Krell Industries MDA-300/500 Stereo Amplifier Owner’s Reference

A. INTRODUCTION
Thank you for your purchase of the KRELL
MDA-300
or
MDA-500
power amplifiers. These amplifiers represent
the latest evolution in amplifier technologyand incorporate manyinnovative design features.
To obtain the best performance from your MDA-300/
500s, careful attention should be paid to placement,
installation and operation. Athoro~ughunderstandingo.f
these details will help insure satistactory op.eration and
long life for the MDA-300/500s
and related system components.
This Owner’sReferenceis divided into several sections,
eac.h designedto perfo__r~_,a different function. Asyou
.read through this. O.w.ners Referenceyou will become
better acquaintedwith the features and functions that
make the MDA-300/500s
a superb value. A Question and
Answersection is also included where answers to commonquestions are provided. Should you have any questions or suggestionsplease feel free to contact your authorized dealer or the KRELL
staff for assistance.
In the unlikely event that your MDA-3.00/50.0s
should
require service youwill be pleasedto ~now~tlaat it is .
backed by a.comprehensive Customerbatistaction.policy
and one of the most advancedservice facilities in the
industry. For detailed information on the terms and conditions of service, please consult your warrantyreg.istration card, your authorized KRELL
Dealer or Distributor.
TABLE OF CONTENTS
4.
UNPACKING AND ASSEMBLY
BASIC INSTALLATION AND OPERATION
INPUT AND OUTPUT CONNECTIONS
8.
AMPLIFIER OPERATION
9.
PROTECTION CIRCUITRY
10.
REAR PANEL DES CRIPTIONS
12.
QUESTIONS AND ANSWERS
14.
SPECIFICATIONS
15.
WARRANTY AND SERVICE
3
INFORMATION
B.
UNPACKING AND ASSEMBLY
NOTE:Do to the extreme weight of the MDA-300
or
MDA-500
it is strongly advised that unpacking and
placementis completedby at least two individuals.
1. Openthe box on one end.
2. Fold back the flaps on all four sides of the box and
carefully roll it over on to the exposedend.
3. Pull the box straight up and off exposingthe foam
packing material.
4. Pull the foampiece from the exposedend of the amplitier.
5. Roll the amplifier carefully onto its handlesand removethe second piece of foam.
Thefollowing items will nowbe visible in each box:
MDA-300/500monaural amplifier
1
1
Warranty card
AC power cord
1
4 or 5 Rubber bottoms (MDA-500
has 5 feet)
NOTE:
If any of these items are not included please
contact your authorized dealer immediatelyf6r assistance.
6. Remove
the plastic bag from the amplifier.
7. Repeatprocedurefor the secondamplifier.
NOTE:
Save all pac.kin~g materials..If you must ship your
MDA-300/500s
in the tuture, repack the unit in its original packagingto prevent transit damage.
CAUTION:
Do not connect the power cords into the AC
mainsbefore completingthe Installation section.
4
C. BASIC INSTALLATION
AND OPERATION
1. Place the MDA-300/500,
on a firm level surface away
from excessive dirt or moisture. Ideally the amplifiers ’
shouldbe placedas close, to the speakersas possible. ,It is
alwayspreferable torun long interconnect cables to tt~e
amplifiers and keep speaker cable length t.o a minimu~m..
Speakercable does add an impedanceat tt~e output ot the
amplifier, regardless of the cable. All KRELL
amplifiers
will drive the lowest im. p.edances with ease. Whenimpedance is added, the amphfier’spoweris litera.lly wastedin
driving cable. Longspeaker cables reduce tlae maximum
powerthat can be dehveredto the speakers.
2. Amplifiers dissipate muchof the powerthey consume
in heat. The MDA-300/500s
should-be installed in a
location that.provides unobstructedventilation. If you
haveto install the units on shelves or in a cabinet, extra
ventilation m~¢be necessary_. This can be accomplished
with "whisper - type fans. Consult your dealer for assistance.
Generally, with the front and rear of a cabinet open, 2-3
inches of clearance on each side and 8 inches of clearance above the amplifiers should provide adequate ventilation.
