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. In order to generate 12.5W on an 8 ohm loudspeaker, a 0.1V signal must be amplifier 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.

The purpose of using Moving Coil Step-Up Transformers (MC SUTs) is 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 be used to raise the signal level 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 also 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), and 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 at our US distributor Erhard Audio LLC:

Moving coil input

PhotoTypeStepup RatioCoreWireSize LxWxHComment
LL16788, 16, 32AmorphousStandard30x23x15Small size
LL1681 13, 26Mu metalStandard48x29x20With Faraday shields
LL1931 8, 16AmorphousOFC43x29x22Premium
LL1931Ag8, 16AmorphousSilver43x29x22Super premium
LL1933 8, 16Mu metalOFC47x28x24Premium
LL1933Ag 8, 16Mu metalSilver47x28x24Super premium
LL194116, 32AmorphousOFC43x29x22Premium
LL1941Ag16, 32AmorphousSilver43x29x22Super premium
LL194316, 32Mu metalOFC47x28x24Premium
LL1943Ag16, 32Mu metalSilver47x28x24Super premium

LL19613.2, 6.4AmorphousOFC43x29x22Premium. With Faraday shields. For solid state systems.
LL19633.1, 6.2Mu metalOFC47x28x24Premium. With Faraday shields. For solid state systems.
LL197112, 24AmorphousOFC43x29x22Premium
LL92265, 10, 20AmorphousStandard30x23x15Small size
LL9226XL5, 10, 20AmorphousStandard33x27x16Bigger size, bigger core. LL9226 pinout.

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