Atma-Sphere P-2 User manual

1742 Selby Av.
St. Paul, MN 55104
651-690-2246
atma-sphere.com
Atma-Sphere Music Preamplifier
model P-2
OWNER'S MANUAL
Please study this docume t carefully before usi g equipme t
RoHS

CONGRATULATIONS!
You have purchased one of the world's f nest preampl f ers and certa nly one
of the most un que. Developed and ref ned s nce 1989 t s (at the t me of
th s wr t ng) the only fully-d fferent al balanced vacuum-tube preamp
technology n the world featur ng a d rect-coupled output. Thus t operates
at a level of performance that others have been struggl ng for years to
ach eve, and l kely w ll for years to come. You don't have to wa t; all you
have to do s set the preampl f er up by follow ng the s mple nstruct ons n
th s manual.
Every part of the preampl f er has been extens vely tested and eng neered so
the product w ll perform flawlessly for years to come..
Please read the manual carefully and follow the nstruct ons closely. If you
have any quest ons, do not hes tate to contact your dealer or Atma-Sphere
Mus c Systems, Inc. Here's to many years of happy l sten ng!
S ncerely,
Ralph Karsten
Atma-Sphere Mus c Systems, Inc., 1742 Selby Av., St. Paul, MN 55104 651.690.2246

MUSIC PREAMPLIFIER SETUP AND OPERATION
Unpack the preampl f er carefully and save the packag ng conta ners for
future sh pment f requ red.
Dur ng operat on, the P-2 gets warm. Adequate vent lat on s mandatory. If
the preampl f er s to be placed n a shelf or rack mount system, allow for
at least 2 nches of open space above the un t. Make sure that the
preampl f er s at least a foot away from any power supply, to avo d hum
problems.
After the preampl f er s properly pos t oned, make sure that the power
sw tch s n the OFF pos t on. Connect the cables for the var ous components
to be used w th the preampl f er.
For super or son c performance, the P-2 does not use a mut ng c rcu t. Allow
the preamplifier to warm up a d stabilize before e ergizi g your power
amplifiers.
WARNING! DO NOT TURN ON THE AMPLIFIERS IN YOUR SYSTEM UNTIL THE PREAMPLIFIER
IS WARMED UP AND STABILIZED! DAMAGE TO SPEAKERS, AMPLIFIERS OR BOTH MAY
RESULT!
Get n the hab t of turn ng down the volume or sw tch ng to an unused nput
anyt me you turn your ampl f er on, when you change a record, etc.
After the preampl f er s turned on, t takes about 30 seconds before t s
ready for use. The preampl f er w ll sound s gn f cantly better after about
45 m nutes of operat on.
OPERATING NOTES
The preampl f er can be left on all the t me, but the phono tubes should be
tested every 4 months f you do so. The l ne stage tubes w ll last
cons derably longer! Be sure to prov de for adequate vent lat on. The un t
w ll sound substant ally better an hour after turn-on, so leav ng the preamp
on all the t me w ll not w n you anyth ng.
The P-2 may be used w th a low mpedance (600 ohm) load at the nput of the
power ampl f er wh ch can be used to reduce hum, buzz and nterconnect cable
art fact. If you do not have a 600 ohm nput on the ampl f ers, nstall a 600
ohm (or s m lar value, up to 1000 ohm, both channels should get the same
value) ½ watt res stor between p n 2 and p n 3 of the output XLRs of each
channel. Th s w ll result n s gn f cantly better sound!
The GAIN TRIM s prov ded to adjust for proper left-r ght balance effect and
to allow for range on the volume control. The P-2 s a zero feedback des gn
so tube cond t on can cause a ga n d fference between left and r ght
channels. Operate the control SLOWLY. The GAIN TRIM controls are not n the
aud o path. They may generate a temporary DC offset (and somet mes no se)
when they are operated. Th s can be reduced or el m nated depend ng on the
balance of the sect ons n the 12AU7 (or 12AT7, n later un ts w th the 3-
tube l ne sect on) used n the h gh level sect on.
Due to the nature of the P-2, expens ve cables between the preampl f er and

