The best way to describe the TubeUlent is a tube amplifier that has been reduced in size and weight, with the final output configured to operate as a preamp. This allows a player to plug the TubeUlent into any piece of equipment that will accept a standard effect. The TubeUlent sounds like a tube amplifier because the core of the TubeUlent is a tube amplifier, so it behaves as if you’re playing a full size tube amp. The TubeUlent will distort when driven hard or will remain clean at lower volumes, all the while maintaining that warm sound that tubes are known for.

No techniques have been used to artificially create distortion in the tubes. No extra gain stages – no artificial clipping techniques – no starving voltages. The distortion created by the TubeUlent is the same type that occurs in full size tube amps. The final output level can be adjusted without causing any changes to the tube response.

The advantages of using the TubeUlent as a preamp verses a full size tube amplifier include:

• Smaller size and lighter weight makes for a more portable performance rig.

• Rugged construction requires less maintenance and provides higher reliability than most amplifiers.

• No major reliance on type or model of final amplifier. Just about any amplifier (tube or solid state) can be used, but the player still benefits from tube amplifier response characteristics, and the warmth of tubes.

• The output power of the final amplifier does not affect the response of the TubeUlent. The amplifier can be a headphone amp, a practice amp, or a medium to high power amp. This facilitates the scaling of the final output volume to suit the situation without affecting tube response – very useful for recording as well as live performance.

• Other effects can be used before and/or after the TubeUlent, providing a broader range of tonal possibilities that in some cases would be difficult to do with full size tube amplifiers, such as reverb after distortion.

Damp and Sag Controls

Other controls have been added to allow the player to adjust parameters of the tube amplifier’s behaviour that are normally not accessible with full size tube amplifiers. These controls not only affect the tone of the amplifier, but also enable you to “dial in” exactly how you would like your tube amplifier to react to your playing.

Damp Control

Most tube amplifiers have what is called a negative feedback loop. This involves taking signal from the output and reintroducing the signal into the amplifier signal path where it is out of phase. When fed back out of phase, larger amplitude frequencies on the output will attenuate those frequencies in the amplifier.

The original purpose of this loop was to reduce the amount of distortion at the output, as the higher output signals that create distortion would be suppressed by the negative feedback loop. This loop also affects how much input signal it takes to get the amp to distort. When the amp did distort the amount of distortion amongst the various frequencies would be more balanced.

The amount of negative feedback used in tube amplifiers varies with each model / manufacturer. Earlier amplifiers had little or no negative feedback, while later amplifiers had more negative feedback. The added negative feedback resulted in amplifiers that were cleaner at loud volumes, but also displayed a more restricted feel.

The TubeUlent simulates the negative feedback loop with the amount of feedback adjusted by the Damp control. Unlike most tube amplifiers you can adjust the amount of negative feedback to a level you like. You can add large amounts of negative feedback (counter-clockwise rotation) to keep you signal cleaner and give a “dampened” feel to your playing or you can lower the amount (clockwise rotation) to the point where negative feedback is essentially removed, giving the tube amplifier an “open” feeling.

Sag Control

When tube amplifiers distort, the tubes are trying to generate more output than the power supply can deliver. When the limits of the power supply are reached using large signals, the amplifier’s response will become restricted, as the power supply attempts to catch up with the power demands. This behaviour is often described as “sag’.

The amount of sag an amplifier has varies with each model, and even from amp to amp of the same model, as there are many factors that determine how much sag an amplifier will have. Solid state vs. tube rectifier; different rectifier tubes; power transformers; power supply filtering; and other factors all control the sag response of a tube amplifier. Earlier tube amplifiers had quite a bit of power supply sag, thus being referred to as “loose” feeling. Later amplifiers had less sag, while modern amplifiers have very little sag and are considered “stiff”.

The TubeUlent not only simulates this amplifier characteristic – you are capable of adjusting how much occurs with the Sag control. Instead of having to change components or use switches one can now dial in the desired amount. The amount can range from a stiff modern response (counter-clockwise rotation) to a loose, vintage amplifier sound (clockwise rotation).

Tubes

Because the TubeUlent‘s core is a tube amplifier, the tubes play an important role in the sound. Many of the same factors that affect the sound of full size tube amps such as different tube brands and in some cases tube types also apply to the TubeUlent.

As with a full size tube amplifier, using different tube brands will change the sound of the TubeUlent. Some players like newer design tubes for brighter sounds. Other players like mellow, smoother tones that older style tubes have. By changing the tubes in the TubeUlent with different brands you can get a sound to suit your preference.

The player can also adjust the gain structure of the TubeUlent by changing the preamp tube to one of a different type/gain. The TubeUlent will accept preamp tubes such as the 12AX7, 5751, 12AT7, 12AY7, 12AV7, 12AU7, etc. (Descending order of gain level)

The TubeUlent is designed to maximize the life span of the tubes without sacrificing tone. Besides reducing maintenance time and costs, one can put resources into finding a set of tubes that suits their taste without having to worry about replacing the tubes a short time later.

Portability and Durability

Unlike full size tube amplifiers the TubeUlent is small and light. Weighing less than 1.5 Kg (3.31 lbs.) with the supplied power adaptor and the TubeUlent itself measuring approximately 145mm x 117mm x 144mm (5.7 inches x 4.6 inches x 5.65 inches), the TubeUlent literally fits in a briefcase. The universal power supply provided with the TubeUlent can be used worldwide with the correct AC cord, or an adaptor of appropriate rating can be used. There is no need for power conversion equipment or modification.

The TubeUlent has been designed and built for the rigours of the performing musician. With the exception of the tubes themselves, TubeUlent can withstand high levels of abuse – be it high force impact or long periods of vibration such as that caused by transport or performance events. External and internal hardware and finishes have been selected for high resilience.

Safety Features

The TubeUlent has many safety features that normal tube amplifiers do not have.

On power-up TubeUlent will run a self-diagnostic routine on tubes and internal circuitry to ensure everything is operating properly and safely before exiting standby mode. The TubeUlent does not have an external standby switch. Instead, the TubeUlent enters standby mode automatically on power-up and remains in that mode until the tubes reach proper operating temperature. Once operating, TubeUlent does not need to be turned off or put in standby until the performance is over. This eliminates issues caused by the misuse of standby switches.

If a failure occurs during operation TubeUlent will turn the tubes and related subsystems off, thus protecting itself and externally connected equipment from damage, and most importantly protecting the user from injury. A slowly blinking front panel LED is an indication of an internal error, at which point TubeUlent will enter standby mode until it is turned off and the issue is addressed. Failures that TubeUlent will recognize range from tube failure to internal circuit problems.