cartridge directly at audio frequencies.
For best results, the phono cable should be shielded.
Note: To avoid noise, avoid New Old Stock (NOS) 12AT7 tubes in the phono
section. Most are far too noisy to be of any real use. The tubes closest to
the rear panel have the most affect on the noise floor.
A step-up transformer is available for very low output cartridges (0.1mv or
less).
High Level Hookup
The auxiliary inputs are high impedance. Thus you may use any input as a
source for the MP-1. A single-ended source can also be used, by applying the
signal between pin 2 of the input XLR and pin 1 (ground). The unused pin three
may have to be shorted to pin 1 to prevent noise. Pin 2 of all the XLR inputs
is the non-inverting input, per industry standard.
The tape outputs are high impedance. Use a high quality cable for best
results, and keep the cable as short as possible. The minimum drive impedance
is 10Kohms.
The tape monitors are a single-ended, non-inverting, high impedance input and
may be used with any single-ended line source.
A note on tubes: As mentioned previously, avoid NOS 12AT7s. Older 6SN7s, on
the other hand, can often provide some improved performance. Only buy from a
reputable vendor, with proper assurance that the tubes can be returned if they
are unsatisfactory! We advise that you do not go overboard with NOS tube
types, as the prices paid for the results can be high compared to other
changes you can make, fleeting, or both. Especially in the case of the phono
tubes, the investment is often not worthwhile.
NOTES ON TUBES
1) The 12AT7s in the rear left of each board are the most critical for low
noise phono operation. DO NOT use NOS tubes: noise
will
be unacceptable.
2) The constant current sources (6SN7s in the center of the boards) should be
chosen for low noise.
3) The 6SN7 in the front right hand location of each circuit board is the most
important to the sound of the line stage.
4) Tube damping rings are recommended.
5) Do not remove tubes while unit is operating. Hazardous or lethal voltages
are present!
6)
*
NEVER
* use Tweek or other contact enhancers on
vacuum tubes, their
sockets or the volume control!
Such use voids the warranty.
Summary of Contents for MP-1 Mk.3.3
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