1 PRODUCTION PARTNER 03/2018. Review. from issue 3/2018

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1 1 PRODUCTION PARTNER 03/2018 Review from issue 3/2018

2 Dual-channel DSP audio amplifier Dynacord L3600FD Cost efficient Dynacord power amplifiers with DSP and MARC software for configuration and remote control Text and measurements: Anselm Goertz Photos: Dieter Stork, Anselm Goertz The news portal for the media world and technology PRODUCTION PARTNER 03/2018 2

3 Test Dynacord L3600FD The new live sound amplifier series from Dynacord offers four models from 1300 W to 3600 W total performance: All power amplifiers are equipped with a DSP system and can be configured, remotely controlled and monitored via USB. With a price range from 680 for the smallest model to 1,390 for the top model L3600FD presented here, it is aimed at the mid-range power amp segment and at the same time differentiates itself from its own top models of the Power-H series. Nevertheless, the live sound amplifiers offer the user everything from 2 ohms stability, with complete speaker processing including FIR drive technology to remote control, which is also available in the larger models just everything somewhat simplified and tailored to smaller applications. With this in mind, the new MARC (Multi Amplifier Remote Control) software was developed for both the live sound and Install-C series power amplifiers, which is used here instead of the much more complex IRIS Net software. The L in the name originally stems from the Linear Precision series, and the C series is in the tradition of Contractor Precision. Interior views of the L3600FD with a classic design consisting of a powerful toroidal transformer with two-stage voltage for the class H circuit and the lateral cooling channels for the two output stages Externally, the live sound amplifiers come in a solid 2U housing, largely unobtrusive. There is a small display and an incremental encoder on the front for controlling the device, Front view of the L3600FD via the display with incremental encoder, the DSP parameters can be set and setups can be loaded; in normal operation, the display acts as a level indicator 3 PRODUCTION PARTNER 03/2018

4 Rear panel of the L3600FD with inputs and link jacks as well as speakers for the speaker outputs, the connection to the PC is established via a USB type B jack used for selecting the setups and also for configuring all other settings. Two fans and the connections for the inputs and outputs share the space at the rear. In the Touring version of the power amplifier, the inputs are equipped with XLR sockets including link connection and the outputs with Speakon sockets. The C series is available as an installation amplifier, which is then equipped with Phoenix connections for the inputs and outputs. In addition, the C series has an additional, fully-fledged standby power supply, so that the main power supply can be switched off via remote control (MARC and switching contact). The C series also has a GPIO interface, which is not available in the L series. For remote control there is a USB type B device socket. With the help of USB hubs and range extenders, several amplifiers can also be remotely controlled and monitored from a PC over longer distances. What is striking about the amplifiers of the L series is the relatively high weight by today s standards: the L3600FD weighs remarkable 18.2kg. The reason for this can be found inside in the form of a powerful toroidal transformer and two large cooling tunnels. The live sound output stages are constructed in classic Class H circuitry and are supplied from a normal low-frequency transformer power supply. This concept, which is rather unusual today, is justified at Dynacord by the fact that power supplies with toroid transformers are on the one hand more robust against unstable power networks and on the other hand offer a level of reliability, which has to be achieved with a switched-mode power supply only by complex, additional protective circuits. Expensive power electronics and DSPs for monitoring and adjusting the power supply are not necessary. The disadvantage is, of course, the higher weight. The live sound audio amplifiers are offered in four output power classes with 2 650W to W. The type designation indicates the total power of both channels loaded with 4 ohms. The power amplifiers can be operated in bridge mode and, according to the data sheet, are also stable in 2 ohms mode. For the L3600FD presented here, the power at 2 ohms is specified as 3000W per channel in dual-channel operation. In the respective price and performance class, Dynacord tries to stand out from the competition with the live sound series above all through a solid design, safe protection circuits and professional and well thought-out operating software. The latter has been completely redesigned for the live sound series and can be used for configuration, operation and moni- PRODUCTION PARTNER 03/2018 4

5 Test Dynacord L3600FD toring of the amplifiers. The Windows software called MARC (Multi Amplifier Remote Control) is free and can be found in the current version on the website. Frequency response and damping factor Frequency response with 2-, 4- and 8-Ohm load resistors and with 4- or 8-Ohm loudspeaker dummy loads (Fig. 1) Starting with the frequency response in the measurement results, one direct advantage of the Class H circuit becomes apparent: Since no passive lowpass filter is required in the output to filter out highfrequency components in the signal, the frequency response to the high frequencies is less dependent on the load. The curves in Fig. 1 at 20kHz show a difference of just 0.1dB between a 2-Ohm and an 8- Ohm load. The gain of the output stage for the setting 0dB in the display is 32dB. Without activating further filters in the DSP, the cut-off frequencies at 5Hz are at the lower end and at 23.2kHz towards the high frequencies. The upper corner frequency is determined by the internal DSP with 48kHz sampling rate. The output stage itself will have a much higher cut-off frequency. AD and DA converters of the DSP system also require a small latency, which is very low at 1.9ms here. Damping factor referred to a 4 Ohm load measured in red via the second output directly at the output stage and measured in blue via the Speakon socket together with the load (Fig. 2) Interference spectrum at the output of the L3600FD (CH1 red, CH2 blue) Total level 67dBu and 69dBu(A), (Fig. 3) Fig. 2 provides a further measurement result on the topic of output filters and internal resistance resp. damping factor. The two curves show the damping factor related to 4Ohm for channel 2 of the L3600FD. The blue curve with values around 100 was measured together with the load via the corresponding Speakon socket. For the measurement of the red curve, the measuring line was connected via the second Speakon socket of channel 1; channel 2 is also connected via pins 2±. This makes it possible to measure the damping factor without the influence of the Speakon connection, since the measuring signal is picked up beforehand. The contact resistance of socket and plug of the load is then not included in the result. As the two curves show, the damping factor changes from 100 to over 200 as a result of this type of measurement. This means the contact resistance is approx. 40mohms. It makes sense to leave this proportion out during the measurement, as the value varies slightly depending on the state of the connector and also with each new connection. In 5 PRODUCTION PARTNER 03/2018

6 THD of the L3600FD at 1kHz (CH1 red, CH2 blue) as a function of the output voltage on the x-axis with loads of 2Ohm (dotted), 4Ohm (solid) and 8Ohm (dashed) (Fig. 4) Distortion spectrum (THD+N) of the L3600FD at 1kHz (CH1 red, CH2 blue) with a power of 2 600W at a 4 Ohm load (Fig. 5) practice, the damping factor effectively achieved for the loudspeaker is primarily determined by the cable resistance, which is many times higher than the contact resistance in the connector. The class-h circuitry concept is clearly visible in the curves of the damping factor, since the curves to the high frequencies also drop, but still have a significant value at 20kHz, so that the loudspeaker still sees an almost ideal voltage source. Signal-to-noise ratio The signal-to-noise ratio of an audio amplifier as the last link in the chain in front of the loudspeaker is an important factor when it comes to use in sensitive and quiet environments. A theatre audience naturally doesn t want to hear noise, or worse, humming or chirping, from a loudspeaker near them. Two aspects are important: firstly, the level of the interfer- THD of the L3600FD (CH1 red, CH2 blue) as a function of frequency at a power of 2 300W at 2Ohm (dotted), 2 300W at 4Ohm (solid) and 2 300W at 8Ohm (dashed) Load (Fig. 6) Intermodulation distortions DIM100 of the L3600FD (CH1 red, CH2 blue) depending on the input level on the x-axis at 2Ohm (dotted), 4Ohm (continuous) and 8Ohm (dashed) Load (Fig. 7) PRODUCTION PARTNER 03/2018 6

