Phono Stages Explained


Phono Stages Explained

 

Buying a record player is not always as easy as acquiring the most expensive turntable you can afford and plugging it into an amp and speakers. In this article I will guide the prospective purchaser through the minefield of phono stages, since upgrading the phono stage can provide one of the most dramatic improvements to sound quality. As a one-time avid reader of the hi-fi press, and a seeker of hi-fi Nirvana, I have experienced the horror of wanting to upgrade the phono stage in my amp, and looking at the prices of dedicated phono stages.

I was inspired to write this article by the contributor to Hi Fi World Magazine, Paul Rigby. The other day I received a tweet with a link to a review of about 10 different phono stages. Judge for yourself here, http://www.factmag.com/2016/04/19/best-phono-amplifiers-turntable-vinyl/ – but I don’t actually think he did more than write, “very nice dear”, about each phono stage. Don’t get me wrong, this reviewer contributes what I would consider to be very informative and educated reviews to my favourite hi fi magazine. I just think on this occasion he missed a trick – and certainly on the point of budgeting I think the poor reader would be left thinking, “Well if phono stage X costs £39 why would anyone want to spend in excess of £1000?” So let’s start at the beginning.

A phono stage is needed for two reasons. The electrical output of a cartridge is far too small to be amplified adequately by simply plugging it into a normal RCA-style line input. These are normally labelled, “CD, Tuner, Aux, Line 1” etc… Despite the fact that physically these sockets look the same and will fit the plugs of a record player, the resultant electrical signal will be too small. In fact, Yours Truly once plugged a very nice Rega Saturn-R CD Player into the phono stage of an amp and ended up with a few seconds of ear-splitting volume and high distortion levels as a result. The electrical signal that a CD player feeds to an amplifier is much higher than a phono cartridge…..

Therefore, any amplifier used by a turntable enthusiast should have an input socket labelled “Phono”, into which a turntable should be plugged. An amplifier of this type will normally also have a grounding post to combat mains hum from the turntable. Most record players (Rega excepted) provide the user with a wire coming from the deck, and terminated in a metal hook, which is looped onto the grounding post and tightened down.

If an amplifier does not have a phono socket, then the user will need to seek out a separate phono stage.  These are usually small components, equipped with an RCA-style input socket suitable for a record player.  There will be an output socket which MUST be plugged into a normal line-in socket on any amplifier.  It will also have a grounding post, for turntables which need them.  In the case of the popular Rega turntables this can be ignored. The result – either from an amplifier’s built-in phono stage or a separate component –  will be  to boost the signal of the turntable cartridge so that it can be amplified in the normal way.

The second reason a phono stage is needed is down to what’s called the RIAA Equalisation (or EQ) curve.  If records were cut with an exact representation of  the bass and treble content, even a stylus fitted to a modern £1000+ cartridge would not be able to track the record correctly. Grooves containing high bass content would be especially large and those containing high treble content would be so tiny that the finer-than-a-human-hair stylus tip that the best needles are equipped with would simply not cope.  Therefore, when a record is cut in the studio, an EQ curve called the RIAA (Recording Industry Association of America) is applied, which cuts bass and boosts the treble.  Exactly how much bass or treble is cut or boosted will depend on the precise frequency.  Very low bass notes need more reduction than not-so-low notes.  In this way, bass grooves end up smaller and treble grooves end up larger.  A turntable stylus therefore has less difficulty tracking the grooves.  However, the phono stage contains circuitry which applies the RIAA curve in reverse, i.e. bass notes are boosted (because they were reduced at the record cutting stage) and previously boosted treble notes are cut back – thereby reproducing, all other parts of the system being good enough, the frequencies that we, the listeners, were intended to hear.  A simple line-in socket intended for a radio tuner, DVD, CD player and the like, does not contain this RIAA correction circuitry.

The phono stage you choose will depend on the record player you have and the type of cartridge you wish to use.  Cartridges come in three types.

