Thule audio pr 250 b brochure
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Thule AudioÕs custom made integrated control circuit( yellow ) for Virtual Class A¨ In this way,Thule Audio has created a new type of class Aamplifier,butwithoutthe well-known physical disadvantages.And for thatreason,we think this new amplifier technology merits the name ÒVirtual Class A¨Ó. Thule Audio has also developed a new Òhigh efficiency technologyÓfor PA250 B,PA350 Band IA350 B. When you play music,mostof the music signals are on a relatively low level,and the music peaks only occasionally.The amplifier mustsupportthe reproduction of both signal sizes so that the voltage peaks are reproduced withoutany compression or distortion.Musical peaks require a high supply voltage butatthe lower levels you can lower the voltage supply and thereby reduce the generation of heat. Thule Audio has developed a dynamic power supply for PA250 B,PA350 Band IA350 Bthatuses this principle.The norm is to use a lower voltage supply,butwith musical peaks a higher voltage supply is used.The voltage supply thereby changes in tune with the music,and the changes occur very rapidly Ð much faster than the musical signals can change. With musical signals,Thule AudioÕs Òhigh efficiency technologyÓreduces heatgeneration by approximately 60% compared to class AB amplifiers.This means that PA250 Bwith 250 Wgenerates no more heatthan a normal 100 Wamplifier. As opposed to class Damplifiers where the outputtransistors themselves switch and thereby influence the signal path directly,Thule AudioÕs Òhigh efficiency technologyÓhas no connection to the actual signal path. Class Dis only a little more effective than Thule AudioÕs Òhigh efficiency technologyÓ,butclass D requires a greatdeal of signal processing and outputfilters in order to function,particularly at higher frequencies,and even here only a few very expensive products have succeeded in creating sound good enough to be used for things other than subwoofers and car radios. The combination of Thule AudioÕs Òhigh efficiency technologyÓand Virtual Class A¨ has created a new way of making amplifiers.For the firsttime ever,you getclass Asound:crisp,clear and with a superb dynamic performance withoutany hardness Ð and the heatgeneration is even significantly lower than traditional class AB amplifiers. SPACEPA 250 B,SPACEPA 350 Band SPACEIA 350 Bare all both stereos and surround sound products. Thule Audio has many years of experience designing high-end sound products for music.And we have used this experience to create the ultimate sound reproduction for music:the PA250 B, PA350 Band the IA350 B.The bestpossible sound reproduction for music actually gives the best sound reproduction of surround sound for film,if the amplifier is equipped with sufficient power to handle the explosive sounds. ThatÕs exactly why you do notneed to compromise by choosing either stereo or surround Ð you can have both.One minute the PA350 Bis a highly powerful stereo amplifier using 2x 350 Wwith a fully balanced signal path,the next,itÕs a state of the artsurround amplifier using 5x 120 W. ItÕs a simple butbrilliantprinciple. If five channels are notenough,in connection with,e.g.DTS ¨ 6.1 or Dolby ¨ EXthe PA250 Band PA350 Bcan be equipped with extra plug-in cards so thatyou can reach up to 7x 100 Wfor the PA250 Band 7x 120 Wfor the PA350 B. The new amplifiers in Thule AudioÕs Space series are all equipped with solid power supplies with 120,000uF capacity and 2x 500 VA / 2x 350 VA transformers for PA350 B,IA350 Band PA250 B respectively,and in addition,the power supply is utilised to an even greater extentin the PA350 B, IA350 Band PA250 Bdue to the Òhigh efficiency technologyÓ:The power supplyÕs capacity is used for music signals instead of for generating heat. The outputtransistors are generously equipped with 36pcs 20 Atransistors in the IA350/ PA350 B and 24pcs 20 Atransistors in the PA250 B. With the PA350 B,IA350 Band PA250 B,only the bestcomponents are used,for example Burr Brown operational amplifiers and high quality relays for signal exchange.PCB tracks are made with extra-thick copper. [ Òhigh efficiency technologyÓsized right for the living room ] PA250 B,PA350 Band IA350 Bare extremely powerful amplifiers with up to 2x 350 W.Normally, amplifiers of this strength are physically very large and space-intensive,because they require a lotof cooling.Thule Audio has used Òhigh efficiency technologyÓin order to constructmore moderate,smaller-sized