7 Test Dynacord L3600FD ence signal at the output of the output stage, and second, the spectral composition. An evenly distributed noise is usually less problematic than mono frequency components in the interference spectrum, which push themselves into the foreground. The interference spectrum in Fig. 3 shows how the L3600FD behaves on this topic. The measurement was performed with short-circuited input at 0dB gain control setting, resulting in 32dB overall gain. The spectral distribution of the signal to be measured at the output consists exclusively of noise. There are no individual spectral lines that peak out. Adding up all spectral lines, the total value is 0.34mV or 67dBu. With A-weighting it is even 2dB less. When you now connect a loudspeaker with a sensitivity of 100dB to 2.83V/1m, this would result in a noise level of 21.6dB at 1m distance. If you are 4m away from the loudspeaker, then just under 10dB noise floor remains and thus a value that can be considered negligible outside a perfect recording studio without hesitation. If the signal-to-noise ratio is set in relation to the maximum output voltage of the amplifier, which is at approx. 90Veff, this results in a signal to noise value of 108dB linearly weighted or 110dB for A-weighting of the signal-to-noise ratio. Power values of the L3600FD to 2Ohm with simultaneous loading of all channels (Fig. 8) Distortion measurements How much distortion may an audio amplifier generate and how should this be evaluated? This frequently asked question cannot be answered in general terms. What is certain, however, is that the weakest link in the signal chain is always the loudspeaker with the greatest distortion component. A closer look reveals that speakers primarily produce 2nd and 3rd order harmonic distortions. However, distortions caused by power amplifiers often also contain distortion components of a higher order, which are less well concealed in the auditory impression and are therefore more unpleasant. Typical distortion values of power amplifiers are for a 1kHz sinusoidal signal in the range of 60 to 100dB. Ideally, the curves run constantly falling to a minimum, which is then kept to the clip limit or just before it. Class-AB classic power amplifiers usually come close to this. Class-H amplifiers, such as the L3600FD presented here, provide similarly good values. The class H circuit can usually be recognized by one or more stages in the course of the distortion curves, which result from switching at higher output voltage to the next stage of the supply voltage. Power values of the L3600FD to 4Ohm with simultaneous loading of all channels (Fig. 9) Power values L3600FD to 8Ohm with simultaneous loading of all channels (Fig. 10) 7 PRODUCTION PARTNER 03/2018

8 Efficiency of the L3600FD in % as a function of the output power (x-axis); in red the curve without base load (60W), the efficiency of the Class H circuit does not reach the values of Class D output stages (Fig. 11) Course of mains voltage (red), mains current (blue) and the calculated power consumption (green) with an RMS value of 4380VA for apparent power; the measured power factor here is 0.83 (Fig. 12) Fig. 4 shows the THD curves of the L3600FD as a function of the output voltage at two-channel loads of 2, 4 and 8Ω. However, the jumping point clearly recognizable here is not (!) due to the Class H circuit (it is too low for that), but to the stacked AD converter of the DSP system. The class H threshold is only slightly visible between 30 and 40V output voltage. The total THD values are between 77 and 70dB, depending on the load, and are therefore of a completely uncritical magnitude. 70dB correspond to a value of 0.03% expressed as a percentage! The maximum output voltage at 40dB THD (1%) at 8Ω is 77V, at 4Ω 70V and at 2Ω 59V. Calculating the sine powers from this, they are 741W at 8Ω, 1225W at 4Ω and 1,740W at 2Ω, each with two-channel load. Since not only the total value but also the spectral composition plays a role in the harmonic distortions, the distortion spectrum from Fig. 4 must also be viewed. The measurement was carried out at 4Ohm loads as a typical value and at an output power 3dB under full scale, according 600W. The distortion spectrum is dominated by good-natured k2 components. Higher-order distortion components also exist, but mostly at significantly lower values below 80dB. Further THD curves from Fig. 6 were measured at a constant level depending on the frequency. The six curves show the two channels of the L3600FD measured at 2, 4 and 8Ohm loads at 300W output power each. At 1kHz the known values from Fig. 4 can be found. The distortion values increase slightly towards the higher and, somewhat unusually, also towards the lower frequencies. Towards the higher frequencies, the increase can be explained by the decreasing negative feedback. The rise to lower frequencies can have various causes in the signal path or circuit design which cannot be clearly determined from this point. The final distortion measurement is the DIM measurement (Dynamic Intermodulation Distortion, Fig. 7), in which a 15kHz sine is superimposed with a steep-edged 3.15kHz rectangle. The resulting intermodulation products are eva - luated. This measurement reveals weaknesses in fast transient signals in particular. Good class AB amplifiers reach values of 80dB and less up to the clip limit. With values from 75dB to 8Ohm, the L3600FD is already approaching this. The jump in the course at 0dBu input level is typical and goes back to the Class-H circuit. At 4 ohms and 2 ohms loads, the distortion values increase by 5dB and 10dB, respectively, since doubling or quadrupling the output current considerably demands the output stage. In all cases, however, the certain advantage of the Class H circuit used here compared to a Class D circuit can be seen, which often has to reveal weaknesses, especially in DIM measurement. PRODUCTION PARTNER 03/2018 8