The exact dimensions for the MDA-300and MDA-500
are in the Specifications Section below.
3. The MDA-300/500s
should have a dedicated 20.amp.
line for each amplifier and should only be operated with
the powercords supplied. Use of other powercords may
damagethe amplifiers or void its warranty. Please consult
KREEL
or your dealer BEFORE
using any devices designed to alter or stabilize the ACpow.er fbr.the MDA300/500s. If you have any questions about placement or
ACpower conditions please consult KREL-L.
4. The feet on the MDA-300/500s
canbe used in several
different ways. They are madefrom machinedDelrin and
are supplied witla separate threaded rubber b~ottoms.The
rubber bottomscan be screwedinto the feet tor protection of fragile surfaces such as hardwoodfloors or furniture. For use on rugs, werecommend
using the fee.t without the rubber bottoms. MDA-300/500s
feet can also
accept the KREL.L AMDs
(A, coustic MassDamper).
These improvethe amplifier s sonic performancein most
installations.
5
D. INPUT AND OUTPUT
CONNECTIONS
CAUTION:
Whenmaking connections to this component
or any other, makesure ttie poweramplifiers are OFFand
the preamplifier is in the MUTE
or STANDBY
mode.
1. Connectthe speaker cables to the output terminals of
each amplifier. The MDA-300/500s
utilize two sets of
parallel 5 waybindingposts for the left and fight amplifiers. This con_figuration makescable connectionsand-biwiring simple.
NOTE:
The binding, posts are of the highest quality but
w.ill breakif over.tigla.tened.In..se.rt wireor spadelug into
the connectoranc~ tigt~ten until there is no movement
fromthe cable.
CAUTION:
Makesure all cable terminations are of the
highest quality, free fromfrayed ends, shorts or cold
solder joints.
2. Connectthe interconnect cables from your preamplifier to the input of each MDA-300/500.
The wiring to and from the amplifiers, and all components in general, should be arrangedin a neat, organized
manner. Specifically, ACwires should be separated from
audio wires. This practice avoids humor ottier unwanted
noise from being induced into the system.
The MDA-300/500shave balanced and single-ended
inputs. The balanced inputs use 3-pin XLRconnectors
and the single-ended inputs use standard RCAconnectors.
CAUTION:
Use only one input to the amplifier at a time.
The MDA-300/500s
are shipped with. shorting pins in the
~LRinputs. These pins shoi~ld remain in the XLRinputs
it you are operating the MDA-300/500s
in the singleelided mode.Whenthe shorting pin is inserted, pin 1 and
pin 3 are. shorted together. Thesfiorting pins mustbe
removecl to connect the MDA-300/500s
for balanced
operation.
6
Thepin assignment for the XLRis:
pin _1-= shiel-d (ground)
p!n 2 = non-inverting input (hot)
pin 3 = inverting input
NOTE:The RCAcenter conductor for each channel is
wired_in, parallel with pin 2, the non-inv, erted input. Only
one ot these inputs Should be connectecl to a preamplifier.
3. Insert the ACpow6r cord into the receptacle located on
the back of eachMDA-300/500.Insert tile other end into
the wall ACreceptacle. (Refer to section C, Basic Installation and Operation, for ACpower requirements)
7
E. AMPLIFIER OPERATION
1. Pushthe black button on the front of both amplifiers to
turn them on. The blue LEDon the front panels above
each switch will illuminate.
Whenturning on the system, the amplifiers should alwaysbe last.-The MDA-300/50.0s
On/Off switch is part
of a multi-level turn-on circuit that goes through several
steps of protection. Uponturn-on, the amplifier’s outputs
are not connectedto the.speak.ers. After ttie protect!on
circuits have determinedthat the unit has completely
stabilized, the speaker relays will be engaged.-You
will
hear a click at this point. Theamplifiers are nowready to
use. Theamplifiers will be at temperatureand soundtheir
best after approximately30 minutes.
2. Withthe preamplifier in the Muteposition, or volume
control fully attenuated, select a source. Turn the volume
control up to yourdesired listening level.
