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Which power amp goes with my Tech 21 RBI?

M

melodicly

Oct 22, 2008
416
0
New Orleans, LA
#1
Hey everybody, I recently got a killer deal on the Sansamp RBI and I would like to put it in my 3 space rack with a clean power amp. I have been using a Peavey 700W with 2 4ohm 2x10 cabs. I would like to have 800w for now and it needs to fit in 2 spaces while being relatively light weight. Heres the problem...I have very little understanding of power amps. :confused:

So what should I be looking for? As a bass player are there certain features I should avoid or look for? Is this even a good idea? Do I need the ability for 'bridged mono' and things like that? Or would two 4ohm minimum channels be sufficient? Can I buy something worth while for around $300? What else might I not be thinking of that I should? :help:I am trying to buy time so I can get a Eden amp and I hope this is a transition that will work until I save up the money.
BTW, I have an SKB hard case 3 space rack. Would I need to worry about ventilation?

Thanks for the education guys. :bassist:
Dale
 
#2
Lots of bassists use PA-type power amps as part of their main rig, so it's a common subject of discussion here (hint hint ;)). For the RBI what you need is a power amp that has an input sensitivity rating of 1V or less. Other than that, most any power amp will work just fine. Check out a used Carvin or QSC for great bang per buck.
 
#4
I use both QSC and Crest power amps. I've found both to be reliable and good deals on the used market. Keep your eyes open for a used QSC RMX 1450. This is a nice Chinese import which does 1400 watts or so in bridged mono with a 4 ohm load ( two 8 ohm cabs daisy-chained together). I have two in our PA rack. I believe I paid $200 for it. Even if you upgrade at some time, you always have use for a decent power amp...PA, powering monitors, powering extra bass cabs, etc.

Riis
 
#5
bongomania said:
[ For the RBI what you need is a power amp that has an input sensitivity rating of 1V or less.
Click to expand...

What do you mean by this? In looking at the QSC RMX 1450/1850HD is seems their input sensitivity is at 1.15V/1.16V respectively. What does this mean? thanks for all the info so far guys. I have found a lot about pre/power amps but not a lot about just power amps and how to use them appropriately. :hiding:
 
#6
If you have two four ohm cabinets you will need an amp that will put out decent power in stereo mode . QSC's 1804 and the Carvin DCM1540L would fit in your small 3 space rack and still have good ventilation. The Carvin puts out 750 watts a side into 4 ohms and the QSC 900 watts a side. The Carvin goes for about $400 new and the QSC around $800. Either would work great with the RBI,be lightweight,fit in your shallow rack and make you forget about ever needing an Eden. The most powerful Eden head won't keep up with either of these poweramps for sheer power and the RBI has a great pro tone. No need for an upgrade if you get the right poweramp with the RBI IMHO. No knock on Eden amps either,they make great amps and cabinets.

PS,I used an RBI with Crown poweramps for 5 or 6 years and still love them. I switched to a Markbass LMII last year an like it a ton too but if I needed a bigger rig again would go back to the RBI/poweramp in a heartbeat.
 
#7
So my Eden is rated at 500W and my poor old SWR is rated at 350W. If I get something that is pushing 600+W per side is that not a good risk of destroying speakers? Every suggestion I have gotten so far has controls on the front for both sides and some sort of limiter/speaker protection, but is there any guarantee that I wouldn't explode my expensive Eden cab I love so much? I.e. how would I know when more than 300W would be going into the SWR? Thanks again for all the info.
 
#8
That's what the volume knob is for. If you hear any distorting or farting sounds from your speakers just turn it down a touch. I used to use an Eden 210XLT with my RBI and about 900 watts of power available at gigs and it worked great. At one gig in a small bar I tried to make it sound like a 410 and boosted the low end quite a bit and I did make the cabinet distort some on a few notes but I cut the bass boost and lowered the volume and it was fine after that. The main thing is to use your ears and common sense. I shouldn't have tried to make the cab sound like something it wasn't. That Eden 210 was very loud and deep sounding for a 210 cab but I got carried away and luckily didn't permanently damage the speakers. Your ears are the best indicator of trouble.
 
#9
For two 4 ohm cabinets, this:

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or

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I would consider getting either one used possibly.

In this day and age buying an old gigantic super heavy amp like a CA9 is a bad decision IMHO. They don't really outperform the lightweight stuff and are a pain to resell because no one wants to carry them.
 
