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 The Behringer PP400 arrived. The unit was a drop-in replacement. There is no hum or other intrusive noise. I have several 33 1/3 rpm LPs designed for testing audio stereo systems. The unit passes, though I had to turn up the volume quite a bit to here high frequency sweeps up to 10kHz in one instance. I would like to record one of the albums' tracks through each preamp, and if possible, without a preamp, hence RIAA bypass, and compare them. A Fourier transform might be revealing.  There was, I believe, a comment in the custom design that the board could be modified for reconfiguration of the RIAA filter. A switch alterable version might be useful in switching between different filters used in different decades.

 Up till now, a diy assembly preamp has been used with the B&O turntable. Yesterday, I decided to listen to some vInyl LPs in my media collection. There has always been a problem with hum and rumble in the preamp. I had problems in the assembly which may account for the noise. There weren't enough ground wires in the unit. I added a couple.  The noise varied with physical location and that points to shielding as the problem. In fact, there is no shielding, only ground wiring connecting the system. There were three possibilities of a solution: 1.) But a new unit ( Behringer Microphono PP400). 2.) Add shielding to the existing unit. 3.) Replace the existing unit's plastic box with a metal box connected to ground. The existing unit is supposed to be an excellent design so a new box is in order. However, I would like to listen to some music and also verify the source of the noise, hence a Behringer Microphono PP400 is on order and will arrive in a few days. A replacement box f...