Preamp - 18 dB Gain too low?

Trust the manufacturer's spec's, especially since they are consonant with your issues.

What is attenuation voltage ratio and what does it tell us?
Nguyen787

read the table header as "rotation", "Db attenuation" & "voltage ratio".
hopefully this clears it up?

The discrepancy between 1V sensitivity (for full rated power output) and 4V is 12dB -- huge! Grant Fidelity and Shuguang really need to get in sync on that one -- it's very confusing/misleading, on such an important spec that can make or break a system.

A 25Watt amp with 4V sensitivity WAY on the low side -- I don't know what the hell they intended that amp to be used with. If would be great for high-output pro sources > 4V. The issues with a typical 2V hifi digital source are one thing; a low-output MC cartridge would be almost impossible to step up enough to coax a satisfying output from those amps.

As a comparison, the Rogue Apollo KT90/KT120 tube amps have a sensitivity of 1V for 250 Watts output. That's 22dB more gain than the Shuguang 845! Yep, they're on the high side of gain.

Another example on the (very) high side: the old Eico HF-87 amp (runs a quad of EL34; cathode bias; 35W/ch), which was spec'd (according to the assembly manual) at 0.34V for +3dB over full output (70 Watts). That's a whopping 26dB over the Shuguangs!

Both the Eico and the Rogue use a 12AX7 input tube...

my 845 amp is very high, 200mv. I wonder if I am losing any performance since my volume is at 9pm for normal listening. it sure sounds good though despite the touchy volume control. the manufacturer said I could swap out two resistors to make it less sensitive, which might do.

Being ignorant how you calculate 22 dB more gain with Rogue Apollo? Any websites or references are appreciated.