GB2472022A

GB2472022A - Musical signal mixing unit for combining a dry audio signal with an effect processed audio signal

Info

Publication number: GB2472022A
Application number: GB0912641A
Authority: GB
Inventors: Mark Thornton Dunn
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-07-21
Filing date: 2009-07-21
Publication date: 2011-01-26
Also published as: GB0912641D0

Abstract

A musical signal mixing unit for connection, in use, between a musical instrument (1) such as a steel guitar, and a loudspeaker (4), comprises a circuit with an input for receiving a signal from the musical instrument and/or a volume pedal. The circuit includes: a first bypass signal path, for transmitting the signal without passing through an effects unit to a summing point of an amplifier; and a second signal path for transmitting the signal to the summing point of the amplifier via an external effects unit such as a reverb or delay pedal. The circuit may include buffer amplifiers and signal conditioners. Two or more effects units, preferably a delay effect unit followed by a reverb effect unit, may be connected in series and a volume adjusting unit may be inserted between the two or more effects units.

Description

MUSICAL SIGNAL MIXING UNIT

Field of the Invention

The invention relates to a musical signal mixing unit. It has particular applications in the field of steel and/or electric guitar when arranging effect pedals or effect units on the signal path between the instrument and loudspeakers. In a preferred implementation, the musical signal mixing unit is located between an instrument and a so called Combo amp (including pre-amp and power amp).

Background to the Invention and Prior Art Known to the Applicant Figure 1 shows a typical steel guitar arrangement where the steel guitar 1 is connected to a volume pedal 2 with a connection lead 3 between the volume pedal and the guitar amplifier 4. As shown in figure 2, by placing a reverb pedal 5 or other similar pedal between the volume pedal and the guitar amp, steel guitarists are able to add one or more effects when using a guitar amp which has no built-in effects. A preferred effect is the reverb effect. When other effects are desired the guitarist adds further individual pedals such as pedal 6 as shown in Figure 3.

Generally prior art pedals either take the form as shown in Figure 4A or the form shown in Figure 4B. The prior art shown in Figure 4A resulted from the introduction of low cost single chip microprocessors. The systems incorporate a buffer transmitting the drive signal to a summing point of an amplifier whilst also sending the signal on a second path through an analogue to digital converter, through a microprocessor of limited processing power, followed by a digital to analogue converter, an effect level adjuster before combining the dry signal with the process signal using analogue circuitry. The second kind of prior art as shown in Figure 4B due to the higher bit resolution of the system allows processing of both the effect signal and dry signal in the systems, the mixing of the effected signal and dry signal takes place within the digital domain and the digital to analogue converter outputs the fully processed signal.

Despite the high clock rates used in modern microprocessors, many clock cycles are required to execute even the simplest of tasks. For this reason even though a microprocessor based effect pedal of the kind shown in Figure 4B may appear to react instantly, on closer examination a small time delay can be measured. The modern fully digitally based effect pedals suffer from this problem and introduce therefore small but musically significant delays. The problem of introducing delays is often referred to as "latency". The problem of latency is significant to the ear of a musician and its listener.

This problem is actually further increased when several pedals of this kind are connected in series as shown in Figure 3.

One of the objects of the invention is to provide a signal mixing unit which may be employed in combination with the modern digital pedals or units without or at least minimising the presence of Latency. A further object of the invention is to provide an improvement in the switching between the combinations of effect pedals located between an instrument and a loudspeaker.

