Lundahl Moving Coil Input Transformers
Moving coil cartridges are low-voltage devices. Typical output levels are below 1 mV, and often as low as 0.1 mV. To generate 12.5W on an 8-ohm loudspeaker, a 0.1V signal must be amplified 100000 times (or 100 dB). In particular, for tube amplifier devices, such a high amplification is very hard to achieve without significant noise additions and signal degradation.
Moving Coil Step-Up Transformers (MC SUTs) are used to step up/increase the low output signal voltage from moving coil cartridges before the signal enters the phono stage. As MC cartridges are very low-impedance devices, transformers can successfully raise the signal level by 20 – 30 dB without any noticeable degradation. This reduces the required remaining amplification significantly.
When you choose between different MC SUTs, we normally suggest that you choose a step-up ratio based on the cartridge output impedance as follows:
Low impedance (1 – 10 ohms) step-up ratio 32 – 24
Medium impedance (10 – 40 ohms) step-up ratio 24 – 8
High impedance (> 40 ohms) step-up ratio < 8
Low turns ratio MC SUTs (turns ratio around 1:5) are sometimes used with low impedance cartridges when combined with solid state phono stages.
Lundahl Transformers make MC SUTs with two different types of core: mu-metal (nickel) lamination core and uncut amorphous cobalt strip core. The laminated mu-metal core is the most classic and commonly used core material. It provides high permeability also at small signal levels, low distortion and a transparent sound. Our uncut amorphous strip cores are sometimes said to be more musical, but due to a lower initial permeability, they are slightly less linear.
Our more prestigious range of SUTs are wound with oxygen-free copper (OFC); some are also available with silver wire.
For more information on MC SUTs, and how to apply proper loading to cartridges, we suggest you visit this page
https://www.erhard-audio.com/SUT_Calculations.html
See PRICES for Lundahl Moving Coil Input Transformers
