input sensitivity?

zone1 · #1 08-20-2010, 05:04 PM

Does the input sensitivity of a power amp change when you connect it to cabs with different ohm specs? For example, I have a BBE BMAX preamp/QSC PLX1804 poweramp that I connect to with a Peavey TVX 4X10(8ohm) cab, and just cant get enough volume out of the rig. The amps input sens. spec. is 1.20V at 8ohm. Will that lower, allowing more preamp voltage in, if I connect a 4ohm cab to it? Or would I be better off using a more powerful preamp?

thudfromafar · #2 08-20-2010, 05:09 PM

Is it connected with an XLR cable? If so, try using a 1/4" instrument cable.

bobcruz · #3 08-21-2010, 11:24 AM

Input sensitivity won't change no matter what cabs you hook up. The QSC's clip indicator lights will tell you if your preamp has enough output to drive the power amp into clipping. If it doesn't, you need a hotter preamp or you can have the QSC modded for greater sensitivity (a simple resistor swap, probably for a tech's minimum bench fee).

RickenBoogie · #4 08-21-2010, 12:07 PM

+1, the input sensitivity has nothing to do with the speaker load, and evetrything to do with the preamps output.

zone1 · #5 08-21-2010, 12:57 PM

I'm using 1/4 cable between the pre and the amp. It seems a more powerfull preamp is the remedy. Any suggestions? Sansamp RPM or something else?

Foz · #6 08-21-2010, 03:16 PM

or a gain step up on the way to the amp...

maybe a nice Ashly?

http://compare.ebay.com/like/1904317...sort=BestMatch

and the dual layout will come in handy if you ever biamp