Invention Patents
Vacuum tube amplification system capable of reducing residual noise and a grounding method thereof 

USA: Invention Patent No. US 11,12,678 B1

Taiwan, R.O.C.; Invention Patent No. I724914

The timbre of the vacuum tube amplifier has long been on the High-End PRO hall. However, the vacuum tube amplifier technology only stays at the level of the PCBA era, and the residual noise has not been further reduced; a HI-FI pentode vacuum tube amplifier residual noise has a range of 5mV~8mV RMS, a triode vacuum tube amplifier has 8mV~10mV RMS, the residual noise can be heard within 30cm~100cm distance under the induction of no power pulse signal.Users have long been accustomed to thinking that this is the normal residual noise level of the vacuum tube.

Nowadays, integrated circuit products of transistors have an average residual noise of 1mV~2mV RMS or less. This makes the vacuum tube useless in this kind of tabletop products in the era of personalization. It can only sit firmly in the High-End professional products and cannot be used as a tabletop mini speaker.

In the early era of the grounding mode of vacuum tube amplifiers, grounding as long as there has a ground wire.The purpose was to make the amplifying circuit work and amplify normally, so that it could be marketed. It was the early stage of the vacuum tube, the sound source on the market had a lot of background noise and the technology was backward. This kind of grounding method is messy. All level amplifiers’ grounding wires have formed a closed loop. The ground wire has already lost its shielding and isolation effect, and produces a hum from closed loop of power supply, the interference of the transformer pulse wave can easily enter all levels and be amplified. Therefore, the final residual noise was extremely poor, and most manufacturershave never faced it as an issue to be solved.

The problem of residual noise was not solved until the electronics industry enters the era of printed circuit boards (PCBA). After the industry developed a power single-point grounding method (also called single-ended grounding method) and a single-point grounding method for signal ends,the problem was greatly reduced without forming a ground loop. The residual noise level of the vacuum tube has been greatly improved to 5-8mV. In this era, there were audio cassettes, MC turntables, MM turntables and CD turntables. The quality of the sound source continues be improved, and even CD turntables with a digital sound source of 48K/24bit have appeared.

It's now a digital generation. The quality of audio source has been greatly improved from the tape, MC turntable, MM turntable, CD disks and even the 48k/24bit disks of digital source. Nowadays, all audio sources has been digitalized; CD, Bluetooth, DAB, USB, DAT, WI-FI and the 48k/24bit of audio formats are just a common level; 96k/24bit, 196k/24bit HI-RES audio source has been a part of our life. The traditional vacuum tube amplifiers are the almost perfect and the most High-End audio products in addition to the residual noise, which is the final issue, so reduce the residual noise is the way to keep the vacuum tube amplifier always on the top level of audio products, and transfer to be personal use similar to transistor tabletop player, to increase market penetration.

Although we know how to reduce the residual noises of vacuum tube amplifier through a large number of transistors to regulate, but this way is not only to increase the cost significantly, and will lose the beautiful sound that the vacuum tube should have. In order to save the cost and keep the authentic sound quality of vacuum tube music player, we invented this patent to have win-win situation, "Vacuum tube amplification system capable of reducing residual noise and a grounding method thereof".

The residual noise has a lot to do with the DC power grounding point, which can help us to find out the minimal noise point and is a necessary shared ground in compliance in with the safety. When it is impossible to separate the residual noise and DC power grounding point, we adopted the concept of floating ground to separate the grounding terminal, and cooperate with the design of power transformer, carry out residual noise testing, improvement and various solutions. One of them is that to adopt a power transformer with two identical high/low voltage windings, the average residual noise is about 2.4mv/1.414=1.845mv RMS in the test, which is a new record of vacuum tube amplifiers residual noise, and it is almost the level as transistor players’ residual noise without the waveform of hum noises from power and the interference of pulsed signals, it achieves the higher expectations of the vacuum tube amplifier developing into a modern tabletop audio products. Based on these patents, we will continue to launch more new concept products powered by vacuum tubes. Stay tuned.

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