Impedance matching between pre and power amps


Hi all,
I am trying to put together a Bass Guitar Amp and I am having issues with power output. I am using a Carvin SX-15 Preamp feeding a TDA8954 Power Amp board purchased on Ebay. The power amp is supposed to deliver 210 WPC into a 4 Ohm Load or 420 Watts in BTL (bridged) Mode into an 8 Ohm Load. I am using it in BTL mode for max power. The problem is, If I use just the Carvin, the power output (at full gain) is weak to say the least. I add my Gigpro beltpack preamp and I gain a significant increase in power but still weak. I then added a DBX-1 compressor (with gain at max) between the Carvin and the power amp and with everything at max levels it just starts to show a little power. It seems like I'm just not getting enough signal from the preamp to the power amp. Input impedance of the power amp is 56K Ohms, Output impedance of the preamp is 5.9K Ohms. Is it just a compatibility issue between the amps or can I use a matching transformer between the two to boost the signal to a usable level? For comparison I connect the Carvin and the DBX to a Peavey 350 WPC power amp (using just 1 channel) and I can shake the house and rattle the windows. Does anybody have any input on this issue (good or bad)?
mandobassman
Have you tried running this un-bridged?  Are you getting a lot of output using just one channel?  What is the impedance on your speaker?  
Had a quick look at this because its an interesting problem. Impedance is an indication of required current flow. A low input impedance is telling you the driving source needs to be capable of good current output. Otherwise if it doesn't have enough current you hear things like weak bass or a less sparkly dynamic sound. 

That's not what you have. What you have is just plain not enough volume. This is a voltage problem. The spec you want is the voltage needed to drive full output. Then if you know that and can measure that much voltage coming out of your preamp then you know you have a problem with the amp. Otherwise if the voltage isn't there then you were right the first time and you need a step-up transformer to increase the voltage. The pics on Amazon show what looks like it might be an optional transformer, can't tell, but seems a clue to me.