3. Understandingthe operation of these amplifiers is very
e.asy. Equally important is an understandingof the care
that should be exercised whenoperating the system as a
whole, in relation to the enormouspoweroutput of the
MDA-300/500s.
Simple mistakes, such as switching
betweenactive sources without muting the preampfifier
9utput, or bumping/miscuing
a cartridge, can generate
large transients at low frequencies. Withthis type of
transient the MDA-300/500s
can generate enough power
to damagemost loudspeakers. AII switching of sources
should be done with the preamplifier level e~ther muted
or fully attenuated. Inputs to the amplifier should not be
changedwhile the amplifier is on.
NOTE:Care must be taken when setting high playback
levels. Becauseof their tremendousreserve of-clean
power, KRELL
amplifiers safely drive speakers to higher
sound pressure levels than other amplifiers. This also .
meansdriving the speakers to their fimit. Alwaysturn the
level downat the first sign of distortion.
Whenturning the system off, the amplifiers should
ALWAYS
be first. This avoids the possibility of a turnoff transient from someother componentgetting to the
speakers.
8
E PROTECTION CIRCUITRY
There are no fuses in the MDA-300/500s.
The amplifiers
are protected by a series of non-intrusive, opto-coupled
circuits that constantly evaluate the amplifier’s operation.
Appropriateprotecti’ce action exists for DCconditions,
stiort circuit, oscillatidn, ACpoweranomalies,high
groundresistance and out-of:phase ground. Collectively
tlae protection circuitry is designedto avoid damageto
the amplifiers or speakers causedby other d.efecti~e
components,faulty wiring, mishandlingof the system oy
amplifier failure. Whenthe protection, circuit is engage(l,
the a.mplifiers will shut off and short tlaeir output. After
resolving either the input or output problemthe amplifiers can 15e turnedon.
Theamplifiers also have circuit breakers on their
backpanelfor the ACpower. Should the button in the
center of the breakerpopout, pushit in to reset the
breaker. If the amplifiers still do not comeback on, call
Krell Industries.
9
H. REAR PANEL DESCRIPTIONS
All descriptions are for each amplifier chassis
INPUTS:
Balanced via 3 pin XERconnector
Single ended via RCAconnector
XLR PIN CONFIGURATION
p!n 1 Shield (ground)
p.ln 2 Non-invertingor 0 degrees (hot)
pan 3 Inverting or 1-80 degrees
OUTPUT:
Twopairs of five-waybinding posts in parallel
OTHER:
Standard ACreceptacle
20 ampcircuit breaker
OPTIONS:
Black Faceplate
11
I.
QUESTIONS AND ANSWERS
Q. Should I leave the MDA-300/500
on at all times?
A. Although you could leave the MDA-300/500
on at all
times without fear of damageto the amplifier, we recommend.30 minutes of warm-upbefore critical listening and
switching the amplifier off whennot in use.
WhenIpush the powerbutton on the front of the
~DA-300/-500,
the amplifier doesn’t turn on. What
shouldI c[o?
A. Unplugthe amplifier from the ACreceptacle and
removethe input from the amplifier. Checkthe output
connections, then plugthe amplifier back in. Checl~the
circuit breakeron the-backof the unit and reset it if necessary. Push the powerbutton on the front panel. If the
problempersists, unplugthe unit and call your dealer or
Krell industries.
Q. WhenI turn the amplifier on there is a loud hum
through the speakers. There was never a humbefore the
MDA-300/500
was in the system. What should I do?
A. Often whena newcomponentis introduced into an
audio system a hummay15ec.omepresent. This is often
causedby_a groundloop in tlae system. _Tryputting a 3
prong to 2 prong ACadaptor (cheate.r plug) on the
powercord, lifting the groundfromthe unit. This sho.uld
makethe humdisappear. If not, try another adaptor elsewherein the system.
NOTE:Always keep one major audio component
grounded.
NOTE:Even though the ground is lifted from the power
amplifier,it .is still gr~ou.nded
via the interconnectcables
throughoutthe rest ot tt~e system.
