AMPEG PB250 Owner's Manual

Owner ’s Guide for the

Amp Head

Made with Pride in the U.S.A. by Ampeg

2

T

ABLE OF CONTENTS

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Important Safeguards and Precautions . . . . . . . . . .3

The Front Panel Controls and Their Use . . . . . . . .4

The Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . .6

System Block Diagram . . . . . . . . . . . . . . . . . . . . . .7

Technical Specifications . . . . . . . . . . . . .back cover

PB250

PortaBass Amp Head

IMPORTANT SAFETY INSTRUCTIONS

• READ, FOLLOW, HEED, AND KEEP ALLINSTRUCTIONS AND WARNINGS.

• DO NOTOPERATE NEAR ANY HEATSOURCE AND DO NOT BLOCK ANY VENTILATION OPENINGS ON THIS APPARATUS. FOR PROPER OPERATION, THIS UNIT REQUIRES 3”

(75CM) OF WELL VENTILATED SPACE AROUND HEATSINKS AND OTHER AIR FLOW PROVISIONS IN THE CABINET.

• DO NOTUSE THIS APPARATUS NEAR SPLASHING, FALLING, SPRAYING, OR STANDING LIQUIDS.

• CLEAN ONLY WITH LINT-FREE DAMP CLOTH AND DO NOTUSE CLEANING AGENTS.

• ONLY CONNECT POWER CORD TO APOLARIZED, SAFETYGROUNDED OUTLETWIRED TO CURRENT ELECTRICAL CODES AND COMPATIBLE WITH VOLTAGE, POWER, AND

FREQUENCY REQUIREMENTS STATED ON THE REAR PANEL OF THE APPARATUS.

• PROTECTTHE POWER CORD FROM DAMAGE DUE TO BEING WALKED ON, PINCHED, OR STRAINED.

• UNPLUG THE APPARATUS DURING LIGHTNING STORMS OR WHEN UNUSED FOR LONG PERIODS OF TIME.

• ONLY USE ATTACHMENTS, ACCESSORIES, STANDS, OR BRACKETS SPECIFIED BY THE MANUFACTURER FOR SAFE OPERATION AND TO AVOID INJURY.

• THIS APPARATUS DOES NOTOPERATE NORMALLYAND REQUIRES SERVICE WITH ANY PHYSICAL DAMAGE FROM IMPACT OR ANY EXPOSURE TO MOISTURE.

• SERVICE MUSTBE PERFORMED BY QUALIFIED PERSONNEL.

• OUR AMPLIFIERS ARE CAPABLE OF PRODUCING HIGH SOUND PRESSURE LEVELS. CONTINUED EXPOSURE TO HIGH SOUND PRESSURE LEVELS CAN CAUSE PERMA-

NENT HEARING IMPAIRMENTOR LOSS. USER CAUTION IS ADVISED AND EAR PROTECTION IS RECOMMENDED IF UNIT IS OPERATED AT HIGH VOLUME.

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

WARNING: TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE
THIS APPARATUS TO RAIN OR MOISTURE. TO REDUCE THE RISK OF ELECTRIC
SHOCK, DO NOT REMOVE COVER. NO USER-SERVICEABLE PARTS INSIDE. REFER
SERVICING TO QUALIFIED SERVICE PERSONNEL.

PRECAUCION

RIESGO DE CORRIENTAZO

NO ABRA

PRECAUCION: PARA REDUCIR EL RIESGO DE INCENDIOS O DESCARGAS ELECTRICAS, NO PER­MITA QUE ESTE APARATO QUEDE EXPUESTO A LA LLUVIA O LA HUMEDAD. PARA DISMINUOIR EL
RIESGO DE CORRIENTAZO. NO ABRA LA CUBIERTA. NO HAY PIEZAS ADENTRO QUE EL USARIO
PUEDO REPARAR DEJE TODO MANTENIMIENTO A LOS TECHNICOS CALIFICADOS.

