Sphere MP-1 Mk.3.3 User manual

1742 Selby Av.
St. Paul, MN 55104
651-690-2246
atma-sphere.com
ATMA-SPHERE MUSIC PREAMPLIFIER
model MP-1 Mk.3.3
OWNER'S MANUAL
Please st dy this doc ment caref lly before sing eq ipment
RoHS

CONGRATULATIONS!
Yo have p rchased the world's finest preamplifier and certainly one of the
most niq e. It has seen over seventeen years of development and represents a
level of performance that others will be str ggling to achieve for years to
come if for no other reason than we control the patents. At the time of this
writing, it is the only f lly balanced differential all-vac m t be design in
the world that also s pports the 600 ohm standard.
Every part of the preamplifier has been extensively tested and engineered so
the prod ct will perform flawlessly for years to come, with little if any
service.
Please read the man al caref lly and follow the instr ctions closely. If yo
have any q estions, do not hesitate to contact yo r dealer and always feel
free to contact s at ATMA-SPHERE MUSIC SYSTEMS. Here's to many years of
happy listening!
Sincerely,
Ralph Karsten
ATMA-SPHERE MUSIC SYSTEMS, Inc., 1742 Selby Av., St. Pa l, MN 55104
651.690.2246 http://www.atma-sphere.com

LIMITED WARRANTY ON ATMA-SPHERE MUSIC SYSTEMS PRODUCTS
This warranty on yo r ATMA-SPHERE MUSIC SYSTEMS prod ct, which is distrib ted
and warranted by ATMA-SPHERE MUSIC SYSTEMS, shall remain in effect for three
(3) years from the date of cons mer p rchase, provided the enclosed
registration form is completed and ret rned to ATMA-SPHERE MUSIC SYSTEMS
within ten days of p rchase.
WHAT IS COVERED:
Except as specified below, this warranty covers all defects in materials and
workmanship. The following are NOT covered by the three year limited warranty:
* T bes are covered for 1 year, with the following excl sions, as per the rest
of the warranty:
* Damage occ rring d ring shipment (present claims to carrier).
* Damage res lting from fail re or inability to follow proper instr ctions.
* Damage res lting from the performance of repairs or modifications by other
than ATMA-SPHERE MUSIC SYSTEMS.
WHAT WE WILL PAY FOR:
ATMA-SPHERE MUSIC SYSTEMS will pay for all labor and material expenses for
repairs covered by this warranty.
HOW TO OBTAIN WARRANTY SERVICE:
If yo r nit req ires repairs covered by this warranty, yo MUST obtain a
ret rn a thorization n mber from ATMA-SPHERE MUSIC SYSTEMS. Yo are
responsible for transporting the nit to ATMA-SPHERE MUSIC SYSTEMS, 1742 Selby
Av., St. Pa l, Minn. 55104. Yo m st pay the initial shipping charges, b t
ATMA-SPHERE MUSIC SYSTEMS will pay the ret rn charges, if the repairs are
covered by the warranty. All prod cts MUST be shipped in the original
carton(s) or in replacement cartons s pplied by ATMA-SPHERE MUSIC SYSTEMS.
Contact ATMA-SPHERE MUSIC SYSTEMS for replacement cartons and cost.
LIABILITY IS LIMITED TO THE REPAIR OR REPLACEMENT, AT OUR OPTION, OF ANY
DEFECTIVE PRODUCT AND SHALL IN NO EVENT INCLUDE INCIDENTAL OR CONSEQUENTIAL
DAMAGE OF ANY KIND.
This warranty is transferable. Implied warranties of merchantability and
fitness for a partic lar p rpose are limited in d ration to the length of this
warranty. This warranty sets forth all expressed warranties made with regard
to the above referenced prod ct. We neither ass me nor a thorize any other
liability in connection with the sale or any shipment of prod cts. This
warranty gives yo specific legal rights and yo may also have other rights
which vary from state to state. We reserve the right to make changes and
improvements in o r prod cts witho t inc rring any obligation to similarly
alter prod cts previo sly p rchased.

