L-Acoustics PAD4-LA48a Used, Second hand

Used PAD4 (RK122) amprack with 4pcs LA48a Power Amplifers,PADO4a Rack Panel and AC Panel.

Photos on request.

More details

1.07.359
Used

4,999.00 €

4,999.00 € per Set

INQUIRE ABOUT THIS

 
About this product

LA48a

The LA48a is a compact, light-weight power amplifier (2 rack units high, 10 kg) designed for high performance touring and fixed installation. Primarily intended for powering V-DOSC and SB218 subwoofers, the LA48a is capable of providing up to 2900 watts per channel into 2 ohms. The LA48a can also be configured to match the power delivered to a wide range of impedance loads using Minimum Load Select (MLS) switches, allowing the amplifier to be customized to suit a variety of L-ACOUSTICS loudspeaker models and applications.
The switch-mode power supply (SMPS) employed in the LA48a is a modern solution to the weight and size problem. With SMPS technology, it is possible to use ferrite transformers instead of the heavy iron transformers and large electrolytic capacitors that are typical of conventional power amplifiers. Combined with the heat dissipation efficiency of the patented Intercooler system, this results in a weight reduction of up to 60% when compared with conventional amplifiers of similar power ratings.
Earlier attempts at using SMPS technology for audio were less than impressive since they directly adopted the type of supply found in computers. The LA48a is different since a regulated SMPS has been implemented using push pull conversion without current limiting on the secondary side of the switching transformer. Instead, sense windings inject a magnetic pulse from the AC line during a pulse time segment which is separate from the output charge current pulse. The net result is a power supply with performance characteristics that are the same as a conventional power supply and capable of delivering high peak power, tight bass and detailed transient response.
Using SMPS technology it is also easy to stabilize the DC-rail voltage allowing the LA48a to deliver full power over a range of up to 20% supply voltage swings and at any AC mains frequency from DC to 400 Hz. This stabilization is obtained by controlling the magnetic energy in the ferrite transformer with pulse width processing and magnetic flux sense windings.
The LA48a has an upgraded version of the switched mode output stage from the LA 24a where the power transistors are cooled by a patented heatsink system termed the Intercooler. Bipolar output devices are directly mounted onto a copper heat sink for improved heat transfer. The heat sink is then mounted horizontally in front of a pressure chamber that is created by two variable speed cooling fans. Specially designed thermal feedback circuitry protects against thermal breakdown and advanced linear active filtering is employed to reduce carrier noise and distortion in accordance with the strictest of EMC and RFI standards.
The LA48a is completely short-circuit protected (even for reactive loads) and specially designed short-circuit protection circuitry allows very high peak currents while holding transistors within their "Safe Operating Area". This makes it possible to run loudspeakers with impedance variations that are considerably lower than the rated impedance of the power amplifier. Six more protection circuits protect the LA48a and the loudspeakers:

  • DC Protection : Two types of D.C. protection - fuses on the supply branches of each channel (IEC 65 requirement) and crowbar type protection that shorts the output.
  • Thermal Protection : Protects the amplifier from overheating and causing damage to the output stages.
  • Clip Limiter : Prevents severely clipped waveforms from reaching the loudspeakers while maintaining full peak power.
  • VHF (Very High Frequency) Protection : Protects the loudspeaker against non-musical signals outside the audible frequency range.
  • AC Protection : Shuts down the outputs if the line voltage is outside the operating voltage of the LA48a.
  • AFS Limiter (Adaptive Fuse Saver) : Limits the mains current to a safe level according to the time lag of an 16 ampere slow blow fuse. All electronics are mounted on four modules that are easily accessible for repair or replacement.

Used L-Acoustics

L-Acoustics is a French manufacturer of loudspeakers, and signal processing devices for rental and installed sound markets. Headquartered in Marcoussis, just south of Paris, the company has satellite operations in the United States, United and Germany, as well as a global Rental Network of production companies deploying and cross-renting its products.

Active: Powered. An active crossover is electrically powered and divides the line-level signal prior to amplification. An active speaker includes an active crossover and built-in amplifier. Amplifier: A component that increases the gain or level of an audio signal.Balanced Input: A connection with three conductors: two identical signal conductors that are 180 degrees out of phase with each other, and one ground. This type of connection is very resistant to line noise. Bandpass: A two-part filter that cuts both higher and lower frequencies around a center band. A bandpass enclosure cuts high frequencies by acoustic cancellation and low frequencies by natural physical limitations on bass response. Bandwidth: In audio, the range of frequencies a device operates within. In video, the range of frequencies passed from the input to the output. Bandwidth can also refer to the transmission capacity of an electronic communications device or system; the speed of data transfer…very important when planning a meeting for the attendees to stay connected. Bass: Low frequencies; those below approximately 200 Hz. CD: Compact Disc. Ubiquitous digital audio format. Uses 16-bit/44.1-kHz sampling rate PCM digital signal to encode roughly 74 or 80 minutes of two- channel, full-range audio onto a 5-inch disc. Channel: In components and systems, a channel is a separate signal path. A four-channel amplifier has at least four separate inputs and four separate outputs.Crossover: A component that divides an audio signal into two or more ranges by frequency, sending, for example, low frequencies to one output and high frequencies to another. An active crossover is powered and divides the line-level audio signal prior to amplification. A passive crossover uses no external power supply and may be used either at line level or, more commonly, at speaker level to divide the signal after amplification and send the low frequencies to the woofer and the high frequencies to the tweeter. Crossover Frequency: The frequency at which an audio signal is divided. 80 Hz is a typical subwoofer crossover point and is the recommended crossover point in theatrical and home THX systems. Frequencies below 80 Hz are sent to the subwoofer; signals above 80 Hz are sent to the main speakers.Decibel (dB): A logarithmic measurement unit that describes a sound's relative loudness, though it can also be used to describe the relative difference between two power levels. A decibel is one tenth of a Bel. In sound, decibels generally measure a scale from 0 (the threshold of hearing) to 120-140 dB (the threshold of pain). A 3dB difference equates to a doubling of power. A 10dB difference is required to double the subjective volume. A 1dB difference over a broad frequency range is noticeable to most people, while a 0.2dB difference can affect the subjective impression of a sound.Delay: The time difference between a sonic event and its perception at the listening position (sound traveling through space is delayed according to the distance it travels). People perceive spaciousness by the delay between the arrival of direct and reflected sound (larger spaces cause longer delays).Diaphragm: The part of a dynamic loudspeaker attached to the voice coil that produces sound. It usually has the shape of a cone or dome.Diffusion: In audio, the scattering of sound waves, reducing the sense of localization. In video, the scattering of light waves, reducing hot spotting, as in a diffusion screen.Digital Audio Server: Essentially a hard drive, a digital audio server stores compressed audio files (like MP3 or WMA). Most include the processing to make the files, and all have the ability to play them back.Dispersion: The spread of sound over a wide area.Distortion: Any undesired change in an audio signal between input and the output.Dolby B: A noise-reduction system that increases the level of high frequencies during recording and decreases them during playback.Dolby C: An improvement on Dolby B that provides about twice as much noise reduction.Dolby Digital: An encoding system that digitally compresses up to 5.1 discrete channels of audio (left front, center, right front, left surround, right surround, and LFE) into a single bitstream, which can be recorded onto a DVD, HDTV broadcast, or other form of digital media. When RF-modulated, it was included on some laser discs, which requires an RF-demodulator before the signal can be decoded. Five channels are full-range; the .1 channel is a band-limited LFE track. A Dolby Digital processor (found in most new receivers, preamps, and some DVD players) can decode this signal back into the 5.1 separate channels. Most films since 1992's Batman Returns have been recorded in a 5.1 digital format, though a number of films before that had 6-channel analog tracks that have been remastered into 5.1.Dolby EX: An enhancement to Dolby Digital that adds a surround back channel to 5.1 soundtracks. The sixth channel is matrixed from the left and right surround channels. Often referred to as 6.1. Sometimes referred to as 7.1 if the system uses two surround back speakers, even though both speakers reproduce the same signal. Software is backwards-compatible with 5.1 systems, but requires an EX or 6.1 processor to obtain additional benefit.Dolby Pro Logic: An enhancement of the Dolby Surround decoding process. Pro Logic decoders derive left, center, right, and a mono surround channel from two-channel Dolby Surround encoded material via matrix techniques. Dolby Pro Logic II: An enhanced version of Pro Logic. Adds improved decoding for two-channel, non-encoded soundtracks and music. Driver: A speaker without an enclosure; also refers to the active element of a speaker system that creates compressions and rarefactions in the air.DSP: Digital Signal Processing. Manipulating an audio signal digitally to create various possible effects at the output. Often refers to artificially generated surround effects derived from and applied to two-channel sources.DTS: Digital Theater Systems. A digital sound recording format, originally developed for theatrical film soundtracks, starting with Jurassic Park. Records 5.1 discrete channels of audio onto a handful of laser discs, CDs, and DVDs. Requires a player with DTS output connected to a DTS processor.DTS ES: An enhanced version of the 5.1 DTS system. Like Dolby's Surround EX, a sixth channel is added. In some cases (DTS ES Discrete), the sixth channel is discrete. Software is backwards-compatible with 5.1 systems, but requires an ES or 6.1 processor to obtain additional benefit. Neo: 6 is a subset of DTS ES that creates 6.1 from material with fewer original channels.Dynamic Range: The difference between the lowest and the highest levels; in audio, it's often expressed in decibels. In video, it's listed as the contrast ratio.Equalizer: A component designed to alter the frequency balance of an audio signal. Equalizers may be graphic, parametric, or a combination of both. Fade: A gradual increase in audio, i.e. a fade-up, or a gradual decrease in audio, i.e. a fade-down.Feedback: The transmission of current or voltage from the output of a device back to the input, where it interacts with the input signal to modify operation of the device. Feedback is positive when it's in phase with the input and negative when it's out of phase. Frequency: The number of cycles (vibrations) per second. In audio, audible frequencies commonly range from 20 to 20,000 cycles per second (Hz). In video, frequency is used to define the image resolution. Low-frequency video images depict large objects or images. Higher frequencies depict smaller objects (finer details). Frequency Response: A measure of what frequencies can be reproduced and how accurately they are reproduced. A measurement of 20 to 20,000 Hz, 3dB means those frequencies between 20 and 20,000 Hz can be reproduced no more than 3 dB above or below a reference frequency level. Full-Range: A speaker designed to reproduce the full range (20 Hz to 20 kHz) of audio frequencies.Gain: Increase in level or amplitude.Gooseneck: This refers to amicrophone with a flexible neck that is most frequently attached to a podium or lectern. It is designed to allow the speaker to raise or lower the microphone to a suitable height.Graphic Equalizer: A type of equalizer with sliding controls that creates a pattern representing a graph of the frequency-response changes. Raising sliders boosts the affected frequencies; lowering sliders cuts (attenuates) the affected frequencies.High Pass: A filter that passes high frequencies, and attenuates low frequencies. Same as low cut.Hz: Hertz or cycles per second. Something that repeats a cycle once each second moves at a rate of 1 Hz.Incue/Inq/In-Point: These words all refer to the initial few seconds of audio signifying the beginning of the production.Impedance: A measure of the impediment to the flow of alternating current, measured in ohms at a given frequency. Larger numbers mean higher resistance to current flow.KHz: Kilohertz or one thousand Hz.Lavaliere: A small microphone that attaches to clothing, allowing the speaker to have a hands-free presentation.Line Array: A group of speakers that have been arrayed or “built up” in the vertical or horizontal plane, which allow for a highly consistent sound field. A Line Array is perfect for medium to large audiences.Midbass: The middle of the bass part of the frequency range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz). Also used as a term for loudspeaker drivers designed to reproduce both bass and midrange frequencies. Midrange: The middle of the audio frequency range. Also used as a term for loudspeaker drivers designed to reproduce this range. Mixer: This is the unit in which audio signals are directed from. A mixer provides for both mic and line input combinations while allowing you to control one or more outputs.MP3: MPEG-1 Audio Layer-3. Compression scheme used to transfer audio files via the Internet and store in portable players and digital audio servers. Natural Sound (NATS): The nonverbal audio that occurs in a non-studio setting. NATS can be used to help characterize the setting.Noise: An unwanted portion of a signal such as hiss, hum, whine, static, or buzzing.Passive: Not active. A passive crossover uses no external power and results in insertion loss. A passive speaker is one without internal amplification.Phase: Time relationship between signals; it's all relative.Power Output: A measure, usually in watts, of how much energy is modulated by a component.Preamplifier: A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers.surround processor portion of the receiver and the input of the amplifier portion of the receiver.Processors: Anything that processes an incoming signal in some way. Surround processors, for example, can decode a Dolby Digital signal to send to an amp so you can hear it.Pulse Code Modulation: (PCM) a way to convert sound or analog information to binary information (0s and 1s) by taking samples of the sound and record the resulting number as binary information. Used on all CDs, DVD-Audio, and just about every other digital audio format. It can sometimes be found on DVD-Video.RF: Radio Frequency. Television signals are modulated onto RF signals and are then demodulated by your television's tuner. VCRs and DBS receivers often include channel 3 or 4 modulators, allowing the output signal to be tuned by the television on those channels. Also, laser discs used an RF signal for modulating Dolby Digital 5.1 soundtracks on some movies. This requires an RF demodulator (usually referred to as an AC3-RF demodulator) before or in the surround processor to decode the signal. RMS: Root Mean Square or the square root of the arithmetic mean (average) of the square's set of values. A reasonably accurate method of describing an amplifier's power output. Signal-to-Noise Ratio: A comparison of the signal level relative to the noise level. Larger numbers are better. Simultaneous Interpretation: This system allows attendees to hear the meeting in their own language. Sound field: The total acoustical characteristics of a space, such as ambience; number, timing, and relative level of reflections; ratio of direct to reflected sound; RT-60 time; etc. Speaker: A component that converts electrical energy into acoustical energy. SPL: Sound-Pressure Level. Measured in dB. Subwoofer: A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.THX: Certification program for home theater equipment. Uses some proprietary features, but mostly assures a base quality level for a given room size. (See THX Select or Ultra.) Is compatible with any and all soundtrack formats. Stands for either Tom Holman's eXperiment, after the engineer who drafted the original standard, or is named after the company's founder George Lucas' first movie, THX 1138. Nobody agrees on which.

30 other products in the same category: