There is usually a spec titled Gain. It is usually given in both preamp and amp specs. It can vary from 3dB to 29dB and probably higher in preamps.
Most preamps are higher gain and, actually, having too much gain in our preamps and amps is more of a problem than having too little. When you have too much gain you keep your volume control below, say, 9 o'clock. This can result in detail being lost.
If Pass says to use a high gain preamp, I'd look for one with a Gain spec of 20dB or more, and there are a lot of them around.
Most preamps are higher gain and, actually, having too much gain in our preamps and amps is more of a problem than having too little. When you have too much gain you keep your volume control below, say, 9 o'clock. This can result in detail being lost.
If Pass says to use a high gain preamp, I'd look for one with a Gain spec of 20dB or more, and there are a lot of them around.