JPH08186900A - Car audio device with high signal output - Google Patents

Abstract

PURPOSE: To realize a car audio equipment with a high signal output at a low cost with the enhanced S/N by using a coupling circuit including a unity gain buffer amplifier to connect four outputs of a deck to an input of a succeeding stage. CONSTITUTION: Four unity gain amplifiers 20-23 are included in four output jacks of a deck before going to a succeeding stage 15, the two amplifiers 20, 22 are noninverting amplifiers and the remaining two amplifiers 21, 23 are inverting amplifiers. The two input jacks 25, 26 are connected as shown in the figure. Thus, the four separate voice channels are connected to left right channels as shown in the figure and a signal level is effectively amplified at output jacks 25, 26. Both of two right channel(RC) speakers 11, 12 are in series with RF, RR deck outputs and both of two left channel(LC) speakers 13, 14 are in series with LF, LR deck outputs.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a car audio device, and more particularly to a signal-to-noise (S / N) of a voice signal output
It relates to an audio circuit for increasing the ratio.

[0002]

BACKGROUND OF THE INVENTION The successful installation of car audio components in a vehicle can be difficult because the vehicle chassis is used as a ground return path for virtually all electrical accessories of the vehicle. Automotive alternators and electrical accessories provide significant changes to the power and control conductors of the accessories and the magnetic fields surrounding the vehicle chassis. When a signal is sent from one component to another, the proximity of the signal path changes the electromagnetic field, which can introduce noise into the device. Also, noise may enter the component via the power supply or internal signal paths. One way to handle a signal in a hostile noisy environment is to increase the level of the signal so that the noise is relatively small, that is, increase the signal level to increase the signal-to-noise ratio. Is.

To be effective, the increase in signal level must occur at the source. Increasing the signal level after the source will also increase the noise floor. In car audio, the source is commonly referred to as the deck or headpiece. The deck typically has four signal outputs to feed a four-speaker stereo system in the vehicle. The name given to this output represents the position of the speaker in the vehicle. That is, the left channel (LC)
Left front (LF) and left rear (LR), right channel (R
C) is front right (RF) and rear right (RR). The maximum signal level output of most decks is about 2.
0 volt rms (root mean square) to about 5.6 volts.
This is because virtually all modern cars are operating at a nominal 12.0 Volt DC, so virtually all modern car audio deck circuits have a nominal 12.0 Volt DC.
This is because it works in. Once this 12.0 volt level has been adjusted and connected to the deck's audio circuitry, the maximum achievable signal level is only about 2.0 volts. This is because the voltage inside the semiconductor device of the deck drops sharply. Therefore, the audio circuit in the deck is 1
Operating at 2.0 volts DC, the signal level is approximately 2.0 volts rms.

One common technique for increasing the signal output level is to convert the nominal 12.0 volt DC of the vehicle to a higher level, such as 20 or 30 volts, with the preamp level output stage increasing the signal level. Is to be able to accommodate. However, using the necessary power converter to increase 12.0 volts makes the deck expensive.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a car audio device having a high signal output.

Another object of the present invention is to provide a low cost car stereo audio system having an improved S / N ratio.

Yet another object of the present invention is to use a deck having four signal outputs to feed four speakers in a vehicle, and to increase the signal output without incidentally increasing the noise level. To provide an audio device.

The present invention is based on several concepts. First, it was recognized that it was necessary to maintain the nominal 12.0 volt supply of the vehicle to avoid undue costs. Second, it has been found that simply adding an amplifier to the system can prevent an increase in S / N ratio as it has the same effect on both signal and noise. Thirdly, it was recognized that in order to obtain any increase in S / N ratio, other desirable properties of the car audio device such as frequency response and distortion should not be sacrificed.

[0009]

According to one aspect of the invention, in a car audio system using a deck having four signal outputs for supplying four speakers, the four outputs of the deck are: A coupling circuit is used to connect to the input of the stage, which may be a conventional equalizer, an electronic crossover, or an amplifier, the output of which is then connected to four speakers. To do. The coupling circuit has only two outputs, one for left channel (LC) and the other for right channel (RC), RF and RR speakers are connected to RC output, LF and LR speakers. Is L
Connect to C output. Therefore, the LF and LR channels are connected to one LC, and the RF and RR channels are connected to one RC. As a result, the signal level was increased by 6 dB and the accompanying noise level was not increased by 6 dB.

