Little Loco Mk2 Phono Stage

Sutherland makes world renowned phono preamps and has done so for a long time. Prior to the Little Loco, all their efforts were focused on traditional phono preamp architecture, what would be called a traditional MM/MC phono preamp, one with the usual adjustments for gain and resistance. However, a few years ago, Ron Sutherland got wind of an exotic mega-buck phono preamp that worked very differently. This uber-expensive phono stage focused exclusively on the MC cartridge's current output, ignoring the voltage output and was thus able to bypass the usual considerations of voltage gain, as well as any resistance characteristics.  This was done by using a technology called transimpedance, which describes the ability of an amplifier to multiply small amounts of current into much higher amounts of voltage.

A transimpedance phono stage only cares about the current output of the cartridge, which is roughly the same across most Moving Coil cartridges, regardless of output voltage. This makes things a lot simpler! With a transimpedance phono stage, there are no dials or selectors. There's no guessing which gain setting or impedance value will deliver the best sonic performance, because the output voltage of the cartridge is now largely irrelevant. 

Another factor which makes a transimpedance design so compelling is the simplicity of the circuit. A transimpedance phono stage doesn't require the long and complex signal paths of a traditional MM/MC phono preamp.

Transimpedance Design
First some background, traditional Moving Coil (MC) phono preamps multiply the exceptionally low output voltage of an MC cartridge in an attempt to raise its output voltage up to line level. A typical 0.5mV (aka 0.005V) cartridge requires 4000% amplification to reach a nominal 2V line level output. This is a tremendous chore, fraught with the potential for noise. Because of this choice, a traditional MC phono cartridge must have multiple gain settings to match with a variety of cartridges and it must also have a number of impedance settings to match up with the various loading options any MC cartridge may require. Every owner of an MC cartridge has agonized over which settings to use on their phono stage, constantly worrying that they may not have selected the optimal setting.

There's a better way, though, Low output MC cartridges have an interesting characteristic! Although their output voltages can vary widely and tend to be exceedingly low, they all tend to have similar levels of current output. A transimpedance phono stage ignores the cartridge's output voltage and instead converts the MC cartridge's current output into voltage. This bypasses many of the issues of traditional MC circuitry including issues with Impedance Loading and Gain Matching. The transimpedance amplification method results in a much more robust signal, with greater integrity, lower noise floor and a much more involving listening experience. A good transimpedance phono stage is much more difficult to engineer than a traditional phono stage because of the huge reliance on the purity of their power supplies. This is where Sutherland distinguishes themselves from every other transimpedance design to date.

"The Mk2 version (as of 2020) is good to go. The transimpedance input stage is improved, the shell of the RCA input jack is now at ground level. There are no more special requirements or concerns for signal interconnection to the turntable. Glad to say all those awkward and confusing discussions are out of the picture!"
– Ron Sutherland

As you may have read, the first version of the Little Loco (aka Mk1) required the owner to jump through a number of technical hurdles in order to connect a Little Loco to the turntable.  Michael Fremer's review of same confirmed this, where he noted specific configuration requirements in order to enable functionality. This all changed in 2020 where Ron Sutherland released an update circuit, this time without any fuss. Any turntable with RCA outputs and an MC cartridge can now be used with a Little Loco, which includes Rega, Pro-Ject, VPI, Clearaudio, basically everyone!

The Little Loco is not compatible with High Output Moving Coil or Moving Iron cartridges.

Gain Options: Standard setting works with the vast majority of MC cartridges. Output can be increased by +6dB by snipping out resistors, but this shouldn't be necessary.
Loading Options: Not Applicable
Dimensions (WHD): 17x2 .5x13″
Weight: 15 lbs