AU712506B1 - A printed circuit board for an amplifier, an amplifier and method for distributing a signal and power in an amplifier - Google Patents

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Name of Applicant: Actual Inventor Address for service is: Mass Enterprises Pty Ltd Hemrikus Yohammus Framsiskus Gabriel Groothuis WRAY ASSOCIATES 239 Adelaide Terrace Perth, WA 6000 Attorney code: WR Invention Title: "A Printed Circuit Board For An Amplifier, An Amplifier And A Method For Distributing A Signal And Power In An Amplifier" The following statement is a full description of this invention, including the best method of performing it known to me:-

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TITLE

"A Printed Circuit Board For An Amplifier, An Amplifier And A Method For Distributing A Signal And Power In An Amplifier" FIELD OF THE INVENTION The present invention relates to a printed circuit board for an amplifier, a amplifier and to a method for distributing a signal and power in an amplifier. The invention was developed to address problems in relation to audio amplifiers.

BACKGROUND ART Intermodulation distortion, crosstalk and distortion induced by AC power supplies are known problems in amplifier technology.

Intermodulation distortion and crosstalk are typically addressed by physically separating the signals for each channel.

Distortion induced from the AC power supply has been addressed to date by the physical layout of the amplifier. For instance, the use of a "star" topology in providing the zero volt or ground wires is well established. Whilst the physical wiring of the amplifier's power supply using this technique has addressed this problem to some extent, the layout of printed circuit boards used in amplifiers has been dominated by considerations of component positioning and track topology.

In addition, existing amplifier designs are not readily expandable. In the case of home theatre systems, the cost of amplifiers for the five to eight channels is a significant expense due to the need to purchase several discreet amplifiers.

-3- DISCLOSURE OF THE INVENTION In accordance with one aspect of this invention, there is provided a printed circuit board (PCB) for an amplifier, comprising: a first section arranged to receive components of the amplifier; a second section comprising a plurality of electrical pathways extending across the PCB, the electrical pathways in use carrying power for the amplifier, a zero voltage and a first signal; wherein the electrical pathway carrying the first signal is separated from the electrical pathways carrying power for the amplifier by at least one electrical pathway carrying zero voltage being interposed therebetween.

Preferably, the electrical pathways are substantially parallel.

Preferably, the electrical pathways are linear.

Preferably, the PCB comprises a multi-layer PCB, the electrical pathway carrying zero voltage comprises a ground plane and the electrical pathways carrying power for the amplifier are provided on an opposite side of the ground plane to the electrical pathway carrying the first signal.

Preferably, an electrical pathway carrying the zero voltage is provided on either side of the electrical pathway carrying the first signal.

Preferably, the second section includes first connection means for connecting the electrical pathways to another PCB.

Preferably, the second portion includes second connection means and the first section includes third connection means; the second and third connection means arranged to connect to a processor board; the second connection means communicating the first signal, power and the zero voltage to the processing board which is arranged to process the first signal; the third connection means *1 -4arranged to communicate a processed signal from the processing board to the amplifier.

Preferably, the amplifier comprises a plurality of amplifier modules; the first section of the PCB arranged to receive components for a plurality of amplifier modules, each amplifier module having a second connection means provided in the second section associated therewith and a third connection means provided in the first section associated therewith.

Preferably, the second section further comprises an electrical pathway carrying a second signal, wherein electrical pathways carrying zero voltage are interposed between the electrical pathway carrying the first signal and the electrical pathway carrying the second signal and between the electrical pathways carrying the first and second signals and the electrical pathways carrying power for the amplifier.

In accordance with a second aspect of this invention, there is provided an amplifier, comprising: a power supply, a PCB according to the first aspect of the invention; and an input circuit; the power supply and the input circuit each including first connection means, the power supply and the input circuit being connected to the PCB via the first connection means.

Preferably, the amplifier comprises a plurality of amplifier modules provided on a plurality of printed circuit boards, the power supply, input circuit and printed circuit boards being connected via the first connection means.

Preferably, the amplifier comprises a plurality of ,amplifier modules, the first section of the PCB being arranged to receive components for the amplifier modules, each amplifier module having a second connection means provided in the second section associated therewith and a third connection means provided in the first section associated therewith.

Preferably, each amplifier module has associated therewith a processor board received on the associated PCB.

