sjc@fmg.bt.co.uk (Steve Colwill) (01/03/91)
I recently acquired a Mod Squad Line Drive (passive volume balance control and input selector) to replace my preamplifier. I have got rid of my turntable and I figured that the preamp was acting as a very expensive and complex attenuator and so I might as well simplify the signal path by getting rid of it. One result of this (which was what initially attracted me) was a quantum leap in treble detail and focus. However of late I have become aware of a slightly odd quality in the bass - an intermittent *very* low bass sound as if a heavy door is quietly shut somewhere else in the house. There also seems to be a tendency almost to resonate on some low bass sounds. Is this something to do with using a passive network? Have any of you electronics whizzos out there any idea what is behind this? Any fixes? The System - Sony CDP 555 ESD player used as a transport driving Musical Fidelity Digilog (though the same effects are noted with Deltec PDM Mk II, and Meridian 203 converters on demo, possibly reduced with MicroMega BS), the Mod Squad. Power amplification is via biamped Musical Fidelity A372 into B&W 801 Matrix Series 2 - one amp per speaker. There is a complication with the amps - each is a dual monobloc and so I use one channel to drive the woofer and the other channel to drive the mid/tweeter assembly of its speaker. The inputs to each amp are bridged internally. When I had the amps upgraded to 372 (from 370) I had the inputs bridged and the channels to be used for the upper freq range biassed more heavily to Class A operation. I look forward to your replies! Steve Colwill email: sjc@fmg.bt.co.uk - I will summarize if sufficient interest/a fix is found.