EP0746122B1 - Monolithically integratable mixing device for an audio control desk - Google Patents

Description

The invention relates to a monolithically integrable mixer device for a Mixing console, which acts as a subcircuit for the control of various sound signal sources in an audio signal processing circuit, e.g. in a PC sound card (= Sound processing board for a personal computer) or in one Car radio receiver, is provided at gradually from an audio signal source another 'to be switched. An application example of this is a soft one Crossfading from a music playback to a current traffic announcement, whereby both signals come from different sources. During the Traffic announcement dampens the channel with the music signal and instead the Traffic announcement shown. As is well known, an abrupt switchover from Signal sources unpleasant crackling noises and possibly also strong ones Volume jumps. Another, increasingly important use for such Mixing devices is the most unnoticeable fade from a disturbed one or weaker reception channel to a better one. This operating mode is also known as diversity reception. Such cross-fades require a pure one electronic mixer device with an intelligent control, e.g. by means of of a processor connected to the actual system via control lines or a bus system Mixer device is connected, can be realized.

The closest prior art is the US Pat. No. 4,357,492, the one automatic mixer device for microphones has the object. For each of the microphones a separate sound channel is made available, which has a fixed one Preamplifier and a controllable amplifier with the associated control devices. The Outputs of all sound channels are combined by means of a summing amplifier, the one adjustable amplifier for common volume control is connected downstream. to Gain control are operational amplifier circuits in connection with LED-controlled Photo resistors used as control elements.

US 5,376,896 is concerned with the reduction of noise and distortion from voltage controlled amplifiers (= VCA) for audio applications. Here too everyone will Sound channel assigned to a VCA and their outputs using a summing amplifier coupled together and amplified together by 6 db.

US 4,885,792 shows another audio mixer device with a single active one Gain element in each audio channel. And a main amplifier for the overall gain all channels. The gain setting is done manually or electromechanically via a Change of resistors, which are designed as sliders and the control voltage for Deliver VCAs.

US 5,309,517 finally shows yet another arrangement of an audio multiplexer in the also a plurality of controllable preamplifiers via a summing bus to different Summing amplifier inputs are switchable. The gain setting in each Sound channels take place via preamplifiers with sliders, which are followed by VCAs. The Summing amplifiers have no setting options.

The circuitry for mixer devices can be very large, in particular if it is professional studio equipment. For Consumption areas, e.g. in the application described for car radio receivers or the application in the PC or in other applications, the requirements are indeed less, but the circuitry for an intelligent mixer device nevertheless so large that a compact, monolithically integrable solution must be found, the Circuit effort, which is ultimately in the required semiconductor crystal area expresses, should remain as low as possible for cost reasons.

A mixer device with active components contains for everyone on the input side Channel a preamplifier with adjustable gain and one on the output side Summing device to the differently amplified signals into a single Summarize signal at one output, cf. Fig. 1. For the preamplifier circuits with operational amplifiers prove to be useful because of them about changing one of a coupling and a feedback resistor formed resistance ratio the respective gain is easily adjustable. This in the case of an analog circuit, this is done using a slider or a potentiometer and in the case of a digital version via a resistor network, which is connected via the Control of taps or by electronically switching, switching on or off Partial resistors - which can also include a parallel or series connection - one The resistance ratio can be changed digitally in a simple manner. The differently amplified signals of the individual channels are then by means of Summing device summarized. If you want one for the summing device Use operational amplifier arrangement, then the known one is available for this summing amplifier circuit that has an input resistance for each channel and has a common feedback resistor for all channels. The Relationship between feedback resistance and input resistance also determines here the respective channel gain component. The advantages of this combination are among other things in the defined channel gain and the low impedance Signal output.

In the arrangement with preamplifier and summing amplifier described above, however disadvantageous that in the case of damping the useful signal in the preamplifier desired value is reduced, the intrinsic or external noise that is always present however, passed on unchanged by the amplification of the summing amplifier or even increased, so that the signal / noise ratio on Output deteriorated unnecessarily.

