Ampeg SVT-CL Bass Guitar Amplifier Owner's Manual | Features, Specs, and Operation

Introduction

The Ampeg SVT-CL Bass Guitar Amplifier redefines the legendary performance of the classic Ampeg SVT. This dynamically powerful bass amp delivers 300 watts of unsurpassed quality, reliability, and tonal flexibility, combining classic tube vibrance with contemporary features. This manual details all features and controls.

Features

The SVT-CL stands alone in high-performance bass amplification. It offers more power, performance, and flexibility than other amplifiers in its class. Key features include:

-15 dB INPUT: Ideal for active basses.
ULTRA LO AND ULTRA HI SWITCHES: Tailor your sound with these switches.
5-POSITION FREQUENCY SELECTOR: Choose from five center frequencies for midrange voicing.
BIAS ADJUSTMENT CONTROLS: Adjust tube bias for proper operation.
SLAVE OUT: Powers another amp from the SVT-CL's preamp.

The Front Panel

The front panel features various controls and indicators for operating the amplifier:

Control Layout (Left to Right):

1. 0 dB INPUT: Accepts signal from passive instruments via a shielded cable.
2. -15 dB INPUT: Accepts signal from active instruments via a shielded cable.
3. GAIN: Adjusts the basic signal level in the preamp.
4. ULTRA HI: Boosts high frequencies when engaged.
5. ULTRA LO: Emphasizes low frequencies and cuts mid frequencies when engaged.
6. BASS: Low frequency control, +/- 12 dB at 40 Hz.
7. MIDRANGE: Midrange control, +/- 20 dB cut or +10 dB boost at the selected frequency.
8. FREQUENCY: Selects the center frequency for the Midrange control (220 Hz, 450 Hz, 800 Hz, 1.6 kHz, 3 kHz).
9. TREBLE: High frequency control, +/- 20 dB cut or +15 dB boost at 4 kHz.
10. MASTER: Controls the signal level to the power amp and overall listening level. Also controls the level to the Preamp Out jack.
11. STANDBY/POWER/FAULT INDICATOR LED: Multifunction LED. Red in Standby, Green when On (high voltage present). Flashes red/green if a power tube fault is detected.
12. STANDBY: Allows tubes to warm up without high voltage, extending tube life. Switch OFF during initial power-up, then ON after 20 seconds. Use for short periods of non-use.
13. POWER: Supplies AC power to the unit. Turn ON before the Standby switch. Must be OFF to reset after a fault.

The Rear Panel

The rear panel provides connections and controls for external devices and power:

Connections and Controls:

14. AC LINE IN: Connects the supplied AC power cord to a grounded outlet. WARNING: Do not defeat the ground prong of the AC plug.
15. FUSE: Protects against overloads and surges. Replace only with the same type and rating.
16. POLARITY: Switch to minimize electrical buzz.
17. BIAS SECTION: Two controls and LED sets for power amp biasing. Refer to "Setting Tube Bias" for details.
18. SLAVE OUT: Outputs the same signal sent to the power amp, useful for powering a slave amp.
19. BALANCED OUT: XLR output from the power amp in, suitable for external power amps, consoles, or PA systems.
20. POWER AMP IN: Accepts a signal for the power amp and Slave Out. Using this jack breaks the path from the Preamp Out jack. Can be used as a post-Master patch point.
21. PREAMP OUT: Carries the post-Master signal without breaking the path to the power amp. Used for feeding external equipment.
22. IMPEDANCE SELECTOR: Matches amp output impedance to speaker(s) (2 Ω or 4 Ω).

Impedance Selector Table:

Cabinet Impedance	Number of Cabinets	Total Impedance
2 Ω	1	2 Ω
4 Ω	1	4 Ω
4 Ω	2	2 Ω
8 Ω	2	4 Ω
8 Ω	4	2 Ω

23. SPEAKER OUT: Two 1/4" phone jacks and one Speakon® jack for speaker connections. Speakon is recommended for higher current handling at high power.

Important Note: Use only non-shielded speaker cables. Shielded instrument cables can overheat.

Changing the Tubes

Tube life depends on usage. Power tubes should be checked annually, or more often with heavy use. Worn power tubes can cause weakness, loss of punch, or altered tone. Power tubes work in a push/pull configuration and should be replaced as a matched set. Preamp tubes typically last longer; failure may cause noise, squealing, or loss of gain. A service center can diagnose preamp tube issues.

