dave_Edwards

ok ok Brahma or W7---that is the best debate i think in a long while in car audio and yet all the W7 lovers hate to see that the Brahma is a better value.

a Clarion ProAudio DXZ615---nothing fancy---it is just a volume knob and a CD player for me---I might be in the market to buy a new one soon though.

out of these 2---which do you like better?I will respond when i see someone elses opinion.

which do you prefer and why? Myself enjoy a good powerful 2 channel instead of a 4 channel.

that would be compromising the tests---don't you think?Take the practice tests and see how you do. Good luck

they don't get too much bigger than this----MS1000 34inches of pure power---1060x2@2 ohm(each side)----my "lil friend"

sorry---it was me Dave---i forgot to log-in-------DUH!

This is my new baby Phoenix Gold MS1000

http://arawndark.netfirms.com/ cool link I have to the internals of amplifers. Daddy likes!!!!

what is your favorite amplifer of all time and why? Mine is a Phoenix Gold M100 i had when I was 16---it was my first amp I ever bought with my own money. close 2nd is my Phoenix Gold MS1000---my wife let me buy(it was kinda like my birthday present 6months early) I still have both of these amps.

Speakers: A speaker converts electrical energy to mechanical/acoustical energy. It uses a coil of wire, which acts as an electromagnet, set inside of a magnetic gap of a permanent magnet.It is pretty simple if you think about it Voice coil motivation: When a current is passed through the coil of wire, called the voice coil, it generates a magnetic field. This electromagnet interacts with the field in the magnetic gap and the voice coil moves. The direction of movement depends on the direction of current flow through the VC. Since audio is an AC waveform, current flows in one direction and then changes polarity, the VC moves either forward or backward from its point of rest. The cone is the part of the speaker that actually makes the sound by alternately creating an area of high and then low air pressure. Magnitude of cone movement: When an amplifier drives a speaker, it is driving the speaker terminals with AC voltage. If the volume is at its minimum position, the speaker doesn't move. If the driving voltage is low, the speaker moves a little. As the voltage increases (when you turn up the volume), the cone moves further from it's point of rest. Higher power amplifiers can drive the speaker with higher voltage and therefore produce more SPL (volume). ********Please note that speakers DO NOT produce power**********. A speaker rated at 1000 watts is not necessarily going to be more efficient than a speaker rated at 50 watts. If they are manufactured by the same company (so that they are rated by the same standards), the speaker rated to handle higher power will be able to produce more sound pressure level because it can be driven with a more powerful amplifier without fear of damage. Many times, a manufacturers cheapest woofers will be more efficient and may be a better choice for a low powered system. Coaxials and Triaxials: It is very difficult (read impossible) to build a single driver capable of accurately and efficiently reproducing the entire audio spectrum. It is much easier to use multiple drivers, each reproducing its own narrow band of frequencies. Coaxial speakers are 2-way speakers which employ a larger driver (for bass and midrange) and a tweeter (for reproducing upper midrange and treble). A triaxial speaker is a 3-way speaker with a woofer, a midrange and a tweeter. Both types of speakers usually include the required crossover components for the midrange and high frequency drivers.