#12
So I am talking with the owner of a Carver/Clair brothers CBA 100 600W/ch@8ohms. I can get (I think) for less than the Carvin DCM1540L (which is about $100 more than I would like to spend). Any thoughts on this? I've heard of Carver, never Clair Bros and know nothing about either one. It is for sale on this site if anybody would like to take a look and let me know what they think.
 
#13
melodicly said:
What do you mean by this? In looking at the QSC RMX 1450/1850HD is seems their input sensitivity is at 1.15V/1.16V respectively. What does this mean?
Click to expand...

Check out the "preamps explained" link in my sig for a lot of detail on this subject. :) But the basic idea is that every piece of audio gear has an ideal range of input signal for best results. In power amps, that ideal range is indicated by the input sensitivity rating. You need to feed it a signal that is at the rated level or higher (within a reasonable range) in order to get the best results from the power amp.

IOW the RBI will work with those amps, but may not necessarily be an ideal match.
 
#14
melodicly said:
So I am talking with the owner of a Carver/Clair brothers CBA 100 600W/ch@8ohms. I can get (I think) for less than the Carvin DCM1540L (which is about $100 more than I would like to spend). Any thoughts on this? I've heard of Carver, never Clair Bros and know nothing about either one. It is for sale on this site if anybody would like to take a look and let me know what they think.
Click to expand...

If my experience with Clair Bro's is any indicator, if you break it I will be impressed.

If you are buying an RBI, another thing to look for is a high damping factor. In essence, the damping factor is the amplifier's ability to halt the loudspeaker cone's residual travel after a signal. Stops the springy boingy boingies. Crown amplifiers usually have a nice high damping factor. And they are nice amplifiers.

Cheers,
Mick
 
#15
Alright Bongo I read your preamps explained and learned a lot. Thanks for putting that together. However now I am a little more confused.
In looking at the manual for the RBI, the front input is factory set to -20dB pad. then it goes to say about the REAR input... "can set the Input level selector switch to its 0dB position when you plug in extra-hot signals, such as the output from active bass guitars." This leads me to believe that I should be using the rear input with the 0dB selected with my active bass, but at the same time it mentions nothing of the "active" button on the front panel. :confused:
Using a Crown XLS402D as an example let me make sure I understand this correctly. The input impedence for the crown is 20 kohms and the output impedence of the RBI is 1kohm, so I am guessing that this is a large enough difference to work well. The XLR output from RBI is -20dB or 0dB while the input sensitvity for the Crown is 1.25V meaning that this preamp/power amp is not the best combination? That would mean that with the RBI I need a power amp with .7V input sensitivity, right? Am I getting this right or totally off base? :eyebrow: Thanks again
 
#17
melodicly said:
In looking at the manual for the RBI, the front input is factory set to -20dB pad. then it goes to say about the REAR input... "can set the Input level selector switch to its 0dB position when you plug in extra-hot signals, such as the output from active bass guitars." This leads me to believe that I should be using the rear input with the 0dB selected with my active bass, but at the same time it mentions nothing of the "active" button on the front panel.
Click to expand...
They are just telling you what the rear input is capable of, not saying what the front input is not capable of. :p
melodicly said:
The input impedence for the crown is 20 kohms and the output impedence of the RBI is 1kohm, so I am guessing that this is a large enough difference to work well. The XLR output from RBI is -20dB or 0dB while the input sensitvity for the Crown is 1.25V meaning that this preamp/power amp is not the best combination? That would mean that with the RBI I need a power amp with .7V input sensitivity, right?
Click to expand...
That's right, although you may have enough success with up to 1V sensitivity, especially if you give the preamp a hot instrument signal.
 
#18
cool, and thanks for the preamps explained but.

I drive a QSC RMX2450 with a BDDI Pedal via the 1/4 inch output, set to line level and it is fine. I am thinking of getting the RBI version, but cannot find any reference to the level of the output from the 1/4 inch output (XLR will feed the PA).

So I am a little confused as to whether this will work out ok - there seems to be no switch on the RBI to set the 1/4 inch ssansamp output to line level, unlike on the pedal version.

Input sens of the RMX2450 is 1.23v.

So, will it work ok?

Thanks

Chris
 
#20
ok, Tech21 support have been emailed.

TO clarify, I would be using the XLR output to feed the front of house PA desk, so knock this out of the discussion. It is the 1/4 inch jack output of the sansamp tone that will be feeding my QSC RMX2450. On the BDDI you can set this to either "instrument" or "line" level. I obviously have it at line level and it sounds fine into the QSC.

However, there is no such adjustment on the RBI, and I need the 1/4 sansamp effected output to be line level and not instrument.

Does anyone run theirs this way, and knows the answer?

Thanks

Chris
 

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