Frequency dependent dual solid-state and vacuum tube power amplifier-section instrument amplifier

An audio amplifier apparatus and method which has a preamp, active 2-way crossover, solid-state power amplifier, and tube power amplifier. Audio input from a musical instrument enters the preamp where pre-amplification, equalization, and other processes such as limiting or compression take place. Audio leaves the preamp and goes to a crossover, wherein frequencies below a crossover point are sent to a solid-state power amp via a first signal path, and wherein audio frequencies above the crossover point are sent to a tube power amp via a second signal path. Outputs from the solid-state power amp and tube power amp are sent to external or internal loudspeakers.

SUMMARY OF THE INVENTION

The present invention is a self-contained musical instrument amplifier that enables the musician to take advantage of both solid-state and vacuum-tube power amp technology, simultaneously.

The topology of the amplifier is as follows: The mono audio input from an instrument, such as an electric bass guitar, is plugged into the amplifier's pre-amp section. The signal then feeds an internal active 2-way crossover, which is a device used in various audio applications to split the audio signal depending on a preset or selectable frequency point. In this application, all frequencies below the crossover point are sent to the solid-state power-amp section, and all frequencies above the crossover point are sent to the tube power-amp section. The outputs of these two power-amp sections are then sent to either internal, or external loudspeakers.

Because of the many desirable audio qualities of vacuum tubes, and in particular power-section tubes, most musicians would prefer to use amplifiers with tube technology (note: many currently available instrument amplifiers that use solid-state power sections do use one or more preamp tubes in the preamp section. This is not however, what creates the desirable ‘tube’ sound that most musicians prefer. This preferable tube-sound is achieved primarily by an amplifier with a power section using output power tubes). However, many musicians that play electric instruments capable of producing lower bass frequencies, such as the electric bass-guitar or keyboard, will often use amplifiers with completely solid-state power sections for mainly two reasons: First, for a tube amp to reproduce and amplify bass frequencies with enough volume without clip (distortion) requires more energy, weight, and expensive hardware, than from a solid-state power amplifier. Second, many of these same musicians do prefer the clean, loud, and ‘tight’ sound of low/bass frequencies through a solid-state amplifier, but as they move upward into the middle and higher frequencies on the instrument, the sound quality becomes less desirable, or more ‘harsh,’ due to the inherent sonic qualities of solid-state amplification.

The present invention allows the musician to take advantage of the most desirable aspects of each of the solid-state and tube power amp sections. Because only the middle and high frequencies will be reproduced and amplified by the tube power section, this power section only needs to produce a fraction of the output power, or wattage, of a tube-only amplifier, since the solid-state power section will be amplifying the more power-requiring lower bass frequencies. For use with a bass guitar or keyboard, the crossover frequency point should be somewhere in the range of approximately 80 Hz to 240 Hz, although this is somewhat subjective, and higher frequency crossover points may be used.

Another advantage of the invention is that even when the amplifier is being input with a bass note that is below the crossover point, and therefore being sent to the solid-state power section, every musical note contains not only the fundamental frequency, but additional overtones (including higher-order harmonics), that are higher in frequency than the fundamental tone. This means that while the fundamental tone/note is sent to the solid-state power amp section, these higher frequency overtones are sent to the tube power section, resulting in a very pleasing and musical result, or timbre, of the two power sections, where the fundamental is tight, clear, and loud, and the overtones are smooth, warm, and round (these are musician vernacular terms for the desirable ‘tube sound’).

There are many features that could be added to the topology which would add versatility, both for sound, and reliability. For example, a blend potentiometer (knob/pot) could be added which would allow the musician to add some (or all) of the middle and high frequencies to the solid-state power section, or vice-versa, thus giving the musician the ability to blend the two ‘sides’ across the whole frequency range of their instrument. A ‘balance’-type potentiometer could be added in conjunction with the master volume to adjust for slight differences in volume taper between the two power-amp sections as the amplifier is turned up, or down. Additionally, or alternatively, a switch could be added which would allow the musician to use just the solid-state section for full-range amplification, or just the tube power section for full-range amplification. This would be desirable for a variety of reasons, but practically for example, if a power-tube were to fail during a performance (which does happen occasionally under normal use), the musician could switch to full-range/solid-state, and finish the performance.

These and further objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings.

DETAILED DESCRIPTION

The drawings are for the purpose of illustrating the inventor's preferred embodiments and not for the purpose of limiting the invention.

FIG. 1shows the amplifier1, which includes the preamp3, active 2-way crossover5, solid-state power amplifier8, and tube power amplifier9. The audio input from a musical instrument is shown2, enters the preamp, where pre-amplification and equalization occur, and other processes such as limiting and/or compression may also take place. The audio4, leaves the preamp and goes to the crossover5, where audio frequencies below the crossover point are sent to the solid-state power amp8, via signal path7. Signal path4is where a common effects-loop and/or direct-out would be located. Audio frequencies above the crossover point are sent to the tube power amp9, via signal path6. The outputs10and11are sent to external loudspeakers.

FIG. 2shows the addition of a switch12which allows the selection of sending the full-range audio12to the solid-state power amp8only, via signal path13, or sending signal12to the tube power amp9only, via signal path14, or sending signal12to the crossover5via signal path15.

FIG. 3shows the addition of a pan/mix/blend potentiometer16placed between the preamp3and crossover5which enables sending a variable amount of full-range audio17to the solid-state power amp8, in addition to signal7that has been sent via15to the crossover5. Alternatively, this process can be done with the tube power amp instead of the solid-state power amp.

FIG. 4shows the addition of a pan/mix/blend potentiometer18placed between the crossover5and the tube power amp9, which enables sending a variable amount of higher frequencies19to the solid-state power amp8. Tube power amp9still receives a variable amount of signal from potentiometer18via signal path20.

FIG. 5shows the amplifier with the addition of internal speakers21and22, supplied with audio via10and11from solid-state power amp8and tube power amp9.