The Russian brand name for FU29 is FY29, and its American brand name is 829B. It is a composite tube that encapsulates two klystron tubes in the same glass shell. Using it in a push-pull output power amplifier can reduce the trouble of tube selection and pairing. The FU29 has a filament voltage of 6.3V, a current of 2.25A, a plate voltage of 600V, a screen grid voltage of 200V, a zero-signal plate current of 40mA, and a full-signal current of 110mA. The grid bias voltage is -18V, the optimal load impedance from the plate to the screen grid is 13750Ω, and the output power (effective value) reaches 44W at full signal. To further simplify the circuit, the pre-amplification and inverting stages are performed by a single composite tube 6N2. This way, a single audio channel can complete the power amplification task using just one 6N2 and one FU29, with a power output of 40W. This amplifier is compact in size and unique in design, yet powerful in thrust. Do not compare the actual thrust of this electronic tube amplifier with the power of general transistors or digital amplifiers, because of its high supply voltage and unique output structure, the internal resistance changes relatively little for high and low frequency signals, providing good low-frequency drive capability, as well as a smooth, warm, and delicate sound. This is also why electronic tube amplifiers have not been completely replaced after the emergence of many new technologies.
This device is suitable for driving general bookshelves and most floor-standing speakers. We have tested it on the challenging Dynaudio Contour 1.8 floor-standing speaker and it still delivers a powerful performance. We have added a new Bluetooth 5.0 receiver module to facilitate wireless connection with portable devices such as smartphones.
The production dates of the domestic electronic tubes we currently have range from the 1960s to the 1980s. Their meticulous craftsmanship is astonishing. It's hard to imagine that we could produce such intricate and complex products in that era, and they exhibit excellent consistency. After conducting comprehensive comparisons between the EL34 and 300B, which are highly recognized in the market, we find that the sound of the FU29 is remarkable and on par with these internationally renowned tubes. Our domestic products also boast excellent quality that we can be proud of. The FU32 electronic tube amplifier we previously produced has achieved good sales in both domestic and international markets, with almost zero return and repair rates. This demonstrates that in any era, excellent products will always gain recognition from the market and users. We will continue to strive!
Initially, we thought that there should be a considerable stock of such electronic tubes in the domestic market. However, when we were working on the FU32 power amplifier, we discovered that it was not as we had imagined. As the number of electronic tubes available on the market decreased, merchants continuously raised prices, forcing us to adjust our sales prices multiple times. The same goes for the FU29 electronic tube used in this machine. When we started searching, we found that many sellers were selling them, and each had a considerable inventory. However, when we actually made the purchase, we found that only a few actually had stock. Therefore, the number of electronic tubes we actually obtained was limited, and the number of machines we could produce was also limited. Players who are interested should act early, as these tubes may become extinct one day
The schematic diagram is as follows:
