General Audio Specifications
|Supported audio interfaces
||Any CoreAudio compatible interface (including built-in audio) with at least 2 input and 2 output channels
|Supported Sample Rates
||44.1, 48, 88.2, 96, 176.4, 192 kHz
|Supported Sample Resolutions
||16, 20, 24, 32 bits
|Internal Signal Processing Path
||64 bit (Double Precision Floating Point)
|File Output Formats (Recorder)
||AIFF, Sound Designer II (Uncompressed); CAF (Apple Lossless), 16, 24, 32 bit
|File Input Formats (Editor)
||AIFF, AIFC, WAVE, Sound Designer II, MP3, M4A, CAF
|File Output Formats (Editor)
||AIFF (Uncompressed); M4A (Apple Lossless); Stereo or Mono, 16, 24 bit
|Rumble Filter (with RIAA Correction)
||Variable Frequency; 12/ 18 / 24 / 36 / 48 / 96 dB/octave
|Automatic Stylus Drop / Lift Recording Triggering
||Adjustable -100 to 0 dBFS
|Built-In Loudspeaker Crossover (2/3/4 way)
||Variable 38 Hz - 8 kHz, 6 / 12 / 18/ 24 dB / octave, Variable Overlap
|Sample Rate Converter, to 96 kHz
||from 192 / 176.4 kHz
|Sample Rate Converter, to 44.1 kHz
||from 192 / 176.4 / 96 / 88.2 / 48 kHz
RIAA Correction Curve Accuracy
Click for information regarding Distortion of Digital RIAA FIlter
Sample Rate 192 kHz / Resolution 24 bit
+0.06, -0.00 dB, 20 Hz - 10 kHz (+0.01, -0.00 dB, from 20 Hz - 3 kHz)
Rising gradually to <+0.2 dB at 20 kHz and +1.0 dB at 50 kHz*
Interchannel Amplitude Deviation: 0 dB
Interchannel Phase Deviation: 0 degrees
*The response rise at high frequencies represents a deliberate compromise between the standard RIAA curve and the newer, "modified" RIAA curve, which calls for an additional compensation filter "corner frequency" (amounting to +3 dB at 50 kHz) to compensate for vinyl cutter head rolloff. We have taken a moderate approach (+1 rather than +3 dB at 50 kHz and +0.175 instead of +0.6 dB at 20 kHz).
Sample Rate Converter - for Converting High Definition 88.2/96/176.4/192 kHz Audio to CD / iTunes / iPod Format (44.1 kHz)
Pure Vinyl Sample Rate Converter and comparisons with other SRCs.
A perfect result is a single spectrogram trace with no spurious generated tones (completely black background). See this page for comparisons with other SRCs.
Pure Vinyl's built-in Sample Rate Converter (SRC) can be used to convert high-resolution audio (up to 192 kHz 24 bit) to CD format, 44.1 kHz (with a choice of either 16 or 24 bit output). (The same sample rate converter design also is used for optional, real-time upsampling playback, to up to 24 bit / 192 kHz, of CD or other format tracks while in music server mode.)
If starting with a "flat" vinyl recording (no RIAA correction curve applied), the RIAA correction optionally can be applied during the conversion step, while the audio is in the 64 bit high precision internal format used by the Pure Vinyl SRC.
Pure Vinyl's SRC works equally well for power of two conversions (from 88.2 or 176.4 kHz) and for factored conversions (from 96 kHz or 192 kHz). Factored conversions take longer to perform, however.
Pure Vinyl Sample Rate Converter: Signal Integrity / Purity Test
A perfect result for a sample rate converter is a single trace with no spurious generated tones (completely black background), and little or no "V" reflection (aliasing) after the sweep passes 22.05 kHz, which is the Nyquist limit (this happens at about 19.5 seconds on the spectrogram display).
Anything besides a single, parabolic trace represents unwanted distortion and audio "dirt" added to the signal.
- Input Sample Rate 96 kHz, 24 bit resolution
- Swept Sine Wave File, 20 Hz to 48 kHz, -1 dB vs. Digital Full Scale
- Sample Rate Conversion to 44.1 kHz, 24 bit format
- Spectrogram amplitude scale -160 dB to 0 dB vs. Digital Full Scale
- Test file duration 46 seconds (only the treble part of the analysis is shown)
- Conversion time measured on 2.1 GHz G5 single-processor iMac
Compare above with the other traces shown here, and with sample rate converters measured here: http://src.infinitewave.ca/ (The frequency axis is reversed in measurements at that website, where high frequencies are displayed at the top of the spectrogram, the opposite of what's conventionally used for spectrogram or "voice print" displays.)
Below are additional results, from testing the sample rate converters of some other Macintosh audio applications, using the same 96 kHz input file, resampling to 44.1 kHz, 24 bit, as above. Also note the conversion time when comparing the sample rate converters. If a choice of "highest" / "best" quality SRC was provided, the highest quality was used. Note that two of the applications apparently use the same SRC algorithm:
Sample Rate Conversion Processing Time: 15 seconds
Sample Rate Conversion Processing Time: 268 seconds
Sample Rate Conversion Processing Time: 24 seconds
Sample Rate Conversion Processing Time: 21 seconds
Sample Rate Conversion Processing Time: 5 seconds
Sample Rate Conversion Processing Time: 5 seconds
Note: there is no inadvertent repetition of two graphs above. Apparently, both software packages use the same sample rate conversion software / algorithm!
Sample Rate Conversion Processing Time: 14 seconds
Note: 24 bit output file, converted from FLAC 24 bit lossless compressed format to uncompressed PCM format (Sound Designer II) for analysis. Audacity only supports 16 bit output when saving audio to uncompressed file formats such as AIFF or WAV. However, 24 bit resolution is available if using FLAC format.
Sample Rate Conversion Processing Time: 250 seconds
Sample Rate Conversion Processing Time: 16 seconds
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Mac OS X 10.5 or 10.6; G4, G5 or Intel CPU.