cr8ted4u

can you help me on what to use,what is the difference between a bd and d mono amp,thinking the best to use with my 10W7 jl audio,thanx alot!!!

rmorris003

iTrader: (7)

no need for double posting

Eli47

It refers to the classification of amplifiers. That is to say how they process the sine wave presented to them by music.., etc

Personally speaking I'd recommend a class B to drive a sub system.
Here are examples of amplifier classifications.

Class A operation is where both devices conduct continuously for the entire cycle of signal swing, or the bias current flows in the output devices at all times. The key ingredient of class A operation is that both devices are always on. There is no condition where one or the other is turned off. Because of this, class A amplifiers in reality are not complementary designs. They are single-ended designs with only one type polarity output devices. They may have "bottom side" transistors but these are operated as fixed current sources, not amplifying devices. Consequently class A is the most inefficient of all power amplifier designs, averaging only around 20% (meaning you draw about 5 times as much power from the source as you deliver to the load!) Thus class A amplifiers are large, heavy and run very hot. All this is due to the amplifier constantly operating at full power. The positive effect of all this is that class A designs are inherently the most linear, with the least amount of distortion. [Much mystique and confusion surrounds the term class A. Many mistakenly think it means circuitry comprised of discrete components (as opposed to integrated circuits). Such is not the case. A great many integrated circuits incorporate class A designs, while just as many discrete component circuits do not use class A designs.]

Class B operation is the opposite of class A. Both output devices are never allowed to be on at the same time, or the bias is set so that current flow in a specific output device is zero when not stimulated with an input signal, i.e., the current in a specific output flows for one half cycle. Thus each output device is on for exactly one half of a complete sinusoidal signal cycle. Due to this operation, class B designs show high efficiency but poor linearity around the crossover region. This is d ue to the time it takes to turn one device off and the other device on, which translates into extreme crossover distortion. Thus restricting class B designs to power consumption critical applications, e.g., battery operated equipment, such as 2-way radio and other communications audio.

Class AB operation is the intermediate case. Here both devices are allowed to be on at the same time (like in class A), but just barely. The output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of class A designs, but enough to keep each device operating so they respond instantly to input voltage demand s. Thus the inherent non-linearity of class B designs is eliminated, without the gross inefficiencies of the class A design. It is this combination of good efficiency (around 50%) with excellent linearity that makes class AB the most popular audio amplifier design.

Class AB plus B design involves two pairs of output devices: one pair operates class AB while the other (slave) pair operates class B.

Class C use is restricted to the broadcast industry for radio frequency (RF) transmission. Its operation is characterized by turning on one device at a time for less than one half cycle. In essence, each output device is pulsed-on for some percentage of the half cycle, instead of operating continuously for the entire half cycle. This makes for an extremely efficient design capable of enormous output power. It is the magic of RF tuned circuits (flywheel effect) that overcomes the distortion create d by class C pulsed operation.

Class D operation is switching, hence the term switching power amplifier. Here the output devices are rapidly switched on and off at least twice for each cycle (Sampling Theorem). Theoretically since the output devices are either completely on or completely off they do not dissipate any power. If a device is on there is a large amount of current flowing through it, but all the voltage is across the load, so the power dissipated by the device is zero (found by multiplying the voltage across the device [zero] times the current flowing through the device [big], so 0 x big = 0); and when the device is off, the voltage is large, but the current is zero so you get the same answer. Consequently class D operation is theoretically 100% efficient, but this requires zero on-impedance switches with infinitely fast switching times -- a product we're still waiting for; meanwhile designs do exist with true efficiencies approaching 90%. [Historical note: the original use of the term "Class D" referred to switching amplifiers that employed a resonant circuit at the output to remove the harmonics of the switching frequency. Todays use is much closer to the original "Class S" designs.

Class E operation involves amplifiers designed for rectangular input pulses, not sinusoidal audio waveforms. The output load is a tuned circuit, with the output voltage resembling a damped single pulse. Normally Class E employs a single transistor driven to act as a switch.

The following terms, while generally agreed upon, are not considered "official" classifications

Class F Also known by such terms as "biharmonic," "polyharmonic," "Class DC," "single-ended Class D," "High-efficiency Class C," and "multiresonator." Another example of a tuned power amplifier, whereby the load is a tuned resonant circuit. One of the differences here is the circuit is tuned for one or more harmonic frequencies as well as the carrier frequency.

Class G operation involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single class AB output stage that is connected to two power supply rails by a diode, or a transistor switch. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks [ thus the nickname rail-switcher]. Another approach uses two class AB output stages, each connected to a different power supply voltage, with the magnitude of the input signal determining the signal path. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is becoming common for pro audio designs. [Historical note: HITACHI is credited with pioneering class G designs with their 1977 Dynaharmony HMA 8300 power amplifier]. *(And the introduction of the M.O.S.F.E.T transistor, added by E.C.)