power ampl f er are not needed. The cable d fferences you hear w ll be m nor
compared to s ngle-ended cables. Thus we have no recommendat on for cables to
be used between the preampl f er and power ampl f er. On the other hand, the
input cables may be very cr t cal, depend ng on the source.
PHONOGRAPH HOOKUP
All phonograph cartr dges (except some old-style Deccas) are balanced
sources. The P-2 allows you to set up your turntable as a fully-balanced
source, to cons derable son c advantage. For best results, follow the
connect on scheme outl ned below:
1) Use a cable that has two s gnal conductors (tw sted pa r) PLUS a sh eld
for each channel. The two conductors are for the plus and m nus outputs of
the cartr dge, and the sh eld connect on becomes the tone arm/turntable
ground connect on and s common to BOTH channels.
2) P n number 1 of any XLR connect on s always be ground per ndustry
standard.
3) P n two of the XLR phono nput corresponds to the "+" or non- nvert ng
output of the cartr dge, and p n three s the "-" or nvert ng output of the
cartr dge. Absolute system phase can be corrected from the front panel.
4) There s no need for an ndependent ground w re from the arm to the preamp.
If you set up the cable correctly, there w ll be no hum. Many tone arms use a f ve p n
connector that plugs nto the bottom of the arm. If th s s the case n your system,
you may order a tone arm cable w th the r ght connect ons from almost any cable
manufacturer. If your arm has RCA connectors at the output, an adapter cable can be
made that w ll work. The sh eld connect on of the RCA must become the connect on to
p n 3 of the XLR connector, and the tone arm ground connect on should be made as
descr bed above. ON NO ACCOUNT should you allow the sh eld connect on of the RCA to
become the sh eld for the cable, as th s may result n a loud hum.
Cartr dge load ng s ach eved by nstall ng res stors on the load ng term nal on the
rear panel. A screwdr ver s all that s needed for attachment. You w ll have to
exper ment to obta n the correct value. The stock load ng value s 47KOhms.
Avo d us ng NOS 12AT7s n the P-2. Desp te frequent cla ms to the contrary, most such
tubes are far too no sy for proper operat on n the P-2! Please purchase new 12AT7s
from your dealer or Atma-Sphere Mus c Systems, Inc.. Most 12AT7s tend to get no sy
after about 3 thousand hours so; f you leave the preamp on 24 hours a day the phono
tubes should be replaced every 3-4 months. They w ll last longer f the preamp s
turned off when not n use. In any event, be VERY susp c ous of any NOS 12AT7s. Most
of them are unacceptable.
For very low output cartr dges you may w sh to have the step-up transformer opt on
nstalled. Contact your dealer for deta ls.
High-Level Hookup
The aux l ary nputs are h gh mpedance. Thus you may use any nput as a
source for the P-2. If you are us ng a low mpedance source, a low mpedance
term nat on s recommended for better sound. A s ngle-ended source can also
be used, by apply ng the s gnal between e ther p n two or p n three of the
nput XLR, and ground. The unused nput (p n three or p n two, respect vely),
may have to be shorted out to prevent no se. P n two of all the XLR nputs s

the non- nvert ng nput, per ndustry standard.
The tape outputs are h gh mpedance. Use a h gh qual ty cable for best
results and keep the cable as short as poss ble. The m n mum dr ve mpedance
s 20Kohms. The tape 2 output s nverted wh le tape 1 s non- nverted.
The tape mon tors are a s ngle-ended, non- nvert ng, h gh mpedance nput.
NOTES ON TUBES
1) The 12AT7s n the rear left of the board are the most cr t cal for low
no se phono operat on.
2) The constant current source tube (the 7th 12AT7 by tself n the rear) s
outs de of the s gnal path. It should not be Ch nese.
3) Matched sect ons n the 12AU7s of the h gh level sect on w ll
reduce DC offset dur ng operat on of the front panel GAIN TRIM controls.
4) Tube damp ng r ngs are recommended.
5) Do not remove tubes wh le un t s operat ng. Hazardous or lethal voltages
are present!
6) NEVER use Tweek, Pro-Gold or other contact enhancers on vacuum tubes!!
7) Long l ve analog!
TROUBLESHOOTING TIPS
Bottom front panel LED won't l ght up: Check the rear panel AC connector and
ver fy that the power cord s plugged n. If so, the nternal 1.5Amp SLOW
BLOW (.75A f 235 Volts) fuse may be blown.
Buzz, hum and/or RF nterference: Make sure that the power cord s plugged
nto a properly grounded outlet and that no other equ pment n the system s
grounded (result ng n a ground loop). Somet mes RF can get nto the
phonograph through poorly sh elded w r ng n or from the tone arm. Th s s
common w th modern stra ght-track ng arms. Buzz can also occur f the nput
of the ampl f er s not properly balanced. Th s can occur f the ampl f er
has an RF f lter at ts nput that s only act ve on the non- nvert ng nput.
There are qu te a few trans stor amps w th balanced nputs that are set up
th s way.
D stort on: Check the output tube (12AU7 or 12AT7) for defects.
R ng ng or 'bell' sound when operat ng volume (m crophon cs): Usually the
tubes n the l ne stage s the most l kely to cause th s fault. The 12AT7s n
the phono sect on can do th s too. If the P-2 s OK on AUX nputs, but r ngs
on the phono, then the phono 12AT7s are most l kely at fault.
**DO NOT USE CONTACT ENHANCERS ON THE TUBE SOCKETS!!**
If none of these suggest ons help, please contact your dealer or Atma-Sphere
Mus c Systems, Inc.
MORE TIPS AND TWEAKS
You can reduce the no se level beyond the spec f cat on by us ng low no se tubes. When
order ng from any source, spec fy tubes for a d fferent al c rcu t (matched tube
sect ons). We have found that the 12AT7 at the nput of the phonograph s the most
aud ble.

We recommend l ne cond t on ng. The f fth harmon c of the power l ne frequency has
been shown to be far more problemat c for good sound then all other types of power
l ne problems (RF, sp kes, etc.) put together.
We have found that the power cord can have aud ble effects! A good cable s
recommended.
The Sound Anchors equ pment stand s one of the f nest we have seen. It s h ghly
recommended. Use t n conjunct on w th the Ultra Resolut on Technolog es v brat on
damp ng platform. NavCom S lencers or other ant -v brat on pads are also recommended.
Tube damp ng r ngs are h ghly recommended.
The preampl f er has been successful w th lower outputs (0.24mV) but t s adv sable
to have the regulator opt on, and one must keep an eye on the cond t on of the phono
tubes for best results. A step-up MC transformer opt on s also ava lable.
NOTES