Preferably, the processor board comprises a filter.

Preferably, the processor board also performs digital to analog conversion on the first signal.

Preferably, each processor board comprises a filter such that each amplifier module amplifies a portion of the first signal.

Preferably, the portions of the first signal are non-overlapping.

Preferably, the output of each amplifier module is directly connected to a sound transducer.

In accordance with a third aspect of this invention, there is provided a method for distributing a first signal and power in an amplifier, comprising: providing a plurality of electrical pathways extending across a PCB, the electrical pathways in use carrying power for the amplifier, a zero voltage and a first signal; arranging the electrical pathways such that the electrical pathway carrying zero voltage is interposed between the electrical pathway carrying the first signal and the electrical pathways carrying power to the amplifier.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will now be described with reference to one embodiment thereof and the accompanying drawings, in which: Figures la and lb show a printed circuit board according to the embodiment of the invention; Figures 2a and 2b show a second printed circuit board for receiving an input circuit; Figures 3a and 3b show a processor board; and Figure 4 shows the connection of the printed circuit boards shown in Figures la to 3b to form an amplifier.

BEST MODE(S) FOR CARRYING OUT THE INVENTION The embodiment is directed towards a printed circuit board for an amplifier and an amplifier using the printed circuit board. The amplifier of the embodiment is directed towards use in a powered loud speaker. In the embodiment, the loud speaker has three sound drivers or transducers.

Figure 1 shows a printed circuit board 10 for an amplifier 12, comprising a first section 14 and a second section 16.

The first section 14 includes tracks 18 arranged to receive components to form an amplifier module 15. The embodiment utilises the monolithic amplifier LM3886T to reduce the space requirement for the first section 14, however, other monolithic amplifiers or discreet components, including SMT components, may be utilised as desired.

The amplifier 12 comprises three amplifier modules 15, one for each of the sound transducers in the loud speaker.

The second section 16 comprises seven tracks 20, 22, 24, 26, 28, 30 and 32, respectively, extending in a substantially parallel manner across the printed circuit board 10. The ends 34 of each track 20-32 are arranged to receive a first connector (not shown).

-7- The table below describes the voltage or signal each track 20-32 carries in use.

Track Number Voltage/Signal Carried First positive voltage 22 First negative voltage 24 Zero volts 26 Signal 28 Zero Volts Second Positive Voltage 32 Second Negative Voltage The first positive and negative voltages carried by the tracks 20 and 22 provide power for the amplifier module 15 in the first section 14 along with the zero voltage carried by the track 24, and accordingly the tracks 20, 22 and 24 are thicker to accommodate the anticipated current flow.

The track 26 carrying the signal is provided between the tracks 24 and 28 carrying zero voltage, thereby reducing the likelihood of distortion being induced in the signal carried in the track 26 from the voltages carried in the tracks 20, 22, and 32. The tracks 24 and 28 are connected at one end thereof.

The second voltages carried by the tracks 30 and 32 are relatively low and, along with the zero voltage carried by the track 28, power a processor board 52 to be described hereinafter. Accordingly, the tracks 28, 30 and 32 need not be as thick as the tracks 20, 22 and 24 because of the reduced power running through them.

-8- The tracks 24, 26, 28, 30 and 32 are arranged to receive a second connecter (not shown) at 36. The second connector is used to pass the zero voltage, the signal and the second voltages to the processor board 52, to be described hereinafter.

The first section 14 is arranged to receive a third connector (not shown) at 38.

The third connector is used to communicate the zero voltage and the signal once processed by the processor board 52 to the amplifier module 15 in the first section 14 as described hereinbelow.

Figure 2 shows a second printed circuit board 40 including a first section 42 arranged to receive components for an amplifier module and arranged to receive a third connector at 44. The second printed circuit board further includes a second section 46 arranged to receive components forming an input circuit that is capable of receiving balanced line as well as RCA inputs. The input circuit shown in Figure 2 acts as a unity gain buffer.

The second printed circuit board 40 is arranged to receive a first connector at 48 and a second connector at 50. The output from the input circuit at 46 is connected to the portions of 48 and 50 which carry the signal.

Figure 3 shows a third printed circuit board 52 in the form of a processor board.

The processor board 52 is arranged to receive components for a filter circuit. In the embodiment, the filter circuit is an active bandpass circuit utilising the TL074 integrated circuit.

