RME Audio ADI-2 Pro, Руководство пользователя

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108
User’s Guide ADI-2/4 Pro SE - v 1.0
34.27 Using a Turntable
The ADI-2/4 Pro SE is directly compatible to turntables with MM cartridge (Moving Magnet). See
also chapter 8.8. Thus it allows digitizing the precious vinyl discs in highest quality.
Connection
To connect a turntable to the two combo XLR/TRS jacks, two
RCA to TS adapters are required, see also photo on page
105.
For the rare case of a
balanced connection of an MM car-
tridge: this requires an adapter to XLR or TRS, depending on
the available connection. Furthermore a resistor of 100
kOhm has to be soldered across the wire pair for correct ter-
mination, since the input has 90 kOhm impedance in bal-
anced mode (90 k and 100 k result in the desired 47 kOhm).
The ground wire of the turntable can be connected to any
ground point of the unit, be it terminals or chassis. The easi-
est way is to clamp it between the screw connection of the
D-sub socket and the breakout cable supplied. In the picture
to the right the D-sub connector is not fully attached to better
show how it works. After screwing the D-sub connector tight,
the fork shoe is fixed and connected to the device
’s ground.
Note: The RIAA mode is a digital function realized by the
ASP (Audio Signal Processor) in the ADC chip. This causes
two limitations:

RIAA mode is only available in PCM mode, DSD is not
supported.

RIAA mode is available up to a sample rate of 192 kHz. 3xx and 7xx kHz are not supported.
Level, Gain and Headroom
To be compatible to the varying output voltages of different MM cartridges the ADI-2/4 Pro SE
has several selectable gain levels in RIAA mode: +14 dB, +20 dB, +26 dB, +32 dB and +38 dB.
In most cases a good leveling is achieved with +26 dB, i.e. the horizontal level meter stays some
dB below 0 dBFS, and there is no over indication.
LPs show very different levels of more than 10 dB, from very low (depending on age and genre)
to very high (45 maxi singles). MM pickups also very much differ in output voltage. Even third-
party replacement needles can lead to level deviations of a few dB. In short: a universally usable
RIAA preamp has to support a wide level range, and this is exactly what is achieved via the
selectable gain of the ADI-2/4 Pro SE. The data given in the Tech Specs section is based on a
headroom of 15 dB. SNR and THD+N will improve with higher levels, meaning less headroom.
Discrete analog RIAA preamps without adjustable gain need a lot of headroom to avoid distortion
at the highest level of a critical record/pickup combination. In addition, the request for a very high
headroom is often found, because allegedly crackling and pop noises of the record reach very
short, but much higher levels. These would then become more audible in attached devices due
to overdriving. That this is not the case becomes obvious when using the ADI-2/4 Pro SE - only
on relatively quiet records pops occur higher than the useful signal, and reach only a few dB
higher levels. A headroom of more than 6 dB is not necessary, the often rumored 20 dB are a
nothing more than a waste of dynamic range.