9 Test Dynacord L3600FD ÙMARC Software: Configuration and Remote The MARC software has been completely redeveloped for the live sound L-Series and for the installation models of the C-Series. The name MARC for Multi Amplifier Remote Control already describes the function quite well. MARC is not only a remote control but also a configuration software, with which the user can assemble his own setups on the power amplifiers and also complete amp racks. The software is suitable for computers with Windows 7 or higher and is currently available free of charge in V1.0.0 on the Dynacord website. The connection between the PC and the power amplifiers is established via USB. A maximum of eight power amplifiers can be connected using one or more USB hubs. For greater distances beyond the officially possible 5m for a USB connection, USB range extenders can be used, which then make cable lengths up to 50m possible. After calling the easy-to-install software, the six icons at the top of the screen define the workflow. In the first step, one to a maximum of eight audio amplifiers can be dragged from the device list into the racks (Fig. 12). This is followed by the Amplifier View, where individual amplifiers are named and defined in their Normal or Bridge mode. If the amplifiers are already online, the firmware version can be read here and, if required, an update can be installed directly. The user defines which tasks the amplifier channels perform in the racks in the Configuration tab. First, channel groups are set up there, which are defined by the loudspeaker types to be operated. This means that all amplifier channels belonging to this group work with Rack composition in the MARC software, workflow taps from rack to operation at the top of the screen (Fig. 12) Graphical EQ in the operation tab of the software (Fig. 14) Configuration of an individual loudspeaker setup in the MARC software, the functions PEQ, X-Over and Limiter on the left side of the screen (Fig. 13) Overview of all output stages in the supervision tab (Fig. 15) 9 PRODUCTION PARTNER 03/2018

10 Power measurement the same speaker setting. This speaker setting can either be loaded from a Dynacord or Electro-Voice library or you can create it yourself. For the latter, all necessary controller functions are clearly arranged in a comprehensive form. A new setup can then be saved as a Configuration Group. Fig. 13 shows an example. In addition to the usual controller functions, the manufacturer libraries also use FIR filters and thermo limiters, which are already familiar from Dynacord s IRIS- Net devices. With the DSP in the live sound amplifiers the corresponding loudspeakers can be operated comparable to the IRIS-Net DSPs in the tour-grade series. In addition to filters and limiters, lower and upper impedance limits can also be specified for the respective loudspeaker so that defective cables and/or loudspeakers are detected. In the next step, control groups are created using the Controls tab, which act as virtual channel groups and enable joint editing. Which functions are possible can be defined here. Choose from a 5-band parametric EQ, a 31-band graphical EQ, and a delay of up to 650ms. The Gain and Mute functions are always available in the control groups. This makes it easy to put together clear groups for the main PA, a delay line, fill systems, etc. These functions for the virtual groups are then operated in the Operation tab. Fig. 14 shows a corresponding example with active graphical EQ. The last tab in the workflow, called Supervision, serves to monitor the output stages. Here all important states of all power amplifiers can be seen at a glance. With appropriate settings for impedance monitoring, it is also possible to detect directly whether there may be a defect in the loudspeakers or in the cabling. For the user or lender of Dynacord systems, the MARC software offers an easy and fast way to configure complete racks or individual power amplifiers and then to operate and monitor them during operation. If you want to use speakers other than those already available in the libraries, the MARC software is an easy to use tool to create your own setups based on given parameters or even your own measurements. However, a basic understanding of the function of a loudspeaker controller is a prerequisite. By concentrating on the essentials and the clear system related workflow the operation of the MARC software is easy. One can disagree about the use of the USB interface. On the other hand, it is also possible to set up a networked system simply and reliably with the help of one or two USB hubs. Finally, the MARC system should also be a suitable alternative for smaller systems, where the powerful IRIS-Net is oversized in its complexity and functional diversity. All power measurements were performed on loads of 2 2Ω, 2 4Ω and 2 8Ω. The output stage was switched off in two cases. First, for the extreme of a sinusoidal signal at 2 2Ω after a duration of 18s, where the internal 15A mains fuse was then triggered. The power consumption from the power grid was 5.8kW. The triggering of the fuse was justified in this respect. In practice, however, this case is unlikely to occur, since a permanent sinusoidal signal, moreover with full modulation, does not actually occur, and if it does, then it is probably not intentional. In the second case, the electronic protection circuit briefly switched off the output stage due to thermal overload, which also occurred at a 2 2 ohms load with a 6dB crest factor signal after approx. four minutes of continuous full modulation. The output stage went into protect mode for approx. 40s. The power values according to IHF-A- 202 or CEA-2006-A are given in the data sheet of the live sound amplifiers. The test is performed with a 1kHz sinusoidal signal whose level jumps by +20dB every 500ms for 20ms. The signal has a crest factor of 16dB. Without compressing the signal in the 20ms long bursts, our laboratory measurements showed performance values from 2,030W to 2Ω, from 1,434W to 4Ω and from 829W to 8Ω, each with two-channel measurement. The values are slightly below the manufacturer s specifications. However, if you compare the manufacturer s values with the laboratory measurements for a noise signal with only 12dB crest factor, these values come significantly closer to or even exceed the manufacturer s specifications despite the lower crest factor and the resulting higher load on the audio amplifier. The reason for the deviations will probably lie in the PRODUCTION PARTNER 03/

