The Audible Illusions Modulus L1 is a high-end, professional pre-amplifier that was manufactured by Audible Illusions during the mid-1990s. It featured a separate headphone amplifier, and later models included a digital-to-analog sound converter as well. It is discontinued as of 2011, but used and refurbished units remain available from private sellers. This model can be used with modern audio equipment even though it is based on vacuum tubes rather than solid state technology.
Headphone Amplifier Specifications
The headphone amplifier that is contained within the Modulus L1 unit uses proprietary dual monolithic Field-Effect Transistor (FET) circuitry. Its signal phase is noninverting and its maximum output is 10 watts per channel at a load of 30 ohms. The headphone amp has a signal-to-noise ratio of 95 dB below 1.5 volts. Its total harmonic distortion is less than 0.02 percent at 1.5 volts from 20 Hz to 20 KHz at a load of 30 ohms. Its frequency response is within half a decibel between 1 KHz and 200 KHz, and its output impedance is 10 ohms.
Line Stage Specs
The gain, or amount of sound increase, of the main vacuum tube pre-amplifier is measured at 28dB. Its features inverting signal phase and a slew rate of 50 volts per microsecond. The main pre-amp has a signal-to-noise ratio of 85 dB below 1.5 volts. Its total harmonic distortion is less than 0.15 percent at 1.5 volts from 20 Hz to 20 KHz at a load of 50,000 ohms or less than 0.12 percent at 0.5 volts from 20 Hz to 20 KHz at "IHF" standard load. Its frequency response is within 1 decibel from 2 to 1000 KHz as measured with a 1:1 probe at a load from 100,000 ohms to 100 picofaradays.
Line Stage Specs - Continued
Input impedance for the main pre-amp is 50 ohms at all line inputs. Output impedance is 1,200 ohms at the main output and 150 ohms for the tape output. Overload is set at 9 volts at 1 KHz for a 50,000-ohm load.
Vacuum Tube Specifications
The Audible Illusions Modulus L1 line stage pre-amplifier requires two E88CC or 6922 vacuum tubes. These tubes, which are equivalent to each other, are of double triode type. As of July 2011, they are still available from specialized dealers.
Tags: Audible Illusions, less than, less than percent, load ohms, percent volts, percent volts from