MUSIC PREAMPLIFIER SETUP AND OPERATION
Unpack the preamplifier and its power s pply caref lly. Save the shipping
container for f t re shipment (replacements are $95.00). Warranty may be void
if the nit is shipped in a different container. If yo do not have a
container, contact ATMA-SPHERE MUSIC SYSTEMS for a replacement.
Normally the t bes are installed; the types are marked on the boards.
D ring operation, the MP-1 gets warm. Adeq ate ventilation is mandatory. If
the preamplifier is to be placed in a shelf or rack mo nt system, allow for at
least 12 inches of open space between the power s pply and head nit to avoid
overheating and h m problems.
After the preamplifier and s pply are properly positioned, make s re that the
main power switch is in the OFF position. Connect the mbilical cable from the
power s pply to the head nit. The connector operates by lining p the correct
key channels and then p shing on it gently while t rning the kn rled threaded
locking ring. It is keyed so that insertion is possible only one way- The
lowest n mbers marked on the pins of the connector sho ld be aligned at the
top of the connector when inserted. Yo may now pl g in the power s pply. The
"POWER AVAILABLE" LED sho ld now light. Connect the cables for the vario s
components to be sed with the preamplifier.
To maximize performance the MP-1 does not se a m ting circ it! Allow the
preamplifier to warm up and stabilize before energizing your power amplifiers.
M ting circ its interfere with so nd q ality and the servo circ its in the
line stage section. Altho gh the DC offsets generated d ring warm p are low
level, this may be a problem for some amplifiers and speakers.
WARNING! DO NOT TURN ON THE AMPLIFIERS IN YOUR SYSTEM UNTIL THE PREAMPLIFIER
IS STABILIZED. DAMAGE TO SPEAKERS, AMPLIFIERS OR BOTH MAY RESULT!
It takes abo t 30 seconds from t rn on before the preamp is ready for se.
D ring the warm p, one or both of the "DC OFFSET" LEDs on the front panel may
light p. This indicates that the servo circ it has detected a DC voltage at
the o tp t of the preamp and is trying to correct it. If the indicator stays
lit for more than a minute, a fault is indicated (usually a bad 6SN tube)
which should be corrected to prevent possible damage to associated equipment.
The preamplifier will so nd significantly better after abo t 45 min tes of
operation.
OPERATING NOTES
The MP-1 takes abo t 1 or 2 ho rs to so nd its best altho gh it is q ite
m sical after only 15 min tes. There is no need to r n the nit 24 ho rs a
day, b t if yo do, test the t bes once every fo r months. Allow for a few
weeks of normal operation to break in the nit; s btle b t l cid improvements
will be noticed.
The MP-1 s pports the se of a low impedance (600 ohm) load at the inp t of
the power amplifier (altho gh it is by no means req ired). S ch practice can
red ce h m and b zz b t more importantly eliminate artifact from the
interconnect cables. An optional terminator is available from ATMA-SPHERE for

amplifiers witho t this provision.
Adj st the GAIN TRIM for proper channel balance. Some minor adj stment is
sometimes req ired as the MP-1 is a zero feedback design. The Gain Trim
controls are a vol me control system employing a sh nt-style control- the
controls themselves are not in series with the a dio signal. Set them so that
the Master control is easy to se.
D e to the low impedance operation of the MP-1, cable q ality between the
preamplifier and power amplifier is considerably less important. Yo may hear
differences in the cables, b t they will be minor compared to the differences
yo may be sed to hearing in single-ended cables. Th s we have no
recommendation for cables to be sed between the preamplifier and power
amplifier. On the other hand, the input cables may be very critical, depending
on the so rce. Atma-Sphere offers a variety of interconnect cables for this
p rpose. Contact yo r dealer or Atma-Sphere for details.
PHONOGRAPH HOOKUP
All phonograph cartridges with fo r signal pins are a balanced so rce. Th s
the MP-1 allows yo to set p yo r t rntable as a f lly balanced so rce, with
considerable sonic advantage. For best res lts, follow the connection scheme
o tlined below:
1) Use a cable that has two signal cond ctors PLUS a shield for each channel.
The two cond ctors are for the pl s and min s o tp ts of the cartridge, and
the shield connection becomes the tone arm/t rntable gro nd connection and is
common to BOTH channels.
2) Pin n mber one of any XLR connection sho ld always be gro nd as per
ind stry standard.
3) Pin two of the XLR phono inp t corresponds to the "+" or non-inverting
o tp t of the cartridge, and pin three is the "-" or inverting o tp t of the
cartridge (absol te system phase can be corrected from the front panel).
4) There is no need for an independent gro nd wire from the arm to the preamp.
If yo set p the cable correctly, there will be NO h m whatsoever. Many tone
arms se a five pin connector that pl gs into the tonearm. If yo have s ch an
arm, yo may order a tone arm cable with the right connections from almost any
cable man fact rer. Sometimes a copy of this page sent to the cable
man fact rer is helpf l. If yo r arm has RCA connectors at the o tp t, an
adapter cable can be made that will work. The shield connection of the RCA
becomes the connection to pin 3 of the XLR connector, and the tone arm gro nd
connection sho ld be made as described above. ON NO ACCOUNT sho ld yo allow
the shield connection of the RCA to become the shield for the cable, as this
will res lt in a lo d h m.
The cartridge loading is accomplished by installing resistors on the loading
terminal above the phono connectors on the rear panel. A screwdriver is all
that is needed for attachment. Yo will find that the MP-1 is relatively
insensitive to loading of low o tp t moving coil cartridges. This is beca se
the MP-1 is very RFI imm ne and loading of low o tp t moving coil cartridges
has most of its effect at Radio Freq encies. If sing a high o tp t cartridge,
things are different and loading can be q ite critical as the load affects the