According to another feature of the invention, the coupling circuit of the invention includes a unity gain buffer amplifier.
As a result, signal loss can be reliably prevented without increasing the noise level.

Applying the coupling circuit of the present invention to a car audio device using a nominal 12.0 volt power supply converts the signal output level of a typical 1.8 volt rms deck to a 3.6 volt rms deck. I understand. In addition, such an improved device provides the advantages of lower inductive noise, lower system noise, and less system hiss, as well as a frequency response of ± 0.05 dB over 20 Hz to 20 KHz and distortion over the range. 0.01% and S / N ratio 120d
It can be maintained above B.

The coupling circuit of the present invention provides maximum benefit when used with conventional 4-channel decks, but can also be used with 2-channel decks. However, the noise entering the circuit is correlated, thus increasing the noise floor.

The constitutions and embodiments of the present invention are listed below.

1. A circuit for coupling an audio deck to a speaker system, the audio deck being at least one coupled to provide first and second RC and third and fourth LC outputs. With two RC and LC outputs, the circuit is (a)
Including first non-inverting amplification means, (b) second inverting amplification means, (c) third non-inverting amplification means, (d) fourth inverting amplification means, and (e) the amplification The means each have an input and an output, and the circuit further comprises (f) connecting the input of the first amplifying means to one of the first and second RC deck outputs, the input of the second amplifying means being the first. And (g) connecting the input of the third amplifying means to one of the first and second LC outputs, and connecting the input of the fourth amplifying means to the first. And means for connecting to the other of the second LC outputs, (h) said first and second amplification means outputs cooperating to provide an audio signal to at least one RC speaker, ( i) The outputs of the third and fourth amplifying means cooperate to provide an audio signal to at least one LC speaker. Characterized by a circuit for coupling an audio deck to the speaker system.

2. An RC output jack having a center conductor and a shield is further included, the center conductor being connected to one of the first and second amplifying means outputs, the shield being
2. The circuit according to 1 above, which is connected to the other of the outputs of the first and second amplifying means.

3. Further comprising an LC output jack having a center conductor and a shield, wherein the center conductor is connected to one of the third and fourth amplifying means outputs and the shield is
The circuit according to 1 above, which is connected to the other of the outputs of the third and fourth amplifying means.

4. 2. The circuit according to 1 above, wherein each of the amplification means includes a unity gain amplifier.

5. A circuit according to claim 4, wherein the amplification means each include a 1: 1 transformer.

6. 5. The circuit according to 4 above, wherein each of the amplification means includes an operational amplifier.

[7] FIG. An audio device comprising: (I) a circuit for coupling an audio deck to a speaker system, the audio deck comprising first and second RCs and third and fourth LCs. The circuit has at least one RC and LC output coupled to provide an output, the circuit comprising: (a) a first non-inverting amplification means, and (b) a second inverting amplification means, c)
A third non-inverting amplification means and (d) a fourth inverting amplification means, (e) said amplification means each having an input and an output, and said circuit further (f) a first amplification means. Means for connecting the input to the one of the first and second RC deck outputs and the input of the second amplifying means to the other of the first and second RC deck outputs, and (g) the third amplifying means. Means for connecting the input of the means to one of the first and second LC outputs and means for connecting the input of the fourth amplifying means to the other of the first and second LC outputs, to an audio deck in a speaker system A circuit for coupling, (II) (a) RF speaker, (b) RR speaker, (c) LF speaker, (d) LR speaker, and (III) the RF and RR speakers , Connected in series with the outputs of the first and second amplification means The LF and LR
An audio device, wherein a speaker is connected in series with the outputs of the second and third amplifying means.

8. An RC output jack having a center conductor and a shield is further included, the center conductor being connected to one of the first and second amplifying means outputs and the shield being connected to the other of the first and second amplifying means outputs. The device according to 7 above.

