Rock Block 12AT7 User manual

Owner’s Manual
Revision 1.0
Description
The Rock Block is a 1 watt vacuum tube guitar amplifier that can also be used as a
distortion/boost pedal. It provides classic overdriven output tube sound at reasonable
volume.
Inputs and Outputs
INPUT: This ¼” mono jack is used to connect to a guitar or the output of an effects
pedal.
SPEAKER: This ¼” mono jack is used to connect to a speaker cabinet. The Rock Block
can drive speakers of 4 to 16 ohms impedance.
OUTPUT TO AMP: This ¼” mono jack is used to connect to the input of another guitar
amplifier or effects pedal.
12V DC: This 5.5/2.5mm jack is used to connect to the supplied external power supply.
This supply is 12V DC (center positive) and is regulated and current-limited. Only this
type of supply should be used.
Controls
POWER: This is the ON/OFF power switch. Push to the right to turn on the amplifier.
The vacuum tubes will glow blue to indicate that the amplifier is turned on. It will take 5-
30 seconds for the vacuum tubes to warm up.
GAIN: This knob is used to control the gain of the amplifier.
TONE: This knob is used to control the treble response,
VOL: This knob is used to control the output volume of the amplifier.
BOOST: This 3-way switch is used to boost the gain of the amplifier. The left position is
the lowest gain, the center position is medium gain, and the right position is maximum
gain.
BASS: This 3-way switch is used to control the bass response. The center position is for
the least bass, the left position is for medium bass, and the right position is for maximum
bass.
OUT VOL: This knob is used when the Rock Block is driving another amplifier to control
the volume to the OUTPUT TO AMP jack.
BYPASS: This footswitch is used to bypass the Rock Block when driving another
amplifier. If the green LED is OFF the Rock Block is bypassed, and the INPUT jack is
connected directly to the OUTPUT TO AMP jack (true bypass).

Operating Instructions
Using the Rock Block as a guitar amplifier
Connect the guitar or effects pedal to the INPUT jack using a guitar cable with a ¼” mono
plug. Also connect a speaker cabinet to the SPEAKER jack using a speaker cable with a
¼” mono plug. The ideal speaker impedance is 8 ohms, but 4 and 16 ohm speakers can
be used while still providing excellent sound. See the “Vacuum Tube Selection” section
for matching the output vacuum tube to the speaker impedance. If a speaker cable is
connected to the SPEAKER jack, then a 4-16 ohm speaker should be connected to the
speaker cable to avoid possible damage to the amplifier.
Connect the supplied external power supply to the 12 DC jack and plug the AC 3-pronged
plug into a wall socket. Turn on the amplifier with the POWER switch. If the green LED
is not ON, then push the footswitch to un-bypass the amplifier. The green LED should be
ON.
For a clean guitar sound: Turn the VOL knob maximum clockwise. Set the BOOST
switch to the left (minimum) position. Adjust the GAIN knob for maximum volume without
distortion. Adjust the BASS switch and TONE knobs to taste.
For a “bluesy” or “crunchy” guitar sound: Turn the VOL knob maximum clockwise. Set
the BOOST switch to either the left or center position. Adjust the GAIN knob for the
desired amount of distortion.
For a “hi-gain” or “lead” guitar sound: Turn the VOL knob maximum clockwise. Set the
BOOST switch to either the center or right position. Adjust the GAIN knob for the desired
amount of distortion, sustain and feedback.
For reduced volume with high gain: Turn VOL knob counter-clockwise. This will reduce
the overall volume of the amplifier. The distortion will transition from output tube to
preamp tube distortion as the volume is reduced.
Using the Rock Block as a distortion/boost pedal
Connect the guitar or effects pedal to the INPUT jack using a guitar cable with a ¼” mono
plug. Also connect the OUTPUT TO AMP jack to another amplifier or effects pedal using
an instrument cable with a ¼” mono plug. Do not plug anything into the SPEAKER jack.
The output volume of the Rock Block, when used as a distortion/boost pedal, is controlled
with the OUT VOL knob. The BYPASS footswitch is used to bypass the Rock Block. All
other controls are used in the same way as when the Rock Block is used as an amplifier
to drive a speaker.
If the Rock Block is driving an amplifier that is grounded (has a 3-prong power cord), then
it is best to use the included AC adapter (3-prong to 2-prong) with the Rock Block to
reduce hum, especially when the Rock Block is bypassed. Plug the Rock Block power
cord into the adapter, and then plug the adapter into the wall socket. If the amplifier the
Rock Block is driving is not grounded or if the Rock Block is driving a speaker, then do
not use the AC adapter so that the Rock Block is grounded and hum is reduced.

