SPA100 1 / 2 - R a c k P o w e r A m p l i f i e r

Speaker Impedances And Power Ratings:

When connecting speaker cabinets, you must observe proper load impedances. Whenever connecting multiple cabinets to an amplifier, the total load impedance must be calculated to insure proper performance from the amplifier. The impedance chart which follows shows the total load impedances of many common parallel speaker combinations:

IMPEDANCE CHART:

SYSTEM ONE

 

SINGLE SPEAKER

TWO SPEAKERS

 

IN PARALLEL

 

 

 

 

 

8

16

8:16

16:16

 

ONE

8

4

5.3

3.2

4

SYSTEM

SPKR

16

5.3

8

4

5.3

TWO

TWO IN

8:16

3.2

4

2.7

3.2

 

PARALLEL

16:16

4

5.3

3.2

4

Note that some combinations result in impedances less than 4 ohms. (the shaded areas) These combi- nations are not recommended for the SPA100 and should be avoided. They are included on the chart for reference only. Too low an impedance will activate the amplifier’s protection circuit.

The formula for this chart is:

1

1/R1 + 1/R2 + ... + 1/RN

Where “R” is the speaker impedance. So, using two 16 ohm speakers in combination with one 8 ohm speaker, the imped- ance would be:

1

=

1

=

1

1/8 +1/16+1/16

 

.125+.0625+.0625

 

.250

= 4 ohm load impedance

You can also determine the combined impedance by means of the Impedance Chart. The combined impedance appears at the intersection of the 16:16 column (System One) and 8row (System Two).

Power Output:

The power output of an amplifier changes in accordance with the load impedance or mode of operation. The total output power of the SPA100 is as follows:

total load impedance:

8 ohms

4 ohms

total output power:

75 watts

100 watts

Output Power Per Speaker Cabinet:

If each parallel connected speaker cabinet has the same rated impedance, divide the total power output by the number of cab- inets used. For example: Four 16 ohm cabinets have a total load impedance of 4 ohms (see the impedance chart above), which allows a total output power of 100 watts RMS: 100/4 = 25 watts RMS for each cabinet.

Speaker cabinets with different rated impedances will draw different amounts of power. To calculate the power output per cabinet, obtain the total load impedances from the impedance chart above and divide it by each speaker impedance. For exam- ple: Three speaker cabinets, one with a rated impedance of 8 ohms and two at 16 ohms are connected in parallel. According to the impedance chart, the total load impedance is 4 ohms, which means a total power output of 100 watts as above. Divide the total impedance by the impedance of each speaker and multiply the results by 100.

Rtotal =

4/8 = 1/2 x 100 = 50 watts for the 8 ohm cabinet

RN

4/16 = 1/4 x 100 = 25 watts for each of the 16 ohm cabinets

 

 

Joining Two Amplifiers For Rack Mounting:

The SPA100 amplifier is shipped with a heavy duty steel joining plate (not attached to the unit). This allows two amplifiers to be mounted side by side in a single rack space (19”W x 1-3/4”H).

(1)Remove one rack mount flange from each amplifier: the flange on the right side of the amplifier on the left and the flange on the left side of the amplifier on the right.

REMOVE THESE 2

REMOVE THE 6

REMOVE THESE 2

SIDE SCREWS

FRONT SCREWS

(3 PER UNIT)

FRONT SCREWS

Power

 

Power

On

 

On

Off

 

Off

Power Signal Limit Protect

 

Power Signal Limit Protect

REMOVE THESE 2

RACK MOUNT FLANGES

(2)Remove two front panel screws from each amplifier: the two screws on the right side of the amplifier on the left and the two screws on the left side of the amplifier on the right.

PLACE UNITS SIDE BY SIDE - ALIGN THROUGH HOLES

IN JOINING PLATE OVER SCREW HOLES IN UNITS

Power

Power

On

On

Off

Off

Power Signal Limit Protect

Power Signal Limit Protect

 

INSERT 4

 

FRONT SCREWS

(3)Position the amplifers side by side, align the holes in the joining plate with the holes in the front panel of the adjacent amplifier. Insert the screws through the joining plate into the front panel of the adjacent amplifier and tighten securely.

TWO UNITS, JOINED AND READY FOR RACK MOUNTING:

Power

 

 

 

Power

 

 

 

On

 

 

 

On

 

 

 

Off

 

 

 

Off

 

 

 

Power

Signal

Limit

Protect

Power

Signal

Limit

Protect

6

Page 6
Image 6
Crate Amplifiers SPA100 manual Speaker Impedances And Power Ratings, Power Output, Output Power Per Speaker Cabinet

SPA100 specifications

The Crate Amplifiers SPA100 is a versatile and powerful amplifier designed for musicians seeking rich tones and robust performance across various musical genres. Renowned for its reliability and sound quality, the SPA100 has become a staple for guitarists and bass players alike.

One of the standout features of the SPA100 is its impressive power output, delivering 100 watts through its two channels. This ensures an ample amount of volume for live performances, making it suitable for anything from intimate gigs to larger venues. The two channels allow musicians to customize their sound, with one channel typically dedicated to clean tones and the other for overdriven or distorted sounds.

In terms of sound shaping capabilities, the SPA100 is equipped with a 3-band EQ for both channels. This equalization system gives players the ability to sculpt their tones precisely, adjusting the bass, mid, and treble frequencies to fit their individual styles or the demands of specific musical pieces. The built-in reverb effect adds an extra layer of depth to the sound, making it perfect for creating atmospheric performances.

The SPA100 features a solid-state design, which contributes to its durability and consistent performance. Solid-state amplifiers are known for their ability to produce high headroom, making them less prone to distortion at higher volumes—a critical advantage for playing live. Additionally, the amp is designed with high-quality components, ensuring reliability on the road.

Another significant aspect of the SPA100 is its lightweight nature, making it easy for musicians to transport. Despite its power, the design focuses on portability, a key consideration for today's gigging musicians. This combination of power and portability means that the SPA100 can deliver sophisticated sound while being easy to manage.

For connectivity, the SPA100 includes multiple input options and effects loops, allowing musicians to integrate various pedals and effects into their setup seamlessly. This flexibility enhances the amplifier’s usability in both studio and live scenarios, accommodating a wide range of instruments and effects.

In summary, the Crate Amplifiers SPA100 is an exemplary amplifier that marries sound quality with user-friendly features. Its robust power, comprehensive EQ, solid-state reliability, and portability make it a preferred choice for musicians on the go. Whether performing live or rehearsing, the SPA100 stands out as a reliable and versatile piece of gear that caters to the diverse needs of contemporary musicians.