Ampeg Bass Combo B328 User Manual

							Owner’s Guide
for the
B3 / B328 / B3158
Bass Amplifier
Made in the U.S.A.by 
						

							2
TABLEOFCONTENTS
Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Features  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Important Safeguards and Precautions  . . . . . . . . . .2
The Front Panel Controls and Their Use  . . . . . . .3,4
The Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . .4,5
Some Suggested Settings  . . . . . . . . . . . . . . . . . . .6
Troubleshooting  . . . . . . . . . . . . . . . . . . . . . . . . . . .7
System Block Diagram  . . . . . . . . . . . . . . . . . . . . . .7
Technical Specifications  . . . . . . . . . . . . .back cover
An Introduction to your new Ampeg
Bass Amplifier
Thank youfor making one of the best choices you will
ever make for your musical career – choosing one of the
finest bass amps available, an Ampeg B3/B328/B3158.
Your new bass amplifier offers many outstanding features.
One hundred fifty watts of pure bass energy, total tone con-
trol, and rugged construction make each a true performer’s
bass amp.
Important Safeguards and Precautions
All Ampeg products are designed for continuous safe operation, as long as common sense is used and steps are taken to help
avoid certain problems. Abiding by the following rules can help prevent damage to your amplifier, yourself and others. 
•The amplifier is equipped with a three-pronged  AC power cord. To reduce the risk of electrical shock, NEVERremove or otherwise
attempt to defeat the ground pin of the power cord.
•Connect the amplifier ONLYto a properly grounded AC outlet of the proper voltage for your amp. 
•Avoid sudden temperature extremes, rain and moisture. Also, avoid sudden and intense impact. (If the unit has been subjected to any
of the preceding abuses, have it looked at by an authorized service center.)
•NEVERset the amplifier on a support that might give out under its weight.
•Whenever using tall or stacked speaker cabinets, use them ONLYon a level surface. NEVERset tall or stacked cabinets on a surface
with more than a five degree incline since tipping or falling could occur, possibly causing serious injuries.
•Always keep the total speaker impedance at or above the rated load.
•Unplug the amplifier before cleaning it. NEVER spray liquid cleaners onto the amplifier. Wipe it with a slightly dampened, lint-free cloth
to remove dirt and film.
•Don’t use the amplifier if it has sustained damage to the chassis, controls, or power cord. Refer the unit to an authorized service cen-
ter for inspection.
•Amplifiers capable of producing high volume levels are also capable of inflicting permanent hearing loss or damage, if the exposure to
such levels is prolonged. Such damage is progressive and irreversible! 
CAUTIONRISK OF ELECTRIC SHOCK
DO NOT OPEN
CAUTION: TO REDUCE THE RISK OF ELECTRIC SHOCK,
DO NOT REMOVE COVER.
NO USER-SERVICEABLE PARTS INSIDE.
REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
ATTENTIONRISQUE DELECTROCUTION
NE PAS OUVRIR
ATTENTION: POUR REDUIRE DELECTROCUTION NE PAS
ENLEVER LE COUVERCLE. AUCUNE PIECE INTERNE NEST REPRABLE
PAR LUTILISATEUR. POUR TOUTE REPARATION, SADRESSER A UN
TECHNICIEN QUALIFIE.
VORSICHTELEKTRISCHE SCHLAGGEFAHR
NICHT OFFENEN
VORSICHT: ZUR MINIMIERUNG ELEKTRISCHER SCHLAGGEFAHR NICHT
DEN DECKEL ABENHMEN. INTERNE TEILE KONNEN NICHT VOM
BENUTZER GEWARTET WERDEN. DIE WARTUNG IS QUALIFIZIERTEM
WARTUNGSPERSONAL ZU UBERLASSEN.
THIS EQUIPMENT HAS BEEN DESIGNED AND ENGINEERED TO PROVIDE SAFE AND RELIABLE OPERATION. IN ORDER TO PROLONG THE LIFE OF THE UNITAND PREVENT ACCIDEN-
TAL DAMAGES OR INJURY, PLEASE FOLLOW THESE PRECAUTIONARY GUIDELINES:
WARNING:TO REDUCE THE RISK OF ELECTRIC SHOCK, DO NOT OPEN CHASSIS; DO NOT DEFEAT OR REMOVE THE GROUND PIN OF THE POWER CORD; CONNECT ONLY TO A PROP-
ERLY GROUNDED AC POWER OUTLET.
