Banner
Banner
cookie-banner

Phono stage tests - Gain

Article Index
Phono stage tests
Gain
Overload
Noise
All Pages


GAIN



WHAT IT TELLS US

Cartridges produce a weak signal that needs amplification before an amplifier can deal with it.  Insufficient gain from a phono stage means volume must be turned right up on the amplifier to compensate and this might not be enough for full volume.


The benchmark amplification figure for Moving Magnet (MM) cartridges is x100, or 40dB, and for Moving Coil (MC) ten times as much, x1000, or 60dB in external phono stages.



PICTURE OF GAIN SWITCHES


In practice these are best seen as minimum values, especially if the phono stage feeds an amplifier whose line inputs have a low 400mV sensitivity, a common figure. An MM cartridge produces just a few millivolts at ordinary music levels (i.e. not peaks) so a phono stage with x100 gain will barely be producing 200mV and volume will have to be turned right up in this situation. Another nuisance here is the big change in volume when switching from LP to CD. Some amplifiers (e.g. Arcams) have adjustable input sensitivity so volume levels can be equalised to avoid this.


Ideally, around x200 gain (46dB) is need for MM cartridges and x1000 -  x3000 (60dB-70dB) for MC cartridges.


Phono stages with an output volume control (e.g. Icon Audio) can be used to drive a power amplifier direct. In this situation roughly x5 (14dB) more gain is needed, as most solid-state power amplifiers need 1V input to deliver full output, although many valve power amplifiers need considerably less, down to 300mV.


HOW WE MEASURE IT

We measure gain at 1kHz. Input voltage is measured direct (i.e. p.d and not generator emf), to get a true input value. Output voltage is measured by a Rohde & Schwarz UPL spectrum analyser. Input levels of around 10mV are used for MM and 1mV for MC.




 

Search

Hi-Fi World, Powered by Joomla!; Hosted by Joomla Wired.