Procedure for changing power tubes (qualified service personnel):

Turn off the amp, unplug it, and let it cool for at least 5 minutes.
Remove screws holding the rear perforated metal screen.
Set the screen aside.
Remove tube retainers by lifting them off the tubes.
Grasp a tube at the top and gently rock it back and forth while lifting it out of its socket.
When inserting new tubes, align the tab on the tube's plastic base with the slot in the socket and press down gently but firmly.
Replace the perforated metal screen and tighten screws.
Power up the amplifier and let it sit for at least 20 minutes before biasing.

Setting Tube Bias

Allow the unit to warm up for at least 20 minutes at proper AC line voltage. With no input signal, adjust each bias control so only the associated green LED is lit. If neither LED is lit, the amp is over-biased (thin sound, distortion). If both green and red LEDs are lit, the amp is under-biased (full sound, reduced tube life).

Bias controls do not need frequent adjustment, only for tube replacement or aging. AC line voltage variations may cause slight LED differences.

Bias Control Functions:

Bias 1 Control: Adjusts the three left power tubes (rear view).
Bias 2 Control: Adjusts the three right power tubes (rear view).

Observing the LEDs as controls are rotated clockwise helps diagnose tube problems.

Tube Bias Diagnosis:

Condition	Problem	Solution
Green comes on, turns red	No problem	Longer green illumination before red indicates better matched tubes.
Red comes on, then green	Tubes not properly matched	Set slightly before green illuminates. Obtain a matched tube set.
Red comes on, no green	One or more tubes are non-functional	Check tube seating. If seated properly, find and replace bad tube(s).
None on	Possibly no high voltage, bad Bias Control, or bad tube(s)	Have unit checked by a service technician.
Both on all the time	Possible bad Bias Control or bad tube(s)	Have unit checked by a service technician.

If tubes are severely faulty, the Fault Indicator LED will signal, and the unit will shut down.

Block Diagram

The SVT-CL utilizes a signal path that includes input stages, tone shaping, preamp, bias adjustment, power amp, and output protection. The signal enters via the 0 dB or -15 dB input, is processed by Gain, Ultra Hi/Lo, Bass, Midrange (with Frequency selection), and Treble controls. The Master control sets the overall level. The signal can be routed to the Power Amp Input or split via Preamp Out and Slave Out. The Power Amp section includes bias adjustment and protection. Outputs are available via Speaker Outs (1/4" and Speakon) and Balanced Out.

Technical Specifications

Parameter	Specification
Preamp Tube	2 x 12AX7
Driver Tube	1 x 12AX7, 2 x 12AU7
Power Amp Tube	6 x 6550
Output Power Rating	300 Watts RMS minimum continuous @ <3% THD into 2 or 4 Ω, 0.4V RMS input
Signal to Noise Ratio	80 dB (20 Hz-20 kHz, unweighted)
Maximum Gain	67 dB @ 1 kHz, tones centered
Tone Controls	Bass: +/-12 dB @ 40 Hz Midrange: +10/-20 dB @ 220 Hz, 450 Hz, 800 Hz, 1.6 kHz or 3 kHz Treble: +15/-20 dB @ 4 kHz Ultra Lo: +2 dB @ 40 Hz, -10 dB @ 500 Hz Ultra Hi: +9 dB @ 8 kHz
Power Requirements	10 A (Slo Blo), 120VAC, 50-60Hz, 460W (SVTCL) 10 A (Slo Blo), 100VAC, 50-60Hz, 460W (SVTCLJ) 4 A (Slo Blo), 230VAC, 50-60Hz, 460W (SVTCLU) 4 A (Slo Blo), 240VAC, 50-60Hz, 460W (SVTCLW)
Size (H x W x D)	11.5 in/292 mm (with feet) x 24.0 in/610 mm x 13.0 in/330 mm
Weight	80 lb/36.3 kg (approximately)

The SVT-CL amplifier is covered with a durable, fabric-backed vinyl material. Clean with a dry, lint-free cloth. Never spray cleaning agents on the SVT-CL. Avoid abrasive cleansers which would damage the finish.

Ampeg continually develops new products and improves upon existing ones. Specifications are subject to change without notice.

Warranty and Support

For warranty information, product registration, or technical support, visit www.ampeg.com.

Technical support can also be reached by phone at 818-575-3600.

Contact Information:
Yamaha Guitar Group, Inc.
26580 Agoura Road, Calabasas, CA 91302-1921 USA Rev. A

© 2019 Yamaha Guitar Group, Inc. All rights reserved. Ampeg, the Ampeg logo, and SVT are trademarks or registered trademarks of Yamaha Guitar Group, Inc. in the U.S. and/or other jurisdictions. Speakon is a registered trademark of Neutrik AG Corporation.

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Ampeg SVT-CL Bass Guitar Amplifier

Owner's Manual