As you have probably heard, some people say that too little power can blow speakers. Well... How can I say this... BS!!!! Too little power will only cause the maximum output level to be low. Abuse and the defective 'wing nut' (an idiot) connected to the volume control blow speakers with low powered amplifiers. If driving a speaker with low power would cause them to fail, speakers would fail every time you lower the volume on the head unit. I will try to explain what happens when speakers are driven with clipped signals but remember... you get what you pay for. Note: This page deals mainly with speaker damage that involves thermal damage of the voice coil. Speakers can also be damaged mechanically by driving it beyond what the suspension can handle. Mechanical damage is generally caused by driving the speaker with too much power but it can also be done when a speaker is in a ported enclosure and is driven with frequencies below the port tuning frequency. Most of the damage I've seen has been thermal damage to the voice coil. When a woofer is driven with a high powered amplifier to high levels, there will be a significant amount of current flowing through the voice coil. Since the voice coil has resistance, there is a voltage drop across the speaker's voice coil (which the amplifier appreciates greatly . This means that there may be a great amount of power being dissipated (in the form of heat) in the voice coil. When a speaker is driven with lots of clean power, the cone moves a great deal (in proportion to the output voltage from the amplifier). For speakers with vented pole pieces (or other types of venting), this movement forces a lot of air to flow in the magnetic gap (area where the voice coil rides). When the woofer moves out of the basket, the chamber that's under the dust cap and around the voice coil expands (increases in volume) which pulls cool air into the magnetic gap. When the woofer moves the other direction, the chamber size is reduced and the hot air is forced out of the vent in the pole piece. This air flow cools the voice coil. If a relatively low powered amplifier is driven into clipping (to a full square wave for a lot of people), a relatively large portion of the time, the voltage delivered to the voice coil no longer resembles a sine wave as it would with an unclipped signal. While the amplifier's output is clipped, the voice coil is not being motivated to move as far as it should for the power that's being delivered to it and therefore is likely not being cooled sufficiently (since the speaker is driven by a linear motor, the voltage applied to the voice coil determines how far the voice coil moves from its point of rest). At points a, b, d, e, f and h the voltage is changing causing the voice coil to move in the gap and therefore pull in fresh cool air. At points c and g, the voice coil may still be moving a little due to momentum but may not be moving enough to cool properly. Remember that during the clipped portion of the waveform current is still flowing through the voice coil. Since the displacement of the voice coil (and therefore the airflow around the voice coil) is no longer proportional to the heat being generated, the voice coil can overheat. This excess heat may cause the voice coil former to be physically distorted and/or melt the insulation off of the voice coil wire and/or cause the adhesives to fail (especially if the speaker is rated to handle no more than the power that the amp can produce cleanly). If your speakers are rated (honestly) to handle the maximum 'clean' power that your amplifier can produce, slight clipping isn't generally a problem. Severe clipping is more likely to cause a problem. Severe Clipping (square wave): It always amazes me when I hear some idiot driving down the road and the audio is clearly distorted (is that possible . Many people drive their amplifiers into what could be called a square wave output . This means that the power is double but the cooling of the voice coil will not increase in proportion with the power increase (since the voice coil isn't moving as much as it needs to be for the given power dissipation). This will lead to the voice coil overheating. If we compared the output of a 100 watt amp (the one that's clipping) to a 200 watt amp, the 200 watt amplifier would be able to push the speaker as much as 40% farther than the 100 watt amp (depending on the frequency of the signal). This extra travel (in each direction from its point of rest) would result in added airflow around the voice coil. The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave it equal to the peak voltage. For 2 waveforms with equal amplitude the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly. Clean Signal Calculations: P = E^2/R P = 20^2/4 (4 ohm speaker) P = 400/4 P = 100 watts RMS Square Wave Signal Calculations: P = E^2/R P = 28.28^2/4 (the RMS voltage is 1.414 times the RMS voltage of the sine wave) P = 800/4 P = 200 watts RMS Note: If your speakers are capable of handling significantly more than your amplifier can produce, driving them with a clipped signal will not likely hurt them. If the speakers can handle 3 or 4 times the power that your amplifier can produce, there's virtually no way to damage your speakers (no matter how clipped the signal is). If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a clipped signal for extended periods of time may cause speaker damage and/or premature failure. If your speakers are rated for the same power handling as your amplifier is capable of producing cleanly, driving them with a square wave signal for extended periods of time will likely cause speaker damage.