CAUTION:TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE.
CAUTION:NO USER-SERVICEABLE PARTS INSIDE. REFER SERVICING TO QUALIFIED SERVICE PERSONNEL.
CAUTION:OUR AMPLIFIERS ARE CAPABLE OF PRODUCING HIGH SOUND PRESSURE LEVELS. CONTINUED EXPOSURE TO HIGH SOUND PRESSURE LEVELS CAN CAUSE PERMANENT
HEARING IMPAIRMENT OR LOSS. USER CAUTION IS ADVISED AND EAR PROTECTION IS RECOMMENDED IF UNIT IS OPERATED AT HIGH VOLUME.  The chart below shows the U.S.
Government Occupational Safety and Health Administration (OSHA) regulations which were in effect at the time of this publication for permissible noise exposure, per 29CRF1910, Table G-16.
According to OSHA, any exposure in excess of those listed above could result in some hearing loss.
IT IS NECESSARY FOR THE USER TO REFER TO THE INSTRUCTION MANUAL
REFERREZ-VOUS AU  MANUAL DUTILISATION
UNBEDINGT IN DER BEDIENUNGSANLEITUNG NACHSCHLAGEN EXPLANATION OF
GRAPHICAL SYMBOLS:
DANGEROUS VOLTAGE
DANGER HAUTE TENSION
GEFAHLICHE SPANNUNG=
=
Features
In the world of high performance bass amps, Ampeg amplifiers
stand alone. In true Ampeg tradition, your new B3/B328/B3158
offers you more power, performance and flexibility than any other
bass amplifier in its class. The outstanding features of your new
amplifier, features which set it apart from the competition, are list-
ed below:
•9-BAND GRAPHIC EQ:Use as a “second channel” for bass
solos, or to shape the sound to your own exacting standards. An
independent level control lets you adjust the Graphic EQ volume
•BALANCED LINE OUTPUTS:Independent level control. XLR
type jack  to patch into house consoles, mixing boards, or external
power amplifiers
•EFFECTS LOOP:Connect your effects here for increased inten-
sity and quieter operation
•DRIVE CONTROL:To add harmonics for tube-like overdrive
•BALANCE CONTROL (B3158 only):To fine tune the mix
between the Biamp High and Biamp Low outputs
SOUND LEVEL dBA DURATION PER DAY
SLOW RESPONSE IN HOURS
90 8
92 6
95 4
97 3
100 2SOUND LEVEL dBA DURATION PER DAY
SLOW RESPONSE IN HOURS
102 1-1/2
105 1
11 0 1 / 2
115 1/4 or less
B3/B328/B3158 Bass Amplifier 
						

							3
The Front Panel Controls and Their Use
MASTER
-12dB 0 +12dB
5kHz 8kHz 900Hz 2kHz 300Hz 150Hz 600Hz 40Hz 80Hz
-15dB
PA DPEAKONLIMIT
GAINDRIVEBASSULTRA MIDTREBLEINPUT
PULL
EQ ONLO FLAT
HI
EQ
ONBALANCE
LOW HIGH
128765410911312141513
B3/B328/B3158 Bass Amplifier
1. INPUT:The signal output from an instru-
ment (active or passive) or a line level signal
may be connected here by means of a shield-
ed instrument cable.
2. -15dB PAD:This switch, when depressed,
attenuates the input signal by 15dB.
Attenuation allows the Gain control (#4) to be
used in a more usable (higher) position. If
clipping is indicated with the Gain control at a
low setting, attenuation is needed.
3. PEAK LED:This LED flashes when the
signal level into the preamp approaches clip-
ping. Adjust the Gain control (#4) until a
strong signal from your instrument causes
this LED to flicker.
NOTE:If the LED flashes frequently with the
Gain at a low setting, use the -15dB pad (#2)
to attenuate the input signal and readjust the
Gain.
4. GAIN:This serves as the input level con-
trol for the amplifier. For the best signal to
noise ratio set this control so the Peak LED
(#3) flashes when you strike a string fairly
hard. 
5. DRIVE:This control is used to overdrive
the preamp in order to get various harmonic
enhancement or distorted sounds. In the fully
counterclockwise position the preamp is in
the cleanest condition. As the control is rotat-ed clockwise, signal level is increased to
drive the preamp harder (into distortion). The
tone of the signal is also changed to provide
a smoother overdrive. (The tone controls may
have to be readjusted to obtain the overall
desired tone.) The Gain control (#4) and -
15dB Pad (#2) interact with the Drive control.