Class H operation takes the class G design one step further and actually modulates the higher power supply voltage by the input signal. This allows the power supply to track the audio input and provide just enough voltage for optimum operation of the output devices [thus the nickname rail-tracker or tracking power amplifier]. The efficiency of class H is comparable to class G designs. [Historical note: Soundcraftsmen is credited with pioneering class H designs with their 1977 Vari-proportional MA5002 power amplifier.]

Class S First invented in 1932, this technique is used for both amplification and amplitude modulation. Similar to Class D except the rectangular PWM ( Pulse Width Modulation ) voltage waveform is applied to a low-pass filter that allows only the slowly varying dc or average voltage component to appear across the load. Essentially this is what is termed "Class D" today.

CLASS-T The underlying technology of Class-T does not use Pulse-Width-Modulation and is not a pure analog approach ( such as Classes -A and -AB). It combines the benefits of both with a completely new approach which is DPP(Digital Power Processing) based in design. Class-T amplifiers provide the signal fidelity of discrete-component linear Class-A and AB designs, while offering high power efficiency and the potential to need simpler engineering, which reduces manufacturing cost for amplifier overhead at high power levels (such as power supply, filtering, and heat venting),in order to achieve high-end audiophile grade sound performance. Class-T claims to provide power conversion efficiencies of 80 percent to more than 90 percent, which is equal to or better than "Class-D" amplifiers. Class-T technology uses both analog circuitry and Digital Power Processing algorithms that modulate the input signal with a high-frequency switching pattern.

df.dima

iTrader: (12)

^ This would be a good topic for our Technical section.

AAAAAAA

iTrader: (7)

I'd say run a class D(or BD) for the subwoofer, class AB is less efficient, that's why everyone has gone class D with their monster sub amplifiers and are now going to class D full range to.

BD is a varation of class D. RF seems to like to have their own naming for everything.

I am not aware of any class B only car amps.

M.C. Ryan

Your question is which would be louder? Well, it all depends on your set up, it's a very hypothetical question. Do you have enough power to run them, gauge of wire, impedance of your woofer(s), what the amplifiers are rated at, at that load, are the woofers in the same box for the comparison? All these variables...

Haunz

iTrader: (3)

Quote:

Originally Posted by AAAAAAA

BD is a varation of class D

This is correct...



IIRC a BD design uses a full bridge output section driven by two PWM supplies each sampling one half of the high frequency carrier signal for each half of the output section....

one advantage of sampling the two halves of the carrier at the same time is that the effective frequency is doubled, and the peak to peak amplitude is reduced by 6db for the same amount of drive (this is an advantage when it comes to filtering out the carrier)

The real advantage..

during normal operation a full bridge class D amp uses a single PWM supply to drive the outputs, cycling them between 50-0 and 50-100 percent duty cycle at the carrier frequency… if one half is running at 1% for the first half of a cycle at the carrier frequency, the second half will be running at 99% for the second half of the cycle..... To sit at zero volts each half runs at a 50% duty cycle so the outputs spend the same amount of time at each rail (average zero volts).... however this tends to cause voltage ripple as the outputs switch back and forth, which has to be filtered by the LC circuit that filters out the carrier.... it also creates increased RFI, and may interfere with feedback circuitry...

In a BD amp the two PWM supplies run the outputs with a zero percent duty cycle for zero output..... and during normal operation they run one half of the output section at a time cycling it between 0 and 100% duty cycle at the carrier frequency, while the second half stays at 0%..... (this is analogous to a class B design, hence the term ‘BD’)

The biggest advantage is a lower idle current draw, and a greater efficiency at lower output levels...... considering music has a 20-30% average duty cycle this is an advantage in an amplifier used for street beating…. although many class D designs come very close in efficiency at low or idle output…….

RF was not the first to design such a system, but they did get a patent for thier specific design.... I am relativly sure they are not the only company that makes a class BD amplifier but I don't know of any others off the top of my head.....

cr8ted4u

Thanx for your INFOs.Glad there are guys like you who can share their skills!
I had just installed my 10W7 jlaudio in a modified HO box w/ the RF501bd AMP
I was just asking which is louder to know the differences.I'm more concern in SQ over SPL so I design the box accordingly.To my delight,I could realize the cleanest BASS I ever had for its what the passers-by are commenting.Had this after putting fiberglass instead of polyfill and placing a sound deadner at the back of the seat,so now its nothing but the driver that rattles.The only thing is that I cant go full volume w/o opening the window for I cant stop the rattling of the whole HondaPrelude,Thanx to ALL!!!