It is therefore an object of the invention for a monolithically integrable Mixer device to specify a circuit arrangement in which the own or Noise-dependent signal / noise ratio in the entire gain and Damping area remains as high as possible.

ein in der Verstärkung (= Vorverstärkung) einstellbarer Vorverstärker für jeden Tonkanal;

ein Summierverstärker, der an die Ausgänge der Vorverstärker gekoppelt ist und dessen Verstärkung (= Summierverstärkung) je Tonkanal unterschiedlich einstellbar ist; und

eine Steuereinrichtung, die mit dem Vorverstärker und dem Summierverstärker gekoppelt ist und der Steuerung der den jeweiligen Tonkanal betreffenden Gesamtverstärkung (= Kanalverstärkung) dient, die zwischen dem Vor- und dem Summierverstärker nach einem vorgegebenen, von der einzustellenden Kanalverstärkung abhängigen Verhältnis aufgeteilt ist, das sich im Dämpfungsbereich bei zunehmender Signaldämpfung dahingehend ändert, daß die Summierverstärkung im Verhältnis stärker reduziert ist als die Vorverstärkung.

This object is achieved according to claim 1 for a monolithically integrable mixer device for a mixer by the following features:

a preamplifier with adjustable gain (= pre-amplification) for each audio channel;

a summing amplifier which is coupled to the outputs of the preamplifiers and whose amplification (= summing amplification) can be set differently for each audio channel; and

a control device which is coupled to the preamplifier and the summing amplifier and serves to control the overall amplification (= channel amplification) relating to the respective sound channel, which is divided between the preamplifier and the summing amplifier according to a predetermined ratio which is dependent on the channel amplification to be set and which changes in the attenuation range with increasing signal attenuation in such a way that the summation gain is relatively more reduced than the preamplification.

It is therefore a matter of realizing an intelligent gain setting, that runs as it were in the background and that does not work without electronic aids is feasible.

Fig. 1 zeigt schematisch eine bekannte Mischereinrichtung mit aktiven Bauelementen,

Fig. 2 zeigt ein Beispiel für ein Widerstandsnetzwerk mit einer Serienschaltung von Teilwiderständen und mit einer Vielzahl von Widerstandsabgriffen,

Fig. 3 zeigt ein ausführlicheres Schaltbild der Mischereinrichtung nach Fig. 1,

Fig. 4 zeigt ein Schaltbild einer Mischereinrichtung nach der Erfindung,

Fig. 5 zeigt in Tabellenform an einem Beispiel, wie die jeweilige Kanalverstärkung oder -dämpfung zwischen dem Vor- und Summierverstärker aufgeteilt ist.

The invention and advantageous embodiments are now explained in more detail with reference to the figures of the drawing:

1 schematically shows a known mixer device with active components,

2 shows an example of a resistor network with a series connection of partial resistors and with a plurality of resistor taps,

3 shows a more detailed circuit diagram of the mixer device according to FIG. 1,

4 shows a circuit diagram of a mixer device according to the invention,

5 shows in table form using an example how the respective channel gain or attenuation is divided between the preamplifier and summing amplifier.

1 shows a mixer device with active circuit parts for three as an example Channels shown with a first, second and third signal input e1, e2, e3 are connected. The active circuit parts consist of first operational amplifiers v1, the first operational amplifier arrangements OP1 with corresponding circuits form and a first, second and third preamplifier for the supplied signals Form M1, M2, M3. The outputs of the preamplifiers are by means of a second one Operational amplifier arrangement OP2 interconnected to the signals of all three Combine channels into a single signal that can be tapped at the output o. The second operational amplifier arrangement OP2 forms a summing amplifier S, which as an active element is an operational amplifier, the second Operational amplifier v2, contains. As active elements in both Operational amplifier arrangements OP1, OP2 also transconductance amplifiers and other active circuits with appropriate wiring can be used. In Fig. 1 the operational amplifier v2 is connected as a summing amplifier and points for everyone Channel an input resistance Rsv and one for all channels Feedback resistor Rsr on.

The amplification of the three preamplifiers M1, M2, M3 is done via one Input resistance Rmv and a feedback resistance Rmr set. The Input resistance Rmv lies between the respective channel input e1, e2, e3 and the inverting input of the first operational amplifier v1. On this Input is also the output signal of the feedback resistor Rmr Operational amplifier v1 fed back.

Other gain adjustment circuits are also known. The in Fig. 1st first and second operational amplifier arrangements OP1, OP2 shown However, this is advantageous in that the respective reinforcements directly through the Ratio of feedback resistance Rmr or Rsr and input resistance Rmv or Rsv can be determined. The gain is set in the first Operational amplifier arrangement OP1 by the input resistance and the Feedback resistance through a potentiometer or slider rs (see Fig. 3) are formed, the tap a1 at the inverting input of the first Operational amplifier v1 and its other two connection nodes k1, k2 are connected to the input e1 or the operational amplifier output. By a Changing the potentiometer or slider setting can cause the signal in the respective sound channel can be amplified or damped over a very wide range.

