Does A Stereo Power Amp Require A Separate Preamp?

[jnammy]

I'm interested in getting the QSC GX5 power amp to power my 4x10 cab, but must I also get a preamp? This might sound dumb, but I really like the built-in preamp and pickups on my bass (Glockenklang and Delano) and I don't want to color it with anything else. I was planning on putting my bass through my DI (JDI) box straight into the QSC amp, which will be connected to my cab. Will this work? Thanks in advance.

 

[bongomania]

Check out the "preamps explained" link in my sig.

Edit: I just accidentally deleted almost a third of that article, and my backup copy is out of date! I'm re-writing the missing parts now.

 

[Mo'Phat]

Short answer: Yes, you still need a preamp to give the power amp enough input signal to be properly driven. Onboard bass preamps and/or DI's don't have that.

Even a simple, cheap microphone preamp will do what you need and hardly color your sound at all.

 

[dougjwray]

On the other hand, I knew a fellow bass player who plugged a G&L L1000 directly into a Crown power amp (actually, he used a compressor/limiter, too) and sounded great. Maybe the G&L had enough output to make it work.

 

[Mo'Phat]

Well...sure, you'll get something out of that power amp when you plug a bass directly into it. Your bass has a preamp with some output voltage. But as bongomania's great link explains, you need to match preamp output voltages with amp sensitivity.

Even some pedals would work directly into a power amp, but can they truly drive the power amp to their full potential?

 

[bobcruz]

QSC amps need a fairly hot signal to reach full power. For something really low volume you can sometimes get by plugging your bass straight into a power amp, especially if your bass has a strong onboard preamp. I can get adequate volume for my quiet church gig plugging my Peavey Cirrus with 18V onboard preamp directly into my Carvin T100 tube power amp bridged into a very efficient speaker, with master volume dials at about 2 o'clock. The Carvin is fairly unique in that it only requires 1/2 volt input to drive it to full power (100 tube watts).

 

[seamonkey]

You can open your active bass up and look to see if there's a trim pot. Many have them. You can usually tweak it to comfortable drive a power amp.

 

[CosmicRay]

You will most likely, more like definitely need a pre-amp. Even if you run the pre-amp flat as not to add any color to your tone, you will need to step up the signal.
IMO - Alembic pre's are sweet, Tech 21 not bad either....I like tube pre-amps as opposed to solid state.
Look around, there's quite a few out there...

 

[BassmanPaul]

Yes you will need a pre-amp however it could just be something like an ART TubeMP. I too like how my basses sound right out of the jack. For a while I just used a TubeMP to drive my carvin and Mackie power amps. For around $40 it's pretty cheap to try one out.

Paul

 

[4Mal]

Something like the ART Studio MP - $50 at GC would do ya fine. You'll probably want the additional gain stage - in that case you might lose the JDI unless you also need to send a line to a house system or recorder...

ART also makes a nice little box called the Tube PAC. It's a half rack item with a preamp and compressor. That one has an internal power supply as opposed to a wall wart. It's a pretty industrially built box. Last I knew, AMS had them for something like $110. You can find those in the GFS pretty often.

 

[bongomania]

Also FWIW the JDI has a -12 dB drop from input to XLR output, so even if your bass had a hot-enough output to drive a given power amp by itself, it sure as heck won't be able to if you run it through the JDI.