The whole project “revolves” around Pure Vinyl software made by Channel D, which uses a completely different method of recording LPs.
Typically, the ADC input signal falls from a standard phono-preamp, which performs two main functions with the signal: strengthening a weak signal from the cartridge (mic preamp) and correction (compensation) of the RIAA curve.
In case the Pure Vinyl signal input goes to ADC without RIAA curve compensation, the so called “flat” (it is recorded in LP, with only amplified mic pre amp to the standard Line output, and curve RIAA is blending in digital form, using a program). The RIAA filter in Pure Vinyl is calculated with 64 bits of precision, using Internal Signal Processing Path 64 bit (Double Precision Floating Point).
More details about all the advantages of Pure Vinyl (and there’s really a lot) you can read more at the manufacturer’s website .
Small dynamic range of LPs
There is a conventional opinion that the signal to noise ratio of analog audio from a vinyl record is between 50 to 70 dB, while 16 bit digital audio has a dynamic range of 96 dB!
This is not true. Normally we use the equipment for playing LPs which is not able to fully display the full technical potential that lies in LP Records.
My current setup in use is MC Cartridge Clearaudio Goldfinger Statement V2, which has a long-unattainable dynamic range of 103dB (Measurement data from the passport of my cartridge).
The first cartridge with integrated RF shielding, the Clearaudio Goldfinger Statement MC phono cartridge is designed to play on the world’s finest analog systems and reproduce the music on the greatest recordings ever made with unstinting clarity, liveliness, dynamics, realism, and responsiveness. Featuring 12 perfectly matched and symmetrical magnets – an unprecedented achievement – surrounding its coils. The Product of the Year Award-winning Goldfinger Statement allows systems to reach the long-unattainable dynamic range of 100dB. And by using 30% thinner 24-karat gold wire for the coils than utilized in its predecessor for lower moving mass, precision-milled gold mounting for the magnet array, and solid 14-karat gold body, Goldfinger Statement accounts for the ultimate in fine-tuned analog luxury. Clearaudio’s world-renowned Micro HD diamond stylus accounts for superlative detail retrieval while a flawless diamond facia rounds out an instrument that sounds as spectacular as it looks. – www.musicdirect.com.
Small frequency range of LPs
“Unlike the Compact Disc (CD) format, vinyl is capable of reproducing frequencies well above the accepted limit of human hearing. While there is debate about whether or not (or how commonly) humans are capable of perceiving frequencies above 20 kHz, the effect of the “brick wall” filter used in CD production, that sharply attenuates frequencies above the 22.05 kHz Nyquist limit, is harmful to the reproduction of audio, by introducing ringing and phase shifts affecting signal frequencies below 20 kHz. Vinyl has no such limitation on the frequency response; just the smooth roll-off imposed by the mechanical properties of the stylus; no brick-wall. If you do not believe that vinyl “has” anything above 20 kHz, check out this example, illustrating why it’s worthwhile to record / archive the audio at the highest possible sample rate.
Frequency response of Clearaudio Goldfinger Statement V2 is 20 Hz – 100 kHz, which far exceeds the specifications cartridge, used by Dr. Robinson for his test.
In this project I use MC Phono Preamplifier Channel D Seta L, which was specially developed by Rob Robinson for best results in tandem with Pure Vinyl.
The main features of this device:
“Flat” outputs XLR perfect for use with Pure Vinyl software RIAA correction;
Ultra wide linear signal bandwidth (DC to 5 MHz!) delivers stunning improvements in smoothness, clarity, definition and 3-D imaging;
The ultra low-impedance, internally located AGM rechargeable battery is capable of supplying 50 amperes of current, outperforming other types of batteries used in audio applications. The battery is conditioned and kept float-charged by a proprietary, uniquely designed rail balancing circuit, rather than use an “off the shelf” microprocessor based conditioning and monitoring circuit, which would introduce unwanted noise;
Minimum Signal Path Design. Direct Coupled circuitry. No Capacitors in signal path;
Fast-responding front end gain stage with a slew rate of over 500 volts per microsecond.
Dr. Rob Robinson about Seta:
Listening evaluations using a variety of reference systems and program material show that an important key to accurate reproduction of vinyl audio involves greatly increasing the signal bandwidth of the preamplifier front end (the first stage of amplification touching the signal from the phono cartridge).
Why? First of all, high quality phono cartridges are capable of reproducing signals well over two octaves above the audio frequency range.
While such signals are inaudible, the preamplifier also must work to amplify these signals, which also are boosted over 20 dB above midrange levels (because of the standard vinyl treble pre-emphasis curve used in the mastering process). A preamplifier unable to handle out of band signals will distort in the ultrasonic region. This distortion will carry over into the audio range, affecting the reproduction of the midrange and treble.
Futhermore, the audibility of one of the most maligned deficiencies of vinyl, “pops and clicks,” is a function of and can be exacerbated by the design of the preamplifier. The reason is that the transient signals caused by the stylus striking a scratch or foreign object in the groove have, in addition to large amplitude, a very fast risetime, and are unlike any musical signal. The fast risetime can cause slewing distortion in traditional narrow bandwidth or inexpensive phono preamplifiers, magnifying the audibility of pops and clicks. It’s quite possible that this nonlinear coloration from a less capable preamplifier is at least partially responsible for causing many music lovers to shun recordings in the vinyl medium! The Seta wide bandwidth design employs a fast-responding front end gain stage with a slew rate of over 500 volts per microsecond (Model L), making it immune to transient distortions induced by pops and clicks, minimizing their impact on the listening experience. (The slew rate of the Seta output is deliberately limited to avoid causing slew rate distortion in any following components.)
How much bandwidth is enough? The rule of thumb for linear signal reproduction is ten times (an order of magnitude) greater than the signal of interest. With that criterion, the amplifier is able to linearly reproduce out of band signals, while preserving the integrity of the midrange and treble without the “haze” caused by, and characteristic of, ultrasonic intermodulation distortion. Going still further, extending the bandwidth by two orders of magnitude delivers a stunning improvement in three-dimensionality and imaging.
ADC interface + Atomic clock
In recent years I have tried many wonderful ADC and chose Antelope Audio production company, which works perfectly for my needs.
Now I use Pure2 (Mastering AD / DA Converter & Clock), which has a fixed line input (factory calibrated to +20dBu) without the possibility of regulating the level of input which helps to achieve better results. Preview Gain Output for digital standard, as well as all other operations go on in the Pure Vinyl, on a program level, using digital filters of the first order (Pure Vinyl uses first-order digital IIR “Infinite Impulse Response” filters. This particular class of filter is noted for behaving identically to its analog, first order (resistor – capacitor) minimum phase counterpart, while being unburdened by the well-known limitations of physical resistors and capacitors). This approach provides significant improvements to outcome.
One of the many great features of Pure2 is a direct 10M Atomic Clock Input. It’s no secret the importance of high-quality digital reproduction Clock, but many reputable professionals of the audio industry consider presence of quality stage synchronization at recording stage, the ADC, more important. Some reputable pros say that the impact on quality Clock on record stage (ADC) can be up to 60-70%, especially in such aspects of sound like realism and “analog”.
So in this respect I did not go to any compromise and use a pair of Pure2 Antelope Audio Audiophile 10M:
10 MHz Rubidium Atomic Reference Generator, 100,000 times more stable than a typical crystal oscillator, the hyperfine energy levels of the non-radioactive rubidium core enable high-precision timing to 0.03 parts per billion, which equates to a loss of just one second per 1000 years!