Pre Amp for Pass Labs X150.5

It simply means you'll turn the volume knob farther on the 4dB preamp, and you may have smaller steps in volume versus the 14 dB preamp. In other words, the 14dB gain preamp will get louder faster than will the 4 dB preamp, and the 14 dB preamp may get too loud, or be too loud, at a low volume control setting.

30 dB gain on an amp is toward the high side from my experience.

just to make sure i get it right. X150.5 has gain of 30 dB and Balanced input impedance of 30,000 Ohm. say i have 2 pre:
A) Balance Output Impedance of 750 Ohm, Gain of 4 dB, every step in volume increment is 3 dB
B) Balance Output Impedance of 80 Ohm, Gain of 14 dB, every step in volume increment is 0.5 dB

Preamp B would give more control and play of the volume right? i.e. I could play my system late at night without getting too loud.

how does the output impedance affect the outcome?

thanks

Hello Driver, To my knowledge preamp output impedance doesn't effect volume. Matching of impedance just assures that the entire audio signal is passed. I looked up your X150.5's input impedance last night @ the Pass Labs website. According to Pass, your amp's balanced input impedance is 22 kohms, just like my X600.5 amps. The gain of my amps is also 30 dB. My Pass Labs X0.2 preamp has a gain of 12 dB balanced, while my old Audio Research Reference 3 preamp had a gain of 11.5 balanced. Both worked well with my system as far as volume goes. If a gain is very high, like a VTL 7.5 markI preamp which has a gain of 20 dB balanced, for example, then you can run into high volume problems no matter how low you set your preamp's volume. Also, with the VTL 7.5 markI, it would depend on an amps output and the amps gain, plus the sensitivity of speakers, etc. However, most preamps have a sensible gain and aren't as high as the VTL 7.5 markI. Hope this helped. Stan

Talon4 described it pretty well.

Impedance mismatch generally results in early bass roll-off.

Gain mismatch generally is an issue if the preamp has to much gain because you may have too much system volume with the preamp at it's lowest setting. Low preamp gain generally just means you have to turn the volume knob farther than you think is normal, but it usually doesn't affect the sound in a negative fashion.

Ability to listen at low volumes late at night is more a factor of speaker/amp match, and good power conditioning contributing to a low noise floor, IMO.

Thanks Talon4 and Tvad.