Krell Industries Monaural Amplifiers KMA-160 Owner's Manual

45 Connair Drive
Orange, CT 06477-0533, USA

KMA-160 OWNER, S MANUAL: INSTALLATION & OPERATION INSTRUCTIONS

JUNE. !,.. 19.89

GENERAL INFORMATION

Thank you for purchasing the KMA-160 Monaural Amplifiers. The
KMA-i60 represents the absolute latest evolution in amplifier
technology and has many innovative design features. It is one of four
amplifiers in the new KRELL Programmable Series, the features of
which are are discussed below. There are several aspects of its
operation that require your special attention and understanding
before installation is begun. Also, this document contains much
general information concerning audio system installation in addition
to specifics of the KMA-160.

PURE CLASS A OPERATION AND POWER CONSIDERATIONS

The KMA-160 is rated as delivering 160 watts of Class A power into 8

ohms. One inherent aspect of Class A operation is the need for a

large amount of current from the AC mains. The amplifier at idle
draws 8 amps. However, the Class A rating does not completely reveal
the true, overall power of the KMA-160, both in terms of output power
or AC power consumption. The amplifiers’ maximum output into 8 ohms
is 240 watts per channel.

That every KRELL product uses Class A circuitry in all gain and
supply stages is a foundation of our design philosophy. A second

design commitment that relates to amplifiers is that every unit be

capable of doubling its output into successively lower impedances.

The KMA-160 will deliver 320 watts per channel into 4 ohms; 640 watts
per channel into 2 ohms and 1280 watts per channel into i ohm. And

there is headroom over these figures! It is capable of driving

impedances below I ohm. Use below i ohm requires adjustment of the

Programmable Low Impedance Limit Set circuit on the Protection Board.
This adjustment is performed by the dealer or distributor.

Given the above, the AC power supplied to the amplifier is crucial to
getting maximum performance. The KMA-160 pair should have a dedicated
20 amp line.

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Amplifiers dissipate much of the power they consume in heat. The

KMA-160 should be installed in a location that provides unobstructed
ventilation. If you have to install the units on shelves or in a
cabinet, extra ventilation might be necessary. This can be easily

done with fans in a variety of ways. Generally, with the front and

rear open, 2 - 3 inches clearance each side and 8 inches above the
amplifier, ventilation will be adequate.

The dimensions of the KMA-160 are: 23" wide x 22" deep x 9 high.
The units weigh 80 pounds each; shipping weight is i00 pounds each.

INPUT CONNECTIONS

The KMA-160 has bo~h balanced and single-ended inputs. The balanced

input uses the 3-pin XLR connector and the single-ended input uses
the RCA connector. The pin assignment for the XLR’s is: pin 1 =
signal ground; pin 2 = non-inverting input; pin 3 = inverting input.
The RCA connector is wired in parallel with pin 2, the non-inverted

input. Only one of these inputs should be connected to a
preamplifier.

The input that is not connected to the preamplifier can be used as an
output to a second amplifier for power-biamp applications. Before
proceeding with such an installation you should consult your Dealer
or the factory.

INSTALLATION

After inspection of the amplifiers for any shipping damage they are

ready for instaila~ion. The wiring to and from the amplifiers, and
all components in general, should be arranged in a neat, organized

manner. Specifically, AC wires should be separated from audio wires.

This avoids hum or other unwanted noise from being induced into the
system.

The KMA-160 has four sets of five-way binding post speaker
connectors. These are wired in parallel and have identical function.

It is always preferable to run long interconnect cables to the
amplifiers and keep speaker cable length to a minimum. Speaker cable

does add impedance between the amplifiers, regardless of its guage.

All KRELL amplifiers will drive the lowest impedances with ease. When

impedance is added in any significant amount, amplifier power is
literally wasted in driving the cable, thereby reducing the maximum

power that can be delivered to the speaker.

The feet on the KMA-160 can be used two different ways. They are made
from machined aluminum and are supplied with separate rubber bottoms
and mounting screws. The rubber bottoms can be screwed into the the
feet for protection of fragile surfaces such as hardwood floors or
furniture. For use on rugs we recommend using the feet without the
rubber bottoms.