Wednesday, May 24, 2023

Liang Zhu from IWISTAO 2X40W FU29 Pull Push Vacuum Tube Amplifier

Liang Zhu from IWISTAO 2X40W  FU29 Pull Push Vacuum Tube Amplifier 

"The Butterfly Lovers Violin Concerto"  often abbreviated as "The Butterfly Lovers" or "Liang Zhu". 

We played it with FU29 pull-push vacuum tube amplifier.

This FU29 vacuum tube named FY29 in Russian, and named 829B in American. It is a composite vacuum tube in which two Cambodian tetrodes are packaged in a same glass shell. It is generally used in power amplifiers with push-pull output, which can reduce tube selection and matching trouble. FU29 filament voltage is 6.3V, current is 2.25A, screen voltage is 600V, curtain grid voltage is 200V, zero letter screen current is 40mA, full letter current is 110mA. The grid bias voltage is -18V, the optimal load impedance from the screen to the screen grid is 13750Ω, and the output power (effective value) reaches 44W when the signal is full.

In order to further simplify the circuit, this unit uses a composite tube 6N2 for preamplification and phase inversion, so that a single channel can use 6N2 and a FU29 to complete the power amplifier task, and it has 40W power output. It is small in size, unique in shape, but strong in driving force. Do not use the power of general transistors or digital power amplifiers to analogize the actual driving force of this tube power amplifier, because the high supply voltage and unique output transformer’s structure, its output internal resistance change for high and low frequency signals is relatively small, and it has a good low frequency driving ability. And the sound is soft and smooth, warm and delicate. This is why the tube amplifier has not been completely replaced after the emergence of many new technologies.


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