Vacuum Tube Selection
The best vacuum tubes to use for the right position (preamp) are either an ECC83/12AX7
or 5751. A 5751 tube will reduce the gain slightly and produce a slightly different
distortion, especially when the VOL knob is turned counter-clockwise.
The only recommended vacuum tubes for the left position (output) are either an
ECC82/12AU7, ECC99 or 12AT7. It is recommended to use an ECC82/12AU7 or 12AT7
if the speaker impedance is 4 ohms. An ECC99 is recommended if the speaker
impedance is 16 ohms, but the ECC82 will work fine. All three tube types are
recommended for 8 or 16 ohm speakers. An ECC99 will result in about 50% more power
and more bass.
Make sure that the vacuum tube pins are straight before inserting the tubes into the
sockets. Apply a slight pressure but do not force the tubes into the sockets or damage to
the sockets may result.
Specifications
12AT7 12AU7 ECC99
Output Power (clean) 0.2 watt 0.4 watt 0.6 watt
(max) 0.8 watt 1.0 watt 1.5 watt
Speaker impedance 4 - 8 ohms (ECC82/12AU7, 12AT7)
8 -16 ohms (ECC99)
Input impedance 1Meg ohms
Output impedance 2.5K ohms
(OUTPUT TO AMP jack)
Warranty and Repair
The warranty period is 2 years. If during the first 2 years the Rock Block needs repair,
Surprise Sound Lab will repair or replace the Rock Block at no charge. The vacuum
tubes are guaranteed for 90 days. The owner will be responsible for shipping charges.
Any problems due to misuse, abuse or modification will not be covered under the
warranty. Any repairs outside of the warranty will be performed by Surprise Sound Lab
for a reasonable fee. Please email [email protected] for any repair
requests.

Voice Switch
The 3-way switch on the left side of the Rock Block, next to the OUTPUT TO AMP jack,
is used to select the type of sound (voice) when the Rock Block is used as a distortion
pedal.
The center switch position selects a "vintage" sound, which is the same as the sound
when the Rock Block is used as an amplifier.
The position towards the front of the Rock Block selects a "modern" sound.
The position towards the back of the Rock Block selects a "metal" sound.
This switch has no effect on the sound when the Rock Block is used as an amplifier
driving a speaker.
Tips for using your Rock Block
Generally keep the VOL control at maximum for output tube overdrive. However, for high
GAIN settings, reducing the VOL by about 1/3 to 1/2 will provide more TONE control.
Decreasing the BASS setting as you increase the BOOST and GAIN settings will produce
the best distortion.
Only use as much GAIN as needed for the desired distortion and sustain to avoid
unpleasant distortion.
For high GAIN settings bridge pickups seem to work especially well.
Recommended Settings
Generally keep the VOL control at maximum for output tube overdrive.
Guitar Style Pickup GAIN BOOST BASS
Strat Clean any 11 o’clock min max
Strat Blues any 2 o’clock min mid
Strat Rock bridge 1 o’clock mid mid
Strat Heavy bridge 2 o’clock max min
Les Paul Clean any 8 o’clock min mid
Les Paul Blues any 12 o’clock min mid
Les Paul Rock bridge 11 o’clock mid min
Les Paul Heavy bridge 1 o’clock max min