Summary of the Invention

In its broadest independent aspect, the invention provides a musical signal mixing unit for connection, in use, between a musical instrument and a loudspeaker, comprising a circuit with an input for receiving a signal from a musical instrument and/or a volume pedal; wherein said circuit incorporates a first signal path for transmitting said signal without passing through an effect pedal or effect unit to a summing point of an amplifier; and a second signal path for transmitting said signal to said summing point of an amplifier; said second signal path incorporating connection points for connecting to the input and output of an effect pedal or effect unit; the connection points being connectable, in use, to the input and output of an effect pedal or effect unit so that said signal is transmitted to said summing point via said effect pedal or effect unit. This configuration is particularly advantageous because it allows the output to a guitar amp to be achieved without the introduction of latency despite employing a modern digitally based effect pedal. It allows the signal mixing unit to be used with a combo amplifier having no tone shaping whilst the unit introduces no delay or Latency into the dry signal. It will also have minimal phase-shift over the useable frequency range of a guitar.

In a subsidiary aspect in accordance with the invention's broadest independent aspect, the effect level adjuster is provided between the effect pedal or effect unit output connection point and a summing point of an amplifier. This configuration is particularly advantageous because it allows the effects to be adjusted by interaction with the signal mixing unit rather than necessarily with the effect pedal or effect unit.

In a further subsidiary aspect, a first buffer is provided at said unit's input; and a second buffer is provided at the unit's output. The first buffer is particularly advantageous because it would allow the so-called dry signal to be sent without any digital modification to the summing point. It also allows the signal to be split off towards an effect pedal without deteriorating the output from the signal mixing unit.

In a further subsidiary aspect, the mixing unit further comprises a conditioner located before the connection point corresponding to the input to an effect pedal or unit; said conditioner being configured to divide said signal. The use of a conditioner would allow the use of particular effect pedals or units. It also allows the otherwise consequential addition of clipping distortion to be avoided. In a preferred embodiment, the conditioner divides the signal in two before sending it.

In a further subsidiary aspect, the mixing unit further comprises a conditioner located after the connection point corresponding to the output of the effect pedal or unit; said conditioner being configured to multiply said signal. This further conditioner also assists in avoiding so-called clipping distortions whilst improving the mixing unit's compatibility with particular kinds of effect pedals or units.

In a further subsidiary aspect, said second signal path transmits, in use, a signal to a first summing point of a summing amplifier via a first kind of effect pedal or unit; and said circuit incorporates a third signal path configured to transmit, in use, a signal to a second summing point of a summing amplifier via a second kind of effect pedal or unit. This configuration has particular benefits in the field of steel guitar and would allow the mixing unit to operate by the integration of both a delay pedal and a reverb pedal. An appropriate switching arrangement would allow a blend of these effects to be achieved without the drawbacks of introducing latency.

In a further subsidiary aspect, a signal path is provided between said first and second summing points for connecting a volume pedal. This configuration allows the so-called "double mode" operation. It avoids the otherwise complex requirement of a special wiring arrangement and a significant re-adjustment of the delay mix control. It allows the delay pedal use to create an extra note in order to provide the illusion that the player is playing twice as fast as he is in reality.

In a further subsidiary aspect, said second signal path transmits, in use, a signal to a summing point of a summing amplifier via both a first kind of effect pedal and a second kind of effect pedal; the first and second kind of effect pedal being connected in series. In this configuration, a pre-delay effect may be added before a reverb effect in order to clean up the initial note without losing the reverb effect. This effect is also achievable without

the introduction of any latency.

Brief Description of the Figures

Figure 1 shows a prior art arrangement in perspective view.

Figure 2 shows a further prior art arrangement in perspective view.

Figure 3 shows a further prior art arrangement in perspective view where effect pedals are employed in series.

Figure 4A shows a circuit diagram of a prior art effect pedal incorporating a summing amplifier of an analogue kind.

Figure 4B shows a circuit diagram of a prior art effect pedal employing a fully digital process.

Figure 5 shows a circuit diagram for a signal mixing unit for use in combination with an effect pedal of the kind shown in Figure 4A and 4B.

Figure 6 shows a circuit diagram of a signal mixing unit comprising a first and second effect pedal.

Figure 7 shows a circuit diagram with a first and second effect pedal which are in a "serial mode".

Figure 8 shows a circuit diagram incorporating a volume pedal.

