Phono cartridge transmission line impedance matching system and method

A phono cartridge transmission line impedance matching system is provided. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances.

FIELD OF THE INVENTION

The present invention relates to impedance matching systems, and more particularly to a system and method for accurately matching the impedance of a phono cartridge and its transmission line connected to an amplifying device.

BACKGROUND OF THE INVENTION

Ideally, a phono cartridge transmission line is terminated with an impedance that matches the combined impedance of its components, the phono cartridge, the tone-arm cabling, the interconnecting cabling, and the amplifying device's input. A properly matched transmission line termination substantially prevents signal reflections and power loss, whereas a transmission line termination mismatch causes signal reflections that produce numerous undesirable effects which cumulatively affect the overall frequency spectral response by way of standing waves, interference, and power loss.

It is important to note that the vinyl phono record is not recorded (cut) with a flat frequency response, but rather, with three time-constants (two zeros, and one pole), and in particular, with a rising high-frequency response that is boosted according to a Recording Industry Association of America (RIAA) standardized system, designed to improve the signal-to-noise ratio during normal record play. This high-frequency pre- and de-emphasis can produce a very distorted and strident upper-frequency sound when the phono cartridge is not accurately loaded.

Incorrect resistance loading limits the phono cartridge's performance, affecting the low- or the high-frequency response, or in some cases both. Over-compensation affects the speed of the phono cartridge's dynamic characteristics by over-dampening; under-compensation exacerbates the high-frequencies to the point of uncontrolled ringing.

In present-day applications, the phono cartridge transmission line is terminated by: the phono cartridge manufacturer pre-terminating the phono cartridge transmission line and enabling the user to terminate the transmission line by choosing between a few pre-selected termination values; or by enabling the user to terminate the transmission line by choosing between a limited number, typically less than 30, of termination values.

Furthermore, in order to change the termination value, the user has to shut down the phono player and the amplifying device, change the termination value, restart the phono player and the amplifying device, and listen again, thus resulting in a tedious and time consuming process until the best termination value has been found, which is further complicated by the fact that this process takes longer than the 15-30 seconds short-term sonic memory of the user.

It is desirable to provide a system and method that enables accurate matching of the impedance of a phono cartridge and its transmission line connected to an amplifying device.

It is also desirable to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device.

It is also desirable to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device during normal record play.

It is also desirable to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device for a large variety of commercially available phono cartridges of different types.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a system and method that enables accurate matching of the impedance of a phono cartridge and its transmission line connected to an amplifying device.

Another object of the present invention is to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device.

Another object of the present invention is to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device during normal record play.

Another object of the present invention is to provide a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device for a large variety of commercially available phono cartridges of different types.

According to one aspect of the present invention, there is provided a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances.

According to the aspect of the present invention, there is provided a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances. An input shunt resistor is interposed between the signal line and ground. Each resistance switching circuit comprises a plurality of resistors connected in series and a multi position selector switch connected to: nodes between adjacent resistors, a first node before a first resistor of the plurality of resistors; and a last resistor of the plurality of resistors, the multi position selector switch being adapted for selectively connecting one of the nodes to a switching output.

According to the aspect of the present invention, there is provided a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances. An input shunt resistor is interposed between the signal line and ground. Each resistance switching circuit comprises a plurality of resistors connected in series and a multi position selector switch connected to: nodes between adjacent resistors, a first node before a first resistor of the plurality of resistors; and a last resistor of the plurality of resistors, the multi position selector switch being adapted for selectively connecting one of the nodes to a switching output. The switching output of the last resistance switching circuit of the plurality of resistance switching circuits is connected to ground and the switching output of each of the other resistance switching circuits is connected to the first node of a successive resistance switching circuit.

According to the aspect of the present invention, there is provided a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances. The resistance switching circuits are determined such that the resistance values of successive resistance switching circuits increase by an order of ten. Each resistance switching circuit switches between ten resistance-load values (including zero) in equal increments.

According to the aspect of the present invention, there is provided a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port adapted for being connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances. Each switching circuit comprises a rotary switch having a control knob such that a control knob position is indicative of a respective resistance value.

According to the aspect of the present invention, there is provided a phono cartridge transmission line impedance matching method. The method comprises providing a phono cartridge transmission line impedance matching system. The phono cartridge transmission line impedance matching system comprises a connecting port connected to a signal line and a ground line of a phono cartridge transmission line. A capacitance switching circuit is connected to the signal line and the ground line in a parallel fashion. The capacitance switching circuit is adapted for selectively switching between different capacitances. A plurality of resistance switching circuits, connected with each other in a serial fashion, are connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit is adapted for selectively switching between different resistances. Using the capacitance switching circuit and the plurality of resistance switching circuits, the capacitance value and the resistance value are set to respective values recommended by a manufacturer of the phono cartridge. Using the phono cartridge, a user plays a record and listens to the record playback. Using the plurality of resistance switching circuits, the user adjusts the resistance value while listening to the record playback until the phono cartridge transmission line impedance is matched.

