hi-fi, marche di hi-fi, informazioni sull'hi-fi, altoparlanti e acustica, speakers and acoustic, valvole, tubes
hi-fi, marche di hi-fi, informazioni
sull'hi-fi, altoparlanti e acustica, speakers and acoustic, valvole, tubes
The purpose of general home audio is to make an enjoyable sound. The "hifi" is short for "high fidelity". The word "fidelity" means the quality or state of being faithful, accuracy in details, exactness and the the degree to which an electronic device (as a record player, radio, or television) accurately reproduces its effect (as sound or picture). The purpose of hi-fi, however, is fidelity: to make a sound faithful to the original performance. Whether it is enjoyable or not! (quite often very good playback system can reveal that the recordings are not ideal). With HiFi-system you get "enjoyable sound" by purchasing enjoyable recordings that sound good when accurately reproduced.
An "enjoyable sound" comes from having good source material, accurate recording and reproduction, and a good listening environment. The goal of most "legitimate" recording is to preserve the original as accurately as possible. Sound recording are intended to be heard through a "neutral" reproduction system which does not color the sound in any way (such thing does not exist, but try to get as close to it as you can).
The purpose of a sound recording media and playback device is to get the sound to the amplifier as accurately as it can. The purpose of an amplifier and speaker is to provide "The closest approach to the original sound". An idea amplifier is "a straight wire with gain". An high fidelity amplifier must, by definition, reproduce an enlarged version of the input, with nothing added, nor taken away. Building a resonable amplifier is nowadays quite easy and any competent electronics engineer should be able to design a power amplifier, if he or she knows their trade.
Speakers is a hard question in any audio system. They are the things which color the sound mostly. You can do a lot of engineering tests on them, but they will tell if a speaker bad one. Spaker tests won't tell if the speaker is the one that sounds good. For this, you have to trust your ears.
The epurpose of interconnection cable is to carry signal between devices without altering them (without noise, interference, frequency response problem etc.) Anything that does any more than than becomes a sound effect unit. There are artifical things you can do to several of those links in the chain to make up for deficiencies. Sometimes one makes the sound one wants, so if indeed one likes certain ACCENTS and COLORS in audio, the system components could be selected for this in mind (and not being as accurate as possible). Some people seem to enjoy music played with certain forms of distortion, rather than a more accurate sound (most well know could be "tube distortion").
Typical distortion caused by audio equipment are noise and harmonic distortion. Harmonic distortion describes a nonlinear property of systems where the output of the system has added energy at frequencies that are at integer multiples of the frequencies input to the system. To describe what is hardmonic distortion let's say you have a 1kHz signal of 1 volt. If you run this signal through an amplifier and spectrum analyzer, you will see that there are also some output voltage at 2kHz, 3kHz -- all the harmonics. These should me many tens of decibels down from the original in a high quality amplifier. If you sum the values of these harmonics the result is "Total Harmonic Distortion".
Harmonic distortion is but one manifestation of the non-linear behavior of systems: it is not a specific "disease" but one easily observable symptom of a condition which has multiple symptoms, also including intermondulation distortion, for example.
Typical consumer AV equipment (like VCRs), may have an audio source impedance of 5-20 Kohms (some equipments like some CD players and PC soundcards have lower impedance). The parallel capacitance of a long cable will certainly react with this relatively high source impedance to cause some high frequency rolloff. Ideal interconnection cable for high impedance output devices is low capacitance cable (for example RG-59 coaxial cables). A good quality microphone cable is also usable for consumer hifi equipment interconnections, but it's high capacitance can be problem with some equipments.
Audio frequencies aren't much sensitive to the details of the cable construction. All you need is heavy braided shielding and well formed connectors. If you have to happen a long run of cable (many meters) and signal source with high output impedance (few kilo-ohms) then a low capacitance cable is preferred.
Gold plated connectors are great if never subjected to vibration or wear. Once they're scratched, the underlying metal corrodes quickly due to electrolysis. The plain old silver kind are more durable is they are subject to movement and many connections/disconnections.
