When you buy an audio system, the amplifier is the heart of your system. 

Usually the modern amplifier box has three internal units : Pre amplifier, amplifier and receiver.

Historically all these units had separate boxes. There are still some very expensive separate amplifier /  preamplifier systems. Made for the real life audio enthusiasts. When stereo and HiFi came in 60's, these three apparels were usually packed together. Just like now. In the 80's there was period, when receivers were sold in separate boxes. Two box systems went out of fashion during the 90's.

 The first HiFi tape recorders and record players had also small built-in pre-amplifier amplifier systems. All-In-One apparel  was the way apparels were made before stereo and HiFi era.

The basic demands for the amplifier are the output channels, output powers and the connectors.

Multi channel amplifier

When buying a multi channel amplifier for music listening, you should check, that all channels can be used with common stereo recording. In some multi channel amplifiers the additional channels are muted during music listening. 

If you have a 6 x 80 W amplifier, and the back channels are muted during stereo play, you get only 2 x 80 W powers for music listening. When the stereo signals are lead to all amplifier units, you get 2 x 240 W maximum powers for listening music.

Power demands

If you are changing your amplifier, without buying new speaker system, the power levels of your amplifier comes from the speaker system. Amplifiers continuous power must always be lower or equal than the continuous power of the speaker system. The peak powers must also go in same way. The music power of the amplifier must be lower than the music power of the speaker system. 

When you buy a complete new speaker set, you must match powers. In the way you do with an existing system. 

When you buy only few new speakers, the matching must be done with the weakest  speaker in the set.

Self made / repaired speakers

If you build speakers from elements, the power demand for each element is equal to the box. Let's say, that you build  a 2-way speaker system for 100 W continuous and 150 W music power, with 4 ohm resistance. All elements ( basses,  and tweeters )  you put in to the speaker must be capable of handling the 100 W continuous and 150 W music power, with 4 ohm resistance.  If some of the element is 8 ohm element, it must handle 50 W continuous and 75 W music power.

You cannot sum the powers, the power which runs in the wires goes to each element. It is the way electricity flows in the wire. If you put the inlet wires in the big bass element first and the next in chain is mid-tones and the last is tweeter, the bass element does not reduce the power which flows to next elements. Speaker system operates with alternate current.

Frequency range

Frequency range of the young, healthy adult is 20 - 20 000 Hz. At the older age your capability to hear high tones fades slowly. 

- The frequency range for synths with standard MIDI / Sound Fonts  is 32Hz - 16 600Hz
- From the common instruments piano has the widest scale : 55Hz - 8 400Hz
- Range for classical-singers are between 150Hz and 2500Hz
- Common male voice is app 700 Hz
- Common female voice is app 1 000 Hz

From the above we learn that, when buying a system, it should have app 30 to 20 000 Hz frequency range. And when you buy the system, it goes with the weakest link. Both amplifier and speakers must fulfill the demand. 

Later we learned - in practice - that playback frequency range follows recording with common volume levels. If the speakers / amplifier sounds good with your favorite music, there is no need to worry about the announced frequency range. [ See the speaker page ]

Output powers - Listening test

Output power on different frequencies

The sound levels in different frequencies are dependent on output powers - your system produces and unleashes to air - within the whole frequency range.

Amplifiers output power is measured from 1 000 KHz frequency, with app 1 % distortion. From the diagram you see, the whole power curve ( from all frequencies ), when amplifier is played with full power. This curve as whole is very important. The curve varies from amplifier to amplifier. 

This curve is also the thing, which makes the difference in bass and treble playbacks. This phenomena was discovered in late 70's, but for some strange reason manufacturers no longer  releases these curves. So, the only way to find the right amplifier is to listen and compare different amplifiers.

In principle you can fix this curve with Graphic Equalizer. In practice you should use analog equalizer. Digital EQ's tend to create all kinds of unwanted sound effects to the sound.

But when you search basses, there are some amplifiers, which ignores bass boosts. + 24dB boost to low frequencies has minor effect in playback. Also then when you play with lower volume levels. When this happens, there is something wrong with transistors. They are already doing the best they can. You can detect this special feature from your amplifier with two amplifiers.

Usually the lack of basses and trebles come from the speakers, but it also possible, that the amplifier has difficulties with playback.

Very typical situation for this to happen, is a situation where a manufacturer tries to attract  you with bigger nominal output power. The power source is changed, pre-amp is tuned so, that it minimizes the distortion at 1 000 kHz, and transistors are the same as a before : Switch to a new, more powerful 5x120W version from the good old 4x40 amplifier, can be a very big disappointment. No longer possible to inform everyone around, that we are having lots of booze and fun tonight.

Separation - Listening test

Separation means amplifier's capability to play individual instruments from the recording. 