The advantage of the present invention is that it provides a system and method that enables accurate matching of the impedance of a phono cartridge and its transmission line connected to an amplifying device.

A further advantage of the present invention is that it provides a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device.

A further advantage of the present invention is that it provides a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device during normal record play.

A further advantage of the present invention is that it provides a system and method that enables precise adjustment of the resistance loading of a phono cartridge connected to an amplifying device for a large variety of commercially available phono cartridges of different types.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIGS.1to9a phono cartridge transmission line impedance matching system100according to a preferred embodiment of the invention is provided. The matching system100is, for example, incorporated in an amplifying unit20, such as a pre-amplifier unit, connected to a stereo record player10, as illustrated inFIG.1. Alternatively, the matching system100may be provided as a stand-alone unit interposed between the record player10and the amplifying unit20. The matching system100matches the impedance of phono cartridge12and its transmission line connected to respective amplifiers22L and22R of the amplifying unit20. The transmission line comprises cabling through tone-arm14and housing11of the record player10as well as cabling16connecting the record player10to the amplifying unit20. The cabling comprises a signal line SL, SRand a ground line GL, GRfor each of a left hand side channel and a right hand side channel of the stereo record player10, respectively. Two matching systems100are employed with one matching system100being connected to the signal line SL, SRand the ground line GL, GRof each of the left hand side stereo channel and the right hand side stereo channel via connecting port102S,102G. Since the two matching systems100for matching the two stereo channels are the same, the description hereinbelow will be limited to a single matching system100for simplicity.

Referring toFIG.2, the matching system100comprises a connecting port102S,102G adapted for being connected to a signal line SL, SRand a ground GL, GRline of one of the left hand side stereo channel and the right hand side stereo channel. Capacitance switching circuit104is connected to the signal line portion102S and the ground line portion102G of the connecting port102S,102G in a parallel fashion. The capacitance switching circuit104is adapted to enable a user to selectively switch between different capacitances. A plurality of resistance switching circuits, for example, five resistance switching circuits106,108,110,112, and114, as illustrated inFIG.2, are connected with each other in a serial fashion via connecting lines B, C, D, and E between successive resistance switching circuits. The first resistance switching circuit106is connected to the signal line of the capacitance switching circuit104via connecting line A and the last resistance switching circuit114is connected to the ground line via connecting line F such that the series of resistance switching circuits106,108,110,112, and114is connected to the signal line and the ground line in a parallel fashion. Each resistance switching circuit106,108,110,112, and114is adapted to enable the user to selectively switch between different resistance-load values.

Preferably, the matching system100comprises an input shunt resistor R1interposed between the signal line and ground, as illustrated inFIG.3. The input shunt resistor R1directly parallels a large value resistance such as, for example, 1 M Ω, between the signal-line and a quiet (non-power connection) ground GND2. Although this technique is more complex when determining the individual resistors of the resistance switching circuits106,108,110,112, and114, it ensures a quiet transition between resistance-load selections by the user, therefore, enabling the user to change the resistance-load during record play.

Referring toFIG.3, the capacitance switching circuit104comprises an input capacitor C1having a capacitance of, for example, 5 pF, connected to the signal line and the ground line in a parallel fashion, followed by a plurality of capacitors such as, for example, ten capacitors C2-C11and a multi position selector switch104S for selectively connecting one of the capacitors C2-C11to the signal line and the ground line in a parallel fashion. For example, each of the capacitors C2-C11is connected to the ground line and to the selector switch104S for selectively connecting one of the capacitors C2-C11to the signal line, as illustrated inFIG.3. Alternatively, each of the capacitors C2-C11may be connected to the signal line and to the selector switch104S for selectively connecting one of the capacitors C2-C11to the ground line.

Referring toFIGS.4to8, each of the resistance switching circuits106,108,110,112, and114comprises a plurality of resistors connected in series to the signal line and a respective multi position selector switch106S,108S,110S,112S, and114S connected to: nodes between adjacent resistors, a first node before the first resistor of the plurality of resistors; and a last resistor of the plurality of resistors, with the nodes being indicated by black circles inFIGS.4to8. The multi position selector switches106S,108S,110S,112S, and114S are adapted for selectively connecting one of the nodes to a respective switching output. The switching output of each of the resistance switching circuits106,108,110, and112is connected to the first node of a successive resistance switching circuit via respective connecting lines B, C, D, and E, and the switching output of the resistance switching circuit114is connected to the ground line via connecting line F.

Alternatively, the resistors of each of the resistance switching circuits106,108,110,112, and114may be connected to the ground line and the switching output of the resistance switching circuit114may be connected to the signal line.

