DE102018004424A1 - DC coupled anode-cathode circuit - Google Patents

Abstract

TECHNICAL PROBLEM OF THE INVENTION = Technical Problem and ObjectiveThe known tube technology has in common is the operation at high anode voltages (up to about 600V) with the associated risk to life and limb, as well as high power supply costs and their very high losses. Several coupled stages require coupling capacitors or transformers, which Produce distortions and negatively affect the tonal properties. The technical task was to find a means to make amplifier tubes usable in a small voltage range and still obtain good characteristics. Solving the problem or the technical problem using a combined anode base circuit (input), DC-coupled with a cathode base circuit (output) as Funktionsblock.Dies works in the anode and in the cathode circuit with all common Tube types (triodes, tetrodes, penthodes) The interconnection of the two tubes is DC-coupled and thus both the input capacitor of the anode circuit and a coupling capacitor to the cathode circuit (sound relevant) omitted omitted.The used in the old circuit technology bypass capacitor (frequency-dependent) and the cathode resistance the cathode of the cathode circuit can also be omitted by the direct connection to ground in the new circuit technology.

Description

State of the art

The tube technique is a fairly old, mature technique, which is considered largely researched and their circuit technology is assumed to be known.

Disadvantages of the prior art

Common to this circuit technology is the operation at high anode voltages (up to about 600V) with the associated danger to life and limb, as well as high power supply costs and their rather high losses.

The negative grid bias necessary for setting the operating point of the amplifier tubes is generated by a cathode resistor, which is bridged by a capacitor on the alternating voltage side

In the case of fast pulses, this circuit technique, due to the properties of real components, works only insufficiently and leads to an accumulation of an excess of electrons at the control grid of the amplifier tube, which can only be dissipated slowly by the high-resistance circuit. This leads to a significant, prolonged and clearly audible deterioration in dynamics.

Multiple coupled stages require coupling capacitors or transformers which produce distortions and adversely affect the sonic properties.

The necessary for the transport of free electrons tube heating (directly or indirectly, depending on the tube type) was carried out with AC voltage, which led to the influence of the useful signal.

The tube heater was designed without inrush current limiting, which was detrimental to the life of the amplifier tube (analogous to a light bulb that often dies at power-on)

Object of the invention

Voltage amplifiers in the low power range with minimized component expenditure and omitting all negative component influences mentioned above

Solution of the task

Use of a combined anode base circuit (input), DC coupled to a cathode base circuit (output).

This works in the anode as in the cathode circuit with all common tube types (triodes, tetrodes, pentode, hexodes)

The interconnection of the two tubes is DC-coupled and thereby both the input capacitor of the anode circuit and a coupling capacitor to the cathode circuit (both very much relevant to the sound) omitted.

The bypass capacitor and the cathode resistance of the cathode circuit can also be omitted by the direct connection of the cathode to ground.

The directly controlled by the anode circuit control grid of the subsequent cathode circuit can, like the anode circuit itself, by the damping of the interaction by the low internal resistance of the anode circuit, no longer accumulate with an excess of electrons, resulting in a much improved dynamics.

In addition, care was taken to put all internal shielding directly at ground potential and thus to avoid any crosstalk between the circuit parts.

The tube heater is heated (using multiple tubes independently) by means of a constant current source with direct current, which contributes to an extension of the tube life; Any resulting crosstalk between control elements (all tube grids) of the tube (s) and the housed in the same glass bulb direct or indirect tube heating is prevented with a bypass capacitor (clearly audible improvement).

Only a capacitor in the output of the circuit for coupling the AC signals is needed. This is far less relevant in terms of sound, since its one plate is acted upon at about half the operating voltage and the useful signal moves with lower amplitude around this operating point, which is accompanied by improved AC transmission characteristics as a result.

Advantages of the invention

• • Both the input capacitor, a coupling capacitor and a bypass capacitor (all very relevant to the sound) can be omitted.
• • No unintentional enrichment of the control grid with an excess of electrons during operation
• • Improved crosstalk (screen grid directly to ground)
• • Improved dynamics (elimination of cathode resistance and bypass capacitor)
• • Low distortion (low-impedance control of the cathode circuit)
• • Low noise (low-impedance input resistance, low-impedance control)
• • Minimized component costs
• • Low reaction of the connected load to the circuit (removal of the useful signal at the single connection of the tube, which can not be used for control tasks)
• • Increased service life due to Soft Start (constant current operated tube heating)
• • compensation of aging phenomena (self-regulating tube heating)
• • eliminations of repercussions between tube heater and intensifier tube (bypass condenser of the tube heater)
• Mutual extensive linearization of the tube characteristics (by the forming negative grid voltage at the anode against the forming positive grid voltage at the cathode circuit)
• • The circuit works without over-all negative feedback
• • Reduced costs through minimized component costs and the potential use of a standard industrial power supply

Further possible embodiment of the invention

The extension to power electronics would be conceivable with the aid of a voltage follower constructed using MOSFET transistors. A structural simplification can be made by using an integrated amplifier tubes, for example: PCL84, ECL 80 ö.ä.

Claims (8)

Use of a power source to power direct or indirect tube heating Use of a (blocking) capacitor electrically parallel to and in close proximity to the tubular heater The control grid of the anode circuit is connected by means of a resistor to ground (GND). The anode of the anode circuit is at operating voltage potential. The cathode of the cathode circuit is connected directly to ground (GND). The cathode of the anode circuit is connected to the control grid of the cathode circuit. The control grid of the cathode circuit is additionally connected by means of a resistor to ground (GND). There is no over-all negative feedback used Internal shields within the tube (s) are connected directly to ground (GND).

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