9. Further comprising an LC output jack having a center conductor and a shield, wherein the center conductor is connected to one of the third and fourth amplifying means outputs and the shield is
Apparatus according to claim 8 connected to the other of the outputs of the third and fourth amplifying means.

10. 11. The apparatus according to claim 10, wherein the amplification means each include a unity gain amplifier.

11. 11. The apparatus according to claim 10, wherein the amplification means each include a 1: 1 transformer.

12. 11. The apparatus according to 10 above, wherein the amplification means each include an operational amplifier.

13. Detects the absence of a differential load,
11. A device as described in 10 above, further comprising means in the device for providing differential inputs.

14. A circuit for coupling an audio deck to a speaker system, the audio deck having RC and LC outputs, the circuit comprising:
(E) a first non-inverting amplification means, (b) a second inverting amplification means, (c) a third non-inverting amplification means, and (d) a fourth inverting amplification means. ) The amplifying means each have an input and an output, the circuit further comprising: (f) connecting the input of the first amplifying means to the RC deck output and the input of the second amplifying means to the RC deck output. Means and (g) connecting the input of the third amplifying means to the LC deck output and connecting the input of the fourth amplifying means to the LC deck output,
(H) for providing an audio signal to at least one RC speaker, said first and second amplification means outputs cooperate, and (i) for providing an audio signal to at least one LC speaker. A circuit for coupling an audio deck to a speaker system, characterized in that the outputs of said third and fourth amplifying means cooperate.

15. An RC output jack having a center conductor and a shield is further included, the center conductor being connected to one of the first and second amplifying means outputs, and the shield being
15. The circuit according to 14 above, which is connected to the other of the outputs of the first and second amplifying means.

16. Further comprising an LC output jack having a center conductor and a shield, the center conductor being connected to one of the third and fourth amplifying means outputs and the shield being
15. The circuit described in 14 above, which is connected to the other of the outputs of the third and fourth amplifying means.

17. 15. The circuit according to the above 14, wherein each of the amplifying means includes a unity gain amplifier.

[0031]

The above and other objects, details and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments when read in conjunction with the accompanying drawings.

FIG. 1 schematically shows a conventional car audio device with four channel outputs from the deck 10 for supplying four speakers 11-14. Deck 10 includes a jack for the right front channel labeled RF, a jack for the right rear channel labeled RR, a jack for the left front channel labeled LF, and a left rear channel labeled LR. You have four jacks for. L and R refer to the conventional L and R channel outputs of a stereo device. The signal output from the RF jack and the RR jack are synchronized,
The signal output from the F jack and the LR jack are also synchronized. A cable connects each jack to a respective speaker via a conventional equalizer, electronic crossover, or amplifier 15. Therefore, RF jack to RF speaker 11, RR jack to RR speaker 12, L
F jack to LF speaker 13, LR jack to L
Connect to the R speaker 14. As is conventional, the deck power supply is a conventional automotive 12.0 volt power supply 16. In a typical transistorized deck, the signal output level at the jack is up to about 1.8 rms volts.

FIG. 2 schematically shows the basic circuit of the coupling circuit according to the present invention. Similar reference numerals are used in FIG. 2 and other numbers are used for elements similar to those used in FIG. The input jacks labeled RF, RR, LF, and LR are cabled to the correspondingly labeled output jacks on deck 10. However,
This circuit includes four unity gain amplifiers 20-23, two 20, 22 of which are non-inverting amplifiers and the other two 21, 2 before going to the next stage 15.
3 is an inverting amplifier. Two output jacks 25, 26
Connect as shown. In particular, the center conductor of the RF input jack is connected to the non-inverting amplifier 20, the output of which is connected to the center conductor of the RC output jack 25, while the center conductor of the RR input jack is routed through the inverting amplifier 21 to R.
It is connected to the shield of the C output jack 25. The LF and LR inputs are similarly connected to the LC output jack 26 via amplifiers 22 and 23. Thus, the one in front of the four separate audio channels is connected to the two left and right channels as shown and each output jack 25, 26
Effectively doubles the signal level at. The output jacks 25, 26 may be connected to the four speakers 11-14 via the following conventional steps, as shown. Actually both RC speakers 11, 12 are in series with the RF and RR deck outputs, and two LC speakers 1
Both 3, 14 are in series with the LF and LR deck outputs.

