56
Troubleshooting
Audible hiss at high volume settings
The input dynamic range of any recordings you have are at
maximum 16 bit. The reason for this is that currently CD, DVD,
and LaserDisc use a 16-bit standard although DVD can support
up to 24-bits. The analogue sources you have cannot achieve
this kind of range. For comparison, analogue sources are likely
to be of the order of:
❍VCR, 12 bits.
❍FM radio, 13 bits.
❍Reel-reel tape, 13 bits.
❍Cassette tape, 12 bits.
❍LP, 11 bits.
Note that there may be a difference between the dynamic range
of the source channel when it is operating, and the noise you
hear in standby. For example, LP normally has lower noise when
the stylus is not in the groove; similarly tape will be quieter when
it is stopped. CD may also be quieter when it is stopped,
producing so called ‘digital silence’.
The 565 has a 16-bit capability on its internal analogue-to-digital
converter, which is used for analogue sources. When the volume
is turned up high you may hear its dither as a hiss when the
sources are stopped. This hiss is lower than the background
noise of your recordings and should be of no consequence.
The 565 has 18-bit output precision on the analogue outputs.
Other sources of hiss may be tracked down using either:
❍The Mute option. When muted the outputs are reduced to the
dither at the selected precision.
❍The Silence test signal; see Test signals, page 44.
Crackling on optical inputs
Some optical sources, in particular some LaserDisc players,
provide poor drive waveforms that do not meet the EIAJ
standard, in that the light modulates but never goes quite ‘black’
between pulses. If you experience crackling on the optical input
or an occasional reluctance to lock, ie provide a sound,
investigate as follows.
❍Try other fibres.
❍Pull the fibre part-way out and see if the problem clears up.
❍Try another player or CD player on the optical input.
❍Contact Meridian for up-to-date advice on this point.