In addition, the processor board 52 is arranged to receive a second connector at 54 and a third connector at 56 which engage with the corresponding connectors 36 and 38 on the first printed circuit board The processor board 52 is also arranged to receive a fourth connector at 58.

The fourth connector is used to communicate a processed signal at 60 to a -9potentiometer or other attenuation device, the output of which is received via the fourth connector at 62. It is to be noted that 60 and 62 are spaced apart in the fourth connector and that the zero voltage is provided to either side of 60 and 62 at 64. The attenuated signal at 62 is communicated to the third connector at 56 for subsequent communication to the amplifier module 15 on the PCB 10 or the PCB Further, the processor board 52 is arranged to receive a fifth connector (not shown) at 66 for connection to an audio transducer, such as a speaker driver.

The fifth connector on the processor board 52 is connected to the third connector 56 thereon to receive signals from the amplifier module 15 for the driver connected to the fifth connector.

Advantageously, the processor board is capable of performing a range of functions. For instance, by changing the component values on the processor board, the filter on the processor board connect as a high pass, a low pass or a band pass filter, whereupon the amplifier module 15 of the printed circuit board to which the processor board 52 is connected would amplify the filtered signal only. Because the filtering of the signal into frequency bands for the respective speaker drivers occurs prior to amplification, a crossover network is not required between the fifth connector and the speaker driver. As a result, the amplifier module 15 directly drives the speaker driver, which is believed to provide better control over the excursion of the loud speaker driver. Further, a Zobel impedance compensating network is similarly not necessary.

Direct connection of the speaker driver to the fifth connector is also believed to reduce distortion from the speaker driver due to cabinet resonance.

In the case of digital audio, the processor board 52 may also include a digital to analog converter. Alternatively, a digital to analog converter can be included in the second printer circuit board 4 4 Figure 4 shows the printed circuit board 10, 40 and 52 connected to form the amplifier 12. The amplifier 12 comprises one of the second printed circuit boards 40 and three printed circuit boards 10. The printed circuit boards 40 and are connected using cables extending between the first connectors on the printed circuit boards 10 and 40 in a chain-like manner.

The printed circuit board 40 forms one end of the chain whilst the power supply (not shown) forms the other end of the chain.

Each of the printed circuit boards 40 and 10 has a processor board 52 received thereon via the second and third connectors. Each of the processor boards includes a filter circuit arranged to communicate a filtered signal to the amplifier on the underlying printed circuit board 40 or 10. Each of the filters on the processor boards 52 is arranged to filter a different portion of the signal to the corresponding amplifier, such that the outputs of the amplifier modules 15 on the printed circuit boards 40 and 10 each correspond with a different frequency range. The outputs from each of the amplifiers is directly connected to a sound transducer thereby providing greater control over the motion of the transducer.

A crossover circuit is not required because of the filtering by the processor boards.

Although three of the printed circuit boards 10 are shown in Figure 4, it should be appreciated that this number be readily increased or decreased by simply inserting or removing a printed circuit board 10 into the chain using the first connectors.

If cable is used to connect the printed circuit boards 40 and 10 it is preferred that the cable be flat or ribbon cable, such that the wires in the cable carrying the signal will be surrounded on either side by wires carrying the zero voltage signal.

It should appreciated that this invention is not limited to the particular embodiment described above. In particular, the specific form of the amplifier -11 circuits, the input circuit and the filter circuit can be varied without departing from the spirit of the invention.

For example, in other embodiments multiple amplifier modules may be provided on a single printed circuit board. In such an embodiment, the tracks 20 32 will extend across the printed circuit board with multiple amplifier modules provided thereon. Each amplifier module would have a processor board associated therewith, and consequently each amplifier module would effectively operate independently of the others, notwithstanding their presence on the same printed circuit board.

Further, it should be appreciated that some or all of the tracks can take the form of planes in a multi-layer printed circuit board.

Additionally, surface mount technology or monolithic amplifier modules may be used.

Still further, in other embodiments the processor board can perform other forms of processing in addition to filtering. In particular, where the invention is applied to a powered loud speaker where the outputs of each amplifier module directly drive a sound transducer, the processor board can be arranged to introduce a delay proportional to the logorythym of the frequency. It is believed that this compensates for the different transmission speed of various sound frequencies through the air to provide better sound imaging and a superior sound stage.