OHM'S law There are 2 base formulae which will help you to understand the relationship between current , voltage , resistance and power . If you have any two of the parameters, you can calculate the other two parameters. OHM'S LAW BASE FORMULAS P=I*E E=I*R TO FIND VOLTAGE E=P/I E=I*R E=SQR(P*R) TO FIND CURRENT I=P/E I=E/R I=SQR(P/R) TO FIND POWER P=I*E P=E2/R P=I2*R TO FIND RESISTANCE R=E2/P R=E/I R=P/I2 P = Power in Watts E = Electromotive Force in Volts I = Electrical Current in Amps R = Electrical Resistance in Ohms SQR = Square Root Note: I use 'E' to represent voltage most of the time but sometimes you'll see 'V' used for voltage. Don't let it confuse you. Remember Fuses: I've been in the electronics repair business since about 1996 and have come to believe that most people don't understand the function of a fuse, or they just like to let the smoke out of electronic devices (transistors, resistors...). Note: Letting the smoke out of an electronic device is a process which converts a useful piece of electronic equipment into a paper weight. Function: A fuse is generally inserted into an electrical circuit for 1 of 2 reasons, either to protect the power source which includes the wire that connects the power supply to the electrical device, or to protect the electronic equipment. The electronic equipment manufacturers specify a fuse rated to open the electrical circuit before damage can be done to the device or open the circuit if the electronic device fails in some way (electronic devices may pull excessive current when they fail). If a fuse larger than the specified fuse is used, a small mistake when installing the equipment may cause catastrophic failure of the equipment. WHEN, not if, WHEN you're thinking of replacing a blown fuse with a higher rated fuse ask yourself if you know more than the engineer who designed the equipment. Don't get in a hurry when installing electronic equipment. Take the time to go get the right fuse. 50 cents for a fuse is better than $50 labor plus the cost of the replacement parts for a repair job. -------------------------------------------------------------------------------- In most cases, the wire size is reduced at the point of distribution. ANY time that the wire size is reduced, you must add a fuse in the line. Using multiple small wires in place of a larger wire: Some people may want to use a bunch of smaller, individually insulated, wires (like ten 14g wires) in place of one larger wire (like a 4g wire). This may be OK as far as current carrying capacity is concerned but the problem comes in when you have to fuse it. A 4g wire can handle about 125 amps. A 14g wire can handle about 15 amps. If one of the strands of the 14g wire is shorted to ground (like where it runs through the firewall), the main 125 amp fuse would not blow and the wire would burn. To properly protect the multiple strands of insulated wire, you'd have to use ten 15 amp fuses in individual holders (each wire would have its own fuse). I know that this may be an 'off the wall' situation but I've had several emails about this (generally concerning two or three 8g wires and a large wafer fuse) so there are, at least, a few people who don't fully understand this. Suggested Fuse Sizes: Wire Gauge Recommended Maximum Fuse Size 00 awg --------400 amps 0 awg--------- 325 amps 1 awg--------- 250 amps 2 awg--------- 200 amps 4 awg--------- 125 amps 6 awg--------- 80 amps 8 awg--------- 50 amps 10 awg------- 30 amps 12 awg------- 20 amps 14 awg-------- 15 amps 16 awg-------- 7.5 amps These are the recommended maximum fuse ratings for the corresponding wire size. Using a smaller fuse than what's recommended here will be perfectly safe. Fuse Opening Time: A fuse does not blow when the current reaches its rated current. It is designed to pass its rated current without opening. A fuse will take varying times to blow under different conditions. A fuse will pass significantly more than its rated current for a very short time. It may take 10 minutes or more to blow a fuse at 25% over its rated current. The table below is an example of the specifications for a slow blow fuse. You can see that a 20 amp fuse may pass 40 amps of current for as long as 5 minutes before blowing although it probably wouldn't take a full 5 minutes to blow. The times for other fuses will be slightly different. %of amp rating Opening time 110% 4 hours minimum 135% 1 hour maximum 200% 5 minutes maximum Circuit Breaker: A circuit breaker's function is, like a fuse, to break a circuit path when a predetermined amount of current is passed. In my opinion, circuit breakers should never be used to protect electronic devices such as radios, amplifiers or crossovers. Most common circuit breakers (thermal snap action) take far too long to open the circuit path. This does not mean that they are not useful. When they are properly selected they do a good job of protecting wiring and devices such as electric motors. Some breakers are self resetting. Others require manual resetting. I strongly recommend using a manual reset type. This will allow you to watch for any problems when the circuit path is restored.

