Helikon SL Details
The Helikon SL is a special low-output version of the regular Lyra Helikon. It is exclusively intended for use with phono preamplifiers with particularly high gain and low noise. It should only be chosen over the regular Helikon when it is absolutely sure the phono amp (or phono preamplifier/transformer combination) will be capable of handling its low output with satisfactory S/N ratio and resolution. Like the regular Helikon it is a medium-weight, medium-compliance cartridge, and was designed for use with high-quality tonearms that allow the cartridge/ tonearm low-frequency resonant point to fall between 8 - 12Hz. Avoid tonearms with loose or overly tight bearings, and avoid those with undamped lift mechanisms, since these can "drop"the cartridge onto the record and shorten the lifespan of the suspension. The tonearm output cables should be connected to a dedicated phono preamplifier or phono input on a preamplifier designed for direct use by a low-output MC cartridge (0.22mV output voltage or less). The phono preamplifier should also have an RIAA curve that is accurate to at least +/- 0.1dB, from 20Hz - 20kHz.
As long as your phono preamplifier uses normal non-inverting circuitry and has no MC stepup transformer, the input impedance can be any value from 10ohms to 47kohms. Normally the higher values result in a more open, spacious sound, and are therefore recommended. However, please feel free to experiment. The Helikon SL can also be connected to a phono preamplifier with a standard 47kohm MM-level input if you add an intermediary step-up transformer (like the Lyra Arion) or head-amp (also called pre-preamplifier). These devices will typically amplify the cartridge signal by 20 - 30dB without any RIAA equalization. In the case of a head-amp, experiment with the head-amp's input impedance (as described above) if such adjustment facilities are provided. When using a step-up transformer, the input impedance of the transformer must closely match the cartridge impedance (3ohms for the Helikon SL), and it must be designed for use with the input impedance value of the phono stage that it will work into. A transformer is an impedance-matching device, and will only work properly if terminated between the output and input impedances it was designed for, otherwise audible and measurable frequency aberrations can occur.
