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Software based RIAA EQ for PC/MAC systems.
Needed components:
- Max/MSP
Runtime (or trial version)
- RIAA_Filter.rar
(15kB, keeps two files, the project file and background image) to
your HD
Additional software:
- Voxengo
Recorder and Voxengo SPAN, extract those into same directory w/
RIAA_Filter (or install using the installer)
Setting all up:
Hardware setup:
- connect the turntable w/o RIAA stage into
PC/MAC audio interface (either through a flat preamp or directly)
-
audio interface needs to be set for recording (I have tried recording
through analog only so I can't be sure if everything works well
through S/PDIF too)
RIAA Filter software:
- open the RIAA_Filter.pat into Max/MSP enviroment
-
open the I/O settings dialog and configure the driver
(samplerate, latency, etc.) and I/O ports properly
- reset
the Filter to defaults
- select Filter samplerate (equal
w/ driver samplerate because of these four filters are matched for
certain samplerate)
- start the engine by pressing the
Start/Stop -button
Additional options (PC):
The
SPAN and Recorder can be called by pressing the Open buttons. If
nothing happens, it's possible that VST .dll files needs to be moved
into same directory with the filter software. These VST's are
connected parallel so the recording level can be set by the SPAN
output graphics/data.
The Rumble/Subsonic filter is not well done (need to be fix it someday).
To edit the project file, least
the trial version of Max/MSP is needed. Editing is enabled through
menu option View -> Edit. It's possible to save the project ans
use it even after the trial period through Max/MSP
runtime.
Issues?
If no audio ... maybe ASIO drivers are
needed. Resetting the filter to defaults or changing subsonic filter
parameters (drag with mouse) can be helpful. If still no audio or no
filter added (i.e. bassless/bright audio coming out) then, maybe all
connections, levels, HW monitoring state, etc. needs to be
adjusted).
I found E-MU 0404 USB troublesome
when changing samplerate on-the-fly. If the filter freezes, just kill
the MaxRT or Max process through task manager (ctrl-alt-del).
I/O Settings:
Additional Filters:
A better subsonic/rumble filtering may be achieved by using AIXCoustic's Electri-Q w/ a preset
Chebyshev I, HP Filter 36dB/oct (subsonic/rumble filter) @ 20Hz / BW20
The result can be seen here (lighter line in graph):
RIAA Filter software specs:
44.1kHz
Maximum error from 0.00 Hz to 20000.00 Hz = ~0.224dB
Maximum phase error from 0.00 Hz to 20000.00 Hz = ~+/- 30 degrees
where the "phase error" is computed after a constant delay is added
or subtracted to make the phase error equiripple
48kHz
Max error from 0.00 Hz to 20000.00 Hz = ~0.14dB
Max phase error from 0.00 Hz to 20000.00 Hz = ~+/- 24 degrees
88.2kHz
Maximum error from 0.00 Hz to 20000.00 Hz = ~0.0082dB
Maximum phase error from 0.00 Hz to 20000.00 Hz = ~+/- 3 degrees
96kHz
Maximum error from 0.00 Hz to 20000.00 Hz = ~0.0057dB
Maximum phase error from 0.00 Hz to 20000.00 Hz = ~+/- 2.4 degrees
Diagram:
Signal path :
ADC L/R ==> RIAA Filters L/R ==> selectors L/R (filter is selected by the samplerate) ==> Rumble/Subsonic Filters L/R ==> output volume controls L/R ==> Output L/R, VST 1 L/R, VST 2 L/R
Controls:
Reset -> resets the volume, rumble/subsonic filters
SR selection -> changes the RIAA filter coefficients feeded into biquad filter
start/stop button
I/O settings control (dsp open)
Volume sliders
2 x VST slot connected parallel w/ output (defaulted to load Voxengo's SPAN and Recorder)