Prior to 1970, there were no easy or affordable methods accepted as standard in the industry for obtaining comparative data about loudspeaker performance. Recognized laboratory tests were expensive and unrealistic for the thousands of individuals needing performance information. Standard measurement criteria were required to enable manufacturers to publish consistent data for customers to make comparisons between various loudspeakers. Thiele-Small Parameters In the early seventies, several technical papers were presented to the AES (Audio Engineering Society) that resulted in the development of what we know today as 'Thiele-Small Parameters'. These papers were authored by A.N.Thiele and Richard H. Small. Thiele was the senior engineer of design and development for the Australian Broadcasting Commission and was responsible at the time for the Federal Engineering Laboratory, as well as for analyzing the design of equipment and systems for sound and vision broadcasting. Small was, at the time, a Commonwealth Post-graduate Research Student in the School of Electrical Engineering at the University of Sydney. Thiele and Small devoted considerable effort to show how the following parameters define the relationship between a speaker and a particular enclosure. However, they can be invaluable in making choices because they tell you far more about the transducer's real performance than the basic benchmarks of size, maximum power rating or average sensitivity. Fs------This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well. Re--------This is the DC resistance of the driver measured with an ohm meter and it is often referred to as the 'DCR'. This measurement will almost always be less than the driver's nominal impedance. Consumers sometimes get concerned the Re is less than the published impedance and fear that amplifiers will be overloaded. Due to the fact that the inductance of a speaker rises with a rise in frequency, it is unlikely that the amplifier will often see the DC resistance as its load. Le--------This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. Q Parameters---------Qms, Qes, and Qts are measurements related to the control of a transducer's suspension when it reaches the resonant frequency (Fs). The suspension must prevent any lateral motion that might allow the voice coil and pole to touch (this would destroy the loudspeaker). The suspension must also act like a shock absorber. Qms is a measurement of the control coming from the speaker's mechanical suspension system (the surround and spider). View these components like springs. Qes is a measurement of the control coming from the speaker's electrical suspension system (the voice coil and magnet). Opposing forces from the mechanical and electrical suspensions act to absorb shock. Qts is called the 'Total Q' of the driver and is derived from an equation where Qes is multiplied by Qms and the result is divided by the sum of the same. As a general guideline, Qts of 0.4 or below indicates a transducer well suited to a vented enclosure. Qts between 0.4 and 0.7 indicates suitability for a sealed enclosure. Qts of 0.7 or above indicates suitability for free-air or infinite baffle applications. However, there are exceptions! The Eminence Kilomax 18 has a Qts of 0.56. This suggests a sealed enclosure, but in reality it works extremely well in a ported enclosure. Please consider all the parameters when selecting loudspeakers. If you are in any doubt, contact your Eminence representative for technical assistance Vas/Cms--------Vas represents the volume of air that when compressed to one cubic meter exerts the same force as the compliance (Cms) of the suspension in a particular speaker. Vas is one of the trickiest parameters to measure because air pressure changes relative to humidity and temperature

Amplifier bridging is simply using 2 driven output channels to drive a common load. For 2 channel amplifiers, one left signal and one right signal is used to drive a mono speaker load. Keep in mind that mono and bridging are not necessarily the same. Mono means that there's only one output signal. There could be more than one speaker but each speaker will have the same output. Bridging means that you are using more than one source of power to drive a load (speaker). The sources of power are one each output from either channel of the amplifier. A long time ago, amplifiers had signal on the positive output speaker terminals only. To bridge one of those amplifiers, you'd have to use some means to invert the signal on one channel (remember the old 'bridging modules' for Orion amplifiers?). Today's bridgeable amplifiers have an inverted channel as part of their design. For many amplifiers, the left positive and right negative are are the signal outputs. A few use the left negative and the right positive. Others still (mostly mono amplifiers that are to be used in bridged pairs) require that you choose 0

hmmm----new power supply---new output devices---new transistors----the usual---should cost about 50$ for the parts and a few hours at the bench. PS---it will be a while for me to touch anything now---i just closed down my test bench area---too cold in North Dakota now to work outside for too long.

what all would you like to know?

just tell me what mods you want----more voltage input--higher current draw---whatever----I am in the process of moving so I won't be able to do it for a while---but I can point you in the right direction on who I would trust to do it.

