I'm looking for an RC-based RIAA preemphasis circuit to apply RIAA equalization before vinyl cutting. This circuit is crucial for validating the theoretical accuracy of my phono amp design in simulations. Ideally, the output post-phono preamp should exhibit a flat response. While practical RC values aren't essential for simulation purposes, the circuit should accurately generate a Preemphasis RIAA curve.
This has schematics for DIY.
https://hagerman-audio-labs.myshopify.com/products/iriaa2-inverse-riaa-filter
https://hagerman-audio-labs.myshopify.com/products/iriaa2-inverse-riaa-filter
If it's just for simulations and if those simulations are in LTSpice, you could use a controlled source with a Laplace statement to make an exact RIAA pre-emphasis characteristic. RC networks are never exact, because their gain doesn't tend to infinity when frequency does.
Here is such an inverse RIAA source. It is a mathematically precise representation of the RIAA pre-emphasis curve. The parameter "n" normalizes the output level at 1 KHz to match the voltage specified for the signal source. For example, if you want the output at 1 KHz to be 5 mV, set the signal level to 5 mV.
The "Enhanced RIAA" curve includes the so-called Neumann 3.18 microsecond time constant, which was championed by Allen Wright and others but which is now largely discredited. I've included it in the model in case you are simulating a circuit which implements it. For more information, see the following link; the discussion begins on page 2 of the article.
https://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization
The "Enhanced RIAA" curve includes the so-called Neumann 3.18 microsecond time constant, which was championed by Allen Wright and others but which is now largely discredited. I've included it in the model in case you are simulating a circuit which implements it. For more information, see the following link; the discussion begins on page 2 of the article.
https://www.stereophile.com/features/cut_and_thrust_riaa_lp_equalization
See also https://en.m.wikipedia.org/wiki/RIAA_equalization under the header "The Mythical 'Neumann pole'".
I wrote some of that Wikipedia entry, after analyzing Wright’s actual words. He really didn’t have a clue. Made up the factoid about Neumann cutters completely; misread Lipshitz; didn’t know a pole from a zero (he didn’t use either term, but included a graph that clearly indicates a zero); and made the absurd suggestion that RIAA should have used a single time constant, like FM.
Last edited:
I suggest just doing the math (or letting a computer do the math). The RIAA curve is precisely defined mathematically.
The 5% tolerance capacitors in the inverse RIAA circuit above are worse than the pre-amp.
Ed
The 5% tolerance capacitors in the inverse RIAA circuit above are worse than the pre-amp.
Ed
The Stereophile piece has mislabeled X axis' on figures 7 and 8, but can be used with the labelling of figure 6.
These things always ignore a cartridge's inherent mechanical and geometric limitations, so have an element of angels dancing on heads of pins, but are fun to worry about.
All good fortune,
Chris
These things always ignore a cartridge's inherent mechanical and geometric limitations, so have an element of angels dancing on heads of pins, but are fun to worry about.
All good fortune,
Chris
Here's the network I've made, together with RIAA test harness:
The old APT-Holman preamp manual has an inverse RIAA circuit on page 52. It uses standard values and says accuracy is 0.1 db. You can easily find the manual by a search.
Ray
Ray
Hi,
here´s my old but reliabe, flexible and very precise inverse RIAA Network precise inverse RIAA
jauu
Calvin
here´s my old but reliabe, flexible and very precise inverse RIAA Network precise inverse RIAA
jauu
Calvin