In part 2, we explored the Amplifier – the heart of the hi-fi system. In part 3, we’re going to discuss source components. A source component is, quite simply, a component designed to allow you to play back a particular music medium. Source components can be both digital (CD Players, Streamers, DAT (Digital Audio Tape) Machines, Digital Radios) or Analogue (Turntables, Cassette Decks, Open Reel Machines, etc). The 4 most common source components in use today include:
The CD Player
As with many of the source components that will follow, the function of the CD player is self-explanatory – it exists simply to play back your CD collection. The digital data form the CD is read by the CD drive, and converted via the DAC (Digital to Analogue Converter) to an analogue signal or waveform. This is then boosted by the CD player’s output stage, and sent on to your amplification of choice.
Different CD players offer variations on the basic functionality. Some feature a mechanism utilising a CD tray on which the CD is placed. Others feature a slot-loading mechanism, and others still feature top-loading mechanisms, necessitating ample space above the player to allow the insertion of a CD. There are even some hi-fidelity multi-disc CD players (more commonly referred to as CD changers) on the market – though they tend to be of lower quality than their single-disc counterparts. While they may offer convenient features, such conveniences come at the price of sound quality – and as such I’d generally advise sticking with a single-disc player.
Other features may include the use of 2 or more DACs (Digital to Analogue Converters). Where as an average CD player uses a single, multi-channel converter to process both the left and right channels of the signal, some players feature 1 or more DACs per channel, processing the left and right channels individually for better stereo separation. Some CD players may offer the ability to act as an external DAC for other digital devices, such as a blu-ray player, set-top box or your computer. Most players include several software-based features, including the ability to program the playback order of tracks on a Cd either randomly or by manually devising a playlist via the CD player’s interface.
The CD Transport
A CD transport is a type of CD player that contains no digital to analogue conversion circuitry. CD transports are designed to be connected directly to an external DAC, or to the digital inputs of a streamer, amplifier or other component that offers a built-in DAC.
CD transports feature many of the software features found in standard CD players, minus of course those concerning the reproduction of analogue audio. A CD transport connected to an external DAC will often result in better sound, thanks to the isolation between the digital and analogue stages and their respective power supplies. Many higher end players are built in this way – while the digital and analogue circuitry is contained within the same physical enclosure, they are kept separate, usually down to the power supply level.
A streamer operates in similar fashion to a CD player – it takes a digital sound source, and outputs an analogue signal. However, rather than being designed to play CD media, a streamer is a product of the modern digital age – designed to connect to your home network and stream content from your network, your computer – or indeed, the internet itself.
Streamers are typically designed to serve as the central source of your digital hi-fi system. Typical features include the ability to stream internet radio, as well as content from external storage attached to your home network and from your computer. Many streamers allow you to stream content from Bluetooth or Apple AirPlay capable devices, as well as from services such as Spotify. Many, aside from some of the cheapest budget models, can stream content from local storage (USB drives, for example), and also serve as a DAC for other digital devices.
Many streamers also incorporate a USB interface supporting the connection of a computer. Usually when such an interface exists, it supports both the USB audio class 1 and 2 protocols. Not to be confused with the various revisions of USB itself, the USB audio class protocols define the data rate that can be transmitted over the USB bus (or connection), and limit the resolution of audio file that can be transmitted to the device. For example, a device operating in USB Audio class 1 mode can transmit data at up to 24-bit, 96KHZ – whereas USB audio class 2 supports resolutions of up to 24-bit, 192KHZ (the current highest standard resolution).
A DAC is nothing more than the same digital to analogue converter as found in the 2 products above. However, whereas the CD Player and Stremer are designed to play back a musical medium without any external components, a DAC contains only the digital to analogue conversion circuitry, and thus must be paired with other components such as a CD transport. Providing they offer digital outputs, a DAC can also often be used to connect devices such as your blu-ray player, TV, step-top box or games console to your audio system for better sound.
Thanks to the recent resurgence in vinyl sales, the turntable has been enjoying a surge in popularity. I’m sure everybody is familiar with the concept – a record is rotated on a platter at 16, 33, 45 or 78 RPM (the former and latter being less common these days), as a stylus tracks the modulations in the record groove, reproducing the sound. A turntable consists of several components:
The plinth of a turntable is, for want of a better description, the ‘main part’ – I.e, the block that houses the tonearm, bearing, and usually the motor. Plinths come in all shapes and sizes and weights – the topic of high mass vs low mass in turntable plinths is a subject of debate amongst audiophiles and manufacturers alike.
There are a wide range of materials used in turntable plinths today – they range from MDF and solid woods such as oak, to artificial stone, to phenolic resin, used extensively by renowned manufacturer Rega Research. Each of these materials are of varying masses, and each have a different sound signature, much like changing the wood of a drum or guitar alters its tone.
The turntable bearing is the rotating part of the turntable that the platter rides, and spins upon. It typically consists of a bearing housing contains a thick film of bearing oil, in which the platter spindle rests. Some turntables utilise magnetic bearings which quite literally float the platter, minimising physical contact and thereby reducing mechanical noise.
The Platter and Subplatter
First, the subplatter. The subplatter is, essentially, a small platter upon which the main platter (the one responsible for supporting the record) sits. The subplatter is directly affixed to the spindle, and typically contains some form of location ‘feet’ or a raised outer rim to support the platter and render the playing surface as flat and level as possible.
The platter is, obviously, the larger playing surface on which the record sits. More often than not the platter is topped by a mat, usually fashioned from felt, silicon or rubber – though depending on the material used in the platters construction such a mat is not always necessary. Platters are of different designs and materials – many turntable feature platters made from MDF, plastic (usually a form of acrylic), metal or glass, whereas some higher end tables feature materials such as delrin, or platters topped with vinyl itself (or a form of vinyl compound).