cartridge directly at a dio freq encies.
For best res lts, the phono cable sho ld be shielded.
Note: To avoid noise, avoid New Old Stock (NOS) 12AT7 t bes in the phono
section. Most are far too noisy to be of any real se. The t bes closest to
the rear panel have the most affect on the noise floor.
A step- p transformer is available for very low o tp t cartridges (0.1mv or
less).
High Level Hookup
The a xiliary inp ts are high impedance. Th s yo may se any inp t as a
so rce for the MP-1. A single-ended so rce can also be sed, by applying the
signal between pin 2 of the inp t XLR and pin 1 (gro nd). The n sed pin three
may have to be shorted to pin 1 to prevent noise. Pin 2 of all the XLR inp ts
is the non-inverting inp t, per ind stry standard.
The tape o tp ts are high impedance. Use a high q ality cable for best
res lts, and keep the cable as short as possible. The minim m drive impedance
is 10Kohms.
The tape monitors are a single-ended, non-inverting, high impedance inp t and
may be sed with any single-ended line so rce.
A note on t bes: As mentioned previo sly, avoid NOS 12AT7s. Older 6SN7s, on
the other hand, can often provide some improved performance. Only b y from a
rep table vendor, with proper ass rance that the t bes can be ret rned if they
are nsatisfactory! We advise that yo do not go overboard with NOS t be
types, as the prices paid for the res lts can be high compared to other
changes yo can make, fleeting, or both. Especially in the case of the phono
t bes, 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 se NOS t bes: noise will be nacceptable.
2) The constant c rrent so rces (6SN7s in the center of the boards) sho ld be
chosen for low noise.
3) The 6SN7 in the front right hand location of each circ it board is the most
important to the so nd of the line stage.
4) T be damping rings are recommended.
5) Do not remove t bes while nit is operating. Hazardo s or lethal voltages
are present!
6) *NEVER* se Tweek or other contact enhancers on vac m t bes, their
sockets or the vol me control! Such use voids the warranty.

