6H30+6AQ5 (6005) active load preamplifier board, low internal resistance, large dynamic, high taste, high-quality preamplifier, without power supply. This line is used after CD before power amplifier.
The characteristic curves of tetrode and pentode and triode are quite different. It can be seen from the characteristic curve family diagram of the tube that for a certain grid negative pressure, the volt-ampere curve is almost a straight line with a small slope (that is, a very horizontal line) after the initial section. It shows that when the grid voltage is fixed, the screen voltage changes in a wide range, but the screen current changes very little (reflected in the figure, it is an almost horizontal line), which has a constant current characteristic. Therefore, the standard connection of the pentode has a brilliant effect when used in a constant current source.
Board size 117×87: dual-channel design, high-quality RC component assembly, high-voltage DC 290V power supply, a set of filament 6.3V, and a set of 3.15V-0-3.15V.
WIMA and other capacitive couplings, silver-plated ceramic sockets, one imported Russian 6H30 and two second-hand 6AQ5 made in the United States, 6.3V for 6H30 electron tubes, 6AQ5 filament voltage dual winding 3.15V power supply, the middle point of the tap is grounded, effectively eliminating AC . All ground wires are grounded at one point and the line is quiet.
In terms of the replayed sound, the sound of a high-voltage regulated power supply will look a bit "tight", while the sound without a regulated power supply will be relaxed and relaxed. The AC filament power supply will make the sound more rich.
LG263E finished board without tube
LG263E finished board with electronic tube, 6H30 Russia, US-made second-hand 6AQ5
Note: The high voltage of this front board needs DC power supply to work, and the transformer high voltage needs to be rectified and filtered before it can be used.
Board code: LG263E 6AQ5, also known as 6005, which can be substituted for 6HG5, 6669
Matching-------65W power transformer: EI76X35mm is wound with high-quality pure copper enameled wire, imported second-hand Z11 iron core, high permeability, piece by piece, fixed by British Red Bull bracket, impregnated with insulating paint process, appearance Beautiful
Input voltage: 220V/235V optional, primary and secondary shielding terminal, secondary high voltage output 0-265V-275V-285V 150mA, filament voltage 8.5V 2A set (for 6H30 filament voltage stabilization), filament voltage 3.15V-0-3.15 One set of V 2A (for 6P14 filament).
The 6AQ5 tube is a small 7-pin beam tetrode specially designed for audio amplification: 6AQ5 is also called 6005, and the alternatives are 6HG5 and 6669.
There are 2 watts of output power in Class A work. China also has similar function tubes such as 6P1 and 6v6, and the former Soviet Union has 6P1P-EV, EL90 and so on. The first American tube is the top grade of audio amplifier.
This tube may not be used by modern enthusiasts, but friends of the older generation must be familiar with him.
This tube specially designed for audio amplification used to make great contributions to radio transceiver equipment, **transceiver equipment, as well as radios and small amplifiers in that era. For example: Drake TR-3; TR-4 radio transceiver, 2-A and 2-B receivers, Collins KWM-1 and Collins KW-1 radio transmitters and 51J-3, 51J-4, 75A-2, 75A-3, 75A-4 receiver.
And Hammarlund HQ-100, HQ-145, HQ-160, HQ-180 receivers and Swan 260/270/270B radio transmitters all use this 6AQ5. In addition, many large companies such as National, Hallicrafters, Racal, Eddystone, IBM, TOSHIBA, etc. also used 6AQ5 extensively in their competitive products at the time. It can be seen that the performance of this small tube in audio amplification is extraordinary.
However, due to its low power, the later development gradually could not meet the needs of high-power amplifiers, and was replaced by some high-power electronic tubes and transistors, and gradually withdrew from its stage.
This batch of tubes are all from early electronic tube equipment. In the early years, these equipments were mostly used in the communication key parts of advanced equipment. After inspection, the condition of these tubes is very good, and they are used to make audio amplifiers to listen to music.