It’s also worth noting that not all turntables feature a subplatter – some, particularly direct drive models, seat their platter directly upon the spindle. Some turntables, such as the legendary direct drive turntables manufactured by Technics, integrated the platter into the motor itself by fixing a magnet to the underside of the platter, and seating it on the spindle with the magnet falling between a set of electronically charged motor coils.
The tonearm, usually referred too as the ‘arm’, is the part of the turntable responsible for allowing the cartridge and stylus to track the record. The most common tonearm is the pivotal tonearm- a design whereby one end of the arm is fixed to a pivotal bearing, allowing the arm to follow the arc of the record groove. Most turntables you’re likely to encounter on the market today employ a pivotal tonearm.
Linear, or ‘parallel’ tracking arms feature an arm carrier that allows the arm to track the record in a straight line, following the path that the cutting head took as the record was cut at the factory. These days, such arms are typically found in higher end turntable designs – though there were a large number of mostly Japanese turntables produced throughout the 80s and 90s which featured a cheaper, mass-produced implementation of a linear tracking mechanism driven by a gear drive and a permanent magnet DC motor. The downside to this approach is that it generates mechanical noise, which can be picked up by the cartridge and stylus and transferred to your speakers. High-end parallel tracking arms typically feature an air bearing or a series of electromagnets to guarantee smooth, noise-free operation.
The tonearm itself consists of several components. The key components are the counterweight (the rear-mounted weight designed to allow you to set the required downward tracking pressure for your cartridge), the HeadShell (the flat area on the end of the tonearm opposite to the counterweight where the cartridge and stylus are located), and the anti-skate, or ‘bias’ mechanism (designed to counter the natural centripetal force generated as the spiralling record groove drags the arm towards the centra of the record).
The cartridge and stylus
First up, the stylus. The stylus, sometimes referred too as the ‘needle’ is the needle-like device that contacts the record surface enabling the cartridge to produce sound. The stylus is comprised of 2 main parts – the cantilever (the shaft) and the stylus tip. Cantilevers can be fashion from all manor of materials – plastic, aluminium and boron being the most common), and there are various shapes and sizes of stylus tips to choose from including Conical, Alyptical, Hyperalyptical, microline, Shibata, etc.
Each of the aforementioned stylus tips are of a different size and shape. Smaller, slimmer tips are able to better penetrate the record groove, digging up more detail and better re-producing the sound, in particular the high frequency information. Better stylus tips also result in less ware to the vinyl groove., Playing a warn record with a small stylus profile will often result in improved sound quality, as the stylus is able to reach areas of the groove that have previously remained unplayed.
The cartridge is the device affixed to the HeadShell end of the tonearm, usually using a screw on either side. The stylus is located on the underside of the cartridge. Discounting optical cartridges, and the ‘Moving Micro Cross’ (MMC) cartridges designed by Bang and Olufsen, there are 4 common types of cartridge in use today:
Ceramic cartridges are typically used in low-end, low-fidelity record players, such as the retro-styled units available on the market today or the cheap, plastic player affixed to the top of your 80s midi system. THey’re favoured for these devices because they’re extremely cheap to manufacturer and don’t require an external phono stage as they produce a high output. However, they usually sound terrible, and due to their cheap styli and high tracking pressure, they’re not particularly kind to your records either.
Moving Magnet (MM)
Now we’re venturing into the realms of hi-fi cartridges. Moving magnet cartridges feature a stereo generator comprised of a pair of coils (1 for each channel). An electromagnet, affixed to the end of the stylus cantilever, vibrates and moves within the coils, generating voltage (usually a few millivolts) and thence an audio signal.
Moving magnet cartridges are the most common cartridges used in budget and even mid-range hi-fi turntables. They sound much, much better than ceramic cartridges and cause far less damage to your records – but they do require a phono stage to amplify their signal (which is nothing more than a tiny electrical voltage) to line level (usually around 2 Volts RMS).
Moving Iron (MI)
Moving iron cartridges are similar in construction and concept to moving magnet designs. They differ in 1 aspect – the magnet is substituted for a tiny piece of iron (or another ferrous alloy), which is lighter, requiring less downward tracking force and improving tracking accuracy.
Moving Coil (MC)
A moving coil cartridge is similar in principal to a moving magnet cartridge – but, as you may have deduced from the name, it is not the magnet that moves but instead the coils themselves. There are 2 types of moving coil cartridge on the market – high output and low output.
All moving coil cartridges will require a phono stage to amplify their signals to line level. Low output Moving coil cartridges generate a signal that is even lower than that of a moving magnet cartridge (in the microvolt range), and thence require an extra stage of amplification or a step-up transformer. High output moving coil cartridges generate a signal more akin to that of a moving magnet cartridge, and can often be connected directly to a moving magnet phono stage.
Moving coil cartridges are typically found mounted on higher end turntables, and are favourited by audiophiles. The cartridge you choose will depend on your budget and the rest of your hi-fi equipment. Budget hi-fi systems typically feature a Moving Magnet cartridge – they’re cheap and require only a basic phono amplifier to boost their signal to that of line level. Many Moving Magnet cartridges also feature a user-replaceable stylus – moving coil cartridges do not, and implementing a replaceable stylus in a moving coil design is impossible due to the coils being directly affixed to the cantilever.
Still with me? So far, we’ve covered 2 key components of a hi-fi system – the amplification and some common source components. Next up in part 4, we’ll discuss the function and various types of loudspeakers. Until then…
Continue to Part 4