Unity gain amplifiers that provide the correct phase of the signal without increasing the noise level can be obtained in various ways. One method is to use R in FIG.
Shown only on the C side, transformers 30 and 31 are provided for the RF and RR channels, and transformer coils are wound to provide non-inverting coupling for the RF channel and inverting coupling for the RR channel. Connect the left channel in the same way. Also, in this and other embodiments,
It is understood that the amplifiers may be exchanged to make the RR channel amplifier non-inverting and the RF channel amplifier inverting to provide the desired signal addition effect when connected in series to the speaker. While transformer couplings are expensive, operational amplifiers (Op-Amps) offer similar functions much cheaper. Such an embodiment is shown in FIG.

The circuit shown in FIG. 4 has four independent Op-
Commercially available TL with Amp 40-43
A 084 conventional quad Op-Amp integrated circuit (IC) is used. It may be replaced with another Op-Amp IC. Connected to each Op-Amp is the same external component to obtain a unity gain amplifier. Non-inverting (+) input of Op-Amp for RF and LF channels or inverting (-) of RR or LR channels
An inverting or non-inverting function was achieved by coupling the input to either of the inputs. Values for exemplary components are shown in the figure. The added voltage (V +) is 1
It was 2 volts DC. When using Op-Amp of another manufacturer, the value of another component may be required. Op-Amp IC manufacturers typically
A sample circuit is provided to achieve unity gain in the IC.

The circuit shown in FIG. 4 doubles the signal output at the RC and LC jacks 25, 26 without degrading the frequency response or distortion and maintaining the S / N ratio above 120 dB. Provide all the benefits. The impedance of the circuit shown is approximately 100 ohms. By doubling the signal level output, the input sensitivity of the amplifier 15 in the next stage can be reduced.
This can enhance the program material output with less hiss.

When using the circuit shown in FIG. 4 with a two-channel deck, it is necessary to install a conventional y-adapter between the two deck outputs and the four circuit inputs of the coupling circuit of the present invention. is there.

The circuit of FIG. 4 may be connected between any two preamplifier level components.

It will be appreciated that in the embodiment shown above, the coupling circuit is not connected directly to the speaker, but is usually connected through a separate step involving a buffer which actually drives the speaker. Thus, it should be understood that the expression "connecting to a speaker" herein includes the conventional inverting audio stage such as an equalizer, electronic crossover, or amplifier.

In the embodiment described above, with four or two inputs, the coupling circuit has a conventional balanced output,
That is, it drives the input to the next stage. However, in some devices the input to the next stage is unbalanced, which means that a coupling circuit with a balanced input will drive the unbalanced output. FIG. 5 is a block diagram of a modified coupling circuit for compensating for this unbalanced condition.

FIG. 5 illustrates half the modification of the coupling circuit, that is, the circuit for the left or right channel. In this circuit, the right or left front signal is applied to the unity gain amplifier 60, and the right or left front signal is applied to the inverting unity gain amplifier 61. The output of amplifier 60 is applied to the non-inverting input of unity gain buffer amplifier 62 via input resistor 63 and to the inverting input of unity gain buffer amplifier 64 via input resistor 65. The output of the buffer amplifier 62 passes through the resistor 66 and the buffer amplifier 64.
Cross-connected to the non-inverting input of buffer amplifier 64, the output of buffer amplifier 64 is connected to the non-inverting input of buffer amplifier 62 via resistor 67.

Since the output of buffer amplifier 64 is inverted with respect to the input of buffer amplifier 62, and the output of buffer amplifier 62 is inverted with respect to the input of buffer amplifier 64, the non-inversion of these amplifiers. The two signals applied to each of the inputs cancel each other so that the output of each amplifier is substantially responsive only to the signal applied to each inverting input.