For greater overdrive, the Pad switch should
be out and the Drive control fully clockwise.
Use the Gain control to set the amount of
overdrive desired. The Peak LED (#3) will illu-
minate steadily when the amp is used in this
manner.
6. BASS:This is the primary low frequency
control which allows for 12dB of cut or boost
at 50Hz.
7. ULTRA MID:This is the primary midrange
control. Rotate this control to the left of center
for a “contoured” sound (more distant, less
midrange output) or to the right of center for a
pronounced (more up-front) tone.
8. TREBLE:This is the primary high frequen-
cy control which allows for 22dB of cut or
17dB of boost at 5kHz. 
9. EQ ON LED: This LED illuminates when
the EQ is turned on by either the Master
Control (#11) or a footswitch (#24, rear
panel).10. GRAPHIC EQ:These sliders control the
output frequencies indicated above each con-
trol. The center position of each control is flat
(no boost or cut).
11. MASTER:Set the overall output level of
the amplifier with this control. Pulling this
knob out actives the Graphic EQ (#10). When
a footswitch is connected (#24, rear panel)
this switch is disabled.
12. BALANCE (B3158 only):This control
proportions the output signal between the low
and high frequency output jacks (see #18,
rear panel) when using the amp in the biamp
mode.
13. LIMIT LED(S):The LED illuminates
whenever the amplifier is near full output,
indicating that the internal limiter is keeping
the output from distorting.
NOTE:There are two Limit LEDs only on the
B3158: one for its low frequency power amp
and one for its high frequency power amp.
14. POWER ON LED:This LED indicator illu-
minates when the POWER switch (#15) is ON.
15. POWER SWITCH:This heavy-duty rock-
er switch applies the power to the amplifier.
The amp is ON when the top of the switch is
depressed, OFF when the bottom of the
switch is depressed.
1. ENTRADA:Conecte aquí su guitarra de bajos
usando un cable blindado para instrumentos.
2. TERMINAL DE -15dB:Si su bajo tiene capta-
dores de alta salida ó circuitos electrónicos activos,
usted tal vez notará que el díodo (LED) de Picos
(#3) parpadea ó permanece iluminado aún en posi-
ciones bajas del control de Ganancia (#4). Conecte
esta Terminal para conservar limpia la señal. Esto
atenuará la señal de entrada hacia el preamplifi-
cador, lo que le permitirá obtener la mejor relación
de señal-a-ruido para su bajo.
3. DIODO (LED) DE PICOS:Este LED se ilumi-
nará cuando cualquier etapa de preamplificación se
encuentre cerca del punto de sobreimpulso. Ajuste
el control de Ganancia (#4) hasta que una señal
fuerte de su bajo cause un parpadeo de este LED.NOTA:Si el LED permanece iluminado aún con la
Ganancia en una posición baja, utilice la Terminal
de -15dB (#2) para atenuar la señal de entrada y
reajuste la Ganancia.
4. GANANCIA: Esto sirve como el control de
nivel de entrada para el amplificador. Para lograr la
mejor relación de señal-a-ruido fije este control para
que el LED de Picos (#3) parpadee cuando usted
pulse con fuerza alguna cuerda.
5. IMPULSO:Este control se usa para sobreim-
pulsar el preamplificador a fin de conseguir varios
realces armónicos ó sonidos de distorsión. En la
posición totalmente contraria a las manecillas del
reloj, el preamplificador se encontrará en la posición
más “limpia”. Conforme el control se gire a favor de
las mane-cillas del reloj, el nivel de la señal se incre-mentará para impulsar el preamplificador con
mayor fuerza (hacia la distorsión). El tono de la
señal también cambia para proveer un sobreimpul-
so más suave. Tal vez tengan que ajustarse los
controles de tono para obtener el tono general
deseado. El control de Ganancia (#4) y la Terminal
de -15dB (#2) interaccionan con el control de
Impulso. Para un sobreimpulso mayor, el interruptor
de la Terminal debe estar apagado y el control de
Impulso totalmente a favor de las manecillas del
reloj. Use el control de Ganancia para fijar la canti-
dad deseada de sobreimpulso. El díodo LED de
Picos (#3) se iluminará en forma constante cuando
el amplificadora se utilice de esta manera.
6. BAJOS:Esta perilla sirve como el control pri-
mordial para las frecuencias bajas. Esto permite un
rango de 8dB de recorte ó de refuerzo a 50Hz. 