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Excerpt from the online information introduction--------for reference!
The origin of the 6H30 tube is the Soviet Union. The 6H30 belongs to the frame grid type electron tube. It adopts a super-reinforced structure with a three-layer mica root bracket as an auxiliary support, which is highly seismic and has a life of up to 10,000 hours. It was applied to the fighter "Su-27" at that time, and the mechanical structure was highly strengthened. At the same time, its electrical characteristics were about two parallel 6DJ8/ECC88, with extremely high transconductance, large output current, low output impedance, and ultra-low. Mute, almost no microphone effect, a bit like the excellent Telefunken E182CC electronic tube of the year, as long as very simple conditions can exert great performance. The ban was not lifted until the end of 2000 only because it was a Soviet weapon, and it was known to tube amplifier manufacturers and tube amplifier enthusiasts.
The famous American tube amplifier ARC uses 4 6H30 in the newly launched Audio Research 3, which is quite indicative. As we all know, this Hi-End brand has always focused on 6922/6DJ8 vacuum tubes. In the latter stage, it has been planned and designed around 6922/6DJ8 for decades. Now it has switched to 6H30 in its top-level reference series. If it is not for its excellent performance and meets its technical specifications, it may be difficult to be selected. Another well-known domestic brand-Ober, in its Reference CD2.3 advanced CD turntable system, the RCA output signal part also uses a buffer circuit constructed by 6H30 as the output. From the above two cases, everyone can know the excellent performance of 6H30. Of course, the price of this tube is relatively high, but compared with the antique tube that costs 1,000 yuan, the price of 200 yuan is still not very expensive. At present, there are Sovtek's ordinary models, golden foot models and EH that can be purchased in China. There are three types of golden feet. The supply is relatively sufficient and the quality is also proven. It is a tube worthy of tapping its potential.
I searched the circuit about 6H30 on the Internet. The single-tube amplifier circuit found two circuits with self-biased voltage and constant current source as load; an amplifier circuit for Italian enthusiasts, which uses fixed bias voltage and inductive load. Screen output circuit; DIYZONE also uses constant current diode as a load test circuit, and found a 6H30 single-tube amplification simulation software, which can display the characteristic curves of various operating points, so it is very convenient to design the circuit
Design Concept:
The initial idea is a single-tube screen output, self-generated bias, and a constant current source load for the screen.
The screen output is mainly due to the fact that there is no gain in the output of the cathode follower, and the bursting may not be able to burst, and the 6H30 cannot be fully utilized. Although the fixed bias voltage can flexibly select the operating point, it is necessary to add an input coupling capacitor, which increases the variables of circuit adjustment, and a good pair of coupling capacitors is also valuable. The use of a constant current source is one that helps to use the gain of the sub, and the other is that I read Japanese amplifier books recently and found that the constant current source is widely used in the circuits of Japanese enthusiasts. The general evaluation is that there are more opportunities for good sound. some.
There are many circuit structures of constant current sources, and the common ones are as follows: constant current diode, field effect tube, LM317, light-emitting LED (diode, TL431) and transistor, op amp and transistor, electron tube, transistor and electron tube, Field effect tubes and electron tubes, the mixed use of integrated circuits and electron tubes, etc., are limited in space, so I won’t elaborate on them here, and we will prepare another article for a comprehensive analysis later. Considering that the screen load of 6H30 needs to withstand a relatively high voltage, I hope to add some pentode-specific sound dyeing, because I have seen foreign pre-design circuits before, 6080 for single-tube circuit amplification, and EL34 for constant Liuyuan, the original author believes that the frequency response of the triode is relatively straight, and the high and low ends are better extended. The sound of the pentode is condensed in the midrange and has strong analytical power. It should be a perfect sound by mixing the two characteristics. Affected by this article, we plan to use a constant current source circuit composed of 6BQ5 (6P14, EL84).