Q. Can I use special audio power c~rds on the MDA-300
’
or MDA’500?
A. Youcan experiment with special powercords as long
as they are groundedon both ends and meet the
amplifier’s I5 amppowerrequirement.
12
Q. After the amplifier is on for about one hour it becomes very hot. Is this normal?
A. Yes. Due to the high bias design of the MDA-300/500
it will become quite warm. After approximately 1 hour
the amplifier will be at its optimumoperating temperature. If the amplifier should-have a severe temperature
inbalance between the. left and right channel, unplug the
unit and call your aut~0rized dealer or Krell.
Q. I tried a new preamplifier in myaudio system and
when I turned the unit on the MDA-300/500
shut off. Is
the amplifier defective?
A. Morethan likely the amplifier is not defective. When
connecting components you should always keep the
amplifier off. Tile amplifer sensed a bad input signal and
slaut off, protecting itself and the speakers.
There also could tiave been a bad cable connection or
excessive DCoffset coming from the output of the preamplifier. Before turning tile amplifier on, check the
input cables. If that doesn’t help, bring the preamplifier to
the dealer for testing.
13
J, SPECIFICATIONS
MDA-300
MDA-500
GAIN
26dB
GAIN
26dB
SIGNAL-TO-NOISE
106dB unweighted
SIGNAL-TO-NOISE
106dB unweighted
THD
1K at 8 ohms
less than .2%
THD
1K at 8 ohms
less than .2%
20K at 8 ohms
less than .4%
20K at 8 ohms
less then .5%
INPUT IMPEDANCE
47,000 ohms (47K)
INPUT IMPEDANCE
47,000 ohms (47K)
INPUT SENSITIVITY
2.5 volts for 300 watts out
INPUT SENSITIVITY
3.2 volts for 500watts out
OUTPUT IMPEDANCE
.2 ohms
OUTPUT IMPEDANCE
¯ 15 ohms
OUTPUT VOLTAGE
139 volts peak to peak
OUTPUT VOLTAGE
179 volts peak to peak
OUTPUT POWER
OUTPUT POWER
All read!ngs
are continuous output
power, per channeI
All readings
are continuous output
power, per channeI
8
4
2
1
8
4
2
1
ohms
ohms
ohms
ohm
300 watts
600 watts
1200 watts
2400 watts
ohms
ohms
ohms
ohm
500 watts
1000 watts
2000 watts
4000 watts
DIMENSIONS
DIMENSIONS
19.0" WIDE
!9.5" DEEPwith handles
8.5" HIGHwith feet
19.0" WIDE
24.0" DEEPwith handles
8.5" HIGHwith feet
SHIPPING WEIGHT
SHIPPING WEIGHT
105 pounds
144 pounds
14
K. WARRANTYAND SERVICE
INFORMATION
There are no user-serviceable parts inside the MDA-300/
500. The MDA-300/500
has a limited warranty of f~ve
years parts and labor. Returnfreight is includedin ~the
warranty. Thewarrantyperiod b.egins on thee date ot
p_u_rchaseand is activated with the return ot the enclosed
Warran.tyCard and a copy of the Sales receipt. Please
return the warranty cardimmediate!yafter successful
installation and operation are completed.
Thewarrantyfor Krell products is valid ~n~in t.he country to whichthey wereoriginally shipped and at tlae
factory. If youtfiink there are problemswith your unit
please contact your dealer, distributor or the factory
immediately.
Plea~s.edo not returl?, any unit to KRELL
for repair without first calling to discuss the problemand to ot~tain a
R..etu..rn Authorizationnumber.-Freightto the factory or
distrit~utor is yourresponsibili.ty. R.~turnfreight to you
will be paid b}, the factoryor dlstrit)utor.
Anyunauthorized updates or modifications performed to
the unit will void the warranty.
15
KRELL INDUSTRIES
35 HIGGINS DRIVE MILFORDCT 06460
SALES203-874-3139 FAX203-878-8373
COPYRIGHT1992 KRELL INDUSTRIES
(MDA9204)