ATTENTION

RISQUE D'ELECTROCUTION

NE PAS OUVRIR

ATTENTION: PROTÉGEZ CET APPAREIL DE LA PLUIE ET DE L'HUMIDITÉ AFIN D'ÉVITER TOUT
RISQUE D'INCENDIE OU D'ÉLECTROCUTION. POUR REDUIRE D'ELECTROCUTION NE PAS ENLEVER
LE COUVERCLE. AUCUNE PIECE INTERNE N'EST REPRABLE PAR L'UTILISATEUR. POUR TOUTE
REPARATION, S'ADRESSER A UN TECHNICIEN QUALIFIE.

"IT IS NECESSARY FOR THE USER TO REFER TO THE INSTRUCTION MANUAL"
“ES NECESARIO QUE EL USUARIO SE REFIERA AL MANUAL DE INSTRUCCIONES.”
"REFERREZ-VOUS AU MANUAL D'UTILISATION"

EXPLANATION OF GRAPHICAL SYMBOLS:
EXPLICACION DE SIMBOLOS GRAFICOS:
EXPLICATION DES SYMBÔLES GRAPHIQUES:

"DANGEROUS VOLTAGE"
“VOLTAJE PELIGROSO”
"DANGER HAUTE TENSION"

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Thank you for choosing the Ampeg PB250 PortaBass Amp Head. The
PB250 features Ampeg’s radical new Micro Dynamic Technology power
amp circuitry. This gives you the ultimate combination of power, tone,
and portability in a small, lightweight package.

In order to obtain maximum performance and enjoyment from your
new Ampeg amplifier, please read these instructions prior to its use.

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PB250

PortaBass Amp Head

In the world of high performance bass amps, Ampeg amplifiers stand alone. In true Ampeg tradition, the PB250
offers you more power , performance and tone than any other bass amplifier in its class. The outstanding features
which set your new amplifier apart from the competition are listed below.

• MDT POWER AMP: Micro Dynamic Technology amplifier circuitry provides maximum power in a
small lightweight package – the efficiency of this design eliminates the need for heavy heat sinks,
transformers and filter capacitors

• FOUR BAND ROTARY EQ: Four bands of equalization and shift controls for the Low and High Mid
provides optimum tone control

• ULTRA LOW, ULTRA HIGH SWITCHES: Enhances flexibility and tone control

• EFFECTS LOOP: Send and Return jacks are combined with an Effects Blend control for virtually

noise-free use of your favorite effects

• TRANSFORMER BALANCED LINE OUTPUT: XLR jack with level control, ground lift, and a
pre/post-EQ switch – for patching into house consoles, mixing boards, or external power amplifiers

• SPEAKON®AND 1/4” SPEAKER OUTPUT JACKS: Compatible with either type of connecting cable

• MADE WITH PRIDE IN THE U.S.A.

Features

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, NEVER remove or otherwise
attempt to defeat the ground pin of the power cord.

• Connect the amplifier ONLY to 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.)

• NEVER set the amplifier on a support that might give out under its weight.

• 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.

• Do not use the amplifier if it has sustained damage to the chassis, controls, or power cord. Refer the unit to an authorized service
center 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! Consider using quality hearing protection devices.

Declaration Of Conformity

#41, Effective 02-01-2002

Manufacturer’s Name: SLM Electronics

Production Facility: 11880 Borman Drive, St. Louis, MO 63146, USA
Production Facility: 700 Hwy 202 W, Yellville, AR 72687, USA
Shipping Facility: 1400 Ferguson Ave., St. Louis, MO 63133, USA
Office Facility: 1400 Ferguson Ave., St. Louis, MO 63133, USA

Product Type: Audio Amplifier
Complies with Standards:

LVD: 92/31/EEC, 93/68/EEC, & 73/23/EWG
Safety: EN60065
EMC: EN55013, EN55020, EN55022, EN61000-3-2,

& EN61000-3-3

Supplementary information provided by:

SLM Electronics - R & D Engineering

1901 Congressional Drive, St Louis, MO 63146, USA

Tel.: [phone], Fax: [phone]

Speakon®is a registered trademark of Neutrik USA

4

The Front Panel Controls and Their Use:

1. 0dB: Connect your bass guitar here by
means of a shielded instrument cable. If
your bass has active electronics or high­output pickups, or if the Peak LED (#3) illu­minates at low signal levels, connect your
bass to the -12dB jack (#2).

