Power Amps... Help!

[MichaelSmalley]

Ladies and Gentlemen-

I'm very excited to say that the time has finally come for me to get a really good rig. One possibility is SWR's Marcus Miller preamp... perhaps a Hartke HyDrive 410 cab.

My question is about the power amp. I was talking to the manager of a local music store and he was sort of steering me towards the QSC rmx1850 HD. In bridged mono mode that would be 1100-1200 watts through the HyDrive 410 (1000 watt cab- lots of headroom).

How do I know if a power amp is suitable to power a bass cab? What about the Crown XLS series? They are considerably cheaper than the RMX series from QSC, but I just don't know enough about these things to make an informed decision. Help!

[Sten]

Here is some information on selecting the right poweramp depending on your preamp:
http://www.ovnilab.com/articles/preamp.shtml

Some things to keep an eye on:
- check the input sensitivity (more info in the link above)
- If you want to bridge our power amp, make sure it is bridgable (also, if you need to run both channels on 2 ohm, check if it can be done etc.)
- Make sure it has all the features and connections you need (for me SpeakOn is an absolute requirement on one)
- If you haul your rig around a lot, consider also the weight issue. Some new poweramps are very light (e.g. Peavey IPR, QSC PLX).
- As for sound, my opinion is that it really does not matter. Some more expensive ones might actually have more headroom for the same given power rating, but if you do not plan to reach it, it is not an important issue.
- reliablility. Compare warranty times, think where can you repair one if you will need to in the future. ...and go for the major brands to be on the sure side (QSC, Crown, Peavey, Carvin etc).

I use Peavey IPR1600. It is light (~7lbs), has all the features and connections I need and is very cheap, considering the features (around 300$ new). It is not bridgable, but it has over 500W per channel at 4ohms and I never need more.

[MichaelSmalley]

Thanks- That article was very helpful.

If anyone has specific recommendations, I'd love to hear them.

[Plstrns]

I had a 1850HD. Nice power, but it's really big and heavy.

[interstatejoe]

Originally Posted by Sten

I use Peavey IPR1600. It is light (~7lbs), has all the features and connections I need and is very cheap, considering the features (around 300$ new). It is not bridgable, but it has over 500W per channel at 4ohms and I never need more.

Sorry don't mean to thread jack, but how do you like the Peavey IPR1600?

[craig.p]

One of my stage rigs is a BDDI into an RMX-1450 into a pair of Avatar B212s. Very satisfied with the RMX. One of its best features is the subsonic filter, switchable between 50 Hz and 30 Hz. I run mine at 30. A real cone-saver, especially in this power class. Yeah, it is heavy -- this one's forty pounds. But the sound has massive weight and authority and clarity. Not saying other amps couldn't deliver the same, just that this 1450 sure does. (Truckloads of it.)

Caveat: plan your rack airflow patterns beforehand; make sure nothing else in the rack is moving air in the opposite direction.

[Sten]

I am very happy with my decision. More volume than I need, light, has the features I need and really not much features that are there to increase the price. Also I kind of like the look of it in a dimly lit room

As I already said, it is not bridgeable, but I do not need this option. For now I have one channel just for backup purposes but you never know when it come handy.

One thing I did not expect is that pressing the power button on the front sets the amp on standby mode, where some of the LEDs inside stay lit. IT felt awkward for me to leave it in that state in the rehearsal room for long periods so it is now plugged into an extension cord with a power switch. I always switch the power off after the rehearsal. I think the idle power consumption is minimal, but it just felt awkward

It has SpeakOn connectors on the back, which seem a little tight (it takes a few seconds to lock my cable into there, but my rackbag allows me not to remove cables from amp so I have not put more thought into it) and 1/4" connectors for through wiring in case I need to send same signal to two cabinets and control them separately. It was great when I had a second cabinet (I currently own Ampeg SVT410HLF but also had Ashdwon MAG210T) to set cabs with different size, impedance and sensitivity to be equally loud.

Since I use Tech21 Bassdriver which can act as a preamp I have never needed a real bass amp. For while I planned to use some micro head for poweramp duties, but when IPR1600 came out for half the price I went for it. For me there was no competition.

