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Power amp suggestions for Demeter Pre and Barefaced cab

#21
For most of us with our abused hearing there will be little difference between the available Classes. I use Class D because they are the lightest option. I have said many times in the past that I feel no difference between the Class AB sleds and the Class D units that replaced them.

Forget about what Class it is and go forth and buy an amp otherwise we’ll still be doing this next year! :)
 
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#23
Bob Lee (QSC) said:
Damping factor is a useless spec except to marketing departments that have a shortage of technical knowledge.
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So Bob, is there some sort of differences between classes about sound quality or 'latency' (in lack of a better word). Since I'll be using the power amp with a instrument, and not a PA, I don't want to have some sort of delay between my attack and the sound that will come out of the cab (if that make any sense). I've read some people say that some amps are 'quicker'. What do you think about it ? Can it really makes any differences ?
 
#24
Cremette said:
So Bob, is there some sort of differences between classes about sound quality or 'latency' (in lack of a better word). Since I'll be using the power amp with a instrument, and not a PA, I don't want to have some sort of delay between my attack and the sound that will come out of the cab (if that make any sense). I've read some people say that some amps are 'quicker'. What do you think about it ? Can it really makes any differences ?
Click to expand...

The only way you would get a noticeable delay in a power amp is if a manufacturer put in some sort of delay circuit, which unless it were adjustable and touted as a feature, would just add expense for no apparent reason. I suspect that when someone says an amp is quick, it means they've dialed in a gain that lets them play at the volume they want with a comfortable touch, without having to really dig in. In my experience having to dig in too much tends to slow me down.

There can be differences in sound quality between well designed amps and poorly designed ones, but amp class is not the deciding factor. That said, it is harder to do more advanced and complex classes like H and D well, compared to, say, class AB, which is relatively simple. But that's where the competence of the designer comes in.
 
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#26
Pat C. said:
I'd recommend an amp with a low input sensitivity for the Demeter preamp.

I know Bob Lee will disagree with me here, but I much preferred my Demeter VTBP201s with a Crown MA2402 over a QSC PLX2402. And the only major difference between those two amps was the input sensitivity.
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What would be a low input sensitivity ? Below 1.4 Vrms or something?

I just want to understand this thing. Does increasing the gain on the pre amp increase the voltage of it's output, so it could match the input of the power amp ? I thought that I just need to raise the gain of the pre until the power amp clip and just roll back a bit. Is it the right way to do this ? I never had a pre/power before.
 
#28
The Crown is 0.775 volts. I'd shoot for that.

Most any preamp should be able to drive any professional power amp. But to me there was the distinct difference in feel and response between the crown and QSC.
Cremette said:
What would be a low input sensitivity ? Below 1.4 Vrms or something?

I just want to understand this thing. Does increasing the gain on the pre amp increase the voltage of it's output, so it could match the input of the power amp ? I thought that I just need to raise the gain of the pre until the power amp clip and just roll back a bit. Is it the right way to do this ? I never had a pre/power before.
Click to expand...
 
#29
The Demeter web site doesn't say what the maximum output level of the VTBP-201S is, and neither does the owner's manual. The HBP-1, OTOH, specs at +24 dBV, which is 16 V rms.

If the output capability of the VTBP-201S is similar that of the HBP-1, then you don't have to worry at all about input sensitivity; the pre would have have plenty of voltage to drive anything ever made. Just dial it in.

If the preamp has a weak output section, though, you'll need a power amp with higher gain.
 
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#30
Cremette said:
What would be a low input sensitivity ? Below 1.4 Vrms or something?

I just want to understand this thing. Does increasing the gain on the pre amp increase the voltage of it's output, so it could match the input of the power amp ? I thought that I just need to raise the gain of the pre until the power amp clip and just roll back a bit. Is it the right way to do this ? I never had a pre/power before.
Click to expand...

The gain is how much a circuit boosts the signal voltage. So your bass puts out a signal, and the preamp processes and multiplies that signal voltage. Some basses (and bass players) put out a stronger signal than others, and some preamps can boost a lot and some, not so much. That's why we have gain knobs for making adjustments—for making stuff work with other stuff.

To optimize your signal-to-noise ratio, try to adjust each stage, from instrument on, to put out a strong signal without clipping. Doing this will reduce hiss, hum, etc. Then you won't need to turn up the power amp gain as much. Understand that a power amp input "sensitivity" voltage spec applies only when the amp is turned up to maximum gain, so it's not as useful as it's often made out to be. As long as the preamp's output voltage capability is equal to or greater than the input "sensitivity" voltage spec of the power amp, you have the ability to dial in whatever it takes to get everything out of the amp. Don't be afraid to turn things up or down as needed. The vast majority of pro power amps have input "sensitivity" voltages that are low enough for even an iPhone or iPod to drive, so they'll be a piece of cake for just about any bass preamp unless it has a peculiarly low output capability.

This is just what my approach would be, but you can use whatever you wish: I'd get the preamp I like, that has the features, performance, reliability, etc., that I want. I'd get the power amp I like, that also has those qualities that I want. Use them. Dial it in. Probably 95% of the time it's good to go. If I really love that preamp but its output is too weak, I'd just put a little signal booster between its output and the power amp input. That way I get to use what I like and make it all work together.
 
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#31
Sorry guys for the delay, I was quite busy lastly.

So I finally decided to buy a QSC PLX 3102 power amp and I'm really happy of it. It sound so great with my Barefaced BB2 cab, and I have plenty of power for my needs. It also pairs well with my Demeter Pre. I choose it because it have a bit more features than the Carvin amp, so it gives me more flexibilities if I want to use it for something else than just a bass amp. The 6 years warranty is a plus too.

Thank you all for your replies and suggestions, I appreciate!
 

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