TROUBLESHOOTING TIPS
Front panel LEDs on the power s pply don't light p: Check the rear panel f se
and verify that the power cord is pl gged in.
B zz, h m: Make s re that the power cord is pl gged into a properly gro nded
o tlet. The MP-1 s pports the AES file 48 (balanced line standard) however a
lot of other high end a dio prod cts do not. This can res lt in gro nd loops.
If yo are trying to operate the o tp t of the preamp with single-ended
eq ipment, b zz may occ r if the conversion from balanced to single-ended is
not handled properly. Contact Atma-Sphere for assistance. In some sit ations
an isolation transformer can be helpf l.
Distortion: Check the o tp t t bes (6SN7, pper right in diagram) and the
associated 6SN7 in front for defects. If any of the o tp t pins of the main
o tp t XLR connectors other than pin one is at gro nd potential, distortion
may res lt. Also check the circ it board f ses in the power s pply:
One or both channels o t: Check all t bes. If OK, there are two f ses located
on the right side of the power s pply circ it board (as yo face the front of
the nit), one for each channel. Replace with the same type slow blow f se (1
Amp for 117 Volt nits, 0.5 Amp for 230 Volt nits). If yo are not q alified,
do not remove the cover. Hazardo s or lethal voltages are present with the
cover removed. Refer service to q alified service personnel.
Noisy phono section: Replace the 12AT7s in the phono section. AVOID 'NOS' (New
Old Stock) TYPES AT ALL COST! Despite claims to the contrary by NOS t be
s ppliers, all NOS 12AT7s are j st too noisy if yo intend to se low o tp t
moving coil cartridges. M llard- Telef nken- don't care. They are too noisy.
The q iet ones were p rchased decades ago.
Low o tp t from one channel: Check t bes.
DC Offset LED lit p contin o sly: Check the 6SN7s (rear right two on circ it
board) in the channel associated with the LED.
NEVER, EVER, USE TWEEK OR ANY CONTACT ENHANCER ON TUBE SOCKETS! Tweek is
resistive at vac m-t be voltages. This will destroy the t be sockets and
possibly the circ it boards!
If none of these s ggestions help, contact yo r dealer or ATMA-SPHERE MUSIC
SYSTEMS.
MORE TIPS AND TWEAKS
For se with s bwoofer and other bi-amplified systems: Have yo r crossover
pdated with correctly balanced inp ts. If this is not possible, a specialized
balanced-to- nbalanced s bwoofer-optimized line transformer is available from
Atma-Sphere and works q ite well. If yo do not se one of these techniq es,
it is likely that yo will enco nter a b zz.
When ordering from any so rce, specify t bes for a differential circ it
(matched t be sections). The 12AT7s at the inp t of the phonograph section and
the 6SN7 at the inp t of the high level section (right front on circ it board)

are perhaps the most a dible. We find NOS 12AT7 t bes to be too noisy.
Harmonics of the power line freq ency have been shown to be far more
problematic for good so nd then all other types of power line problems (RF,
spikes, etc.) p t together. Be s re that the conditioner yo se can filter
line freq ency harmonics, partic larly the fifth (300 Hz on 60Hz line). A
prono nced 5th harmonic can ca se any power transformer to become mechanically
noisy! Beware that any line conditioner with a transformer in it can add
harmonics if operated at more than 50% of its capacity.
The power cord can have a dible effects! A good cable is recommended.
The So nd Anchors eq ipment stand and the Silent R nning stands are the finest
we have seen. They are highly recommended. Use them in conj nction with the
Ultra Resol tion Technologies vibration damping platform. NavCom Silencers or
other anti-vibration pads can be helpf l as are t be damping rings.
Most cartridges with more than 0.15mv seem to work fine. The higher the o tp t
the better, tempered with a m sical presentation. Some recommended choices:
The Grado Statement and Master Reference, Lyra series, Dynavector and Micro
Benz. There are of co rse many others.
If a high o tp t cartridge is sed, a j mper pl g that replaces one of the
phono t bes can be installed to red ce gain. Contact Atma-Sphere for details.
A moving coil step- p transformer option is also available for cartridges of
less than 0.1mV. It can be sed to red ce noise, even with higher o tp t
cartridges, at a slight cost of m sicality. The techniq e is to se the
aforementioned j mper pl g as well. The gain tends to be similar to the normal
phono section witho t the transformer, only with abo t 15 db less noise. If
yo can, avoid the transformer option, it is likely that the so nd will be
better; all transformers ca se signal degradation.
NOTES

WARRANTY REGISTRATION FORM
IMPORTANT: This form m st be filled o t and ret rned to ATMA-SPHERE MUSIC
SYSTEMS within 10 days of p rchase to validate the warranty! Please type or
print clearly.
NAME__________________________________________________________________________
Address_______________________________________________________________________
City or town ____________________________________State______zip code__________
Co ntry_______________________________________________________________________
Name of dealership____________________________________________________________
MP-1 Mk. 3.3 Date of p rchase_____________serial #___________price paid_________
Optional section for o r records and information:
Comments concerning yo r dealer_______________________________________________
Comments concerning this prod ct _____________________________________________
_____________________________________________________________________________
list the components in yo r system____________________________________________
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comments, s ggestions_________________________________________________________
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MAIL TO: ATMA-SPHERE MUSIC SYSTEMS, 1742 Selby Av., St. Pa l, MN 55104 USA