Hello all, My name is Dave Edwards, I'm staioned in Grand Forks AFB, North Dakota, I WAS in the Air Force, I just finished a 5 year tour. I am so damn close to my BSEE degree I can smell it---4 years in work. I have been into car audio for about 12 years, I rebuilt my first amp when I was 13, now I build amps,subwoofers,crossovers, pretty much anything I need. I worked as a System Designer/Consultant for Ampmanaudio.com before it went under. I try to learn as much as I can on the subject and I hope to pass my knowledge onto you.

thank you all----I will be here when needed.

hi----it's me---Dave Edwards here

copied from the Basic Car audio web site and from FXN A power amplifier takes an input signal, usually a preamp level signal, which has both low current and low voltage characteristics, and produces an output which will have higher current and voltage levels. The power supply available to the audio output IC in a head unit is limited to the battery voltage of the vehicle. This means that the head unit can produce an audio signal with a limited (by the battery voltage) voltage swing, and therefore a limited power output to the speaker. Most amplifiers have a special circuit (switching power supply) to boost the available battery/charging system voltage to a higher voltage. The higher voltage developed in the amplifier's internal switching power supply will allow the audio output voltage swing to be greater. This allows the amplifier to produce more power into the speakers connected to the amplifier's output terminals. Most amplifiers will have some sort of level or "gain" control. This control is used to match the output of the head unit to an amplifier. The maximum audio output voltage from different head units will vary. If there were no gain controls, some head units would not be able to drive the amplifier to its maximum power level. Other head units may drive the amplifier to full power at a fraction of its volume control's range. Virtually all amplifiers have battery, ground and remote connections which must be connected for the amp to operate. The battery connection is the high current +B source that's connected to the battery via a properly fused wire. The size of the power wire is determined by the current the amplifier draws and the length of the wire (from the battery to the amplifier). The ground is another high current connection and is connected to the chassis (body/floor pan) of the vehicle. The ground wire is typically as large as the power wire. The remote connection is a low current control input that tells the power supply of the amplifier to power up. The remote input current for amplifiers varies with the amplifier and the model. Some draw minimal current. Others draw a little more. The upper limit of a properly functioning amplifier is approximately 50ma (0.05 amps). If you're using/controlling more than 2 amplifiers, it is (in my opinion) much better to use a relay to control the amplifiers. Actually I really prefer having a relay in the remote circuit (no matter how many amplifiers I'm using) because it protects the head unit's remote output circuit in case of a short circuit. The input circuit (sometimes called the 'front end') generally employs a noise cancelling circuit which compares the signal on the center conductor (the audio signal) to the signal on the RCA shield (which generally has little or no signal and is only used as a reference) and amplifies the difference between the two. The input impedance is the impedance (that the signal source 'sees') from the center conductor to the shield on an unbalanced input circuit. A typical input impedance would be ~10,000 ohms but some amplifiers may have an input impedance of more than 50,000. If the input circuit uses a mini DIN type connector, the input impedance could be measured from one signal terminal to the other or from the signal terminals to the shield ground. Ideally, the impedance should remain constant throughout the audio band. More than a few amplifiers employ some sort of high frequency noise filter which will cause the input impedance to fall slightly at the upper end of the audio spectrum. These filters are designed to reject high frequency noise from the amplifier's switching power supply. It should also remain constant regardless of the position of the gain control. Some amplifiers (especially budget amplifiers) will have varying input impedance when the position of the gain control is changed. Head units (or equalizers, crossovers...) with low output impedance will handle these variations better than standard head units. Generally, a head unit with high output impedance will have reduced high frequency response if the amplifier's input impedance isn't consistant across the audio spectrum. Unbalanced Input Circuit: This type of circuit has a shield ground that's not directly connected to the chassis ground but may have only a few hundred ohms of impedance from the shield to ground. This type of circuit would be designed to accept a single ended signal (signal only on the center conductor). Balanced