Preferably, the resistors of the resistance switching circuits106,108,110,112, and114are determined such that the resistance-load values of successive resistance switching circuits increase by an order of ten, and each resistance switching circuit106,108,110,112, and114switches between ten resistance-load values (including zero) in equal increments. For example, the resistors of the resistance switching circuits:106are determined such that the user is enabled to increase the resistance-load value from 0Ω to 9Ω in 1Ω increments;108are determined such that the user is enabled to increase the resistance-load value from 0Ω to 90Ω in 10Ω increments;110are determined such that the user is enabled to increase the resistance-load value from 0Ω to 900Ω in 100Ω increments;112are determined such that the user is enabled to increase the resistance-load value from 0Ω to 9 k Ω in 1 k Ω increments; and114are determined such that the user is enabled to increase the resistance-load value from 0Ω to 90 k Ω in 10 k Ω increments, consequently, providing 99,999 switching options between 0Ω and 99,999Ω in 1Ω increments, as illustrated inFIG.9.

The matching system100enables accurate matching of the impedance of a phono cartridge and its transmission line connected to an amplifying device by enabling precise adjustment of the resistance-loading of a phono cartridge12connected to an amplifying device20during normal record play. Furthermore, by providing 99,999 switching options the matching system100enables precise adjustment of the resistance loading of a phono cartridge12connected to an amplifying device20during normal record play for a large variety of commercially available phono cartridges of different types such as, for example, moving magnet cartridges, moving iron cartridges, and moving coil cartridges.

As is evident to those skilled in the art, the matching system100is not limited thereto, but may be implemented using a different number of switches, a different number of selections per switch, different resistance-load values per switch, and different increments, depending on design preferences. For example, to ensure resistance-load matching compatibility with not only all presently commercially available moving-coil cartridges, moving-magnet cartridges, and moving-iron phono cartridges, but also some of the unique load-matching requirements for crystal cartridges, ceramic (piezoelectric effect) cartridges, and high-precision strain gauge cartridges, increasing the number of resistance switching circuits to, for example, six, increases the number of user selectable resistance-load values from 99,999 to 999,999 in a range from 0Ω to 999,999Ω in 1Ω increments.

Preferably, each of the multi position selector switches104S,106S,108S,110S,112S, and114S is provided as a rotary switch having a respective control knob104K,106K,108K,110K,112K, and114K such that control knob position is indicative of a respective capacitance or resistance-load value, enabling the user to directly read the respective values by the multi-position selector switch control-knob positions, as illustrated inFIG.9. This is in contrast to presently commercially available products that use Dual In-line Package (DIP) switches instead of rotary switches, which often require a truth table to decode the toggled values, in order to calculate the selected values. The matching system100is implemented, for example, on a Printed Circuit Board (PCB)101, with the multi position selector switches104S,106S,108S,110S,112S, and114S being disposed thereon such that their locations correspond to respective locations of their respective knobs104K,106K,108K,110K,112K, and114K on the user interface120, as illustrated inFIG.9.

Preferably, to ensure reliable and predictable operation, the resistance switching circuits106,108,110,112, and114are implemented using commercially available resistors that have low thermal noise, low current noise, and a low temperature coefficient of, for example, 25 ppm or less. Further preferably, to reduce thermal drift, and to improve accuracy, larger resistance values are implemented by using two smaller resistance value resistors connected in series, as illustrated inFIGS.7and8for the resistance switching circuits112and114.

The matching system100enables user-selectable adjustments that are operationally, and sonically, unobtrusive, i.e. without circuit interruptions due to open circuit voltage level shifts, thus avoiding thumps, or other disruptive noises that would otherwise occur if the input of amplifying circuitry were to be disconnected, even momentarily. This is accomplished by configuring all of the connected multi-position selector resistance switches in series, including all of the individual resistors. The use of a series connected configuration provides several advantages:1) readily available non-shorting rotary switches can be used, which ensure consistent manufacturability;2) calculation of the user-selectable adjustments, is the sum of the individual values; and,3) no noise disruptions caused by open circuit voltage shifts.

The matching system100enables user to optimize resistance-load matching for most phono cartridges, without adding any hum and noise, or audio distortion products during normal record play, regardless of the positions of the multi position selector switches, or how often these switches are adjusted during normal record play. The optimized resistance-load matching provides improved dynamic resolution, lower high-frequency peaking or ringing, and an improved low-frequency extension.

Using the matching system100the user is enabled to achieve the phono cartridge transmission line impedance matching in a number of easy steps:1) using the capacitance switching circuit104and the resistance switching circuits106,108,110,112, and114, the capacitance value and the resistance value are set to respective values recommended by a manufacturer of the phono cartridge;2) using the phono cartridge, playing a variety of records and while listening to the record playback take note of any dynamic compression, or anomalous resonances, such as high-frequency ringing, or a truncated or bloated low-frequency response; and,3) using the plurality of resistance switching circuits, adjusting the resistance-load value while listening to the record playback until the phono cartridge transmission line impedance is matched.

The present invention has been described herein with regard to preferred embodiments. However, it will be obvious to persons skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as described herein.