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One channel has some whistling/humming sound which wont go even you turn the volume knob to 0. The other channel is not that much amazing. Changed both preamp tubes to a vintage RCA one. The noise went off. Also changed the power tubes to J & J. Now it is crystal clear, no hums/noticeable noise. Pros: 1) A better start for an audiophile who just want to explore class A tube (warm audio). Assume this board as a practical board to gain confidence for building a good tube amp in future 2) The chassis is decent and good finishing. Cons: 1) If you have only hobby experience, dont try this as wiring is not easy. Dangerous voltages are inside that may be life hazardous. 2) No photographs - lot of confusions while wiring. 3) Circuit and wire description is in Chinese lang (few English).. again confusion 4) Transformer wiring also confuse you. 5) Tubes are not high quality. 6) Not worth of money - As you may need to replace all the 4 tubes with a quality one. 60~100$ 6) The power switch is designed in the chassis very close to one of the pre-amp tube. There is not shielding. Chance of electromagnetic noise is high Note: If you plan for a a 110 and 230 volt transformer, ask the seller upfront and share this comment / my experience. Read full review
Verified purchase: Yes | Condition: New
If you're building the kit, head over to diyaudio and check out the Boyuu A9 thread. There are quite a few mods that have been been documented there. These mods will 100% improve the overall sound quality of the amplifier, and honestly they should be something that the manufacturer is providing. Before I implemented the mods, the output was noisy with a 60Hz hum, and was quite fatiguing to listen to. After the mods were performed, the amp sounds positively amazing. I've switched the tubes out as follows: RCA 5U4G diode, matched GE 6SL7 input triodes, and apex-matched JJ KT77 output tubes. I also opted for an Alps 100KAX2 100K ohm stereo input potentiometer with logarithmic taper Other mods that I did that probably didn't have as much impact on the final result: Dayton Audio poly input caps for the ones in series between input and output stages. WBT silver 4% solder in the signal path. Canare Star Quad shielded cabling for the input signal path. Dayton Audio insulated RCA jacks, and 100% of the kit resistors and caps were replaced with better spec'd versions from Digikey. Anyway, after everything above, this amp sounds amazing. Zero noise/hum, very well behaved, but the distortion is quite pleasant when you turn it up. 10/10 would DIY again.Read full review
Verified purchase: Yes | Condition: New
The "kit" is a great project for those with at least an intermediate level of knowledge with reading schematics and understanding of components. Having done these types of projects and building communication equipment from scratch I found it easy to construct. But I've been doing this for over 50 years. There's a lot of good info out there for helping one assemble it. If you have absolutely zero experience don't be afraid to take this on. Just understand that it may be quite frustrating. Best way to approach this is to have someone knowledgeable that can help you along the way
Verified purchase: Yes | Condition: New
The kit is quite complete from a parts standpoint. The only thing the builder need supply is a few feet of 18 ga hookup wire. However, the instructions are nearly non-existent: a schematic and a photo of an assembled unit. You will need to understand you are building in order to be sure you are assembling it correctly. It’s a blessing and a burden, but you will likely learn more than you would from a kit with detailed instructions.
Verified purchase: Yes | Condition: New
The kit is 95% in the way I built it. The kit is pretty skimpy on wires and had to supplement some from my own stash. It had a prominent buzz when placed In a system that was clean using a solid state amp. Be prepared to sleuth some fixes on DIY audio, which has pages of useful info. I was able to fix the buzz by adding 100 ohm resistors to ground for the preamp heaters and 2.2 kohm grid stoppers to the input of the preamp tubes.the input selector has problems too and will replace with a proper switch. Wire quality on the transformers is poor, I tore a wire just braiding it. However, it Sounds glorious now!
Verified purchase: Yes | Condition: New