Poor amplifier mixes all instruments together, you cannot for example hear Boys' brightness attractions very clearly. Small attractions makes your listening experience far more enjoyable, than the mixed mess / noise you get from the poor quality amplifier.

There isn't a system with what you can measure this feature. Only the listening tests are available. People who writes reviews from audio apparels, usually write a comment about the way amplifier performs the separation.

Good quality headsets are the best devices for the separation capability check. They fade the external noises, and you hear the music and it's details clearly. 

The speakers have a similar kind feature.

Connectors

Connectivity is rather important thing in remote controlled amplifier. If you have analog apparels, the amplifier must have analog RCA connector in the back. If you have digital / optical apparels, you got to check that there are enough connectors in the amplifier.  

Besides microphones and record players, you can plug the apparels into a randomly selected connector in the back plate. They are compatible with each other, the names in the back plate refer to the names and lights in the front and remote control, only.

If you have a record player with analog output, the record player needs specific connectors. milliVolts and resistances are different than in other analog devices. 

Analog microphone needs also specific connectors. They can be connected to microphone jacks only. milliVolts and resistances are different from all the others.

If you have an equalizer or some other external sound enhancer apparel, there aren't very many new multi-channel amplifiers, where you can do Enhance-All-Line Inputs-With-One Apparel connectors.

If you have very old European apparels with three or five pin DIN connectors, these apparels can be attached to the RCA jacks. The rules are the same than in RCA connectors. DIN plugs have shared ground wire, and therefore there aren't pins for each and every wire in RCA-connection. Input - output RCA connection has 8 wires, and 5-pin Din has only 6.

HDMI-Connector

HDMI is a digital connector, which transfers multi-channel audio and video stream in one wire. In the better multimedia amplifiers each line input has also HDMI input and coaxial input for analog video. Then they have one to two output connectors for display and tv-set.

When you use multimedia amplifier as your primary device, and you have more than one video source, the picture on the screen changes when you change the current line input in amplifier.

When you use your Tv set as primary device, you can bring the digital sound to amplifier and sound system with HDMI wire.

In our studio / restroom system there are wires to both directions.  The TV set takes Blue Ray and VHS videos in, and sends analog sound signals to amplifiers. The music and videos from the computers go to the amplifier first, then the video signal - if any - goes to big screen with one HDMI wire. In the system there are 6 CD-DVD players in the computer network. The multimedia disk files comes also from the computer network. Web-stuff comes from the isolated web-feeder computer.

Future reservation

Cheaper Blue Ray players have only digital RCA output and HDMI output for getting music and video out from the player. Therefore it is important, that your amplifier has both HDMI and digital RCA inputs. At least one for the Blue Ray player. Blue Ray players do not last as long as other apparels, during the lifetime, you are almost certain to buy new players for the system. 

If your current player works with analog connectors, HDMI and digital RCA can be considered as future reservations.

HDMI and DVI

Video signals in  HDMI and computers' DVI connectors are compatible with each other.  The difference is in the thing, that the DVI connector at the back computer do not have audio output signals. There aren't any standards for connecting graphics cards and sound cards into single HDMI output. 

Adapters with what you could create HDMI connection from computers display and audio outputs are rare and hard to find. There are adapters for converting DVI to HDMI ( without audio ) and adpaters for creating HDMI signal from VGA and analog audio outputs.

USB-Connector

New audio-visual apparels have USB connectors. These connectors have usually limited capabilities to handle multimedia files. 

USB connectors need FAT-32 formatted USB memory cards / sticks and hard disks. 

USB devices take the power from the USB-connector. The USB hard disks needs more power than memory cards. If cards work and disks don't, the USB connector does not provide enough power for the disk. There are two headed USB wires for hard disks. The thinner wire is power wire, it can be connected to any USB connector. It doubles the power the disk gets.

The supported files are usually listed in apparels technical specifications. USB connectors in multimedia amplifiers usually handle only music files. MP3, WMA and WAV are the common music file formats. 

MPG-1, MPG-2, MP4, WMV and AVI are the most common video-file formats. All these video files can be created without either sound or video. In Web there are two additional common file types :  The Adobe flash player's FLV, and Real Player's RM files. These are video files. You need a software player for playing back these files.

LAN-Connector

New audio-visual apparels have quite often LAN connectors. If you have a router ( wirelss of wired ) for your web-connection, you can access some web-based multimedia disk storages through the LAN-WEB connection.

Usually the LAN connectors have the same capabilities than USB connectors. If you have a FAT-32 formatted hard disk volumes in your computer, you can access the multimedia files on the shared FAT-32 hard disk volumes  In the property sheets for the volumes there is tab for sharing files.