  1.  The Ceramic (sometimes called the piezo-electric) cartridge.  I mention these only in passing, simply because they still exist.  They are used on very inexpensive record players that often contain built in amplification and speakers.  Most of these devices also provide a line-out RCA socket to enable the sound to be boosted by an external amplifier.  The record player that springs to mind is the Crosley Cruiser available very cheaply on today’s High Streets, although there are others.  Ceramic cartridges have a higher electrical output than Moving Magnet or Moving Coil cartridges and as such they DO NOT NEED a phono stage.  Record players using these can simply be plugged into a line-in socket if the user wishes to bypass the built-in speakers.  However, these cartridges (or the decks themselves) should not be considered Hi-Fi.  For one thing, I doubt whether today’s record players that use these cartridges provide any form of RIAA correction, meaning that there will be no bass to speak of and treble will be very bright.
  2. The Moving Magnet (MM) cartridge.  These cartridges are very versatile and popular, with prices ranging from about £25 (for the Audio-Technica AT95E or Rega Carbon) to about £500 for the Ortofon 2M Black.  They work very well with record players costing from about £150 (for the Pro-ject Elemental) to around £900 (for a Rega RP6).  Because of their ubiquitousness, all phono stages make provision for Moving Magnet cartridges.
  3. The Moving Coil (MC) cartridge.  These cartridges tend to be the most expensive.  They are capable of truly stunning audio reproduction, and every turntable enthusiast should make it their goal to at least hear one!  Look to spend upwards of £1000 on a decent one, although there are cheaper.  The more involved manufacturing process tends to mean that a better Moving Magnet will outperform a Moving Coil of the same price.  Moving Coil cartridges produce an even lower signal than Moving Magnets, and need their own dedicated input.  They should not be plugged into a Moving Magnet Phono Stage!  Very very few amplifiers offer provision for Moving Coil cartridges.  If they offer a phono stage at all, it will be MM only.

As far as budgeting for a phono stage goes, bear these pointers in mind:

  • As a rule of thumb I suggest spending no more than the MRP of your amplifier on a phono stage.  As a further guide, think about the MRP of your turntable and chosen cartridge COMBINED and look to spending about a third to a half of that figure.
  • If you have a cheaper audiophile turntable costing from about £150 to £400 and no phono stage on your amplifier, then consider any of the sub-£100 suggestions from the aforementioned Paul Rigby review.  Note however that built-in phono stages and the cheaper separate units should only be considered as a “get-you-going” solution.  Many turntables only offer a basic cartridge, and the tonearms are usually capable of accepting much better cartridges.  Especially if your record deck cost around the £400 mark, it might make sense to buy a SLIGHTLY more expensive phono stage in the first place to make provision for a cartridge upgrade.  Whilst we are discussing budget turntables, there are some record players which include a built-in phono stage, so that a person whose amplifier doesn’t include a phono stage can simply plug the deck into a line input.  Some even provide a built in USB socket for connection to a laptop, enabling one to digitise one’s vinyl.  These gimmicks can normally be be switched out of the signal path.  If your amplifier has a built-in phono stage, then use that, as it will likely result in better sound.  Needless to say, it is better to put the few pounds extra towards a better budget deck that does NOT include a phono/USB facility, since the budget will have been  spent on parts of the turntable that matter.
  • If you possess a more elaborate turntable and one of the better Moving Magnets (e.g. the Goldring 1042 at nearly £300) then apply the deck plus cartridge formula more rigidly.  The only firm product recommendation I will suggest, simply because I used it successfully for many years with a Rega P5/Goldring 1042 turntable/cartridge system, is the Creek OBH-15, now in Mark 2 guise. The P5 and Goldring totalled roughly £900 and the Creek cost a few pounds shy of £300 MRP, i.e. a 3:1 ratio.  This phono stage catered for both Moving Coils and Moving Magnets, although I would not recommend the MC input as anything but a stopgap, or for use with a sub-£300 Moving Coil – yes these do exist!  The sonic benefits of its Moving Magnet input above the already-quite-good phono stage in my amp were nothing short of startling.  Firstly, the mains noise floor was substantially reduced, allowing the listener to hear into the recording more and follow instrument lines in dense mixes.  Secondly, the sound was more powerful, slightly louder yes, but the bass was much more solid and overall more punchy and rhythmic.  Treble was well-controlled, and overall I felt that the sound was very natural.  Lively enough to make me Moonwalk across the floor to Thriller, but nothing to grate on the nerves.  These qualities are all present in the Goldring 1042 cartridge – and adding the Creek OB-15 phono stage simply brought the capabilities of the cartridge into focus and showed me what it could do.
  • If you wish to buy a phono stage for use with a Moving Coil cartridge, I would suggest very careful listening and research, as well as applying my budget formula.  Ideally phono stage and cartridge should be bought together, since an MC phono stage will be equipped with jumper switches to allow the user to tailor its resistance and capacitance (2 terms which I don’t understand!!) to suit the exact cartridge.

Whichever your choice, I hope this article has whetted your appetite and given you food for thought, whether you are upgrading from an amplifier phono input or buying a vinyl-based hi-fi system for the first time.

 

Mark Pearce May 2016


About Mark Pearce

Mark Pearce is the author of the YouTube Channel MarkPMus. Check it out if you're interested in Hi Fi, songwriting and music reviews. Nuggets include 2 series of ABBA Gold Anomalies / More ABBA Gold Anomalies, the Magical Musical Moments series and Hi Fi 101. You'll also find examples of the author's songwriting and photography.

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