A cable in audio applications for carrying microphone and line level signals can be modeled as a low-pas filter. A first-order high-cut (or low-pass) filter is formed by an output's source impedance and the capacitance of the cable. The frequency at which a filter attenuates 3 dB is called its "corner frequency". With short cables (low capacitance) and low output impedances, the corner frequency typically occurs well above the audio band. With longer cables and higher output impedances, the corner frequency drops and may drop into the audio band. The formula for the corner frequency is:
1
F = --------------
2 * PI * R * C
where F is the corner frequency in Hz, PI is 3.14, R is the source's output impedance in Ohms, and C is the cable's total capacitance in Farads. A first-order filter has a slope of 6 dB per octave. This means that beyond the corner frequency, the response will drop 6 dB for each doubling of frequency. Generally it doesn't seem likely that you would get detectable loss even at 20kHz unless you have one or more of these conditions: unusually high source impedance (many kilo-ohms), unusually high capacitance cable or unusually long cable length (tens of meters).
There's no need to go nuts with speaker wire either. Use high quality copper to reduce oxidation at the connections. Super-sizing the guage doesn't help since speakers have at least 3 ohms of their own resistance. Just make sure the total cable resistance is very small in comparison.
There is a group of people who truely apriciate their turntables for the subtle differences in sound compared to the other media. You often hear words like 'warmer' and 'true to the art' and 'more natural'. Many HIFI people have stuck to their vinyl guns are listening to their turntables through tube amps
Vinyl, for all it's charm, is technically terribly flawed and inconsistent a medium it simply cannot even be considered in the same class as properly executed cd technology. Vinyl records have limitations in frequency response, signal to noise ratio and many other things. But in many cases talented people in recording company have succeeded to get out very pleasing sounds out of this very limited medium.
By all means make or buy the best turntable you can - there's lots of great music not even available on cd, and there were many cd's improperly mastered using masters intended for LP's. These particular recordings contributed to a bad reputation for cd technology early on, and the LP of same might sound better if you don't mind the surface noise, etc. It is true that certain CD recordings were not as true to the original vinyl versions as some listeners used to those vinyl versions would like. Sometimes there can be differences in loudness and punch with vinyl versions sounding better or more pleasing.
Typical record player cartridge outputs a very low level signal (typically 0..5mV). This signal is typically transported through audio cable (RCA connnectors) to the hifi amplifier which includes a phono input (sometimes separate phono preamplifiers are used instead). Phono input of hifi amplifier (phono preamplifier) is designed to take a up to few millivolt signal from phono pickup and amplify it. The amplifier stage does also some equalization based on standardized RIAA curve. That RIAA equalization is used in the playback to reduce the high pitch noise and maximize bass dynamics in the phono playback. The audio material which is rocorded to the record has been pre-equalized so that the frequency response of the whole chain from the mixing desk to your speaker will give flat frequency response.
Because the low signal levels from record player cartridge, the signal wires from the record player to amplifier can easily pick up noise. Most typical noise is mains frequency humming. The hum usually disappears when well shielded cables are uses and a separate ground wire is connected from the phono ground on the receiver to a phono gounding screw point on the back of the amplifier.
Valve amplifiers are regarded by many to be the ne plus ultra when it comes to processing audio signals. Tube amplifiers are classical technology which does not always give the best performance on the measurements but many people prefer "tube amplifier sound" to be more "natural" than devices that use transistors.
Valve (tube) guitar amps are in fact nearly identical to early hi-fi amps. The sort of audio stages fited to old radios and radiograms are used in most guitar amps. Basic push-pull class AB valve circuits with little or no feedback driving 12 inch paper cone speakers in open back enclosures were all the rage in the 1940s and 50s in the better quality home (mono) sound equipment. Most guitar amps sold today are built to this same formula. Improved versions of the above with bigger output transformers and more feedback driving bass reflex boxes with woofers and tweeters became known as Hi-Fi.