Summit Audio 2BA-221 Mic and Line Preamplifier - Manual (Page 15)

Model 2BA-221 Microphone Preamplifier 15
Block Diagram
The summing amplifier drives the Stack Output, which is
designed to feed the Stack Input of another 2BA-221.
This signal is also sent to the Insert jack output, which can
be used to insert another device, such as a compressor
before the tube stage.
The highpass filter has a variable cutoff frequency
(20Hz -200Hz). This control is designed to remove low fre-
quency rumble caused by stage vibration and other factors
which may be picked up by the microphone.
The 2BA-221 features a vacuum tube amplifier driving an
electronically balanced output stage. The balanced output
drivers provide a low output impedance for driving cables and
600Ω loads. Both XLR and 1/4” outputs are provided.