Input Circuit: Some Amplifiers have balanced inputs. This means that both the center conductor and the shield (if they're using RCA type connectors) can accept an audio signal. If the amplifier uses RCA type connectors and has balanced inputs, it likely uses the chassis ground as a reference (which is a testimony to the noise rejection abilities of a balanced input circuit). If the amp uses a mini DIN or some sort of professional audio connector, the connector will have provisions for two audio signals per channel and a dedicated ground (reference) connection. Highly regulated amplifiers employ PWM switching power supplies. Unregulated amplifiers don't use Pulse Width Modulation to maintain a constant rail voltage. This does not necessarily make one design inherently better than the other. Both designs have their advantages and disadvantages. Capacitor: A capacitor is an electronic device which consists of two plates (electrically conductive material) separated by an insulator. The capacitor's value (its 'capacitance') is largely determined by the total surface area of the plates and the distance between the plates (determined by the insulator's thickness). A capacitor's value is commonly referred to in microfarads, one millionth of a farad. It is expressed in micro farads because the farad is such a large amount of capacitance that it would be impractical to use in most situations. Capacitor and DC voltage: When a DC voltage source is applied to a capacitor there is an initial surge of current, when the voltage across the terminals of the capacitor is equal to the applied voltage, the current flow stops. When the current stops flowing from the power supply to the capacitor, the capacitor is 'charged'. If the DC source is removed from the capacitor, the capacitor will retain a voltage across its terminals (it will remain charged). The capacitor can be discharged by touching the capacitor's external leads together. When using very large capacitors (1/2 farad or more) in your car, the capacitor partially discharges into the amplifier's power supply when the voltage from the alternator or battery starts to fall. Keep in mind that the discharge is only for a fraction of a second. The capacitor can not act like a battery. It only serves to fill in what would otherwise be very small dips in the supply voltage. Capacitors and AC voltage: Generally, if an AC voltage source is connected to a capacitor, the current will flow through the capacitor until the source is removed. There are exceptions to this situation and the A.C. current flow through any capacitor is dependent on the frequency of the applied A.C. signal and the value of the capacitor. TECH TIP: For a good ground: Get a 3/8 inch bolt, nut and lock washer, find a place on the body that can be accessed from the inside of the vehicle and out. You must be able to get to both sides so that you can hold the nut from turning when tightening it up. Drill a 3/8" hole for the bolt, making sure NOT to drill through any fuel lines, brake lines, the gas tank or anything else. Scrape the area under the bolt (inside the vehicle) to remove ALL paint and primer then bolt the ground wire's ring terminal down with the 3/8 inch bolt. As a side note: For grounding devices that draw only a few amps (like crossovers, head units and equalizers), you can use virtually any type of screw. Many people warn against using the black oxide coated screws but it won't make a big difference because the electrical connection is between the ring terminal and the metal surface that's been sanded clean and not through the screw. The screw simply holds the ring terminal to the metal. Amplifier mounting: DO NOT mount an amplifier on your subwoofer box. I know that there has been a great deal of discussion over mounting an amplifier to an enclosure and many people do it all of the time with no problems but those people probably build good enclosures from 3/4" (or thicker) MDF with extensive bracing. Most people (especially young impatient people) are too lazy to do that and build unbraced enclosures from 5/8 MDF. These enclosures will flex considerably more than a proper enclosure and will likely cause amplifier failure if the amp is mounted to the enclosure. REASON: When the woofer(s) moves in or out, the box flexes and therefore causes the sides of the box to vibrate. This vibration is transferred to the amplifier mounted to the box. All of the electrical components in the amplifier have mass. Inertia (an object in motion tends to stay in motion, an object at rest tends to stay at rest) tells them to stay at rest, the box vibration is trying to make them move. The energy from the box's vibration is transferred to the components through the electrical leads which are soldered into the circuit board. All of this will cause the components to break loose and therefore cause the amplifier to fail prematurely. Basically, the amplifier will commit suicide! I'm not telling you this because someone told me it was bad. I've been repairing amplifiers since ~1985. Virtually every amplifier