There are two KT88 EH (KT120 or KT150) and one 12AX7 EHG tubes in each block. Thunderbird Monoblock requires the preamplifier signal. Dedicated devices are tube preamps: Firebird and Blazebird available in the offer of White Bird Amplification. The stereo preamplifier signal is given to the RCA input of each of the two monoblocks, which in are connected to one loudspeaker. Each of the monoblocks has the option of selecting a load impedance of 4Ω or 8Ω (for the impedance of 6Ω loudspeakers, the setting 8Ω is selected). The switch on the back panel offers this capability. Thunderbird Monoblock is not equipped with a volume control – the signal is fed directly from the input to its tube circuits. This allows you to completely eliminate the influence of regulators (potentiometer or attenuator) on the signal. Analogue VU meters are installed on the front panels to indicate the level of control of a given block. They have a backlight function, which also informs if device is turned on with power switch. Each of the mono blocks is equipped with an IEC type network connector. At client’s request, it is possible to use components other than standard ones. This applies to the type of tubes and all signal sockets.
Single Thunderbird Monoblock uses a pair of KT150 EH which allows it to transmit without distortion continuous power to the speakers of about 1 x 70W. 12AX7 EHG works as a driver tube, one of the internal triodes amplifies the input signal voltage and the other acts as a phase inverter. Due to the implementation of the phase inverter on a single triode, the signal halves in the counterphases are precise. Amplifier is characterized by very small distortions even at high volume levels. Such a system also provides it with precise control over the acoustic band. The sound is spatial and balanced in every bandwidth. The use of a single duotriode in the pre-stage and an inverter also allows to avoid the need for pairing of driver tubes in each of the channels, which takes place in most PP amplifier designs. The user can therefore modify the sound with a minimum investment in the driver tubes (2 x ECC83 type tube for both monoblocks).
Single Thunderbird Monoblock has dedicated audio-grade power transformer. This allows us to cancel the transformer’s vibrations and silence its work. The transformer supplies the voltage to the anode power supply, power tubes, control lamp and heater (the tube shines with constant current, stabilized by electronics which eliminates disturbances of the power network), bias power supply and VU meter backlight on the front panel, which is an indicator of the amplifier’s volume.
In the output section of the Thunderbird Monoblock amplifier, there is a Edis LO-PP80-1 loudspeaker transformer, which enables the amplifier to cooperate with a load of 4Ω, 6Ω and 8Ω. There is a 4Ω / 8Ω selection selector on the rear panel (for an impedance of 6Ω loudspeakers the 8Ω setting is selected). The loudspeaker transformer gives the possibility to set the mode of the power tubes in the so-called ultralinear and as triode. At customer’s request it is possible to use an additional switch that allows selection of work between the two modes. Version without such a selector is set to the ultralinear mode by default. In the triode mode the amplifier has a lower gain, and the sound is more rounded with a slightly slower sound. The ultralinear mode provides the greatest amplification and dynamics. It combines the advantages of triode and pentodes. Both transformers are located inside the chassis. Thanks to this, it was possible to avoid putting them on the top panel, which often happens in many designs of tube amplifiers. Although, as a standard, we use standard transformers with non-morphic cores, but it is also possible to order a copy of the Silverbird amplifier equipped with a pair of output transformers with amorphous cores manufactured by Edis – L. Olgonowski. They provide absolutely uncompromised sound quality.
Thunderbird Monoblock is made in a large metal casing to which high-quality brand sockets are mounted. However, it is possible to choose non-standard connectors according to the customer’s wishes. The amplifier stands on solid, wide stands made of high quality aluminum. The stands at the bottom have a rubber layer which additionally to its mass – about 15kg – stabilizes the amplifier on the surface.