The analog setting is made with a potentiometer or slider rs in the Usually by hand or using a servomotor. Electronic adjustment is easier possible if only discrete gain values need to be set, whose Increment may, however, be narrow. Enough for the intended consumption area for example a step size of 1.5 dB. For this, the input resistance is Rmv and the feedback resistor Rmr of the preamplifier M as Resistor network rp (cf. FIG. 2) from a large number of partial resistors r formed, which can be switched on, off or on via electronic switches, where also a series connection or parallel connection of partial resistors r is possible.

A particularly simple arrangement for such a resistance network rp a resistance chain consisting of mostly different partial resistances r, where a Part or all of the connection nodes k of the partial resistors are provided with taps ai. By a switching device s shown schematically in Fig. 3, the one Corresponding sliding contact with a slider rs, one of the taps ai connected to the inverting input of the first operational amplifier v1 become. A single switch contact divides the tapped via the respective tap a1 Resistor network rp in two parts and forms a first and one with it coupled second resistor R1, R2.

For this resistance chain, the invention only requires a second grinding or switching contact s2, with which the total resistance value of the resistance chain is divided particularly easily into three resistors R1, R2, R3. The Realization of the tapped resistance network rp as a resistance chain is also very suitable for monolithic integration. This chain of resistance allows thus that the resistance ratio in the case of the two resistors R1, R2 and the three resistors R1, R2, R3 in a very simple way in a wide ratio can be changed. With a fine gradation, this is indicated by a large number of Partial resistances r bought, which thus form a relatively long chain. The number of On the other hand, partial resistances r can be reduced if the structure of the Resistor network rp can be changed by the switching device, this however requires a complex switching device. Of course there is also one Combination of both methods possible. Because all in the resistance chain three resistors R1, R2, R3 are coupled together, the change affects of a resistance directly to the value of the neighboring one, i.e. with the same Tap ai connected resistance and changes it. Through a parallel Shifting both taps a1, a2 can also change the resistance be carried out that only the two external resistances R1, R3 change and the mean resistance R2 remains constant. In the embodiment of the invention 4, the mutual coupling of the three resistors R1, R2, R3 cleverly used to effect a sliding reinforcement distribution.

3 shows the circuit arrangement of FIG. 1, in particular in the area the first operational amplifier arrangement OP1 shown in more detail. The Gain control in preamplifier M1 contains an adjustment resistor Slider rs its tap a1 via a sliding contact s on the inverting Input of the first operational amplifier v1 is connected. The entrance of the Slider rs, the first circuit node k1, is via a fixed resistor Rmv ' connected to the signal input e1. The resistance of the Slider rs divided into two parts and forms the first and second resistor R1 or R2. The output of the slider by a second Circuit node k2 is formed with the output of the first Operational amplifier v1 and with the one connection of a fixed resistor Rsv ' connected as the input resistance Rsv of the summing amplifier S for this channel serves. In the case of the first operational amplifier arrangement OP1, the Sum resistance from the fixed resistor Rmv 'and the first resistor R1 den Input resistance Rmv and the second resistance R2 den Feedback resistor Rmr (see Fig. 1). The connection point between the Fixed resistors Rsv and Rsr form a third circuit node k3, which has a Summing line s1 with the inverting input of the second operational amplifier v2 is connected. To this summing line s1 there are further input resistors a second or a third preamplifier M2 or M3 connected. The actuation of the slide controller rs, s can be done manually or electronically via an auxiliary device can be controlled by a control device P. In a digital version of the Slider rs or potentiometer, electronic control becomes easier, by actuating only electronic switching devices, as already stated Need to become. The slider rs or the potentiometer is activated by a Resistor network rp replaced with taps ai.

The differences of the invention are clearly evident in FIG. 4 compared to FIG. 3 recognize, the same circuit parts are provided with the same reference numerals and therefore no longer need to be explained. In the preamplifier M is the Slider rs replaced by a resistor network rp. A first and a second Electronic switches s1 or s2 set one to the first or tap a1 or a2 Connection, whereby the resistor network is divided into three sections which form the first, second and third resistor R1, R2, R3. The permissible ranges for the first and second taps a1 and a2 overlap not doing that. 4, the associated areas are shown schematically by the length of the respective sliding contact lines.