that's come into my shop with parts rattling around inside them have been mounted on the speaker box. It causes the legs of the semiconductors to break (which causes amplifier failure). It causes the capacitors to break off of the board (which can cause catastrophic amplifier failure). It causes solder joints to break on the semiconductors mounted to the heat sink. It causes transformer windings to grind into one another (which causes lots of smoke to pour out of your amplifier). People who repeatedly tell others to mount their amps on the speaker box because they've never had a problem remind me of people who drink and drive and say there's nothing wrong with it because they've never crashed their vehicle. Eventually, in both cases, problems will arise. AMPLIFIER INSTALLATION NOTES: When installing an amplifier: ----Disconnect the ground wire from the battery. It doesn't really matter which one is removed because removing either connection from the battery (positive or ground) will break the circuit but if you let the wrench touch to ground (any metal surface) when removing the positive wire, you may do significant damage or seriously injure yourself. If you let the wrench ground out when removing the ground wire, you won't have any problems (except maybe scratching the paint). ---- If you don't remove the wire from the battery, at the VERY least remove the fuse (or open the breaker) from the power wire which delivers power to the amplifiers. -----When making the power and ground connections on the amplifier, connect the ground wire first. I know it is tempting to connect the RCA cables first because it is instant gratification (having made a connection) but you may damage the head unit or the input section of the amplifier if the amplifier tries to ground through the RCA shield connection. -----If the amplifier has screw down terminal blocks which are designed to accept either bare wire or spade terminals, use the spade terminals. If you insert bare wire into the blocks, you may have a strand or two of wire touch to the neighboring terminal which is easily enough to convert the amplifier into a paperweight. -----Mount the amplifier down before moving the vehicle. If the amplifier falls or slides against anything, there is a chance that it will be damaged seriously enough to warrant a trip to a repair shop. I know how cool you are (because I know how cool I was at 15 or 16 years old) and nothing could possibly happen but... mount it down anyway. -----When making the ground connection for the amplifier, the floor pan of the vehicle is a better choice than some of the braces and other metal structures that you may want to use for ground. Braces and other such structures are sometimes connected to the vehicle's chassis (body) by a few spot welds which will provide a less than optimum ground return path. ------If the amplifier's ground is properly connected to the body of the vehicle, it will provide a better return path to the charging system's ground than will a ground wire run back to the battery. This is especially true if the ground strap from the engine block to the chassis is upgraded. Amplifier Classes: Most mobile amplifiers use complementary transistor pairs to drive the speakers. In this configuration there is a transistor (or group of transistors) which conducts current from the positive power supply voltage for the positive half of the audio waveform and a different transistor (or group of transistors) which conducts current from the negative power supply voltage for the negative half of the waveform. There are some amplifiers which use the same transistor(s) to drive both the positive and the negative halves of the waveform. NOTE:Amplifiers in classes A, B, and AB operate their output transistors in a 'linear' mode. Class 'D' amplifiers operate their outputs in 'switch' mode. Mode examples: Linear mode: Imagine that you are the amplifier's output device(s) and you must support a 10 pound iron weight (the speaker load). The most difficult method (linear mode) would be to hold the weight straight out in front of you. This would very roughly simulate the linear mode architecture. Your muscles would start to ache in a short amount of time. Think of this pain as the power dissipation in output transistors. Switch mode: In this example, you can support the weight in one of two positions. In the first position, you can hold the iron weight directly over your head with your elbows locked so that your're not really using very much effort to support the weight. In the second position, you would let the weight hang down by your side. This would also use very little effort from your muscles. If you held it directly over your head half of the time and by your side for the other half of the time, it's position would 'average' out to be the same as if you held it out straight in front of you like in the previous (linear mode) example. This would roughly simulate the switch mode which we will discuss later in this page. You can see that with this method (switch mode), there would also be little