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Marketing wise the Phono Loco is a disaster. There was a complete disregard for market acceptability. All design decisions were based on optimal engineering. It was all about performance possibilities. Marketing was thrown under the bus.Unlike the other designs, the Phono Loco is totally focused as a specialized transimpedance unit. There is no concession to flexibility and options. With that clutter removed, the circuit can be refined and optimized to ONE goal. The Phono Loco does not hedge it’s bets. It is ALL on transimpedance.The Phono Loco demands a balanced input signal. The circuit requires both connections from the cartridge coil to float with respect to ground. There was no bending around, or patching, or compromising to make it accept a single-ended signal. Do not waste your money on expensive RCA to XLR adapters. Get the correctly balanced XLR cable from a good cable manufacturer. If you are not willing to get a balanced cable for the input connections, you should buy a more conventional phono preamp.
A transimpedance amplifier input looks like a virtual short to the input signal. The input voltage is therefore zero. The input signal is the current going in/out of that virtual short. The input current is multiplied by the gain (in Ohms) to give an output voltage corresponding to the input current.
There are no loading options or concerns. A current input stage (transimpedance) input is a virtual short. That topology obviates load resistor selection. The current going into that short is then amplified.
You are welcome to try. It is unlikely to work very well.
We expect the Phono Loco to work very well with most MC cartridges. But there is not yet a body of info available. We will keep a user forum page updated so experiences can be shared.
Conventional voltage amplifiers express gain in dB (as the ratio between the input voltage and the output voltage). With a transimpedance amplifier, input is current and the output is voltage. For that topology, gain is expressed in Ohms. Gain is approximately 10k Ohms at 1 kHz.
Most MC cartridges will work well at the medium gain setting. There is also a low (voltage down 6dB) setting and a high (voltage up 6dB) setting.
Most audio signal cables are designed to transfer voltage changes. The Phono Loco input voltage is zero and doesn’t change. What does change is current. That is generally a favorable condition for cable performance
If your dealer has taken on the Phono Loco, they will have the experience to help build a superb analog playback front end. Your dealer will have explored various combinations. You don’t have to spend your money until you personally experience the winning combination.
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