And for reference: the parameters for Koren's ELAPLACE (PSpice) network, hard to copy from his figures, are:
ELAPLACE
EXPR = V(%IN+, %IN-)
XFORM = 0.001*(1+T3*s)*(1+T1*s)/(1+T2*s)
T1 = {3180e-6}
T2 = {318e-6}
T3 = {75e-6}
ELAPLACE
EXPR = V(%IN+, %IN-)
XFORM = 0.001*(1+T3*s)*(1+T1*s)/(1+T2*s)
T1 = {3180e-6}
T2 = {318e-6}
T3 = {75e-6}
Hi Scott, I've just found this old comment of yours. Great idea (to be able to switch on or off, Allen Wright's 50kHz boost) ... but do you have to be careful how you arrange the wires from the switch to the RIAA network? If you simply twist together the wires - is that OK?
Thanks,
Andy
Has anybody ever tested the RIAA accuracy of common record lathes? I would not be shocked to see fairly gross errors.
I would be shocked if a stock Neumann or Scully had anywhere near 1dB error 50Hz-15KHz.
Most high-class cutting facilities are further tweaked so the total response (not just the lathe) is as the engineer wishes.
There are "simple precise" ways to calibrate a cut independent of the pickup's foibles. One elegant way is to cut a series of high tones, and then shine a light at an angle. Typically this gives a "wedge" reflection, and the straightness of the reflection edges IS the cutter's response at the groove.
My comment was for doing it digitally with an FIR or IIR filter. Any shorting of the wires should be OK, BTW the effect of this extra time constant is very small in any case.
I don't think FIR would be a good choice. On RIAA decode you are adding a lot of low end. I would expect the pre ringing to be audible.
No need to keep reposting 🙂
As a new poster all your posts are moderated which means they have to be read and approved.
As a new poster all your posts are moderated which means they have to be read and approved.
You can create a minimum phase FIR RIAA that has virtually no pre-ringing. In any case the pre-ringing is not at a low frequency. BTW Audacity has only a linear phase FIR which has substantial deviation from ideal and no one seems to notice.
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All the FIR filters i have run into are linear phase. I thought linear phase was inherent to FIR as minimum phase was inherent to IIR.
Not true How to Design Minimum-Phase FIR Filters - dspGuru
I published a trick in Linear Audio for RIAA that works pretty nicely.
Well I couldn’t get past the first few sentences but a guess a lot of trickery is involved. I think I am correct in that an FIR filter is naturally linear phase.
Here is what Neumann claimed in 1973:
15Hz...16000Hz +/-0.5dB
For 1973, half-dB accuracy was pretty good stuff.
I have seen the electronics of later cutting amps. They are very precise equalizers with parts selected to 1% precision (0.08dB).
Attachments
The SX-74 is very linear. The secondary self resonance is at about 16k. It will be very linear up to there.
PRR asked me about the RIAA circuits. I had asked him not to post the schematic because of the religious nature of some concerning vinyl. I am a cutter by profession and some mystery to the unwashed is helpful. This seems like calm technical bunch. So here goes.
The link is to the later SE66 IC based RIAA encode module. There is an earlier discreet version. This is from the earlier VG66 amplifier rack.The later SAL74 amplifier rack is vastly more common. It was introduced in 1974.
Neumann SE66 - Pro Audio Design Forum
PRR asked me about the RIAA circuits. I had asked him not to post the schematic because of the religious nature of some concerning vinyl. I am a cutter by profession and some mystery to the unwashed is helpful. This seems like calm technical bunch. So here goes.
The link is to the later SE66 IC based RIAA encode module. There is an earlier discreet version. This is from the earlier VG66 amplifier rack.The later SAL74 amplifier rack is vastly more common. It was introduced in 1974.
Neumann SE66 - Pro Audio Design Forum
Very interesting, a 35kHz "Neumann" 2nd order Sallen and Key low pass after the premphasis circuit. Those 709s must have been suffering if there was HF content on the tape.
That is called the Buchmann and Meyer light pattern method. Most of the important papers on disc recording pre date the AES and were published by the Acoustical Society of America in the U.S. The book “Disc Recording and Playback” Edited by H.E. Roys holds all the secrets. The AES compendiums should be subtitled “ weird, wacky and esoteric papers on disc recording and playback. The Roys book has the good stuff.
I know this is OT but what are some practical reasons you would want to use an FIR minimum phase filter instead of a plain old IIR?
Not particularly but an accurate IIR for RIAA requires a little trickery itself at low sampling rates especially if you are trying to bother with the 50k time constant. In this world people tend to obsess over mathematical perfection. It has all appeared here over the years in several threads.
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