What is the difference between the PBX and PBX2 line of preamps?
[A] PBX preamps have 1-pole filtering on both the upper and lower bandpass. PBX2 preamps have 2-pole filtering on the low-cutoff (high-pass) side, and 4-pole filtering on the high-cutoff (low-pass) side. Only the PBX preamp has the programmable referencing option, as controlled by the REF2 software. This is identified by the “-r” in the preamp description, such as PBX/32sp-r/16fp. The “-r” at the end of the spike board description means that programmable referencing is available on the spike boards.
