BAS Message
July 2019

1.  BAS Speaker V40n4 has been published. This completes the fourth volume in our CDR series of BAS archive documents (dating back to our first issue). It features coverage of the 145th AES convention by David Weinberg and CEDIA Expo 2018 by Kenneth Wacks and Favorite Recordings Meeting 2016 by David Hadaway.

2.  RIAA  In the Stereophile review of the Levinson No. 5805 Integrated Amplifier, John Atkinson notes that the RIAA phono response is up .6 dB at 20 Hz. The Audia Flight FLS1 ($6995) is down 3 dB at 20 Hz.

At first I thought the Audia was yet another example of high priced poor design, but then I realized it was implementing the IEC recommended low frequency rolloff, designed to reduced rumble problems. However there is no corresponding boost in recording LPs (and never likely to be) so it is simply an audible error (-1 dB at 40 Hz). Space is at a premium on records and low frequencies take up a disproportionate amount of space. As Bert Whyte famously said “If I had a dime for every record cut with a high pass filter I would be sipping Don Perignon on my yacht.” If you need to reduce rumble the proper solution is an 18 dB Butterworth (maximally flat) low filter which effectively reduces the lows without affecting the audio. The Davis-Brinton Preamp used an even steeper initial cutoff, a Chebychev filter, at the expense of ripple in the pass band.

There is no excuse for not doing the RIAA right — calculating the values and implementing them.

For comparison the DB Systems DB-8 Phono Preamplifier (1995) is +/-.04 dB, 20 Hz to 20 kHz ($175).

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updated 7/15/19