						

							4
The Front Panel Controls and Their Use
The Rear Panel 
CAUTIONRISK OF ELECTRIC SHOCK
DO NOT OPENAVIS:WARNING: TO REDUCE THE RISK OF FIRE OR 
ELECTRIC SHOCK, SO NO EXPOSE THIS EQUIP-
MENT TO RAIN OR MOISTURE.RISQUE DE CHOC ELECTRIQUE
NE PAS OUVRIR
SPEAKERSEFFECTS
LOOP
BAL.
OUTFOOT
SWITCH RETURN SENDHIGH
50 WATTS
@8 OHMS
8 OHM MIN.LOW
100 WATTS
@4 OHMS
4 OHM MIN.
MODEL
SERIAL #B-3158
500 WATTS MAX.
115VAC-60Hz
POST
PRE
-20dB
0dB
181920232421221617
FOR 100-120VAC, 50/60Hz:       T5A, 250V
FOR 220-240VAC, 50/60Hz:       T2.5A, 250V
16. FUSE:This protects the unit from dam-
age due to overload conditions or power
line surges. In case of failure, replace it only
with the same size and type.
17. AC LINE IN:Firmly insert the supplied
AC power cord into this socket until it is fully
seated. Plug the male end of the cord into a
grounded AC  outlet. DO NOT DEFEAT
THE GROUND PRONG OF THE AC
PLUG!
18. SPEAKER OUTPUT(S):This section is
different for each of the three models. The
B3158 is shown in the illustration above. 
The B3158 has two internal amplifiers,
one for the high frequencies, one for the
low. Each amplifier section has its own
speaker output jack, factory-wired to the
internal speakers. To use external speaker
cabinets, unplug the connectors from the
jacks and use speaker cables with 1/4”
plugs to connect the LOW jack to your low
frequency cabinet and the HIGH jack to the
high frequency cabinet. Use the Balance
control (#12, front panel) to proportion theoutput signal between the low and high fre-
quency output jacks. Observe the minimum
impedance ratings for each output (8 ohms
for high, 4 ohms for low). 
The B3 has a single speaker output jack
(wired at the factory to its speaker enclo-
sure). To use an external speaker cabinet,
disconnect the amplifier from the enclosure
and connect it to the external cabinet, using
a speaker cable with 1/4” plugs. Observe
the 4 ohm minimum impedance rating.
The B328 has a single speaker output
jack, and two input jacks on its speaker cab-
inet: WITH TWEETER and WITHOUT
TWEETER. Connect the speaker cable to
the jack which gives you the best sound. To
use an external speaker cabinet, discon-
nect the amplifier from the enclosure and
connect it to the external cabinet, using a
speaker cable with 1/4” plugs. Observe the
4 ohm minimum impedance rating.The following chart shows the total
impedance load when connecting speaker
cabinets in parallel:
Cabinet # of Total
Impedance Cabs Impedance
8Ω24Ω
16Ω28Ω
16Ω44Ω
19. EFFECTS RETURN:To use an external
effects device or other signal processor,
connect the OUTPUT of the device to this
jack using a shielded cable. This returns the
processed signal into the amplifier’s master
section.
20. EFFECTS SEND:Connect the output
from this jack to the INPUT of an external
effects device using a shielded cable. This
sends a post-EQ signal to your effects.
Since plugging a cable in here does not
break the through connection to the power
amp, this jack can also be used as an
unbalanced line out jack.
B3/B328/B3158 Bass Amplifier
7. ULTRA-MEDIANOS: Este es el control primor-
dial para el rango de las frecuencias medianas. Gire
el control del centro hacia la izquierda para lograr
un sonido de contorno (más distante, menor salida
en el rango mediano) ó del centro hacia la derecha
para obtener un sonido realmente penetrante.
8. AGUDOS:Esta perilla sirve como el control pri-
mordial para las frecuencias altas. Esto permite un
rango de 17dB de refuerzo ó 22dB de recorte a
5kHz.
9. EQ EN LED: Este dÌodo LED indicador se ilu-
mina cuando usted activa el EQ mediante el control
Maestro (#14) del panel delantero ó el interruptor de
pie (#24) del panel posterior.
10. EQ GRAFICO:Estos controles deslizantes
(cursores) le permiten ajustar la salida de las fre-
cuencias que se muestran junto a cada control. La
posición central de cada control es plana (sinrefuerzo ni recorte). Estos controles sólo afectan el
sonido cuando el EQ esé prendido.