Figure 9 shows a circuit diagram for switching between multiple modes of operation.

Figure 10 shows a diagram of the power supply distribution.

Detailed Description of the Figures

Figure 5 shows a simple circuitry which may be used to remove the effect of latency when employing separate effect pedal units. The circuit may be housed in a housing separate from the effect pedal in order to allow the operator flexibility in the choice of effect pedal employed. In this embodiment, a connector is provided for receiving the connection lead of a volume pedal which then feeds the buffer which is used to amplify the signal in order to safely generate two outputs. The first output is directed along a first signal path directly to a summing amplifier. The dry signal is therefore not subjected to any digital effect. The second output is directed on a second signal path to a connection point for connecting to the input of an effect pedal which in this embodiment may be a reverb pedal. On the second signal path, there is provided a second connection point for receiving the output from a reverb pedal. The effect signal is then passed through an effect level adjuster such as a level controlling potentiometer before joining the summing amplifier.

The signal and/signals resulting from the summing amplifier are then submitted to a second buffer before the output which may be fed to a guitar amp. The gain of the buffer and summing amplifier may be set to unity in a preferred embodiment. This arrangement allows when operating in conjunction with a modern digital reverb pedal the effect to be applied to the signal without introducing latency into the dry signal.

Whilst the signal mixing unit may have a single mode of use as illustrated in the embodiment of Figure 5, technical and musical advantages arise from providing a signal mixing unit which facilitates a plurality of modes of operation. For example, the signal mixing unit may incorporate connections to one or more effect pedals such as a delay and a reverb effect pedal and/or connections to a volume pedal. A switching arrangement may be provided with which a musician may interface in order to switch between modes of operation.

A particularly advantageous combination of effect pedals is shown in Figure 6. The circuitry provided within the signal mixing unit is highlighted by the dash-dot box.

Describing the various components from left to right, the signal mixing unit incorporates a guitar input or receiver. The unit also incorporates an input and output for connecting a volume pedal. The connection between the circuitry and the volume pedal is provided before the first buffer which amplifies the signal. As in the previous embodiment, the dry signal passes along a first transmission path between the first buffer and the second buffer.

The dry signal which is transmitted between buffers is not submitted to any signal modification. Between the first and second buffer there are provided a first summing point and a second summing point. Immediately after the first buffer, there is a second path along which a conditioner is provided.

The conditioner conditions the signal. This kind of conditioning allows a musician to use powered effects pedals of a particular voltage. The conditioning also minimises the risk of clipping distortion. In a preferred embodiment, the conditioner provided on this second pair would divide the signal by a factor which may be 2. The conditioner is provided before the connection point corresponding to the input to a delay effect pedal.

The delay effect pedal may incorporate an arrangement of buffer followed by analogue to digital converter, microprocessor, digital to analogue converter and a further buffer.

Following the delay effect pedal a connection is provided on its output in order to connect with a further receiver of the unit.

A further conditioner is then provided which may multiply the signal after receiving it. The conditioner is then followed by a delay leveL adjuster which may take the form of a potentiometer. The adjuster then outputs to a delay summing point.

In this configuration the delay is added in parallel with the dry signal and the combined signal is then added in parallel with reverb. A third path of transmission sends the signal through a further conditioner to a connection point corresponding to the input of the reverb pedal. The reverb pedal then incorporates an output which engages a further connection point of the unit. The signal which has then been modified by the reverb effect is then conditioned and passed through a reverb level adjustor which may take the form of a potentiometer. The dry signal plus delay signal is then added to the reverb effect at the final summing point on the first path between the two buffers. The second buffer or output buffer is provided for an output connection point which may receive a connection lead to a guitar amp or other appropriate device. In this configuration if the musician disconnects the delay and reverb units, or sets the level of the controls to zero, the signal which would exit the unit would be exactly the same as sent from the volume pedal. In other words, the dry signal is maintained in as near original condition as possible.

