Four Patented Inventions




Vacuum tubes have excellent linear output characteristics, so a conventional vacuum tube audio amplifier that uses vacuum tubes for processing audio signals can provide superior sound quality. A conventional vacuum tube audio amplifier has the following circuit structure, a conventional vacuum tube audio amplifier receives an audio signal input and then outputs the signal to a loudspeaker. Moreover, the conventional vacuum tube audio amplifier includes a power circuit, a vacuum tube amplifying circuit, an audio output transforming circuit, and a grounding metal bottom plate, wherein the power circuit is utilized to receive a mains electricity input and provide power to the vacuum tube amplifying circuit and the audio output transforming circuit. The grounding metal bottom plate is employed to provide grounding shield to the power circuit, the vacuum tube amplifying circuit, and the audio output transforming circuit. 



In the circuit diagram of a conventional vacuum tube audio amplifier, to wherein with respect power source, the mains electricity input is transformed and rectified through the power circuit, filtered by a choke (CHK) and then provided to the vacuum tube amplifying circuit and the audio output transforming circuit. An audio signal input is amplified by the vacuum tube amplifying circuit, transformed by the audio output transforming circuit and then transmitted to the loudspeaker. With respect to grounding, point A in the power circuit, or the negative terminal (point B) of the input terminal signal of the vacuum tube amplifying circuit is used as the only ground terminal in a conventional vacuum tube audio amplifier to be coupled with a single ground terminal with the grounding metal bottom plate to provide grounding shield to the conventional vacuum tube audio amplifier.



However, even though the grounding metal bottom plate of a conventional vacuum tube audio amplifier may provide grounding shield, it cannot eliminate the residual AC noise and impulse noise, resulting in that the user could hear clearly the residual hum and impulse hum in the sound played by the loudspeaker at a short distance (within about a meter). Also, the choke in the power circuit would be coupled with high-frequency noise and further aggravate the problem of humming. Moreover, the grounding metal bottom plate results in huge volume of the amplifier and expensive cost, and as the grounding metal bottom plate 6 is mostly designed integrally with the casing, which further leads to leakage in a conventional vacuum tube audio amplifier.  Even though the conventional vacuum tube audio amplifier has superior sound quality, due to bulky volume and the problem of humming within a short distance, a desktop model cannot be developed nor do such vacuum tube audio amplifiers fit in ordinary households.



In order to solve the above shortcomings and develop an All-In-One vacuum tube music player that is affordable, and can be placed on the table or on the audio rack, the Echowell audio team has been continuously developing and verifying for many years, has successively designed many innovative solutions, and filed four patent applications in many countries, some of which have patented from many countries, and some are under review. The names of the four patents and the numbers of the patent certificates that have been patented in various countries are as follows.




1. Grounding Structure and Grounding Method of Vacuum Tube Audio Amplifier


Taiwan, ROC: Innovation Patent No.I650934


USA: US 10,135,402 B1


Russia: Patent for Invention No. 2695048


Australia: Patent number: 2018222961


Korea:  Patent No. 10-2077092




2. Vacuum Tube Audio Amplifier


Taiwan R.O.C.: Innovation patent no.I703815


USA: US 10,218,320 B1



3. Vacuum Tube Rear Device



4. Vacuum tube amplification system capable of reducing residual noise and a grounding method thereof



A brief introduction is as follows, and you can refer to the patent bulletin for details.



The application provides a grounding structure of a vacuum tube audio amplifier, which includes, in aspect of the power thereof, utilizing a power circuit without choke, an anti-cross circuit and a filament regulator circuit; and in aspect of the ground thereof, utilizing an output negative terminal of an audio output transformer circuit or a negative terminal of filter capacitor of the power circuit as a single ground terminal of the vacuum tube audio amplifier, and arranging no metal ground bottom plate thereof, in order to achieve a lightweight desktop vacuum tube audio amplifier, and further avoid leakage..



The grounding structure of the vacuum tube audio amplifier is provided by the present invention. The vacuum tube audio amplifier transmits an output signal according to an input signal, and includes a power circuit that supplies power to a vacuum tube amplifying circuit and an audio output transforming circuit. The audio output amplifying circuit amplifies the input signal and transmits it to the audio output transforming circuit, which delivers the output signal to the loudspeaker. Besides, the negative output terminal of the audio output transforming circuit or the negative terminal of a filter capacitor in the power circuit is used in the vacuum tube audio amplifier as the single ground terminal, which is not coupled to a grounding metal bottom plate. Also, through a filament voltage regulator circuit, the power is supplied to a filament of a vacuum tube in the vacuum tube audio amplifying circuit.



Regarding the vacuum tube power amplifier, most design engineers know that the key characters are must be with a highly magnetic flux density, low magnetic losses, sufficient inductance and the low internal resistance losses to ensure the flat response of vacuum tube power amplifier keep at 20Hz~20KHz.The flat response means that the frequency response can be kept flat within the frequency response range of 20Hz~20KHz.The HI-FI flat response specification is from the starting point 20Hz to the end point 20KHz +/-3dB.



In the early 30~50s, due to the excessive carbon volume of the silicon steel sheet material, the frequency response is always between 45Hz to 16KHz, which is still far away from the standard requirement, but now, the silicon steel Z11 (35Z155 or 35JG155) or the low-carbon of large audio transformer is capable to reach the HI-FI standard at 20Hz ~ 20KHz, which also let the timbre of the vacuum tube come into play extreme, and enter the High End hall. 



It's a mission impossible to accomplish without these advanced materials and costly resources, that's why the price of vacuum tube amplifiers are always expensive for most people. Most design engineers are familiar that the audio output transformer is the most critical component in addition to the vacuum tubes, of course there are so many different options or backup solutions available to select, but designers understand that the wrong choice will result in poor frequency response, and make the product un-commercialized, unable to be put into production, unsold, or even irremediable. Therefore, the material of the audio transformer is not an optional component.



