Pass Labs HPA-1

The SIT-3 has extremely low gain for a power amp, the spec being 11.5 db and Stereophile’s measurements indicating 11.3 db. In contrast, most Pass amps (and many others as well) have specified gains of 26 db.

Based on the 11.3 db gain it can be calculated that the SIT-3 will require an input of about 3.3 volts to reach its specified 18 watt maximum output power capability into 8 ohms.

The HPA-1 has a specified gain of 8 db, which corresponds to a voltage multiplication of 2.5 times. Assuming the 8 db figure applies to its preamp output, that means the source component would have to provide a voltage of 3.3/2.5 = about 1.3 volts for the amp to be driven to full power, ***with the volume control set at max.*** Most cartridge/phono stage combinations will not provide that much voltage with most recordings, while most digital sources will just provide modest margins relative to that figure when expressed in db.

So unless your speakers are highly efficient or you use digital sources providing output voltages that are significantly greater than average, or you listen at particularly low volumes, you would probably find yourself on the verge of running out of range on the volume control.  With at least some recordings if not many.

The two Pass preamps you mentioned have specified gains of 10 db, which is just a bit better. The SIT-3 requires very careful system matching as a result of its low gain.

Regards,
-- Al

Thanks, kingdeezie and almarg.

Yes, the lack of a remote and the lower gain on the HPA-1 are points against it for this particular application. I won't be running a phono cartridge, just A DAC with 2.2V output. 

I think I can strike the HPA from the list of contenders.