XONO PHONO PREAMPLIFIER
The Xono is a high performance phono
preamplifier for use with moving magnet and
moving coil cartridges. It features extremely
low noise and distortion, very high output
swing, variable cartridge loading, variable gain,
and balanced output.
The main gain stage uses a combination of
active and passive equalization to achieve the
RIAA characteristic. The active equalization
works in the mid-band of the audio range
and the passive equalization determines the
characteristic and the highest and lowest
frequencies. The stage has a fixed gain value
of 40 dB at 1 KHz.
referenced to 1 millivolt input, giving a -81 dB
unweighted audio band noise figure.
The Xono is adjustable to very high gain,
76 dB @ 1 KHz, which makes it capable of
delivering .5 V line level output for cartridges
with 80 microvolts output. This appears to be
the best figure in the audio industry.
The power supply for the Xono is contained in
a separate chassis and consists of an oversized,
shielded toroidal power transformer delivering
an unregulated 85 volts peak to peak DC
through separate rectifiers and capacitors
for each channel which is then passively RC
filtered before being sent to the main Xono
chassis. A custom manufactured shielded cable
carries the DC power from the supply to the
main Xono chassis. The main chassis of the
Xono has separate stages of active regulation
for each channel followed by passive filtering
and then feeding the constant current sources
which bias the various gain stages. There is a
total of 120, 000 mfd of filter capacitance and
five stages of filtering and regulation.
Cartridge loading of the Xono is very flexible.
Moving Magnet cartridges can be loaded with
capacitance from 0 to 650 pF in increments
of about 100 pF. There is provision for two
load positions for any additional value that
the user may choose to insert. Moving Coil
cartridge loading ranges from 5 to 1000 ohms
to 47 Kohms using eight switches with binary
weighting and providing 256 different values.
The Xono has a very accurate RIAA
equalization characteristic, varying plus or
minus 1/10 of a decibel from 10 to 20 KHz.
This accuracy does not vary with gain or
loading.
The preamplifier has extremely low noise.
The Moving Magnet noise floor at more than
-100 dB below a 10 millivolt input, which gives
it an unweighted total noise of -90 dB. The
Moving Coil noise floor is better than -90 dB
The Xono is based on the design pioneered
in the Aleph Ono. The basic Ono design has
not changed but been extend and refined.
The separate power supply combined with
the additional filtering and dual mono power
supply design contribute to the lower noise
floor and sonic improvements. The main
circuit board layout has been completely
revised to reduce noise, shorten the signal
path and reduce the length of connecting
wires. Sonically critical parts have been
optimized and upgraded through continued
extensive listening tests.
The Xono like the ono design was based on
listening and not measurements. Considering
this, it is perhaps remarkable that the final
product displays such spectacular objective
qualities. However, we view the specifications
as a secondary source of pride in this
product.
Pass Labs, PO Box 219, Foresthill, CA 95631, Tel: 530.367.3690, Fax: 530.367.2193, www.passlabs.com
PASS LABS