When the output lead of the amplifier is grounded as indicated by the diagonal connecting this output to ground,
There is no signal applied from this output line to the non-inverting output of buffer amplifier 62 and amplifier 60 to buffer amplifier 62
It will be appreciated that the signal applied to the non-inverting input of is no longer canceled by the output signal of buffer amplifier 64. Therefore, the output of buffer amplifier 62 increases substantially doubling its original amplitude, substantially the same as when the output of amplifier 64 is not grounded at the output of the circuit between terminals 70 and 71. Supply signals of the same amplitude. Obviously, the same effect can be obtained when the output of the buffer amplifier 62 is grounded.

Thus, the circuit of FIG. 5 provides an output signal of greater amplitude than that shown in FIGS. 2-4 when none of its output lines are grounded, and when one of the output lines is grounded. Also, the output level is substantially maintained.

While the presently preferred embodiments of the invention have been described, it should be understood that the invention may be embodied in other specific forms without departing from its basic features. Is. Therefore, this embodiment is
It should be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than the foregoing description.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a conventional car audio device using a 4-channel deck.

FIG. 2 is a schematic diagram of one form of a coupling circuit of the present invention.

FIG. 3 is a schematic view of a portion of another form of the coupling circuit of the present invention.

FIG. 4 is a schematic diagram of yet another form of the coupling circuit of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04S 7/00 Z (72) Inventor Richard El Clark 27215, Burlington, Westover, North Carolina, USAー Terrace, 2112

Claims (3)

[Claims] 1. A circuit for coupling an audio deck to a speaker system, the audio deck for providing first and second right channel and third and fourth left channel outputs. Having at least one right channel and left channel output coupled, said circuit comprising: (a) a first non-inverting amplifying means, (b) a second inverting amplifying means, and (c) a third. A non-inverting amplification means of (d) and a fourth inverting amplification means of
(E) said amplifying means each having an input and an output, said circuit further (f) connecting the input of the first amplifying means to one of the first and second right channel deck outputs to provide a second amplifying means Means for connecting the input of the means to the other of the first and second right channel deck outputs, and (g) connecting the input of the third amplifying means to one of the first and second left channel outputs, Means for connecting the input of the amplifying means to the other of the first and second left channel outputs, and (h) the first and second amplifying means outputs to at least one right channel speaker. And (i) the outputs of the third and fourth amplifying means cooperate to provide an audio signal to at least one left channel speaker. To the speaker system Circuit for. 2. An audio device, the device comprising: (I) a circuit for coupling an audio deck to a speaker system, the audio deck comprising a first and a second right channel and a second right channel. A circuit having at least one right channel and left channel output coupled to provide a third and fourth left channel output, the circuit comprising: (a) first non-inverting amplification means;
(B) second inverting amplification means, (c) third non-inverting amplification means, (d) fourth inverting amplification means, and (e) said amplification means has an input and an output, respectively. The circuit further comprises (f) connecting the input of the first amplifying means to one of the first and second right channel deck outputs and the input of the second amplifying means to the first and second right channel deck outputs. And (g) connecting the input of the third amplifying means to one of the outputs of the first and second left channels, and connecting the input of the fourth amplifying means to the first and second left channels. A circuit for coupling the audio deck to the speaker system, including means for connecting to the other of the outputs, (II) (a) right front speaker, (b) right rear speaker, (c) left front speaker, (D) including a left rear speaker, (III) the right front And the right rear speaker are connected in series with the outputs of the first and second amplifying means, and the left front and rear left speakers are connected in series with the outputs of the second and third amplifying means. . 3. A circuit for coupling an audio deck to a speaker system, said audio deck having right channel and left channel outputs, said circuit comprising: (a) first non-inverting amplifier means. , (B) second inverting amplification means, (c) third non-inverting amplification means,
(D) fourth inverting amplification means, (e) said amplification means each having an input and an output, said circuit further comprising: (f)
Means for connecting the input of the first amplifying means to the output of the right channel deck and connecting the input of the second amplifying means to the output of the right channel deck; and (g) input of the third amplifying means to the output of the left channel deck. Means for connecting and connecting the input of the fourth amplifying means to the left channel deck output, (h)
The first and second amplification means outputs cooperate to provide an audio signal to at least one right channel speaker, and (i) provide an audio signal to at least one left channel speaker, A circuit for coupling an audio deck to a speaker system, characterized in that the outputs of said third and fourth amplifying means cooperate.