PRODUCT UPDATE ANNOUNCEMENT: AVAILABILTY OF A SHARP-CUTOFF SUBSONIC FILTER
We have developed a fixed custom-slope low-frequency filter that is sonically transparent enough to be left in the circuit at all times, but is intended only for users who need it. We foresee three main scenarios where this could be of potential benefit: 1) Subwoofers with a gain structure optimized for digital sources, 2) Limited turntable acoustic isolation, 3) Moderately-to-substantially-underdamped tonearm/cartridge resonance.
We now offer this
fixed Subsonic Filter per client request at no cost. It is available for the MM-5, MM-6, and MP-7. As we expect relatively limited interest, buyers can place a regular order via our website and then email us with the order number.
https://www.darlingtonlabs.com/shop
This filter is nominally a 12dB/octave low-cut (‘high-pass’) using a transfer function of our own design. It is optimized to provide good transient response, and minimum excess phase shift, while being musically unobtrusive.
Specifications are as follows:
70Hz +0.05dB;
50Hz 0dB;
30Hz -0.5dB;
25Hz -1dB;
20Hz -2dB;
17Hz -3dB;
12Hz -6dB;
10Hz -8dB;
5Hz -19dB.
The existing gain elements are used as buffering nodes to eliminate filter section interaction. This means
NO additional active gain elements in the circuitry for the best sound quality. The curve is also unaffected by external loading, because the output stage does not contain a section of the filter.
It can be deployed in our MM-5, MM-6 and MP-7 at user request and at
no additional cost when ordered
in a new unit. Current users may contact us for a retrofit quote.
Note that our current
standard RIAA equalization is now even flatter in the lowest few octaves, as we have eliminated the slight low-frequency contour seen in the July 2021 measured graph. The overall frequency response is now quoted as 20Hz to 20kHz, +0.25/-0.25dB (MM-5), +/-0.23dB (MM-6) and +/-0.2dB (MP-7). rather than the previous
50Hz to 20kHz.