Digital Software RIAA EQ for Vinyl

I guess I will answer my own question....

Based on researching other forums, talking to various people etc... I tracked down 3 options.. (hope this helps the next persons trying to find his/her way along this path!)

1) Custom PlugIn developed by various people based on the hard core math..... (mostly Windows focused but the data is generic, and the options is there to implement it for mac)
http://jiiteepee.fortunecity.com/riaafilter/index.html
http://www.vacuumsound.de/plugins.html

The best seems to be the Synthedit VST plugins developed by Juha (jiiteepee)

I am using this, and have tested it with various test tones, inverse RIAA EQ, pink noise etc.... seems to work well.

2) Diamond Cut commercial software (Windows):
http://www.diamondcut.com/store/index.php

I will be pulling down a trial version of this to test, but I am happy with my current recording software, and really don't want a 4th or 5th piece of recording software... that all do most of the same functions..... - DC should really market the RIAA EQ part separately (as a plugin) as well as the entire package...

3) Pure Vinyl (Mac)

this one has the greatest backing amongst audiophiles.... but it is MAC Only - so not an option for me. (No I am not willing to get to know an entire environment just for a single piece of software...)

All the other options out there (including some of the ones on jiiteepee's page like IIEQ) only do the amplitude RQ of RIAA, and don't touch the Phase. (or at least don't consciously touch the phase... :-) ) - this includes all the Graphic and Parametric equaliser options which have profiles for RIAA and Inverse RIAA.... (I experimented with several of these including the ones for CoolEdit, Audacity, Audition, and a bunch of VST plugin EQ's as well)

If anyone is aware of other options that have been written to correct both amplitude and phase - please make a posting to add to the information I have been able to collect to date.

bye for now

David

Also ClickRepair Equalizer - Freeware RIAA EQ that apparently covers phase as well as amplitude...

http://www.clickrepair.net/software_download/equalizer.html

Hi Kirkus,

Indeed there is - and care needs to be taken with the gain/amplification methods.... whether analogue or digital.

But even in the final heyday of vinyl in the early 90's - work was done/proposed and presented at a couple of engineers conventions with regards to Digital RIAA either straight digital or Hybrid.

I have seen lots of talk about the constraints of Digital being worse than analogue for RIAA... but no real measurements.

Also I currently have 3 phono stages - none of which have the required adjustability to optimise MM/MI cartridges properly. They are all set as 47k/220pf.... but some cartridges require 68k100pf or 22k/600pf etc...

Also the main difficulty in analogue RIAA (which also introduces distortion, noise and non-linearities) is that there needs to be enough gain to compensate for the 40db loss in the RIAA filter/EQ. - Same problem either way!

Doing it digitally implies using a MicPre at the input to adjust gain properly into the ADC... the digital RIAA processing is far more trouble free in theory than the analogue version, the problems are with keeping the signal in the optimum range without an increase in noise/distortion etc... which can happen if the signal drops too far.

I did happen to have MicPre that suited, and wanted to try this method out before dumping a bunch of dough for yet another Phono stage- phono stages with the necessary adjustability are rare and relatively expensive...

So an experiment in loading for MM/Mi cartridges turned into an experiment in Digital RIAA...

I will post my results from both experiments in various forums....

Hi Kirkus,

your technical capabilites are well beyond mine....

I understand the strengths and weaknesses of the digital environment (computers are where I make my living).

And yep things get worse... as you drop signal levels below the -50db digital zone (which allowing for +18db signals as a max - as per HFN test records torture track means a real signal at -32db....) the THD % starts to rise substantially... and gets worse as the signal gets lower.

So assuming 70db S/N + 18db headroom (88db !) LP's can definitely push the limits of digital's capabilities.

I am however doing the best of digital by using 24bit ADC (real measured S/N of 118db is not too shabby.... around 20bit res.)

Then staying at 32bit and Floating point in the digital domain....

I had to get a new ADC when my previous one went belly up, it was after I ordered the new one that I realised it had a HiZ (High Impedance - 1M ohm) MicPre (for Ribbon Mic's or Instrument input).... which launched my exercise in MicPre based input.

I was originally planning to purchase a new Phono Stage capable of the flexibility I require for tuning MM's... but this has saved me some $$$ and allowed me to begin measuring and trying out the various cartridges.

I've used pink noise tracks to analyse one of my cartridges at 5 capacitances and 5 impedances (all permutations and combinations) - and graphed the results.... it allows me to then focus in on the optimal settings for each cartridge.

Which is not to say that my ultimate result might not be an Analogue stage....

I also find it interesting that you propose something very similar to what was proposed in the early 1990's - a paper was presented at the AES (? I think ?) proposing a hybrid digital/analogue RIAA design - but I believe it was never taken any further.

Today there are digital RIAA stages both at the budget end (basically analogue with USB ADC)- and some very high end units that appear to be truly digital (only? Hybrid?)

Chances are a hybrid approach makes the most sense until such time as Digital Audio can really move into true 32bit+ resolution at the ADC level. (there's plenty of 64bit software around already...)

With regards to peaks/troughs in cartridge / stylus performance... my Shure 1000e with SAS stylus has an electrical generated peak at around 19KHz, and a mechanically generated peak at 13.5KHz - these add up to what is more or less a HF shelf of up to +6db (with 100k impedance) - I can drop the shelf by dropping the impedance load - but then I get a midrange slump.... I still havn't gotten as far as determining the best balance between loading and EQ.

My initial (analogue based) instinct was to get the F/R as flat as possible across the critical midrange, then use digital EQ to adjust the peak (HF) and rolloff (LF)... with the shure I may also need to depress the 100Hz to 500Hz area (there's a reason they are known as a warm cartridge)

But as you've pointed out - the resonances boost the signal and may cause trouble with the ADC headroom (which reduces my available real effective dynamic range) - so I may be better off lowering the resonant peaks with cartridge loading - and then compensating the F/R variations involved with EQ....

Food for thought - Thank you

David