[Sten]

craig.p, the BDDI has built in speaker emulator which means it already has a low cut, so I doubt it sends anything below 30Hz to the poweramp anyway.

[craig.p]

Thanks, Sten, but I simply can't take the chance at these power levels. I'd want to see that documented somewhere, with response curves. (Maybe it is -- I admit I might have missed it.) Anyway, having in-circuit a true subsonic with a known knee point and known slope falls squarely under live-sound "best practices."

[Plstrns]

I like my IPR as well.

It is bridgeable btw. You have to use both inputs, then using 2 Neutrik output connectors CH1 +1, CH2 -1 to the cabinet. 4 ohm minimum

Craig, I used the 50hz filter for my 810. Does the 30hz filter do that much for you?

[Sten]

Well yeah, if I had such filter on my poweramp I would have it engaged aswell - it definitely won't hurt But I would not make my buying decision based on it.

[Sten]

Originally Posted by Plstrns

It is bridgeable btw. You have to use both inputs, then using 2 Neutrik output connectors CH1 +1, CH2 -1 to the cabinet. 4 ohm minimum

Yes I know, but:
1) like I said, I will not need it
2) your warranty will probably be void, if something happens when using this setup.

[craig.p]

Originally Posted by Plstrns

Craig, I used the 50hz filter for my 810. Does the 30hz filter do that much for you?

Yes, cuts way back on cone hop. Sometimes I need to emulate an upright that was given a very deep slot in the mix in the original recording. (The C&W song Kiss an Angel Good Morning by Charlie Pride, for example; lots of bass boost required, which is just "asking for it" in terms of cone damage at stage volume.) In all honesty, though, you're right, 50 would probably be fine, or maybe even better relative to where I expect those cabs start unloading their drivers, but I set the switches for 30 to start with, and it seems to be working great in terms of the cones not flopping around. But you've piqued my interest... I might try 50 next time.

1850 with an 8x10 must've been outrageous.

[Plstrns]

Well, the Ampeg 810 can't handle even 50hz that well... The 1850HD didn't get worked so hard, but that was the plan. We all know durability doesn't happen when everything's dimed.

[Zooberwerx]

I'll second the QSC RMX option. I use nothing but RMX 1450's and 2450's. They're real workhorses, heavier than ****, bridge-able, and can be had very inexpensively on the used market. A 1450 in bridged mono will push ~850 watts into 8 ohms which should be more than adequate.

Riis

[bassman1185]

I'm pretty darn happy with my Peavey IPR1600 as well. I haven't even bothered building a bridging cable for it because one channel puts out enough power for me. Plus, as already been mentioned, it's cheap and light. My rack only weighs about 25 pounds right now.

[MichaelSmalley]

Thanks,
So if the Specs say the sensitivity on the preamp is +4dBu and the sensitivity on the poweramp is 1.25, do they work together, assuming the rest of the specs match?

Is it cool if the preamp has a higher sensitivity than the poweramp?

[Jim Carr]

Originally Posted by MichaelSmalley

... was talking to the manager of a local music store and he was sort of steering me towards the QSC rmx1850 HD...

How do I know if a power amp is suitable to power a bass cab? What about the Crown XLS series? They are considerably cheaper than the RMX series from QSC, but I just don't know enough about these things to make an informed decision. Help!

The QSC RMS, Crown XLS, and Crest CA series are all fine for what you want. I use a Crest CA6 and have never run out of steam, though they don't call them lead sleds for nothing.

Essentially that means no one will ever voluntarily carry it for you without your help!

[Sten]

Originally Posted by MichaelSmalley

Is it cool if the preamp has a higher sensitivity than the poweramp?

As far as I know, the problem can be only when the output of preamp is too low for poweramp, so you should be just fine.

Actually, you could get by with the preamp output being lower than the poweramp input, but it just might degrade your sound. When preamp output is higher, I see no problem at all.

[Sickneedhelp]

Originally Posted by Sten

.......2) your warranty will probably be void, if something happens when using this setup.

No worries regarding the warranty. Bridging the 1600 won't cause any undue stress or abuse to the amp. Peavey customer service will be happy to confirm that.