11 Test Dynacord L3600FD Filter functions of a preset with FIR filters from the speaker library for the Dynacord Cobra system (Fig. 16) Allpass filter for creating individual speaker presets (Fig. 17) evaluation of the CEA burst measurement, which allows a relatively large scope for interpretation. All details of the power measurements for 2-, 4- and 8-ohm loads can be found in the diagrams in Figures 8, 9 and 10. The most important power values should be those for 4-ohm loads from Fig. 9. For 60s, the power amplifier delivers a stable 1kHz sinusoidal signal 2 1,225W and a crest factor noise 2 1,686W over a test period of six minutes. The power value for the noise signal is calculated from the peak-to-peak voltage value divided by 2.82, which allows a direct comparison with the sine measurement. The actual average power is of course much lower at 240W per channel for the 12dB signal. If the crest factor is reduced to already quite extreme 6dB, then 1,600W per channel are still reached at 4Ohm with an average power of 729W, which are limited to 420W in the endurance test after 90s. Taking the values for a 12dB crest factor signal as the final scale, it is 2,684W for 2Ohm, 1,686W for 4Ohm and 917W for 8Ohm. These values correspond quite exactly to the manufacturer s specifications in the data sheet. Mains load through the audio amplifier Three key points have to be considered when it comes to the issue of mains load caused by power amplifiers: Firstly, efficiency, where the aim is to provide as much power as possible for the loudspeakers without generating a great deal of heat loss. A high degree of efficiency reduces direct power consumption from the grid and also indirectly saves electricity if an external cooling system is used, which then has to absorb less waste heat. The second point concerns the mains current. This should follow the voltage as closely as possible in its course and the audio amplifier should thus behave as a load for the power supply system comparable to a resistive load. The measured power factor, which is 0.6 to 0.83, depending on the load on the L3600FD, describes how well this is achieved. The third relevant parameter is the base load or resting power already mentioned. This value is always important when the devices are permanently in operation, as is the case in many fixed installations. With 60W, the L3600FD is quite convenient. However, there is no automatic standby or sleep function that would further reduce energy consumption. Probably this aspect is also not so important for typical applications in small PA systems, since the operating time is usually limited to the actual event. The efficiency of the L3600FD reaches 60% at full capacity. Due to the circuit design, however, the value drops significantly at powers below full load, so that at 250W 40% is still achieved and at 63W still approx. 20%. As a matter of principle, the Class H concept cannot reach the values of Class 11 PRODUCTION PARTNER 03/2018