2. -12dB: Connect your bass guitar here
by means of a shielded instrument cable, if
your bass has passive electronics or low­output pickups. If the Peak LED (#3) does
not illuminate at high signal levels, connect
your bass to the 0dB jack (#1).

3. PEAK: This LED will illuminate when the
level of the preamp signal begins to over­drive the amplifier. For the best signal to
noise ratio, set the Gain control (#4) so the
Peak LED flashes on strong signal spikes
during normal playing of your instrument.

4. GAIN: Use this control to adjust the level
of the signal going into the preamp. Adjust
this control until the Peak LED (#3) flashes
on strong signal peaks.

5. LOW: Use this control to adjust the low
frequency level of the amplifier. This control
allows an adjustment of +/-14dB at 100Hz.

6. ULTRA LOW: This switch, when de­pressed, increases the low frequency out­put by 6dB at 40Hz.

7. LOW MID: Use this control to adjust the
lower midrange frequency level of the
amplifier. This control allows an adjustment
of +/-15dB at 270Hz, or +/- 15dB at 400Hz,
depending on the setting of the Shift switch
(#8).

8. SHIFT (LOW MID): This switch, when
depressed, shifts the frequency of the Low
Mid control (#7) from 270Hz to 400Hz.

9. HIGH MID: Use this control to adjust the
upper midrange frequency level of the
amplifier. This control allows an adjustment
of +/-14dB at 900Hz, or +/- 15dB at 1.9kHz,
depending on the setting of the Shift switch
(#10).

10. SHIFT (HIGH MID): This switch, when
depressed, shifts the frequency of the High
Mid control (#9) from 900Hz to 1.9kHz.

11. HIGH: Use this control to adjust the
high frequency level of the amplifier. This
control allows an adjustment of +/-13dB at
6kHz.

12. ULTRA HIGH: This switch, when de­pressed, increases the high frequency out­put by 8dB at 10kHz.

13. EFFECTS BLEND: Use this control to
adjust the level of external effects that are
connected to the Effects Send and Return
jacks (#23 and #22, rear panel). With this
control in the fully counterclockwise posi­tion no effect is applied to the signal. As
you rotate the control clockwise the level of
the effect increases.

NOTE: When using the effects loop with a
compressor/limiter, this control must be
rotated fully clockwise for optimum results.

14. LIMIT: This LED illuminates when the
internal limit circuit is activated. This indi­cates that the amplifier is nearing full out­put and the limiter is keeping the amplifier
from clipping the output signal.

15. MASTER: Use this control to adjust the
output level of the amplifier. If the Limit LED
illuminates, reduce this control until the
Limit LED only flashes on strong signals.

16. POWER ON INDICATOR: This light
illuminates when the amplifier is turned on.

17. POWER: Use this switch to apply
power to the amplifier. The amp is on when
the top of the switch is depressed and off
when the bottom of the switch is
depressed.

PB250

PortaBass Amp Head

5

The Rear Panel:

18. AC LINE IN: Firmly insert the female
end of the supplied AC power cord into this
socket. The grounded power cord should
only be plugged into a grounded power
outlet that meets all applicable electrical
codes and is compatible with the voltage,
power, and frequency requirements stated
on the rear panel. Do not attempt to

defeat the safety ground connection.

19. CIRCUIT BREAKER: The circuit

breaker protects the unit from damage
caused by excessive current demands. If
the amplifier stops working, check the cir­cuit breaker. If it has opened, the button will
protrude showing a contrasting color.
Reset the circuit breaker by depressing it
until it latches. The breaker must cool down
for a short time before the button will latch.
If the circuit breaker opens repeatedly,
have the amplifier inspected by a qualified
service person.