Throughout the specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (17)

1. A printed circuit board (PCB) for an amplifier, comprising: a first section arranged to receive components of the amplifier; a second section comprising a plurality of electrical pathways extending across the PCB, the electrical pathways in use carrying power for the amplifier, a zero voltage and a first signal; wherein the electrical pathway carrying the first signal is separated from the electrical pathways carrying power for the amplifier by at least one electrical pathway carrying zero voltage being interposed therebetween.

2. A PCB as claimed in claim 1, wherein the electrical pathways are substantially parallel.

3. A PCB as claimed in claim 1 or 2, wherein the electrical pathways are linear.

4. A PCB as claimed in any one of the preceding claims, wherein the PCB comprises a multi-layer PCB, the electrical pathway carrying zero voltage comprises a ground plane and the electrical pathways carrying power for the amplifier are provided on an opposite side of the ground plane to the electrical pathway carrying the first signal. A PCB as claimed in any one of the preceding claims, wherein an electrical pathway carrying the zero voltage is provided on either side of the electrical pathway carrying the first signal.

6. A PCB as claimed in any one of the preceding claims, wherein the second section includes first connection means for connecting the electrical pathways to another PCB.

7. A PCB as claimed in any one of the preceding claims, wherein the second portion includes second connection means and the first section includes third connection means; the second and third connection means arranged to -13- connect to a processor board; the second connection means communicating the first signal, power and the zero voltage to the processing board which is arranged to process the signal; the third connection means arranged to communicate a processed signal from the processing board to the amplifier.

8. A PCB as claimed in any one of the preceding claims, wherein the amplifier comprises a plurality of amplifier modules; the first section of the PCB arranged to receive components for a plurality of amplifier modules, each amplifier module having a second connection means provided in the second section associated therewith and a third connection means provided in the first section associated therewith.

9. A PCB as claimed in any one of the preceding claims, wherein the second section further comprises an electrical pathway carrying a second signal, wherein electrical pathways carrying zero voltage are interposed between the electrical pathway carrying the first signal and the electrical pathway carrying the second signal and between the electrical pathways carrying the first and second signals and the electrical pathways carrying power for the amplifier. PCB substantially as described herein with reference to the accompanying drawings.

11.An amplifier, comprising: a power supply, a PCB as defined in any one of claims 1 to 10; and an input circuit; the power supply and the input circuit each including first connection means, the power supply and the input circuit being connected to the PCB via the first connection means.

12.An amplifier as claimed in claim 11, the amplifier comprising a plurality of amplifier modules provided on a plurality of printed circuit boards, the power supply, input circuit and printed circuit boards being connected via the first connection means. -14-

13.An amplifier as claimed in claim 11, the amplifier comprising a plurality of amplifier modules, the first section of the PCB being arranged to receive components for the amplifier modules, each amplifier module having a second connection means provided in the second section associated therewith and a third connection means provided in the first section associated therewith.

14.An amplifier as claimed in claim 12 or 13, wherein each amplifier module has associated therewith a processor board received on the associated PCB. amplifier as claimed in claim 14, wherein the processor board comprises a filter.

16.An amplifier as claimed in claim 15, wherein the processor board also performs digital to analog conversion on the first signal.

17.An amplifier as claimed in claim 14, wherein each processor board comprises a filter such that each amplifier module amplifies a portion of the first signal.

18.An amplifier as claimed in claim 17, wherein the portions of the first signal are non-overlapping.

19.An amplifier as claimed in any one of claims 11 to 18, wherein the output of each amplifier module is directly connected to a sound transducer. amplifier substantially as described herein with reference to the accompanying drawings.

21. A method for distributing a first signal and power in an amplifier, comprising: providing a plurality of electrical pathways extending across a PCB, the electrical pathways in use carrying power for the amplifier, a zero voltage and a first signal; arranging the electrical pathways such that the electrical pathway carrying zero voltage is interposed between the electrical pathway carrying the first signal and the electrical pathways carrying power to the amplifier. Dated this TWENTY SIXTH day of NOVEMBER 1998. Mass Enterprises Pty Ltd Applicant Wray Associates Perth, Western Australia Patent Attorneys for the Applicant