Surprise Sound Lab Rock Block


Surprise Sound Lab

The Rock Block is a 1 watt vacuum tube guitar amplifier. It is designed to provide enough volume for practicing and recording and maybe even live performance in small venues. It can also be used as a distortion pedal with full volume and bypass control. Using the Gain, Volume and Boost controls, the Rock Block can provide output tube distortion, preamp tube distortion, or a combination of both.

Even when used as a distortion pedal, the signal goes through the output tube and output transformer to an internal dummy speaker load. Therefore, the Rock Block sounds the same whether it's used as an amp or a pedal.

The design allows for several different types of vacuum tubes to be used, and tube-swapping is encouraged to find just the right sound. The premium JJ vacuum tubes that are supplied with the Rock Block were carefully chosen for sound quality and durability.

Why a 1 watt amplifier?

Most electric guitar players agree that the most desirable guitar amp sound is the distortion produced by an overdriven output tube. To achieve this with an amp of 15 watts or more results in extremely high sound levels, especially in the home. Even a 5 watt amplifier is often way too loud. The usual solution is to turn down the volume and turn up the gain on the amp. This results in preamp tube distortion, which is not the same as output tube distortion. 1 watt is the perfect power level for achieving output tube distortion at reasonable sound levels for in-home use and for recording. The Rock Block produces classic overdriven output tube distortion at reasonable sound levels. Using a typical 12" guitar speaker with a sensitivity of 100db per watt, the Rock Block can produce a sound level of 100db, which is still pretty loud, but not overpowering.

The Rock Block has an all-tube Class A single-ended triode signal path, which is the most desirable for that classic warm rock guitar sound. Careful stage-to-stage distortion control and unique tone-shaping results in a vintage rock guitar sound with just enough "bite". The sound of the Rock Block has been described by owners as ranging from Vox to Marshall depending on how the controls are set.

The separate Gain and Volume controls allow for power tube distortion, preamp tube distortion, or a mixture of both. Even when used as a distortion pedal, output tube distortion is possible unlike other tube distortion pedals which only provide preamp tube distortion. Great for practicing, recording, or performance in small venues.

Rock Block provides 7X clean power and 2X max power compared to the ZVex Nano Head. Unlike other micro-power amps, the Rock Block has usable clean headroom. It also has much more flexibility and control. Most importantly, it just sounds better. The Rock Block has Gain, Volume and Tone knobs and a separate Volume knob for the output that drives another amp when the Rock Block is used as a distortion pedal. It also has 3-way Boost and Bass switches, a Power switch, and a Bypass stompswitch.

The key to providing enough power in such a small enclosure is the internal power supply. External 12V DC is supplied to the Rock Block with a universal external regulated switched power supply. The internal supply is a proprietary design that converts the 12V DC to 320V DC. This supply is so efficient that very little heat is generated, and a noisy fan is not needed. The filaments of the tubes are driven directly with the regulated 12V DC supply.

When used as a distortion pedal, the Rock Block provides output tube distortion by using the internal output transformer and an internal speaker load with special EQ. Preamp tube distortion can also be acheived by using the Gain and Volume controls. This is very different from other vacuum tube distortion pedals that provide only preamp tube distortion.

Tube-swapping, especially the output tube can provide different distortion sounds and volume levels. The recommended output tubes for the Rock Block are the ECC82/ECC802/12AU7, ECC99 or ECC81/12AT7. The ECC99 provides 0.7 watts of clean power and 1.5 watts maximum power. The 12AU7 provides 0.4 watts clean power and 1 watt maximum power, and the 12AT7 provides 0.12 watts clean power and 0.8 watts maximum power. The ECC99 has the darkest sound with the most bass. The 12AT7 has the brightest sound, and the 12AU7 is in between. All three have a great unique sound.

The Rock Block is only 3 3/4" by 5 3/4", about the size of an effects pedal, and weighs about 2 pounds.

Recommended Speakers

The recommended speaker cabinet for the Rock Block is an 8 ohm 1x12 open back, but any guitar speaker will work fine as long as the correct output tube is used. Even 2x12 or 4x12 cabs are fine. One cabinet that seems to work particularly well with the Rock Block is the Avatar 1x12 Cube with the Hellatone 30 speaker.


The Rock Block cannot drive headphones directly. For headphone use we recommend connecting the OUTPUT TO AMP jack of the Rock Block to a portable device such as the Line6 Pocket POD, which has a headphone output. This combination works very well as long as the distortion is produced in the Rock Block and the POD is used to add chorus and reverb.

The POD settings that work well with the Rock Block for headphone use are:

  • Amp: Boutique 1 Effects: Chorus 1 (12 o'clock)
  • Reverb: 1/2 Delay: Add to taste
  • Drive: max Bass, Mid, Treble: 1/2


The Rock Block is handcrafted with premium parts in the USA. The aluminum enclosure is powder coated with an extremely durable finish, and the labels are silk-screen printed with epoxy paint and baked on. The control knobs are chrome plated solid brass.

All of the components were selected for sound and quality. All of the capacitors in the signal path are Mallory 150M series for that smooth vintage sound. The small value EQ capacitors are silver mica. Almost all of the resistors are precision 1% metal film resistors. The electrolytic capacitors are extra long life. The vacuum tube sockets are ceramic. The custom printed circuit board is double-sided with extra thick 2 oz. copper traces.

Each Rock Block is run for a few hours and re-tested for output power and sound before it is released for shipping.

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