In a preferred configuration, the first or input buffer may be capacitor coupled whilst the other stages may be DC coupled to minimise phase shift at low frequency.

In a further configuration, instead of providing the effect units on separate second and third paths, they are arranged in series on a second path. By adding the deLay effect unit before the reverb effect unit a so-called "pre-delay" effect is achieved which cleans up the attack of the note whilst maintaining a significant reverb effect. In this configuration although the delay and reverb effects are connected in series the reverb output is still added in parallel with the dry signal. The configuration shown in Figure 7 incorporates the same connection points as described in detail with reference to Figure 6. The primary difference between the two figures is that the connection point corresponding to the output from the delay effect unit is connected to the connection point corresponding to the input of the reverb effect without passing through a delay summing point. Instead of configuring the circuitry necessarily to operate in a single mode, a switch may be provided to either lay the output of the second delay effect conditioner with the delay level adjuster or to connect the second delay effect conditioner with the first reverb effect conditioner.

In the mode of operation shown in Figure 7 the delay level adjustor is not used. A switching system which automatically adjusts the delay output signal may be provided to adjust the level such that the reverb will be of a similar magnitude to that obtained in a parallel mode of operation. In this mode of operation if the reverb level adjustor is set to zero, the pure unaffected dry signal will output the unit.

Figure 8 shows a further mode of operation. In this configuration the delay pedal creates an extra note in order to provide the illusion that the player is playing twice as fast as he is in reality. In this configuration, the first path of signal transmission incorporates connection points in order to connect the volume pedal. The first signal path therefore incorporates the first buffer in order to impedance match the signal. The dry signal then passes to a delay summing point. The delay summing point is then linked to a connection point corresponding to the input to the volume pedal. The volume pedal output is then fed through a further connection point and to a further buffer before reaching a double mode preset volume adjustor. The signal then reaches a final summing point before the output buffer. Returning to the first buffer or input buffer as described the buffer outputs to both a first path and a second path. On the second path, a first conditioner is provided before the connection point corresponding to the input to a delay effect pedal. The delay effect pedal then outputs to a further connection point with a conditioner followed by a double mode repeat level preset adjuster. The output from the adjuster is then summed with the dry signal at a delay summing point. A third transmission path spLits off from the first path with a further conditioner leading to the connection point corresponding to the reverb effect unit. The reverb effect unit then outputs to a further connection point. The signal then passes through a conditioner and a reverb level adjustor before reaching the final summing point.

Whilst a signal mixing unit may be provided to achieve any of the preceding modes of operation, any appropriate combination of these circuits may be achieved through appropriate positioning of switches in order to allow an operator to switch between modes of operation without having to rewire the connections to a signal mixing unit.

A potential arrangement of switches is shown in detail in Figure 9. In this configuration parallel, serial mode and double mode may be achieved dependent upon the selection of a musician. In the configuration shown in Figure 9, the input from a guitar enters at a first connection point before reaching a switch. The switch may either send the signal to the delay effect before the volume pedal or as shown sends the signal to the connection points corresponding to the volume pedal. After outputting the volume pedal, a further connection point is linked to a further switching point between double mode and parallel/serial mode operation. In the configuration shown, the switch is in its parallel/serial mode position. The signal then reaches the first buffer. The dry signal then outputs the first buffer and is either channelled to the delay summing point or to the delay effect pedal. The dry signal after reaching the delay summing point then aLso reaches a further switch between double mode and parallel/serial mode. A further switch between parallel/single mode is provided and then reaches the final summing point preceding the buffer output.

The configuration shown is when the switches are arranged to achieve the parallel mode of operation. The signal which is transmitted through the delay effect pedal is then channelled to the delay summing point by the delay level adjuster. Between the delay level adjuster and the second conditioner of the delay effect portion of the circuitry, a first switch for switching between parallel and serial mode is provided and a second switch is provided for switching between double mode and either parallel or serial mode. In addition to the components concerned with the various modes of operation, a further buffer is provided for an output to a tuner or to an auxiliary output.

