Marshall ST20H Guitar Amp Head User Guide
- June 13, 2024
- Marshall
Table of Contents
Marshall ST20H Guitar Amp Head
Product Information
The Marshall Studio JTM is a guitar amplifier available in two models: ST20H and ST20C. It is a versatile amp with 20W or 5W power options. The amp features high-quality valves including 2 x ECC83, 1 x ECC83 (phase splitter), and 2 x 5881. It has a single channel with four separate inputs and controls for high treble, normal loudness, treble, middle, bass, and presence. The amp is equipped with 5 x 1/4 jack sockets for speaker outputs. The ST20H model weighs 9.25kg and has a unit width of 500mm, height of 240mm, and depth of 230mm. The ST20C model also includes a DI output.
Product Usage Instructions
- Read the safety instructions in the manual carefully before using the amp.
- Plug your guitar into one of the input jack sockets on the front panel.
- Turn on the front panel power switch and wait a couple of minutes for the amp to warm up.
- Select between 20W or 5W power using the standby switch.
- Adjust the volume to your preferred level and start playing.
Mains Input & Fuse
Make sure to check the specific mains input voltage rating indicated on the rear panel of the amp. Connect the detachable mains (power) lead to the mains input socket on the rear panel. Use the correct value and type of mains fuse specified on the rear panel and never attempt to bypass or use incorrect fuses.
Transporting Your Equipment
- Before moving the amp, ensure it is switched off, unplugged from the mains electricity supply, and all removable cables have been disconnected.
- Do not stack the amp on top of a cabinet or other equipment while moving it to avoid damage.
SAFETY INSTRUCTIONS
Please read this manual carefully before plugging in. Follow all instructions and heed all warnings.
Warning: before going any further, make sure that your amp is compatible with your mains electricity supply. If you have any doubt, please seek help from a qualified technician – your Marshall dealer can help you with this.
MAINS INPUT & FUSE
- The specific mains input voltage rating that your amp has been manufactured for is indicated on the rear panel of the amp. Your amp is provided with a detachable mains (power) lead, which should be connected to the mains input socket on the rear panel of the amp. The correct value and type of mains fuse is specified on the rear panel of the amp.
- Never attempt to bypass the fuse or fit one of the incorrect value or type.
IMPORTANT SET UP INFORMATION
- When using your amp with one or more speaker cabinets, make sure that they are connected to the correct loudspeaker jack sockets.
- Warning: failure to do the above may damage your amp. When connecting a speaker cabinet make sure that you use a proper speaker cable. Never use a screened (shielded) guitar cable for this purpose.
- Ensure that the power switch is set to the off position and the standby switch is set to standby.
- Connect the supplied mains (power) lead into the mains input on the rear panel first and then into an electricity outlet.
- Ensure that any master, volume and/or output level controls on the front panel are set to zero.
- Plug your guitar into one of the input jack sockets on the front panel.
- Turn the front panel power switch on and wait a couple of minutes.
- Select between 20W / 5W using the standby switch.
- Turn the volume up to your preferred level and you’re ready to play.
TRANSPORTING YOUR EQUIPMENT
- Please ensure that your amp is switched off, unplugged from the mains electricity supply and all removable cables have been disconnected from your equipment before attempting to move it.
- Only move the amp on its own; do not attempt to move it while it is stacked on top of a cabinet or other equipment.
SPECIFICATION
The amp that started it all is back. The JTM is a welcome addition to the Studio range, offering players authentic, smooth, and valve-driven break-up at lower volumes – perfect for home or studio use. Creating a sound that defined a generation, the JTM delivers the legendary loud blend of crunch and cleanness recognized the world over.
ST20H
| Power | 20W or 5W |
|---|---|
| Valves | 2 x ECC83, 1 x ECC83 |
(phase splitter) and 2 x 5881
Channels
| Single channel with four
separate inputs
High treble and normal loudness controls
Equalisation| Treble, middle, bass and
presence
Speaker Outputs| 5 x 1/4” jack sockets (16Ω load / 8Ω load / 4Ω load)
Outputs| DI output
Unit weight| 9.25kg
Unit width| 500mm
Unit height| 240mm
Unit depth| 230mm
ST28C
| Power | 20W or 5W |
|---|---|
| Valves | 2 x ECC83, 1 x ECC83 |
(phase splitter) and 2 x 5881
Channels
| Single channel with four
separate inputs
High treble and normal loudness controls
Equalisation| Treble, middle, bass and
presence
Speaker Outputs| 5 x 1/4” jack sockets (16Ω load / 8Ω load / 4Ω load)
Outputs| DI output
Speaker
config.
| 1 x 12”
Speaker model| Celestion G12M-65 Creamback (16Ω, 65W)
Unit weight| 17.8kg
Unit width| 500mm
Unit height| 460mm
Unit depth| 265mm
FRONT PANEL FUNCTIONS
ST20H
ST20C
- 1. POWER SWITCH
- Mains power is on when set to the on position.