pain (power dissipation) involved in supporting the weight. CLASS 'A' Many class A amplifiers use the same transistor(s) for both halves of the audio waveform. In this configuration, the output transistor(s) always has current flowing through it, even if it has no audio signal (the output transistors never 'turn off'). The current flowing through it is D.C. A pure class 'A' amplifier is very inefficient and generally runs very hot even when there is no audio output. The current flowing through the output transistor(s) (with no audio signal) may be as much as the current which will be driven through the speaker load at FULL audio output power. Many people believe class 'A' amps to sound better than other configurations (and this may have been true at some point in time) but a well designed amplifier won't have any 'sound' and even the most critical 'ear' would be hard-pressed to tell one design from another. NOTE: Some class A amplifiers use complimentary (separate transistors for positive and negative halves of the waveform) transistors for their output stage. CLASS 'B' A class 'B' amplifier uses complimentary transistors for each half of the waveform. A true class 'B' amplifier is NOT generally used for audio. In a class 'B' amplifier, there is a small part of the waveform which will be distorted. In a pure class 'B' amplifier, the output transistors are not "biased" to an 'on' state of operation. This means that the the part of the waveform which falls within this .6 volt window will not be reproduced accurately. The output transistors for each half of the waveform (positive and negative) will each have a .6 volt area in which they will not be conducting. The distorted part of the waveform is called 'crossover' or 'notch' distortion. Remember that distortion is any unwanted variation in a signal (compared to the original signal). CLASS 'AB' As we said earlier, a class 'A' amplifier is very inefficient. This is not good for a car audio amplifier. We also said that a class 'B' amplifier will cause a signal to be distorted, which is not good in any audio amplifier. A class 'AB' amplifier is the best compromise. A class 'AB' amplifier is a class 'B' amplifier which has a small amount of "bias" current flowing through the output transistors at all times. This eliminates virtually all of the crossover distortion. The bias current is flowing because the output transistors are always conducting current (even without an audio signal). This differs from a pure class 'A' amplifier in the amount of current flow. A pure class 'A' amplifier has an enormous amount of current flowing through its output transistors with NO audio signal. A pure class 'B' amplifier has NO current flowing through its outputs with no input signal. A class 'AB' amplifier is much more efficient than the class 'A' but without the distortion of the class 'B'. MANY of the car audio amplifiers which claim to be a class 'A' amplifier are just a high bias class 'AB' design. These amplifiers are only class 'A' at very low power output levels. At higher power levels, one of the output transistors will switch off while the other output transistor is conducting. I don't want you to think that I am telling you that there are no class 'A' amplifiers. There are a few high quality mobile amplifiers which are a true class 'A' design. CLASS 'D' We said that class 'A' amplifiers were VERY inefficient. Class 'AB' amplifiers are also inefficient but are more more efficient than class 'A' amplifiers. Class 'AB' mobile amplifiers are generally 60% efficient when driving a 4 ohm load at maximum power (just before clipping). The reason that these amplifier configurations are inefficient is because there is a difference of potential (voltage) across the output transistors and current flowing through the output transistors. When you have voltage across the device and current flow through the device, there will be power dissipation in the form of heat. The power needed to produce this heat is wasted power. When there is (virtually) no voltage drop across a device (such as a large piece of wire or a transistor), there can be a significant amount of CURRENT flow through the device with (virtually) no power dissipation. This means that there is virtually no heat given off (highly efficient). The inverse is also true. If you have a significant amount of VOLTAGE across the device (transistor, wire...) but no current flow through the device, again, there will be no wasted power. OK, now to the point. A class 'D' amplifier, which may also be known as a switching amplifier or a digital amplifier, utilizes output transistors which are either completely turned on or completely turned off (they're operating in switch mode). This means that when the transistors are conducting (switched on) there is virtually no voltage across the transistor and when there is a significant voltage across the transistor (switched off), there is no current flowing through the transistor. This is very similar to the operation of a switching power supply which is very efficient. Dave Edwards