2 each for GE6U8A and Beijing FU-29, and 1 for silicon rectifier

【Circuit Description】
FU29 is a composite tube with two rapid-fire tetrodes encapsulated in the same glass bulb. It is used in push-pull output power amplifiers, which can save the trouble of pairing tubes. The filament voltage of FU29 is 6.3V, the current is 2.4A, the screen limit voltage is 750V (650V for this machine), the curtain grid voltage is 200V, the full letter current can reach 110MA, and the effective value of the output power can reach 44W. The optimum load impedance is 13750 ohms. This unit uses 12K ohms. In order to simplify the circuit as much as possible, there are fewer incense burners and fewer ghosts. The pre-amplification and phase inversion are completed with a composite tube 6F2, so that only two tubes are needed for one channel to complete the playback task. 6F2 Western European tubes are very cheap and are a very cost-effective tube.

【Sound description】
6U8+fu29 fever tube amplifier, FU-29’s low-frequency control is free, full of elasticity without being fat, high-frequency is transparent and elegant, spiritual; the mid-frequency is sweet and mellow, as fragrant as old wine; the whole frequency range is very balanced . The vocal positioning is accurate, as if the singer is standing in front of you. What is particularly prominent is the strong and powerful low frequency, which is not the effect of ordinary amplifiers.

【Material Description】
◆ All AC filaments are used to light the lamp, and it is close to the horn with a sensitivity of 90DB, and no hum noise can be heard.
◆Adopt fu29 Class A amplifier circuit driven by 6U8, output 35w+35w power. It is suitable for speakers with impedance of (4-8) ohms with a sensitivity of 88db or more, and speakers with a sensitivity of 8-10 inches or more than 90db have no problem at all.
◆Using metal film resistors and imported electrolytic capacitors with an accuracy of up to 1%. The coupling adopts Hong Kong TE MKP film capacitors and German WIMA capacitors, and the sound quality is transparent and open.
◆ CRLC multi-stage filtering, high signal-to-noise ratio. The filter capacitor is made of Korea Sanyo and Japan Chemical Electrolysis, combined with high-power metal oxide film resistors and 5H 0.35A Z11 silicon steel sheet inductors (optional) to form a crlc filter network, which has a strong ability to suppress hum!
◆Standard electronic tubes Our shop adopts new j-class products: 2 each of GE6U8A and Beijing FU-29, and 1 silicon rectifier. Buyers can also purchase 274B and other rectifier tubes to replace the original silicon rectifier seat, but 230MA output current rectifier tubes such as 274B or 5Z3PA will have distortion when the volume is turned on, it is recommended to use silicon rectifier seat rectification first. If you push low-power speakers, you can use a bile rectifier.
◆Power transformer and output transformer need to be purchased separately: FU-29 (12K) 100W output cow (search number OP965007) and 400W power supply cow (search number 1146501) are made by our shop, with stable and reliable quality! The power transformer has a power of 400W, the size of the iron core is 114×65, and the domestic H18 0.35MM thick annealed silicon steel sheet is not heated and has a top cover. The output transformer is wound with a 4-clip 3-winding method, the iron core specification is 95*50, and it is made of Z11 silicon steel sheet with a thickness of 0.35MM from Japan. The magnetic permeability of the Z11 sheet will be higher, and the low frequency will be lower. The effect is much better than the domestic H14, H18 silicon steel sheet. Because the transformer accounts for most of the cost of the machine, it needs special instructions.
◆PCB circuit board adopts 1.6MM thick double-sided copper-clad fiberglass board, the circuit board is designed with thicker copper foil, one-point grounding layout, and the noise floor is basically inaudible. Size: 355MM*145MM
◆Rated output power of this board: 35w*2 (because the electronic tube has the advantage of strong overload capacity, the actual output power without distortion is equivalent to the 150w+150w transistor power amplifier!). Speakers with high sensitivity (above 90DB) should be selected for this board, and a 10-inch 200W power box is recommended. Since the tubes at all levels work in the state of Class A amplification, the distortion is small, the sound is sweet and soft, and the hearing resistance is extremely high!