Integrated Amplifiers

Pass Labs INT-30A Pure Class A Integrated Stereo Amplifier


The Design

Like the INT-150, the INT-30A's preamplifier section has an input relay selector that routes the signal to an analog volume control, and this feeds a Class A FET unity gain buffer. The output of this buffer goes to the preamp output stage and, from there, to the power amplifier section. The INT-30A has a lower rail voltage than the INT-150, in keeping with its lower power output specification.

The front panel has a horizontal row of buttons, the first of which is the power on/off, and the rest are for selecting the input. The volume is read in 0.5 units, up to 63, so it is a relative scale, not dBV.

The rear panel has, from left to right, a set of preamp outputs, which includes both RCA unbalanced and XLR balanced. To the right of the pre-outs are the inputs, with three sets of unbalanced RCA jacks, followed by two sets of balanced XLR jacks that also have adjacent unbalanced RCA jacks. The AC receptacle is three-pin grounded. The main power on/off toggle is next to the receptacle. So, when it is on, the front on/off button serves as standby and power on. The speaker binding posts are really intended for cables with spade terminations, as the rear end of the binding posts are blocked with plastic plugs. Note that there are U-shaped jumpers that short two of the pins in the XLR input jacks. These have to be there if you use the RCA inputs. For balanced use, simply pull the pins out and put them in a safe place.


The remote control is the same as with the INT-150. Very nicely manufactured, in metal, with simple, straightforward buttons. All the buttons are shaped the same, but there are so few, it is not a problem to do what you want in a darkened room, such as changing the volume.