In order to further reduce the cost and weight of the vacuum tube amplifier, and make it affordable, based on the patent of "Grounding Structure of Vacuum Tube Audio Amplifier", we chose the impossible task, use the lowest cost H50 as the audio output transformer with the silicon steel sheet size below EI48, which works with the CR equalizer and become a set of modules, successfully overcome the shortcomings of small and low-cost audio transformers, further reduce the weight and cost of the vacuum tube machine transformer, and make up its own character of frequency response.



Vacuum tube audio amplifiers can give very good and pleasant sounds. However, as these amplifiers are generally expensive, bulky and tend to have heat dissipation problems, they are typically designed as high-end products that are still impossible to become common household products. Compared with integrated circuit (digital) audio amplifiers, which are now more popular, vacuum tube audio amplifiers tend to consume larger space with fragile tubes; moreover, when operating, they generate intense heat while the high current is flowing through the filaments within the vacuum tubes. Thus, most of the vacuum tube audio amplifiers are designed to have top-mounted (mostly in high-end type products) or internally mounted vacuum tubes.



The traditional built-in vacuum tube speaker device uses a wooden shell, which is designed to enclose a prior art vacuum tube amplifier and probably a speaker in the device. The housing can protect vacuum tubes from colliding with one another and prevent the user from being scalded by the vacuum tubes when they are operating and generating intense heat. However, the housing makes it difficult for the vacuum tube amplifier to dissipate heat. As a result, the main drawback with the design of an audio device with internally mounted vacuum tubes is its heat dissipation problems; poor heat dissipation will shorten the lifespan of vacuum tubes. In addition, this prior art vacuum tube amplifier includes a metal grounding plate at the bottom part, arranged close to the circuit of the amplifier to reduce the noise generated from the circuit when operating. However, such arrangement causes the prior art vacuum tube amplifier to consume a lot of space and become very bulky. If testing operations need to be carried out, the vacuum tube amplifier with the above design will have to wait until it is assembled with the housing of the speaker device. The testing operations for the whole audio system cannot be performed until the vacuum tube amplifier and the housing are assembled together. The bulky device is thus disadvantageous for establishing an automation production line that includes a testing procedure.



Another prior art vacuum tube audio amplifier apparatus has top-mounted vacuum tubes, which can be separate from speakers to improve heat dissipation. Protective frames are used to provide simple protection for vacuum tubes. Still, the vacuum tube audio amplifier apparatus includes a metal grounding plate (may be a metal housing) at the bottom part for reducing noise; moreover, the apparatus needs to be connected to an external speaker device and thus the whole audio system will consume even more space. In addition, the vacuum tube audio amplifier apparatus has the vacuum tubes arranged on the top of the device to facilitate heat dissipation and system configurations. However, such design makes it impossible for the devices to be stacked up on one another like integrated circuit (digital) audio amplifiers, thus making them impossible to become common household products. Also, as the circuit board of the amplifier is positioned within the apparatus housing while the vacuum tubes are positioned on top of the apparatus housing, testing operations are difficult to be carried out with the non-modular design. Similarly, the testing operations for the whole audio system cannot be performed until the vacuum tube amplifier apparatus is completely assembled, and the bulky device is disadvantageous for establishing an automation production line that includes a testing procedure.



As described above, prior art vacuum tube audio amplifiers have drawbacks associated with space consumption, stacking and heat dissipation, and thus the materials used for them could be restricted (therefore with high costs). In view of the above problems, the present invention provides a device with rear-mounted vacuum tubes, wherein the device can be arranged in a vacuum tube audio amplifier apparatus. The device with rear-mounted vacuum tubes comprises a rear panel, a front panel and a housing. The housing is assembled with the front and rear panels along the horizontal direction. The vacuum tubes are arranged, through an opening of the rear panel, from the inside to the outside of the device, and mounted at the rear of a vacuum tube audio amplifier apparatus; thus, the heat generated by the vacuum tubes can be dissipated to the outside of the device (i.e., into the air). The device with rear-mounted vacuum tubes can be used in a vacuum tube audio amplifier apparatus. The device according to the present invention allows the amplifier apparatuses to be vertically stacked and facilitates mass production of the amplifier apparatuses. In addition, the device with rear-mounted vacuum tubes according to the present invention can achieve the objective of reducing the cost for the machine housing. As the vacuum tubes are located at the rear of the machine, heat dissipation can be improved and the lifespan of vacuum tubes can be prolonged, which, in turn, is favorable for the selection of the machine housing (selection of the materials will not be restricted in order to address the thermal endurance problem). Heat resistance is no longer a problem, and virtually all housing materials can be used, such as PVC veneers or plastic housings which are of lower cost.



In addition, the device with rear-mounted vacuum tubes according to the present invention can reduce the residual noise related to power supply and grounding, thereby eliminating the humming sound effectively; moreover, a metal grounding plate at the bottom part is not needed. Please also refer to U.S.A. Patented No. 10,135,402 B1 for relevant techniques; said application discloses that reducing the size of a vacuum tube amplifier apparatus can avoid leakage currents.


To address the problems described above, the present invention provides a device with a rear-mounted vacuum tube, the device comprising at least one protective cover, a rear panel and at least one PCB, wherein: the at least one protective cover comprises a plurality of heat dissipation holes, a containing space and an opening edge; the rear panel comprises at least one rear panel opening, the opening edge being joined to the rear panel opening; and the at least one PCB is electrically connected to at least one vacuum tube. Moreover, the PCB is mounted to the rear panel opening, so that the vacuum tube is arranged within the containing space of the protective cover.



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 manufacturers have 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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