Rane MA 6S 1994 version User Manual

Page 8

Manual-6

©Rane Corporation 10802 47th Ave. W., Mukilteo WA 98275-5098 TEL 425-355-6000 FAX 425-347-7757 WEB www.rane.com

OPERATION

Voltage Controlled Attenuators

The voltage controlled attenuators (VCAs) in the MA 6S

allow a signiﬁcant increase in usable volume levels without exces-

sive clipping or interference from conventional distortion causing

muting circuits. The VCAs do not aﬀect dynamic response,

distortion or noise levels of any material within the rated output

speciﬁcations of the ampliﬁer. They simply monitor the diﬀer-

ence between Input and Output signals, and the power dissi-

pated in the output devices. In the event of clipping or excessive

dissipation in the output devices, the VCAs “jump in” (out of

hiding, as it were) and turn down the Input level to correct the

overdrive condition.

This means that whenever a CLIP LIMIT ﬂashes, a musical

peak has been quickly turned down to avoid excessive clipping.

This allows you to run the ampliﬁer at a higher continuous level,

typically about 4 dB SPL higher than without VCAs. And that

4 dB of increased SPL is the equivalent of a 250 watt ampliﬁer

without VCAs.

If an SOA LIMIT ﬂashes, the Input level has been quickly

turned down to prevent over-dissipation in the output devices

due to excess phase shift or abnormally low impedances which

may occur at some frequencies. This protection occurs without

distorting or interrupting the program.

Keep an eye on the LEDs on the MA 6S front panel. Occa-

sional ﬂashing of a CLIP LIMIT and/or occasional ﬂashing of a

SOA LIMIT means you are getting the most SPL out of the am-

pliﬁer. Continual lighting of either LED indicates excessive input

overdrive, or too low impedance of load. If a green READY goes

oﬀ, a load has been encountered that could not be corrected by

the VCAs, or the ampliﬁer has oﬀset. If this occurs, the ampliﬁer

must be turned oﬀ and the problem corrected before the channel

can be operated. If the READY LED will not light with the load

disconnected, then an internal fault has occurred and the ampli-

ﬁer is in need of repair.

Adapting the MA 6S to Your Changing Needs

With six channels to choose from and built-in Bridging,

there are a number of diﬀerent combinations available to suit

your present and growing needs. The nice thing about the MA

6S is that you can re-conﬁgure it instead of losing money on an

obsolete, used piece of gear you no longer need.

You can start out with 6 channels at 100 watts or three chan-

nels at 300 watts. When the time comes, you can step up to six

channels at 300 watts by obtaining another MA 6S and keeping

the original. Upgrading to biamped monitors or tri-amped mains

becomes easy as well, by simply adding a second MA 6S, both

taking up only 10.5" rack space.

The MA 6S and Circuit Breakers

The MA6S will easily deliver over 900 watts of audio power,

requiring as much as 15 amps of current from the AC outlet. 15

amps is not an uncommon value for household and some insti-

tutional circuitbreakers, though 20 amp versions are becoming

more common. The bottom line is that the MA 6S is capable

of tripping a 15 amp circuit breaker under normal operation. An

amp that delivers a lot of power, drinks a lot of power to do so.

It is not likely that you will trip a breaker, but it is wise to be

aware of the possibility so you don’t panic if it happens.

INTERNAL JUMPERS

Each ampliﬁer card contains a jumper block that gives the

option of inserting an 80 Hz High-Pass Filter into the Input sig-

nal. This is required in 70 or 100 volt systems when excessive bass

can saturate the transformers, reduce the output, and possibly

blow a fuse at high output levels.

The MA 6S is shipped with these jumpers in the out position

(ﬁlters defeated). Moving this jumper to the in position activates

the ﬁlter.

CAUTION: WAIT ABOUT 15 MINUTES AFTER THE
AMPLIFIER HAS BEEN POWERED DOWN BEFORE
BEGINNING DISASSEMBLY, TO ALLOW THE POWER
SUPPLY CAPACITORS TO DISCHARGE.

1. Remove the bottom cover

: 4 each #6 x 3/8" phillips screws

on the bottom of the side rails and 12 each #6 x 1/4" phillips

screws on the bottom cover.

2. 80 Hz High-Pass Internal Jumpers:

To access the jumper

on each ampliﬁer card, locate J2 (LOW FILTER). The MA

6S is shipped with these jumpers in the OUT position (ﬁlters

defeated). Moving this jumper to the IN position activates the

ﬁlter.

107213

In the event that 80 Hz is not a high enough cutoﬀ frequency,

values may be changed to replace 3 resistors on each ampliﬁer

card. This operation requires dissasembly and soldering as out-

lined in the MA 6S SERVICE INFORMATION section, and

should only be performed by qualiﬁed service personnel.