- 2. STANDBY SWITCH
- The unit power is in low power mode (5W) when set to low, it is set to standby when in the middle position and when set to high power the unit runs at full power (20W).
- Standby mode: this should be used during breaks in performances, instead of leaving the amp on full power. Always turn the power on for two minutes before using the standby switch.
- 3. POWER INDICATOR
- Illuminates when unit is switched on.
- 4. PRESENCE
- Adjusts the high frequencies of the power amp.
- Increasing the high frequencies adds more bite to your sound.
- 5. BASS
- Adjusts the low frequencies of the amp. It will add bottom end and depth to your sound.
- 6. MIDDLE
- Adjusts the mid frequencies of the amp. Giving you anything from a fat and full sound to an aggressive tone.
- 7. TREBLE
- Adjusts the upper frequencies of the amp. Your tone will get brighter as it is turned up.
- 8. HIGH TREBLE / LOUDNESS 1
- A volume control that changes the loudness of the high treble inputs.
- 9. NORMAL / LOUDNESS 2
- A volume control that changes the loudness of the normal inputs.
- 10 & 11. HIGH TREBLE INPUTS (1)
- The high treble voicing provides a bright, crisp tone. Plug your guitar into the high sensitivity input (10) for higher gain (or to compensate for low output pickups) or low sensitivity input (11) for cleaner tones (or to compensate for higher output pickups).
- 12 & 13. NORMAL INPUTS (2)
- The normal voicing provides a more rounded, full tone. Plug your guitar into the high sensitivity input (12) for higher gain (or to compensate for low output pickups) or low sensitivity input (13) for cleaner tones (or to compensate for higher output pickups).
REAR PANEL FUNCTIONS
ST20H
ST20C
Note: the high treble and normal inputs can be linked together with a 1/4” patch cable to blend and create the tone that suits the player.
- SPEAKER OUT
- 1/4” socket for 16 Ohm speaker connection.
- SPEAKER OUT
- 1/4” socket for 8 Ohm speaker connection – use this in conjunction with socket 3 when plugging in 2 x 16 Ohm cabinets.
- SPEAKER OUT
- 1/4” socket for 8 Ohm speaker connection – use this in conjunction with socket 2 when plugging in 2 x 16 Ohm cabinets.
- SPEAKER OUT
- 1/4” socket for 4 Ohm speaker connection – use this in conjunction with socket 5 when plugging in 2 x 8 Ohm cabinets.
- SPEAKER OUT
- 1/4” socket for 4 Ohm speaker connection – use this in conjunction with socket 4 when plugging in 2 x 8 Ohm cabinets.
- Warning: never attempt to connect more speakers than rated. The safe combinations are those listed in this manual. Any other speaker combinations may stress the power amp and potentially lead to valve failure.
- Note: never use this amp without a speaker load.
- DI OUTPUT
- Connect your amp to an external recording device or sound desk using this output socket.
- Note: the DI output has added loudspeaker emulation.
- LOOP SWITCH
- This turns the effects loop of the amp on or off to completely remove the loop from the signal path when switched off.
- EFFECTS LOOP SEND
- Sends signal to effects loop / outboard equipment.
- EFFECTS LOOP RETURN
- Returns signal to effects loop / outboard equipment.
- POWER INLET
- The supplied mains power lead is connected here.
MORE INFORMATION
Whilst the information contained herein is correct at the time of publication, due to its policy of constant improvement and development, Marshall Amplification Plc reserves the right to alter specifications without prior notice.
- MARSHALL AMPLIFICATION PLC, DENBIGH ROAD, BLETCHLEY, MILTON KEYNES, MK1 1DQ, ENGLAND.
- T: +44 (0) 1908 375411
- MARSHALL AMPLIFICATION PLC REGISTERED IN ENGLAND
- REGISTERED NUMBER: 805676
- CATS-00261-05