[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.pdfAverage 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