20. SPEAKER OUTPUTS: Connect the
amplifier to your speaker cabinet(s) using
heavy gauge speaker cables terminated
with the appropriate connectors. The
Speakon®jack is recommended when play­ing at full output levels.

NOTE: These are balanced output jacks.
Neither conductor should be allowed to
come in contact with a ground point.

ATTENTION: When connecting speaker
cabinets to the amplifier, the minimum
total impedance load must not be lower
than four ohms. The following chart shows

the total impedance load when connecting
multiple speaker cabinets in parallel:

21. LINE OUT: Use this 1/4” jack to send a
post-EQ line level signal to an external
amplifier, mixing console or recording
equipment.

22. EFFECTS RETURN: When using an
external effect, connect the effect’s output
into this jack by means of a shielded signal
cable.

23. EFFECTS SEND: When using an
external effect, connect this jack to the
effect’s input by means of a shielded signal
cable.

24. LEVEL: Use this control to adjust the
level of the signal at the Transformer bal­anced Line Out jack (#25).

25. TRANSFORMER BAL. LINE OUT:

Use this XLR jack to send a line level sig­nal to an external amplifier, mixing console
or recording equipment. The signal at this
jack may be pre or post-EQ, depending on
the setting of the Pre/Post switch (#27).

26. LIFT/GND: When this switch is in the
out position the ground pin of the
Transformer Balanced Line Out jack (#25)
is interrupted. This may reduce residual
hum and buzz which is sometimes picked
up by line out signal cables. This switch
does not affect signal at the 1/4” Line Out
jack (#21).

27. PRE/POST: This switch determines
whether the signal at the Transformer
Balanced Line Out jack (#25) is pre-EQ
(switch out) or post-EQ (switch depressed).

Cabinet # of Total

Impedance Cabs Impedance

8Ω 24Ω
16Ω 28Ω
16Ω 44Ω

Speakon®is a registered trademark of Neutrik USA

PB250

PortaBass Amp Head

6

PB250

PortaBass Amp Head

Troubleshooting

In the unlikely event that your PB250 should malfunction, take a few minutes to troubleshoot it before you call for serv­ice. Sometimes you can save yourself time and money by doing it yourself, and often the cure for the problem is simple.

If the problem isn’t covered above, or if the steps lead you here, then contact your Ampeg dealer for service infor­mation. Also, you should refer your amp to an authorized service center for servicing if it gets dropped, has liquid spilled
into it, or sustains damage to its power cord (see page 3).

7

PB250

PortaBass Amp Head

System Block Diagram

Ampeg reserves the right to change specifications without notice.

Made with Pride in the U.S.A. by Ampeg • ©2002 SLM Electronics, 1400 Ferguson Avenue, St. Louis, MO 63133 U.S.A.

P/N 47-053-01 • 112102

PB250

PortaBass Amp Head

Technical Specifications

OUTPUT POWER RATING 250 Watts RMS, 4 ohm load, 120VAC

150 Watts RMS, 8 ohm load, 120VAC

TONE CONTROLS

Ultra Low: +6dB @ 40Hz

Low: ±14dB @ 100Hz

Low Mid: ±15dB @ 270Hz

Low Mid Shift: ±15dB @ 400Hz

High Mid: ±14dB @ 900Hz

High Mid Shift: ±15dB @ 1.9kHz

High: ±13dB @ 6kHz

Ultra High: +8dB @ 10kHz
GAIN 69dB
SIGNAL TO NOISE RATIO 75dB typical
POWER REQUIREMENTS

Domestic: 120VAC, 60Hz, 50VA typical (310VA @ full power)

Export: 100/120VAC, 50/60Hz, 50VA typical (310VA @ full power)

230-240VAC, 50/60Hz, 50VA typical (310VA @ full power)

SIZE AND WEIGHT 12.5” W x 3.75” H x 10.5” D; 14 lbs.

www.ampeg.com