on: January 22, 2022, 09:58:37 AM »
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

And the problem even goes further than that. the tolerance rating n a resistor is a tolerance across the lifetime of the piece. it is not uncommon for a resistor to shift value over time. A 1% resistor is rated to be no more than 10% away from its rated value at all times. but this means that it could be 10% when it is brand new and end up at -10% as it aged, meaning it can have a 20% swing over time and still be within it's rated specs. Of course you would not use 10% resistors if you were building a precision phono stage, but just the same, no matter how high precision resistors you use they can all shift over time and not necessarily in the same direction. This was a very big problem with some of the early CD players when resistor value shifts in the servo feedback curcuits caused big problems with CD players starting to mistrack.

So as close as you get it to the curve when it is built, resistor value shifts can easily get it out of spec over time. How audible will this be, who knows, but my point is if you are trying to get a perfect match to the RIAA curve it is very difficult to do (and maintain over time) in the analog realm.
Remember, it's all about the music........

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Offline P.I.

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Re: RIAA Accuracy
« Reply #6 on: January 22, 2022, 02:33:05 PM »
[quote author=tmazz link=topic=8387.msg103763#msg103763 date=1642874317
And the problem even goes further than that. the tolerance rating n a resistor is a tolerance across the lifetime of the piece. it is not uncommon for a resistor to shift value over time. A 1% resistor is rated to be no more than 10% away from its rated value at all times. but this means that it could be 10% when it is brand new and end up at -10% as it aged, meaning it can have a 20% swing over time and still be within it's rated specs. Of course you would not use 10% resistors if you were building a precision phono stage, but just the same, no matter how high precision resistors you use they can all shift over time and not necessarily in the same direction. This was a very big problem with some of the early CD players when resistor value shifts in the servo feedback curcuits caused big problems with CD players starting to mistrack.

So as close as you get it to the curve when it is built, resistor value shifts can easily get it out of spec over time. How audible will this be, who knows, but my point is if you are trying to get a perfect match to the RIAA curve it is very difficult to do (and maintain over time) in the analog realm.
[/quote]

That is why you buy stupidly expensive resistors from these guys:

http://texascomponents.com/pdf/tx2575.pdf

Average price is ~ $16.00 each.

Since preamps with inverse RIAA networks average between 14-22 resistors, if your goal is perfect(as near to as possible) the cost of the resistors is acceptable given the cost of most phono stages, I would think.
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Offline tmazz

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Re: RIAA Accuracy
« Reply #7 on: January 22, 2022, 07:07:53 PM »
Dave actually I think the best solution is to just get it as close as you can and once it sounds good stop stressing over how close it measures on paper and just sit back and enjoy the music.
Remember, it's all about the music........

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Offline P.I.

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Re: RIAA Accuracy
« Reply #8 on: January 22, 2022, 09:13:39 PM »
Dave actually I think the best solution is to just get it as close as you can and once it sounds good stop stressing over how close it measures on paper and just sit back and enjoy the music.
Well, there's that!   :thumb:
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Offline steve

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Re: RIAA Accuracy
« Reply #9 on: January 23, 2022, 07:06:49 PM »
[quote author=tmazz link=topic=8387.msg103763#msg103763 date=1642874317
And the problem even goes further than that. the tolerance rating n a resistor is a tolerance across the lifetime of the piece. it is not uncommon for a resistor to shift value over time. A 1% resistor is rated to be no more than 10% away from its rated value at all times. but this means that it could be 10% when it is brand new and end up at -10% as it aged, meaning it can have a 20% swing over time and still be within it's rated specs. Of course you would not use 10% resistors if you were building a precision phono stage, but just the same, no matter how high precision resistors you use they can all shift over time and not necessarily in the same direction. This was a very big problem with some of the early CD players when resistor value shifts in the servo feedback curcuits caused big problems with CD players starting to mistrack.

So as close as you get it to the curve when it is built, resistor value shifts can easily get it out of spec over time. How audible will this be, who knows, but my point is if you are trying to get a perfect match to the RIAA curve it is very difficult to do (and maintain over time) in the analog realm.

That is why you buy stupidly expensive resistors from these guys:

http://texascomponents.com/pdf/tx2575.pdf

Average price is ~ $16.00 each.

Since preamps with inverse RIAA networks average between 14-22 resistors, if your goal is perfect(as near to as possible) the cost of the resistors is acceptable given the cost of most phono stages, I would think.
[/quote][/quote]



To whom it concerns.

I started this string to help the public maximize their LP experience, to help diyers, but what is with the negative comments. Why hate accuracy and resistors while exhorting expensive NOS tubes and capacitors costing hundreds of dollars, sometimes for each tube and capacitor? No one has to spend big bucks in the phono design to obtain the correct RIAA part values. So what is it to you guys what we do?

To the general public.

I checked the link (PI's post) and compared the passive capacitor values to Stanley's, and the discrepancy was 8.5%, the same or more error than my computer program. That is a whopping 0,7% db off the RIAA standard and clearly perceivable because a discrepancy exists over many octaves (similar to preamplifiers and amplifiers), affecting the music in virtually every category from bass through treble.
So why dice accurate RIAA design?

(The link I listed in my initial post provides resistor values to obtain very very close to optimum values using Stanley's Lipshitz's equations. It does not cost any more if one does not wish to spend more.)

In response, a measurement is not just a spec on paper, as the RIAA audio response curvature across the entire audio band changes, degrading the natural music in virtually all ways. Why purchase expensive capacitors just to have the sound degraded due to improper RIAA response? It does not make sense.

For Tom, are you stating that a 1% tolerance resistor's ohmage changes 10% of the 1% tolerance over time, or that a 1% tolerance resistor changes 10% of its total ohmage over time?

If changing 10% of 1% of a 10K resistor, the change would only be 10 ohms, which would result in a very minor RIAA db change, in the low milli dbs (thousandths of 1 db). 

In my own, 25 year old test phono stage, the parts stayed extremely accurate. I did recently change the value of the parts when I used the calculator based on Stanley Lipshitz's equations. The music is clearly better. (pun intended)

I started the string so as to help the public, to ask questions when purchasing, and diyers to obtain the most from their designs. Why settle for less when one can have more?

cheers

steve
« Last Edit: January 24, 2022, 08:54:28 AM by steve »
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Offline P.I.

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Re: RIAA Accuracy
« Reply #10 on: January 23, 2022, 07:18:35 PM »
No.

The link is to naked resistors with tolerances as close as 0.001% with TCR of 1ppm.

Are you sure you went to the right site?
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Offline steve

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Re: RIAA Accuracy
« Reply #11 on: January 23, 2022, 07:55:03 PM »
No.

The link is to naked resistors with tolerances as close as 0.001% with TCR of 1ppm.

Are you sure you went to the right site?

I went to your link. I also edited my previous post. Again, are you claiming a 1% resistor changes 10% of its total resistance over time, or 10% of the 1% tolerance over time? I thought about purchasing super tight tolerant resistors, but I don't play the TT that often. The RIAA is extremely accurate.

One does not have to purchase naked, expensive resistors to be RIAA accurate.

Cheers

steve
« Last Edit: January 23, 2022, 10:13:54 PM by steve »
Steve Sammet (Owner, Designer, Electron Eng, SAS Audio Labs, Ret)
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Offline steve

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Re: RIAA Accuracy
« Reply #12 on: January 23, 2022, 08:06:43 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

It is called trimming, to obtain accuracy. Resistors change virtually zero, at least in my designs. Yes, one measures each part and matches, which is not your run of the mill phono section. So we should also not? But then many purchase expensive tubes and capacitors, for what purpose. In a passive design, there is minimal tolerance stacking. My designs stayed tight tolerance for 2 decades or longer, until I adjusted using Stanley's designs.

Maybe, just maybe, some of us like higher quality.

cheers
steve
« Last Edit: January 23, 2022, 10:18:31 PM by steve »
Steve Sammet (Owner, Designer, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Accutex 320 iii STR Mov Iron Cart
SAS 11A Perfect Tube Preamp
SAS 25 W Reference Triode/UL Monoblocks
2 way Floor standing Test Speakers

Offline P.I.

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Re: RIAA Accuracy
« Reply #13 on: January 23, 2022, 10:30:22 PM »
No.

The link is to naked resistors with tolerances as close as 0.001% with TCR of 1ppm.

Are you sure you went to the right site?

I went to your link. I also edited my previous post. Again, are you claiming a 1% resistor changes 10% of its total resistance over time, or 10% of the 1% tolerance over time? I thought about purchasing super tight tolerant resistors, but I don't play the TT that often. The RIAA is extremely accurate.

One does not have to purchase naked, expensive resistors to be RIAA accurate.

Cheers

steve
Steve, at no time did I ever claim ANY percentage changes over time.  That was Tom's point.  For whatever reason, my response was not broken out from his.

I can tell you this:  in the long in the tooth dB Audio Labs DAC, changing the I/V resistor and a couple of others in that DAC made profound improvements in SQ.  A very much modified version of that DAC is one of the 3 that I rely upon. NOS DACs for Redbook (the only format I use), when done right, are my overwhelming choice for musical ENJOYMENT.  I'm not a 'more data' freak.  But that is a totally different discussion.  Perhaps I'll create a thread on "What, to you, comprises a musical DAC?"
« Last Edit: January 24, 2022, 08:36:14 AM by P.I. »
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Offline steve

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Re: RIAA Accuracy
« Reply #14 on: January 24, 2022, 08:01:27 AM »
No.

The link is to naked resistors with tolerances as close as 0.001% with TCR of 1ppm.

Are you sure you went to the right site?

I went to your link. I also edited my previous post. Again, are you claiming a 1% resistor changes 10% of its total resistance over time, or 10% of the 1% tolerance over time? I thought about purchasing super tight tolerant resistors, but I don't play the TT that often. The RIAA is extremely accurate.

One does not have to purchase naked, expensive resistors to be RIAA accurate.

Cheers

steve
Steve, at no time did I ever claim ANY percentage changes over time.  That was Tom's point.  For whatever reason, my response was not broken out from his.

I can tell you this:  in the long in the tooth dB Audio Labs DAC, changing the I/V resistor and a couple of others in that DAC made profound improvements in SQ.  A very much modified version of that DAC is one of the 3 that I rely upon. NOS DACs for Redbook (the only format I use), when done right, are my overwhelming choice for musical ENJOYMENT.  I'm not a 'more data' freak.  But that is a totally different discussion.  Perhaps I'll create a thread on "What, to you, comprises a musical DAC?"

I noticed that quoting seems to be messed up a bit. That was Tom's point; I understand and will alter my previous post to Tom mentioning it, not you.

In general, I do support custom manufacturers, I was one myself, as I think many advances come from our segment of the industry. Large manufacturers do have a role to contribute as expensive improvements, such as cone materials require a substantial investment.

Looks like this thread has run its course. I hope that the information has been useful.

cheers

steve

« Last Edit: January 24, 2022, 08:05:38 AM by steve »
Steve Sammet (Owner, Designer, Electron Eng, SAS Audio Labs, Ret)
SAS "V" 39pf/m 6N copper ICs,
SAS Test Phono Stage
Accutex 320 iii STR Mov Iron Cart
SAS 11A Perfect Tube Preamp
SAS 25 W Reference Triode/UL Monoblocks
2 way Floor standing Test Speakers