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Joined: Jul 2012
Posts: 103
Apprentice
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Apprentice
Joined: Jul 2012
Posts: 103 |
Class B is the more common design used for solid state amps, especially smaller and older amps. The class also applies to tube amps, but only talking about solid state amps here.
In a class B amp, the output transistors must dissipate some of the total power being supplied to the output stage. The rest is delivered to the load. At full output, most of the power is sent to the speaker, but about 25% is lost by the output transistors as heat. At lower levels, the percentage of power lost in the transistors is higher. For example at 1/2 power, 50% is lost in the output transistors. This means that the transistors must be relatively large and mounted on a large heat sink. This adds size and weight to the amp. Also, these amps often use linear power supplies - 60 Hz transformer, rectifier, etc. These large transformers also add a lot of weight.
In a class D amp, the ouput transistors are operated as switches; they are either full on, or full off, hence the name switch mode. When a transistor is off, there is no current through it, and the power dissipated by the transistor is zero. When the transistor is on, the voltage across the transistor is zero, so again the power dissipated is zero. Think of the switch on a toaster. When it is off there is no current through the switch or the heating element. No current, no power. When the switch is on, the switch remains cold even though it is carrying the full current to the element. So the class D amp approaches 100% efficiency, delivering all of the power to the speaker and having very little lost in itself. This means smaller transistors and heat sinks. These amps often also have switching power supplies (same principle as the amp) and eliminate the heavy 60 Hz transformer. A much smaller high frequency transformer is used. So lots of size and weight savings.
The classes (A, B, AB, C) refer to the biasing of the transistor or tube used in an amplifier stage. Class A is biased in it's linear operating region. Class B is biased at or near it's off state. In an audio amp, Class B is used if the stage is "push pull" with one transistor handling the positive portion of the signal and one transistor handling the negative. Class AB is biased in the linear region, but not in the center of the region like class A, but closer to the off state (the "cutoff" point). Although the device itself is operated in a nonlinear manner, the overall response of the amplifier stage can be linear, and will be for audio amps. Class C is biased beyond cutoff and used in certain RF stages.
Class D is not a biasing scheme in the same sense as the others. It was simply assigned the next available letter, if I'm not mistaken. It does not stand for "digital".
So how do you get audio out of a couple of switches? The transistors are switched at a very high rate. If you look at the average voltage level at the output transistors, you will see a value that depends on the relative on / off times of the two two transistors. If each are on for equal time periods, the average will be zero. This is what occurs during a zero signal condition. If the positive transistor is on for a longer period than the negative one, then the average will be some positive value. And the longer it is on, relative to the negative side, the more positive the average will be. The same is true if the negative transistor is on for a longer time compared to the positive. Except now the average will be some negative value. The circuit that drives these output transistors uses the audio signal to control the relative on and off times. The result is an on /off time for the transistors that very closely follows the voltage level of the signal. This means that the average voltage level at the transistor output also closely follows the audio signal. Now all you need to do is remove the high switching frequency from the output, which is done by filtering as it is above the audio range. All that remains then is the average, which is a perfect analog of the input signal.
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Ask sales and support questions about Band-in-a-Box using natural language.
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User Video: Next-Level AI Music Editing with ACE Studio and Band-in-a-Box®
Band-in-a-Box® 2024 German for Windows is Here!
Band-in-a-Box® 2024 für Windows Deutsch ist verfügbar!
Wir waren fleißig und haben über 50 neue Funktionen und eine erstaunliche Sammlung neuer Inhalte hinzugefügt, darunter 222 RealTracks, neue RealStyles, MIDI SuperTracks, Instrumental Studies, "Songs with Vocals" Artist Performance Sets, abspielbare RealTracks Set 3, abspielbare RealDrums Set 2, zwei neue Sets von "RealDrums Stems", XPro Styles PAK 6, Xtra Styles PAK 17 und mehr!
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Update Your PowerTracks Pro Audio 2024 Today!
The Newest RealBand 2024 Update is Here!
The newest RealBand 2024 Build 5 update is now available!
Download and install this to your RealBand 2024 for updated print options, streamlined loading and saving of .SGU & MGU (BB) files, and to add a number of program adjustments that address user-reported bugs and concerns.
This free update is available to all RealBand 2024 users. To learn more about this update and download it, head to www.pgmusic.com/support.realband.htm#20245
The Band-in-a-Box® Flash Drive Backup Option
Today (April 5) is National Flash Drive Day!
Did you know... not only can you download your Band-in-a-Box® Pro, MegaPAK, or PlusPAK purchase - you can also choose to add a flash drive backup copy with the installation files for only $15? It even comes with a Band-in-a-Box® keychain!
For the larger Band-in-a-Box® packages (UltraPAK, UltraPAK+, Audiophile Edition), the hard drive backup copy is available for only $25. This will include a preinstalled and ready to use program, along with your installation files.
Backup copies are offered during the checkout process on our website.
Already purchased your e-delivery version, and now you wish you had a backup copy? It's not too late! If your purchase was for the current version of Band-in-a-Box®, you can still reach out to our team directly to place your backup copy order!
Note: the Band-in-a-Box® keychain is only included with flash drive backup copies, and cannot be purchased separately.
Handy flash drive tip: Always try plugging in a USB device the wrong way first? If your flash drive (or other USB plug) doesn't have a symbol to indicate which way is up, look for the side with a seam on the metal connector (it only has a line across one side) - that's the side that either faces down or to the left, depending on your port placement.
Update your Band-in-a-Box® 2024 for Windows® Today!
Update your Band-in-a-Box® 2024 for Windows for free with build 1111!
With this update, there's more control when saving images from the Print Preview window, we've added defaults to the MultiPicker for sorting and font size, updated printing options, updated RealTracks and other content, and addressed user-reported issues with the StylePicker, MIDI Soloists, key signature changes, and more!
Learn more about this free update for Band-in-a-Box® 2024 for Windows at www.pgmusic.com/support_windowsupdates.htm#1111
Band-in-a-Box® 2024 Review: 4.75 out of 5 Stars!
If you're looking for a in-depth review of the newest Band-in-a-Box® 2024 for Windows version, you'll definitely find it with Sound-Guy's latest review, Band-in-a-Box® 2024 for Windows Review: Incredible new capabilities to experiment, compose, arrange and mix songs.
A few excerpts:
"The Tracks view is possibly the single most powerful addition in 2024 and opens up a new way to edit and generate accompaniments. Combined with the new MultiPicker Library Window, it makes BIAB nearly perfect as an 'intelligent' composer/arranger program."
"MIDI SuperTracks partial generation showing six variations – each time the section is generated it can be instantly auditioned, re-generated or backed out to a previous generation – and you can do this with any track type. This is MAJOR! This takes musical experimentation and honing an arrangement to a new level, and faster than ever."
"Band in a Box continues to be an expansive musical tool-set for both novice and experienced musicians to experiment, compose, arrange and mix songs, as well as an extensive educational resource. It is huge, with hundreds of functions, more than any one person is likely to ever use. Yet, so is any DAW that I have used. BIAB can do some things that no DAW does, and this year BIAB has more DAW-like functions than ever."
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