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The inventions and products featured on these pages were chosen either for their uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough to warrant an appearance.

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Super Mini Vacuum Tube Headphone Amplifier - RF CafeJust as vinyl records have made a comeback in the last decade, so, too, have vacuum tube amplifiers and radios. Many vintage vinyl albums from the pre-CD (compact disc) era, as well as from groups in the 1990s and early 2000s (most from the latter group I have never heard of), are being pressed again. In fact, companies are having a hard time keeping up with demand. Melanie and I have a respectable collection of original 45 rpm Singles and 33-1/3 rpm LPs (long-playing) records from groups in the 1960s through early 1980s, that is to say, up through our tweens and early twenties ... but I digress.

Mini Vacuum Tube Headphone Amplifier - RF Cafe

With 3.5mm AUX input and 3.5mm headphone jack output, can be used as a headphone amp and a stereo preamp, compatible with most audio source such as MP3, iPod, phone, tablet, computer, CD player etc. and output can connect headphone, amplifier, active speaker etc. to greatly improve the sound quality. Adopting classic 6N3 vacuum tube to effectively eliminate the harsh digital sound, providing HiFi clear, soft and smooth, warm and sweet tube sound. The sound field is wide, especially suitable for vocals, strings, light music, classical music, etc. Adopting solid state design, preamp part uses vacuum tube for amplification to make the input audio signal more natural with high dynamic range, and amp part uses NE5532P op amp to ensure the speed and power of audio signal transmission.

Little Bear Mini Vacuum Tube Stereo Preamplifier - RF Cafe

Not only as a headphone amplifier, compatible with wide impedance range (12-200Ω), but also as a preamp for your other power amplifier, convenient and efficient to improve sound quality. 1*3.5 mm stereo jack input, can be connected to computer, CD, mobile phone and lossless player. 2*3.5 mm output can also be connected to digital amplifiers and active multimedia audio devices. Default Beijing FU32 vacuum tube, can be upgraded to GU-32/832; Default NE5532 op amp, can be upgraded to OPA2604, JRC4558, OPA2132, OP275 and so on for enjoying different tones.

What inspired this article is having just seen a Google Ad here on RF Cafe promoting a Mini Vacuum Tube Headphone Amplifier (see screen capture to the left). By Google's rules, I can't click on it to see where it leads because it would be considered a fraudulent click that costs the advertiser money. I did a search on Amazon and found what appears to be the same thing. However, the vendor there wants more than $300, whereas identical Mini Vacuum Tube Headset Amplifier models can be had on eBay for under $50 (image on right). It uses a 6N3 duotriode tube (inexpensive and easily replaced), which helps ensure matching characteristics between the left and right channels. Cathode voltage is 150 V, so it needs to convert the 12 Vdc input to 150 V.

That is a pretty basic stereo amplifier with a more modern look. If you want a real conversation piece that looks like a retro section of a radar, then you'll want to opt for this Little Bear Vacuum Tube Headphone Amplifier. They should consider branding it with a more eloquent name like the Ursa Minor Vacuum Tube Amplifier. That FU-32 vacuum tube is the very definition of "way cool." It is evidently an equivalent of the RCA 832 tube, which can be bought on eBay for under $10. You can bet if I had a spare $80 in my pocket, I'd be getting me a Little Bear.

Finally, if you need a wireless amplifier to feed speakers across the room, back yard, garage, or basement, consider something like this vacuum tube Bluetooth stereo amplifier. I couldn't find a WiFi-connected version. Dozens of designs are available for both wired and wireless vacuum tube stereo amplifiers.

Vacuum tube Bluetooth stereo amplifier - RF Cafe

 

 

Posted August 10, 2023

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