In the first operational amplifier arrangement OP1, as in FIG Fixed resistor Rmv 'together with the first resistor R1 Input resistance Rmv (see. Fig. 1) and the second resistance R2 den Feedback resistance Rmr. In the second operational amplifier arrangement OP2 The third resistor R3 forms together with the fixed resistor Rsv ' Input resistance Rsv (ex. Fig. 1). Since the feedback resistor Rsr the second operational amplifier arrangement OP2 is constant, its gain or damping controlled by changing the third resistor R3. Since the second tap a2 via the second switch s2 with the output of the first Operational amplifier v1 is connected, the gain vm of the preamplifier M both on the position of the first switch s1 and on the position of the second switch s2 can be controlled together or independently. The Gain vm of the preamplifier M is determined by the ratio of the second resistor R2 to the sum of the fixed resistor Rmv 'and the first resistor R1 formed. It should be noted that the resistors Rmv ', Rsv' and Rsr of course also in the resistor network rp can be included.

The control of the electronic switches s1, s2 and possibly other switches takes place by means of the control device P which uses a stored table T assigns the respective position of the switches s1, s2 to the desired channel gain vk. The total channel gain vk results from the channel-related Gain product vk = vm x vs of the preamplifier and summing amplifier M or S.

In Fig. 5 is an example of such a division of the table Channel gain shown for each gain and Damping areas specify an appropriate division to the desired To solve the task.

The entire modulation range from +12 dB to -34.5 dB is divided into two areas 1 and 2 (see FIG. 5) divided, the first range 1 from +12 dB to about -6 dB and the second range 2 ranges from about -6 dB to -34.5 dB.

In the first area 1, which is the entire channel gain range from 0 dB to +12 dB and also includes the weak attenuation range down to -6 dB, remains Summation gain vs constant at 0 dB. The setting of the channel gain vk is only done by changing the resistance ratio in the preamplifier M, for which the position of the first tap a1 is varied. If the two Fixed resistors Rsv 'and Rsr of the second operational amplifier arrangement OP2 are the same are large, in the assumed example of FIG. 4 each 3 kOhm, then is the second tap a2 is identical to the second for this gain range Circuit node k2. The input resistance Rsv (where Rsv = Rsv '+ R3) of the Summing amplifier S has its minimum value, namely only that Fixed resistance value Rsv '. At the maximum gain of +12 dB, this corresponds to first tap a1 to the first circuit node k1. The feedback resistor Rmr of the preamplifier M, which is formed by the second resistor R2, takes thus its maximum value, namely the value of the entire resistor network rp, where R1 = R3 = 0. As the gain decreases, tap a1 moves in Direction of the second circuit node k2 until finally with the channel amplification - 6 dB is a maximum value for the first resistor R1 (and thus the entire Input resistance Rmv, with Rmv = Rmv '+ R1) is reached, which a tap almax equivalent.

According to the knowledge of the invention should in the damping area, especially in strong Damping, which corresponds to the lower part of the second region 2 in Fig. 5, the Channel gain vk be divided so that the attenuation in the Summing amplifier S and not in the preamplifier M. This is achieved that the first resistor R1 no longer changes after reaching the maximum value becomes. The preamplification vm therefore only changes relatively due to the slight reduction of the second resistor R2 in the second area 2 only still between -6 dB and -7.5 dB, while the total channel gain vk changes between -6 dB and -34.5 dB. For this purpose, the second tap a2 is in the direction (starting from the second circuit node k2) of the first circuit node k1 changed until the third resistor R3 (and thus the entire input resistance Rsv, with Rsv = Rsv '+ R3) reaches a maximum value which a tap a2min (the Counting direction begins at kl). This increases the input resistance Rsv from 6 kOhm to approx. 67 kOhm. This corresponds to a change in Summing gain vs from -0 dB to -27 dB.

If in certain reinforcement and damping areas, e.g. 5 in the first and in the second area 1 or 2, each can be moved uniformly, e.g. the fact that only a single tap ai has to be changed then simplifies it the table T to be stored in the control device P. Its scope also depends on the smallest increment of the gain change, for those in the assumed Example 1.5 dB is sufficient. The function of the control device P can optionally also take over a processor integrated on the semiconductor chip. Of course, the control of the gain distribution and ultimately the Of course, the control of the gain distribution and ultimately the Control of the taps also via a more or less descriptive formula that is then calculated in the processor. For the formulaic Representation of the gain distribution, in which the function even in sections can be defined differently, the channel gain vk forms the variable. The formulaic representation is particularly simple if for individual areas or A linear dependency is given as an approximation because then the sections Intermediate values can be easily calculated using a linear interpolation.

Claims (9)

1. A monolithically integrable mixer network for a mixer console with several sound channels,

   each of the sound channels containing a variable-gain, i.e., variable-preamplification (vm), preamplifier (M) whose gain is adjustable via first resistors (Rmv, Rmr), and

   the outputs of the preamplifiers (M) being coupled to inputs of a summing amplifier (S) whose gain, the summing gain (vs), is adjustable via second resistors (Rsv, Rsr),

   characterized by the following features:

   the summing gain (vs) of the summing amplifier (S) is adjustable differently for each sound channel via the second resistors (Rsv, Rsr); and

   a control unit (P) is coupled to the preamplifiers (M) and the summing amplifier (S) and serves to control an overall gain relating to the respective sound channel, the channel gain (vk), according to a ratio between the gains of the respective preamplifier (M) and the summing amplifier (S), with

   the control unit (P) controlling the adjustment of the first and second resistors (Rmv, Rsv; Rmr, Rsr) of each preamplifier (M) and of the summing amplifier (S) in such a way that in the attenuation range, with increasing channel attenuation, the summing gain (vs) is reduced more than the preamplification (vm).
2. A mixer network as claimed in claim 1, characterized in that the respective preamplification (vm) and the associated summing gain (vs) are digitally adjustable, for which purpose the preamplifier (M) and the summing amplifier (S) form a first operational-amplifier arrangement (OP1) and a second operational-amplifier arrangement (OP2), respectively, whose channel gain (vk) is digitally adjustable via a tapped resistor network (rp) and an electronic switching device (s1, s2).
3. A mixer network as claimed in claim 2, characterized in that in the preamplifier (M), the tapped resistor network (rp) is connected via the electronic switching device (s1, s2), which is coupled to the control unit (P), to a first operational amplifier (v1) to form the first operational-amplifier arrangement (op1) such that a first portion of the tapped resistor network (rp), which forms a first resistor (r1), is associated with an input resistor (Rmv), while a second portion of the tapped resistor network (rp), which forms a second resistor (R2), is associated with a feedback resistor (Rmr).
4. A mixer network as claimed in claim 3, characterized in that the second operational-amplifier arrangement (OP2) comprises a second operational amplifier (v2) as well as a first fixed resistor (Rsv') and a second fixed resistor (Rsr), which are associated with the input resistor (Rsv) and the feedback resistor (Rsr), respectively, of the second operational-amplifier arrangement (OP2).
5. A mixer network as claimed in claim 4, characterized in that a third portion of the tapped resistor network (rp), a third resistor (R3), is associated with the input resistor (Rsv) of the second operational-amplifier arrangement (OP2).
6. A mixer network as claimed in claim 5, characterized in that the tapped resistor network (rp) comprises a series combination of resistors (r), and that some nodes (k) of the resistors are designed as taps (ai) which form the first, second, and third resistors (R1, R2, R3) by means of a first electronic switch (s1), which is associated with a first tap (a1), and by means of second electronic switch (s2), which is associated with a second tap (a2).
7. A mixer network as claimed in claim 6, characterized in that in a first channel-gain range (1), which corresponds to a high-gain signal amplification, the input resistor (Rsv, R3) of the second operational-amplifier arrangement (OP2) is set at a minimum value (Rsv') and the respective value of the channel gain (vk) is defined via the position of the first tap (a1), while in a second channel-gain range (2), which corresponds to a high signal attenuation, the first resistor (r1) is set at a maximum value and the respective value of the channel gain (vk) is defined via the position of the second tap (a2).
8. A mixer network as claimed in claim 7, characterized in that in an intermediate channel-gain range, which corresponds to a low-gain signal amplification and/or a low signal attenuation, the input resistor (Rsv; R3, Rsv') of the second operational-amplifier arrangement (OP2) is set at a minimum value (Rsv') and the respective value of the channel gain (vk) is defined via the position of the first tap (a1).
9. A mixer network as claimed in any one of claims 2 to 8, characterized in that in order to divide the channel gain (vk) between the preamplification (vm) and the summing gain (vs), the control unit (P), possibly an integrated processor, is so designed that the division is effected in accordance with a linked table (T) and/or in accordance with a computation.

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