The Tomato Blaster is a tube-hybrid amplifier, which is not only of interest to beginners with its 3-Watt performance.
Like all members of the LoV-family, the Tomato Blaster works with 12 V DC voltage, which is also completely risk-free for beginners, and which can be easily and safely provided with an AC or DC plug. Anyone who prefers DIY will therefore never have to come into contact with mains or high voltage.
The starting point of the Tomato Blaster is the Banana Booster, which has been well-known on the market for years, but with a few modifications: The cathode resistance of the first tube was replaced by a combination of permanent resistor and potentiometer, which makes changes to the operating point of the tube possible. The operating point directly impacts the amplification as well as the severity of overdrive and thus also the sound. This version will not fully replace a gain controller as known from the big amps, but it does offer a simple option for influencing the tone color and the degree of overdrive.
For the power amplifier, a 3.5-Watt amp-module by Kemo was used that is easy to operate, sensitive enough for the preamplifier and also runs with 12 V DC. It should be added that the 3.5 Watts of the power amplifier will be reached at a load of 4 Ohm. The performance will decrease at 8 or even 16 Ohm, but that decrease is negligible for this circuit and amplifier concept. The Tomato Blaster can rock properly even with 16 Ohm.
Even if the Tomato Blaster runs at "only" 12 V: do not overestimate your knowledge! Basic technical, electrical knowledge and sure handling of a soldering iron are indispensable; otherwise this work should not be attempted.
Most of the components are safely and conveniently mounted to a small circuit board, which is installed in a case together with a few additional external components, such as potentiometer, switches and sockets. The available cases for the Tomato Blaster are made of acrylic and are (partially) transparent, so that you can enjoy not only the sound but also the core values of the amplifier. Remember: work cleanly and properly during installation so that the final result will not have to be hidden away.
As you can see in the circuit diagram, a few different modes are possible. The preset standard version is the most common.
C3: this bypass capacitor has the effect of a boost across almost the entire frequency range and will seriously increase the volume. The disadvantage of this setup is the consequence that the potentiometer P1 becomes largely ineffective and the preamplifier will pretty much overdrive. If you want maximum performance and can do without the impact of the "dirt" potentiometer, you should definitely install C3. It can also be made switchable with the help of an additional toggle switch, which can be attached to the case.
P1: The settings range from Clean to Drive can be extended through the use of a potentiometer with a larger resistance value. Instead of 5k, 10k or even 25k would be possible, but do not expect too much from this modification. If potentiometers with such values are available, go ahead and try them. If not, it’s not a problem.
The assembly kit includes a rectifier as used with other LoV-projects. It can be operated with AC as well as DC. The best results are produced with a 12 V AC / 700 mA plug - not so easy to find these days, but you may have one left in a drawer somewhere.
A normal 12 V DC switching power supply can also be used. However, it may cause slight interference due to the functionality of the switching power supply. It also makes sense to attempt using different switching power supplies, as they may clock differently, which may in turn affect possible background noise. This interference is generally not bad and mostly unnoticeable, but some people are bothered by it and prefer the AC power supply. If a 12 V DC power supply is available, and some minor losses can be accepted, there is no need to purchase another power supply.
The Tomato Blaster is not a "Clean" amp like Fender's Twin etc. but a bit more for Blues and old school fans with its slightly rough, warm basic sound. The degree of overdrive cannot only be easily controlled with the "Dirt" controller, but the Tomato Blaster also reacts sensitively to the input level, meaning it can be well tuned with the Vol potentiometer on the guitar.
Even though the tube in the Tomato Blaster is only operated with 12 V, it has significant impact on the sound as can be seen from the modifications listed above. You should not expect the sound to change too much by using the tubes of other manufacturers. The Tomato Blaster is designed for 12AU7 / ECC82 types and if a real 12U7 should be available, it can most certainly be used as well. The amplifier can also be operated with a 12AT7 / ECC81, also with a 12AX7 / ECC83, HOWEVER, the latter option may result in quieter sound from the amplifier than with a 12AU7. Just try different options and decide which one you like best.
Other LoV projects or tube devices with low voltages at the anode have always shown that JJ-tubes do not handle such low voltages well. It could be that you find a specimen which will work properly, but it could also be that the tube does not operate as intended. We do not therefore even recommend starting to experiment with JJ-tubes in this amplifier. All the Chinese and Russian tubes, however, work flawlessly.
All in all, the Tomato Blaster is a small powerhouse which brings a lot of joy, not only during assembly, but also with its pleasant sound with a touch of tube.
The kit is available in the online-shop