12 Limiter functions for a setting with a threshold of 25V pk and different time constants for attack and release, in blue the original unlimited signal (Fig. 18) Bell filter in the MARC software with wide setting ranges and correctly compensated high frequency response (Fig. 19) D power amplifiers, which can consistently reach values of 80-90%. However, the multistage supply voltage of the Class H circuit still offers efficiency advantages over a pure Class AB circuit, especially in the important lower and medium power range. Fig. 12 shows the mains voltage together with the current and the power consumed. The measurement was performed under full load with a total of 2,450W output power. The active power consumed from the power grid was 3,620W and the apparent power 4,380W, resulting in a power factor of Typical for the current characteristic of a LF transformer power supply are the relatively short current peaks, which become shorter and shorter with less power. Accordingly, the power factor decreases with increasing harmonic content. PRODUCTION PARTNER 03/

13 Test Dynacord L3600FD DSP functions The DSP system in the live sound audio amplifier offers the user the complete range of functions of a modern loudspeaker controller. For each output, X-Over filters with all common characteristics from 6 to 24dB/Oct., a gain trim as well as delay and phase reverse are available. A filter bank with six parametric EQs, including shelving filters and allpass filters can be used to filter the output paths. Finally at the output there is a peak limiter. With these functions the user can create his own speaker settings if there are no suitable ones in the libraries. For the factory speaker settings, FIR filters and thermo limiters are also used, which are not available for free configuration this also makes sense in both cases. FIR filters require in-depth knowledge of filter calculation and, if the speakers are to be equalized with the FIR filters, perfect free-field measurements of the speakers. If these are not available, the advantages of FIR filtering can quickly reverse and lead to unwanted results. The parameters for the thermo limiter are similar. With fully active systems you can still trust the specifications of the chassis manufacturers (AES 2h Performance), but for passively separated speakers it is hardly possible to set safe values without developer knowledge. Fig. 16 shows a nice example of a setting with FIR filtering from the Dynacord library for the well-known Cobra system. Here the top is rectified in detail with the FIR filter and also corrected during the phase. However, the FIR filter also increases the controller s latency from 1.9ms to 9.3ms. For all settings from the libraries, the parameters are not visible and cannot be changed. From the many setting options, two variants are to be considered in more detail. First, there is the all-pass filter found in the parametric EQ for individual speaker settings. As the name Allpass suggests, the filter allows everything to pass regardless of frequency. Concretely, this means that the filter function for the amplitude is a straight line. Besides the amplitude, there is also the phase of a filter and here an allpass causes a phase rotation of 180 or 360, depending on the setting of the first or second order. Fig. 17 shows an example with all-pass filters at 1kHz of the first or second order. For the second-order all-pass, the Q grade can also be set between 0.4 and 2.0. All-pass filters are required whenever a loudspeaker of a two- or three-way cabinett is to be adjusted in phase to another loudspeaker without changing the amplitude. The limiters have an important function within a controller. A distinction must be made between the usual peak limiters and long-term or RMS limiters. Peak limiters operate with very short time constants and prevent the output stages from being overloaded and the loudspeakers from being over- 13 PRODUCTION PARTNER 03/2018