cabinets with an elegant,timeless design.The back plates of the amplifiers are equipped with genuine WBT¨ speaker plugs,The Platinum Series. [ more operating possibilities ] The IA350 Bcan be operated both with and withoutremote control. Shifting between two- or multiple-channel operation for PA250 B/PA350 Bcan be done in three differentways:You can use a single knob directly on the frontof the amplifier.Or,the shiftcan occur automatically with the help of an internal control circuitin the amplifier which senses which channels carry signals.If you have connected a Thule Audio PR250 B,the control can take place through a data connection between your equipment. [ put together your thule audio equipment so that you can gain a fully balanced signal path ] PA250 Bor PA350 Bwill both be the strong cornerstone of your home cinema,and the obvious solution is to pair one of these amplifiers with the processor/preamp Thule Audio SPACEPR 250 B, so you are assured a fully balanced signal path. Perhaps you wantto startby acquiring a IA350 Bthatgoes with stereo products such as Thule Audio CD150 Band Thule Audio TU100,so you are secured for the future and can later change to multiple channel operations in connection with the building of your home cinema system. IA350 B can also be connected to PR250 Bwith a data interface,and will automatically convertinto a power amplifier with same performance as PA350 B. PA250B/ PA350BRearpanel IA350BRearpanel
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[ how virtual class a¨ works ] In the normal class AB amplifiers, the negative and positive output transistors are switching in tune with the music signal, when the output current to the speakers is larger than twice the idle current. For example at the figure on the left side, if the idle current is 100mA, transistor Q2 switches off when transistor Q1 delivers 200mA to the speaker with a positive musical signal, and vice versa with a negative musical signal. In the picture, you see the current through the output transistors when one sinus pulse is delivered to the speaker. It shows that for Virtual Class A¨ (green line) both the negative and positive output transistors remain active the entire time (Òno switchingÓ), because the lower edges of the scale are approximately 100mA respectively over and under zero. In Class AB(red line) the output transistors are switched on and off in tune with the music signal. In Virtual Class A¨ operation the output transistors are always active, therefore they are both always ready to start fast when the music signal changes polarity. It is the same way with auto- mobiles, which also start faster from idle than from the ignition. Because of this faster reaction with Virtual Class A¨, glitches and other transient currents are avoided. In class AB operation the output transistors are turned on and off during zero crossing. This switching can generate glitches and transients, which blur small treble details. With class ABoperation, there is a characteristic change in the output impedance from the amplifier when one of the output transistors switches off. This switching introduces an unequal distortion that sounds particularly harsh and unmusical, called Òcrossover distortionÓ. This means that several types of feedback must be used to compensate for the crossover distortion, but the feedback itself in some cases sounds even worse than the original distortion because of increased instability (flat Japanese sound). With Virtual Class A¨ the output impedance sequence is significantly smoother, ensuring that the Virtual Class A¨ generates much less distortion. sense output current -Vcc+Vcc Q1 I idle Q2 variable control voltage music signal speaker With Virtual Class A¨, a variable control voltage in tune with the musical sig- nal, is used to set the idle current, so that the idle cur- rent is maintained through both output transistors regardless of the output current. This means that both output transistors stay active the entire time. +Vcc -VccQ1 I idle Q2 fixed control voltage music signal speaker 0 400 mA -400 mA virtual class a¨ principle no switching switch off Virtual Class A¨ Class AB output impedance at zero crossing Virtual Class A¨ Class AB 0.200.25 0.30impedance Re=0.22 ohm, I idle=200mA 0.15 0.10 0.05 0.00 ohms output current 0 -350 350 mA Òcrossover distortionÓ CONVENTIONAL CLASS AB OUTPUT STAGE VIRTUAL CLASS A ¨ OUTPUT STAGE I idle changes with music signal Virtual Class Acontrol circuit I idle is constant