Irrespective of the mode of operation selected the dry path signal is not degraded by the process. This results in no latency and minimum phase shift over the required frequency range.

Whilst the embodiment of Figure 9 shows the reverb as a mono effect, the invention envisages that the signal mixing unit may be configured with stereo reverb return inputs and stereo main outputs.

The circuitry described in the previous figures may be housed in a box. In addition to the box, a remote control box may be employed to allow a guitarist to make adjustments to the reverb and/or delay effects. The remote control box may be provided with a clip sized and shaped to be secured to a steel guitar frame or leg. The circuitry of the unit may be configured to operate in conjunction with a dual rail +/-12 volt DC supply. A 12 volt DC single-ended supply may be used and internally converted into a dual rail supply using a DC to DC converter.

In order to ensure that the power supply could be used world-wide a switch-mode design may be employed. This may operate over the input supply range of 100 to 240 volts AC.

In addition, an internal regulator may be employed to convert the 12 volt DC supply into a regulated 9 volt DC supply.

The unit may be configured to have a maximum load of 300mA from three 9 volts DC supply outlets. Whilst the various pedals and the unit may be housed separately, a plate may be provided to fit the various units into sufficient proximity and optimum spacing to allow the interaction with the musician. The plate may incorporate an attachment means in order to secure the components in an appropriate position relative to a steel guitar. The plate may be substantially flat with a number of right angle side sections for additional rigidity and to locate the various components. The mounting plate may be made of aluminium which may be coated. A number of rubber strips or high friction pads may be provided under the plate in order to prevent the plate from sliding when placed on a floor.

The plate may incorporate a number of holes drilled on the bottom which would be placed in alignment with preset potentiometers of the unit making access to the settings possible once attached to the mounting.

Claims

CLAIMS1. A musical signal mixing unit for connection, in use, between a musical instrument and a loudspeaker, comprising a circuit with an input for receiving a signal from a musical instrument and/or a volume pedal; wherein said circuit incorporates a first signal path for transmitting said signal without passing through an effect unit to a summing point of an amplifier; and a second signal path for transmitting said signal to said summing point of an amplifier; said second signal path incorporating connection points for connecting to the input and output of an effect unit; the connection points being connectable, in use, to the input and output of an effect unit so that said signal on said second path is transmitted to said summing point via said effect unit.
2. A mixing unit according to claim 1, wherein an effect level adjuster is provided between the effect unit output connection point and a summing point of an amplifier.
3. A mixing unit according to either of the preceding claims, wherein a first buffer is provided at said units input; and a second buffer is provided at the unit's output.
4. A mixing unit according to any of the preceding claims, further comprising a conditioner located before the connection point corresponding to the input to an effect unit; said conditioner being configured to divide said signal.
5. A mixing unit according to any of the preceding claims, further comprising a conditioner located after the connection point corresponding to the output of said effect unit; said conditioner being configured to multiply said signal.
6. A mixing unit according to any of the preceding claims, wherein said second signal path transmits, in use, a signal to a first summing point of a summing amplifier via a first kind of effect unit; and said circuit incorporates a third signal path configured to transmit, in use, a signal to a second summing point of a summing amplifier via a second kind of effect unit.
7. A mixing unit according to claim 6, wherein said first kind of effect unit is a delay effect unit and said second kind of effect unit is a reverb effect unit.
8. A mixing unit according to either of the preceding claims, wherein a signal path is provided between said first and second summing points for connecting a volume adjusting unit.
9. A mixing unit according to any of claims 1 to 6, wherein said second signal path transmits, in use, a signal to a summing point of a summing amplifier via both a first kind of effect unit and a second kind of effect unit; the first and second kind of effect unit being connected in series.
10. A mixing unit substantially as hereinbefore described and/or illustrated in any appropriate combination of the accompanying text and/or figures.