14 loaded with signal peaks. In most cases, a peak voltage value (V pk ) is set here, which is specified either by the clip limit of the output stage or the power rating of the loudspeaker. If you only have the typical AES 2h power rating of a loudspeaker, then you can convert it into a RMS voltage value with the help of the impedance. When this is doubled, this corresponds to the voltage peak value for a signal with 6dB crest factor. This value can then be used as a guide for the peak limiter. However, the correct value for the setting is only helpful if the controller also implements the setting in a comprehensible manner. Exactly at this point there is often confusion with different values and their meaning. The MARC software handles this better. Our measurements in Fig. 18 clearly show that the set parameters are implemented exactly. The limit value set in Vpk is strictly adhered to. The same applies to the attack and release time constants that can also be set. The red curve in Fig. 18 was measured with an attack time constant of 100ms and a release time constant of 1s, both of which can be traced directly. In addition to the functions for individual speaker settings, a parametric 5-band EQ and a 31-band graphic EQ can also be activated in the cross-device control groups of the power amplifiers. The settings that are possible here are shown in Figures 19 and 20. The parametric EQs range from 20Hz to 20kHz and can be set in gain between 18 and +12dB. Values from 0.4 to 40 are possible for the Q factor, so that even very fine notch filters can be created as they are required, for example, to suppress feedback frequencies. The red filter curves in the upper third of Fig. 19 show the Bell filter for frequencies from 20Hz to 20kHz. The compression of the bell curve resulting from the calculations for higher frequencies near half the sampling rate of digital filters is correctly compensated here. The bell curves get their shape independent of the frequency up to 20kHz. How far-reaching the Q factor setting is for the Bell filters can be seen in the lower part of Fig. 19. Graphic one-third octave band EQs are still popular despite their limited capabilities compared to parametric filter banks. Many users have internalized the effect of a graphical EQ so much from their long experience that they do not want to do without it. Thanks to the digital filter technology, all these wishes can also be fulfilled without having to accept disadvantages. The same applies to the parametric filters for the graphic EQs in the live sound audio amplifiers. The curves are compensated for high frequencies close to half the sampling rate, so that their course corresponds exactly to that of an analog filter. Fig. 20 in the upper third shows individual Graphical EQ in the MARC software, the individual curves overlap relatively far, which can result in a strong increase or decrease with several adjacent filters (Fig. 20) filters from 20Hz to 20kHz with a gain of +12dB. The individual filters are designed quite broadly, so that there is a clear overlap. If you now operate several adjacent filters, then a much greater increase or decrease results from it than the fader position suggests. Thanks to the graph for the filter curve in the MARC software (Fig. 14), however, you can immediately see how the overall result will turn out and you can adapt accordingly. In summary, the DSP functions in the live sound amps allow us to say that all the necessary functions are available and the set values are also implemented precisely. This applies to both the filters and the limiters. Conclusion Dynacord s new amplifier series has been developed for use in small and medium-sized sound reinforcement systems. The power values from 1.3 to 3.6kW in total for two channels each are suitably dimensioned for this. Cost-effective and robust in use, the power amplifiers are designed as class H circuits with conventional LF transformer power supply. The somewhat higher weight caused by this should also not be decisive for typical applications. The MARC software for configuration and operation of the amplifiers was developed to match this concept. The software is based on the system concept and enables the user to quickly and easily assemble PRODUCTION PARTNER 03/

15 Test Dynacord L3600FD Overview: Dynacord L3600FD Output Power Sin 12 db CF Peak 4 Ω/2 Ch 60 s 360 s 1 ms in W per ch Noise dbu dbu(a) Dynamics db db(a) f[hz] 20 1 k 20 k Gain db Phase HP filter TP filter 5 Hz 23.2 khz f[hz] k 10 k CTC db CMRR db DF rel. 4Ω suitable racks or individual devices and divide them directly into groups for specific tasks. With the help of the workflow tabs in the software, this can be done within a few minutes, even without training. The L3600FD power amplifier and the integrated DSP system delivered good to very good results in the measurement laboratory. The Class H circuits can even show their advantages over the more modern Class D power amplifiers here and there. The efficiency is not quite as good due to the class-h circuit principle. The equipment of the DSPs for the live sound series is in full swing. All important functions are abundant and work perfectly. Even the premium features of FIR filtering and thermolimiter for the speakers have been adopted from the top models of the Tour Grade series with IRIS-Net. All in all, the live sound amplifiers have a lot to offer. Combined with the wellknown Dynacord quality and an almost captivatingly low price (list prices, gross incl. VAT: L3600FD DSP: 1,390, L2800FD DSP: 1,020, L1800FD DSP: 840, L1300FD DSP: 680), these amplifiers are a real recommendation. 25% Power Min. before clip THD 1 khz DIM Power consumption No signal Full power 12 db Full power sine 60 W Ω bei 12 db CF Ω 1 khz sine Weight in kg 18.2 Height 2 RU RRP incl. VAT 1,390 Street price in 1,190 S.No Power supply LF transformer Switching Class H Remote Dynacord MARC 15 PRODUCTION PARTNER 03/2018