Owner`s manual

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) Matched sections in the front-most 6SN7 of the preamp will reduce noise
during operation of the front panel GAIN TRIM control. This 6SN7 is also 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.
TROUBLESHOOTING TIPS
Front panel LEDs on the power supply don't light up
Check the rear panel fuse and verify that the power cord is plugged in.
Buzz, hum:
Make sure that the power cord is plugged into a properly grounded outlet and that no other equipment in the
system is grounded (resulting in a ground loop). If you are trying to operate the output of the preamp with single-
ended equipment, buzz may occur if the conversion from balanced to single-ended is not handled properly.
Contact Atma-Sphere for assistance. In some situations an isolation transformer can be helpful.