11. MAESTRO: Fije mediante este control el nivel
general de salida del amplificador. El Circuito de
Efectos y la Salida Equilibrada (#19, 20, 23) no se
verán afectadas por el control Maestro. Jalando el
control Maestro se prende el EQ Gráfico (#10).
Cuando se utiliza el interruptor de pie, se pasa por
alto el interruptor del panel delantero.
12. EQUILIBRIO (SOLO EN EL B358):Este con-
trol varía el nivel de la señal entre las salidas de
bajas y altas frecuencias (véase el #18) para ade-
cuar aún más el sonido).
13. DIODOS LED DE LIMITE:Este LED indicador
parpadeará cada vez que se requiera el circuito lim-
itador interno para conservar limpia la señal de sal-
ida del amplificador. Esto indica que el amplificador
está aproximándose a su salida máxima y que ellimitador está impidiendo el aplanamiento (“clip-
ping”) de la señal de salida.
NOTA:Hay dos circuitos Limitadores  dentro del
B3158:  uno para su amplificador de potencia de
frecuencias bajas y otro para su amplificador de
potencia de frecuencias altas. Todos los demás
modelos tienen un solo circuito Limitador, y por lo
tanto un solo LED de Limite.
14. DIODO LED DE POTENCIA ENCENDIDA:
Este LED indicador se ilumina cuando se prende el
interruptor de Potencia (#15).
15. INTERRUPTOR DE POTENCIA: Este interrup-
tor de servicio pesado tipo vaivén aplica la energía
de CA al amplificador:  el amplificador se PRENDE
en la posición hacia arriba (“I”), y se APAGA en la
posición hacia abajo  
						

							5
21. PRE/POST SWITCH:You can select
either pre or post-EQ for the signal at the
Balanced Out jack (#23) with this switch.
With the switch in the OUT position, the sig-
nal at the jacks will be pre-EQ. This is a
direct output which is not affected by any
EQ or boost settings. With the switch
depressed, the signal is post-EQ and is
controlled and modified by the tone con-
trols, Graphic EQ and Effects Loop.
22. -20dB SWITCH:This switch adjusts theoutput level at the Balanced Out jack (#23).
The switch works independently from the
front panel Master control. Depressing the
switch activates the -20dB pad, which
allows patching into a mixer’s mic input
without overdriving it.
23. BALANCED OUT:This XLR-type con-
nection supplies a balanced preamp output
signal for connecting to a house mixing
board, recording console or external ampli-
fiers with balanced inputs. The signal can beset to pre or post-EQ by the Pre/Post switch
(#21). The level can be adjusted for either
mic or line type inputs using the -20dB
switch (#22).
24. FOOTSWITCH:This jack accepts the
1/4” plug from a 1-button footswitch, allow-
ing remote control of the Graphic EQ on/off
function. When a footswitch is used, the
front panel Master Pull EQ On switch (#11)
is bypassed.
The Rear Panel
B3/B328/B3158 Bass Amplifier
16. FUSIBLE:Esto protege a la unidad con-
tra daños debidos a condiciones de sobrecar-
ga 
ósobretensiones transitorias en la línea de
energía. Si el fusible se quema, rep
óngalo
sólo con el mismo tipo y tamaño.
17. ENTRADA DE LA LINEA DE CA:
Conecte firmemente a este receptáculo el
cable suministrado de corriente de CA, oprim-
iéndolo hasta que quede totalmente asenta-
do. Enchufe el extremo macho del cord
ón a
una salida aterrizada de CA.  ¡NO PASE POR
ALTO EL BORNE DE TIERRA DE LA CLAV-
IJA DE CA!
18. SALIDA(S) DE LA(S) BOCINA(S):Esta
secci
ón es diferente para cada de los tres
modelos.  El B3158 aparece en la ilustración
arriba.
El B3158 tiene dos amplificadores inter-
nos, uno para las frecuencias agudas, uno
para las graves. Cada secci
ón de amplifi-
cadores tiene su propio “jack” de salida para
bocinas. Este modelo viene cableado desde
la fábrica a su propio gabinete de bocinas:  el
conector negro “cola de cochino” va al “jack”
BAJO, el gris al “jack” AGUDO. Para utilizar
gabinetes de bocinas externos, desenchufe
los conectores de los “jacks” y use cables
para bocinas con  clavijas de 1/4” para conec-
tar el “jack” BAJO a su gabinete de frecuen-
cias bajas y el “jack” de AGUDOS al gabinete
de frecuencias altas. Observe la especifi-
caci
ón de impedancias mínimas para cada
“jack” (8 ohms para los agudos, 4 ohms para
los bajos).