Problems in LAN connections are in Windows operating systems. Windows Me ( from the year 2000 ) is the very last operating system, which allowed you format big hard disks to FAT-32 system. The actual size limit for the FAT-32 hard disk is app 2 000 GB, and the Windows Operating systems, starting from Windows 2000 allows you to format only 32 GB FAT-32 partitions / volumes. The same limitations are in force also when you play with memory cards / sticks. After you are through with the formatting, your problems are over. There aren't any problems with FAT-32 disk usage.

 

Where are they

In ready made speaker boxes powers and ohms are always printed in the back panel.
Amplifier's power are in the owners manual. In the technical specifications.

Nowadays musical, maximum and peak powers are the same. When HiFi came, all three were always measured and announced powers were different. No one knew what they were.

Real life play

In real life, sounds always come from certain direction. Usually front. Then there is small echo from the walls. When classical orchestra plays the audience is quiet during the play. When commercial band makes live performance the audiences keeps noise during the play.

From this diagram you see common stage layout for small pop-rock band. Singer stands in front center. Guitarist and bassist on left and right.

In the back row there are drums in the center, chorus and keyboards. Quite often there are background singers and keyboard players on both sides.

The required space for the pop-rock group is small. Less than 10 meters in width and less than 5 meters in depth.

Putting all together

After we compose these facts together, we notice that the current multi channel system is made for movies only.

In musical multi channel system you use one additional channel pair in front. New outer left-right channels are much like stereo effect enhancers. They concentrate more on the instruments on their sides.

When composed from the diagram, the new Left-Outer would play chorus and solo guitarist louder than other channels. The new Right-Outer would play bass and keyboard louder than the other channels.

In 6 channel system you have small additional speakers on the sidewalls. These small speakers plays back music from all channels, with equal weight. The sounds in the small sidewall speakers are the echoes from walls and noises from audiences.

Ooops !

Where do I get the music for my brand new 6-channel audio system ?
Nowhere. The stereo recordings are the only available recordings from the music. 
But you can use the theory, when you plan the places for the speakers. 

In this diagram you see the ideal speaker system layout for listening music. In stereo.

The channels for the speakers should be set so, that front speakers are connected to channels 1+2 and 5+6. The smaller yellow boxes go to the channels 3+4, 

This layout is fully compatible with surround systems, which are used in  movies. Channels 5+6 can and should be assigned as top-front speakers. It is a standard option in 7.1 channel surround systems. It is hidden to amplifiers speaker layout settings. 

The wide magenta box in the middle is display or TV-set. 

Tower speakers

Left-right front speaker pairs can be installed above each other. When you listen stereo music, the tower has no effect to stereo impression. On the other hand tower saves floor space. The tower makes it very easy to update 4 channel speaker system to 6 channel system.

When you build the tower the upper box goes upside down. In between the boxes you need a thin padding. Cloth, etc. The cloth prevents resonance noises and movements of the upper box.

High two meter towers, made from the same speakers, looks usually better, than two speakers on the floor.

In this diagram you see the double amplifier system, which is used for checking Boys' music.

There are two systems, which can be used separately and together. The back system is the old good quality audio system. Which was used for tests. The primary system has high towers in the front and small speakers near the side walls. 

Small speakers were placed near towers, because towers faded the mid-tones. The small speakers bring mid-tones back to the play.

The gray box beside the display, contains Blue-Ray player and VHS recorder.

The total continuous amplifying power of the system is 2 x 900 Watts / 6 ohms.

With current speaker configuration the maximum continuous power is 2 x 410 W / 8 ohms.

Mixing music and playback

When you mix music with audio apparels, frequencies are not equal. Mid-A is used to tune instruments. In music Mid-A vibrates 440Hz. But in electronics the same vibration is 880Hz.

The same system goes to all frequencies. They are either multiplied or divided by 2. 

In audio world frequencies are calculated so, that positive and negative bouncing are counted. In music world positive and negative bouncing are counted as one vibration, only:

In music world human voices varies from 83 to 1050 Hz. But when you enhance sound with Graphic Equalizer, human voices are adjusted with 1 000 Hz slider.

Male voice	Notes	Music	Audio
Bass	E2-E4	83-330	166-660
Baritone	F2-F4	87-350	175-700
Tenor	C3-C5	130-530	260-1060
Counter-Tenor	G3-D5	147-587	300-1180
Females
Contralto	F3-F5	165-700	330-1400
Mezzo-Soprano	A3-A5	220-880	440-1760
Soprano	C4-C6	260-1050	520-2100

From this table you find out the common ranges for the classical voices. C4 is the C in the center of the piano's keyboard.

Difference between piano and synth

The difference between piano and synth is two octaves. When piano has three octaves around the center, synths have four octaves. Without pedals and switches synth has 9 + 88 + 12 keys, 109 in total.

Modern Piano has 88 keys. In the low end, piano starts from A0. Not from C1, which would make full octave difference. In the high end piano ends to C6 and synth to C7.