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Playing with impedance

When we first began playing with step-up-transformers (SUT) here at lencomotion audio, we wanted an easy way to vary the secondary loading. We had a variety of transformers, all of which sounded different with each cartridge, and to get an accurate idea of what each SUT was capable of, we had to be able to change the impedance for each cartridge. It needed to be something that allowed us to make changes without having to run to the solder station in the workshop. A quick rummage through our parts box led to the construction of the following pair of cables.

These were easy to make using standard male and female RCA phono plugs, a short length of high-quality cable, and a pair of standard DIL sockets mounted on project board and protected with heat shrink tubing. The DIL sockets are mounted in parallel with the signal cable, and allow resistors to be easily added to the circuit by plugging them in to the DIL socket.

The cables are now a permanent fixture in the listening room, allowing us to easily adjust impedance when playing with cartridges and step-up-transformers. Anyone currently using a SUT with a fixed impedance should have a go making a set of similar cables, and have a go varying the impedance of the system. If you find that adding a resistor improves the sound, then a similar value resistor can easily be more permanently soldered to the phono outputs. For those folks who are not interested in DIY-ing their own cables, contact us, and we would be happy to make up a set for you.

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