El B3 tiene un ‘jack” de salida para una
sola bocina (que viene cableado desde la
fábrica a su propio gabinete de bocinas). Para
usar un gabinete externo de bocinas, des-
enchufe el amplificador del gabinete y con-nectarlo a el gabinete externo. Use un cable
para bocinas con clavijas de 1/4”. Observe la
especificaci
ón de 4 ohms de impedancia
como mínimo.
El B328 tiene un ‘jack” de salida para
bocinas, y dos “jacks” de entrada en el gabi-
nete de los bocinas internal: “WITH TWEET-
ER” (con la bocina de las agudos) y “WITH-
OUT TWEETER” (sin la bocina de las agu-
dos). Para usar un gabinete externo de boci-
nas, desenchufe el amplificador del gabinete
y connectarlo a el gabinete externo. Use un
cable para bocinas con clavijas de 1/4”.
Observe la especificaci
ón de 4 ohms de
impedancia como mínimo.
La tabla a continuaci
ón muestra la carga
de impedancia total cuando se conecten gabi-
netes de bocinas en paralelo: 
Impedancia de # de Impedancia
cada Gabinete Gabinetes Total 
8 ohms 2 4 ohms
16 ohms 2 8 ohms
16 ohms 4 4 ohms
19. RETORNO DE EFECTOS:Para utilizar
un dispositivo de efectos externo ú otro proce-
sador de señales, conecte la SALIDA del dis-
positivo a este “jack” usando un cable blinda-
do. Esto alimenta la señal procesada a la sec-
ci
ón maestra del amplificador.
20. ENVIO DE EFECTOS:Conecte la salida
de este “jack” a la ENTRADA de un dispositi-
vo de efectos externo usando un cable blinda-
do. Esto envía una señal post-EQ a sus efec-
tos. Siendo que la conexi
ón de un cable en
este lugar no rompe la conexión directa al
amplificador de potencia, esto se puede uti-
lizar como otra linea hacia afuera.21. INTERRUPTOR PRE/POST:Usted
puede seleccionar por medio de este inter-
ruptor ya sea pre 
ópost-EQ para la señal en
el “jack” de Salida Equilibrada (#23). Con el
interruptor en la posición de FUERA, la señal
en los “jacks” será pre-EQ. Esta es una salida
directa no afectada por ningunas posiciones
del EQ ó de refuerzo. Con el interruptor hacia
adentro, la señal es post-EQ y se controla y
modifica mediante los controles de tono, el
EQ Gráfico y el Circuito de Efectos.
22. INTERRUPTOR DE -20dB:Este interrup-
tor ajusta el nivel de salida en el “jack” de
Salida Equilibrada (#23). El interruptor fun-
ciona independientemente del control
Maestro del panel delantero. Al oprimirse el
interruptor hacia adentro se activa la terminal
de los -20dB, lo que permite conectarse a las
entradas para micrófonos en un mezclador
sin sobreimpulsarlos.
23. SALIDA EQUILIBRADA:Esta conexión
tipo XLR proporciona una señal de salida
equilibrada de preamplificación para conec-
tarse a un tablero mezclador local, una con-
sola  grabadora ó amplificadores externos
con entradas equilibradas. La señal se puede
establecer como pre ó post-EQ mediante el
interruptor Pre / Post (#21). El nivel se puede
ajustar para entradas de tipos ya sean de
micrófono ó de línea utilizando el interruptor
de -20dB (#22).
24. INTERRUPTOR DE PIE:Este “jack”
acepta la clavija de 1/4” de un interruptor de
pie de un solo botón, lo que permite un con-
trol remoto de la función de prender / apagar
del EQ Gráfico. Cuando se utiliza un interrup-
tor de pie, se pasa por alto el interruptor
Maestro para Prender ó Jalar el EQ (#11). 
						

							6
GAINDRIVEBASSULTRA MIDTREBLE
GAINDRIVEBASSULTRA MIDTREBLE
GAINDRIVEBASSULTRA MIDTREBLE
GAINDRIVEBASSULTRA MIDTREBLE
Some Suggested Settings*
JAZZ: ROCK:
COUNTRY:
FUNK “POPPING:”B3/B328/B3158 Bass Amplifier
The setting of the
Gain control
depends on your
particular instrument.
The Master control
should be set to pro-
duce the appropriate
output volume level.
The Graphic EQ can
be used to tailor the
amplifier to your
speaker cabinets, to
compensate for
room acoustics and
to “fine tune” your
sound. 
						

							7
Troubleshooting
In the unlikely event that your B3/B328/B3158 should malfunction, take a few minutes to troubleshoot it before you call
for service. You can save yourself time and money by doing it yourself, and often the cure for the problem is something
quite simple.
If the problem isn’t covered above, or if the steps lead you here, then contact your Ampeg dealer for service informa-
tion. Also, you should refer your amp for servicing if it gets dropped, has liquid spilled into it, or sustains damage to its
power cord (see page 2).
System Block Diagram
NO SOUND
LEDs LIGHT
Check amp controls, check
for signal from instrument
NO SOUND
Listen for hum
SOUND OK
NO HUM
Check speaker
SPEAKER OK
SOUND OK
HUM
Unplug instrument,
touch tip of cable
NO CHANGELOUD HUM
Replace cableCheck bass pickup
NO CHANGESOUND OK
SEE BELOW
LEDs DON’T LIGHT
Check AC outlet 
OUTLET OKNO POWER
Check power cord,
fuse, power switch Check house fusebox
or circuit breaker 
OK
NO SOUND
SOUND OK
Check instrument, cables
POOR SOUND
Check speaker(s)
SPEAKER(S) OK,
POOR SOUNDSPEAKER(S)
DEFECTIVE
Replace speaker(s)
SOUND OKPOOR SOUND
SEE BELOW
TONES9 BAND EQ PEAK LED
INPUT
GAIN
-15dB
PADDRIVE
BASS
ULTRA MIDTREBLE
FOOT
SWITCH
EFFECTS 
SENDEFFECTS 
RETURN
EQ ON
MASTER
PRE
-20dB2
3 POST
BALANCE
LOW
SPEAKER
OUT
LOW
FREQ
POWER
AMP
HIGH
FREQ
POWER
AMPLOW LIMIT LED
HIGH
SPEAKER
OUT
HIGH LIMIT LED
BIAMP
X-OVERSPEAKER
OUT
POWER
AMP
LIMIT LED
B3, B328
B3158
BALANCED
OUT
B3/B328/B3158 Bass Amplifier 
						

							Ampeg reserves the right to change specifications without notice.
Ampeg is proudly Made in America. ©1999 SLM Electronics, 1400 Ferguson Avenue, St. Louis, MO 63133 U.S.A.
P/N 47-588-03 • 10/99
B3/B328/B3158 Bass Amplifier
Technical Specifications
OUTPUT POWER RATING
B3, B328:150 Watts RMS, 4Ωload 
B3158:Low Freq - 100 Watts RMS, 4Ωload 
High Freq - 50 Watts RMS, 8Ωload 
POWER REQUIREMENTS120VAC, 60Hz, 170VA
100/115VAC, 50/60Hz, 170VA
220-240VAC, 50/60Hz, 170VA
TONE CONTROL RANGE
Bass:±8dB @ 50Hz
Ultra-Mid:+5, -17dB @500HZ
Treble:+17, -22dB @ 5KHZ
GRAPHIC EQ RANGE±11dB @ 40Hz; ±8dB @ 80, 150, 300, 600, 900, 2kHz; ±9dB @ 9kHz
GAIN66dB typical, tones @ center
SIGNAL TO NOISE RATIO75dB typical
INTERNAL SPEAKERS B3 B328 B3158
Low Frequency: Size/Type:15” Ampeg Custom (1) 8”Polypropylene (2) 15” Ampeg Custom (1)
Magnet:56 oz 30 oz  56 oz
Voice Coil:2.5”1.5”2.5”
Impedance:4Ω8Ω4Ω
High Frequency: Size/Type:N/A Hi-Efficiency Piezo (1) 8”Polypropylene (1)
Magnet:30 oz
Voice Coil:1”
Impedance:8Ω
SIZE AND WEIGHT B3 B328 B3158
(W x H x D)20”x26”x13.5”20”x18.75”x13.5”20”x34.5”x14.5”
68 lbs. 57 lbs. 84 lbs.
www.ampeg.com