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School me on power amp/pre-amp setups

#41
Agree that there's a real sweet spot in the 4u to 6u range; 2u is too easy to tip over, and more than 6u becomes too hard to move about.

I'm inclined to say that a 4u rack would be a good starting point if you had a 1u preamp, and that a 6u rack would be a good starting point if you had a 2u preamp.

My thinking on this is that if you start with a 4u rack, then your SS amp is going to take up 2u, and if you use a 1u preamp that leaves 1u open for a 1u tuner or a 1u wireless kit. If you have a 2u amp and a 2u preamp, you could fit it into a 4u rack, but a 6u rack would allow you the space to add something useful, like a tuner or a wireless.

Another nice thing about the 6u rack is that if you don't fill it, then you can adjust the position of the gear for better balance when it's on it's side, and put a ventilated panel in the open space to allow better air flow.

If you go beyond 6u things get cumbersome and heavy. Then it's time to start thinking about stacking a pair of 4u racks. That is, unless you're one of the guys who can deal with a 12u to 16u megarack on wheels.
 
#42
Wireless or tuner is a handy thing to have.

"Rack people" have this thing where they feel a need to fill up all the spaces in their racks, so, I probably wouldn't go bigger than 6U, or your wallet will get light as a feather. :p
 
#43
Thanks for posting that block diagram, Charlie. I think it helps to clarify things.

I had decided to avoid posting schematics becuase I thought doing that would be too nitpicky, and becuase as soon as you post one schematic you've limited your argument to one case that is easily overturned. the block diagram is helpful because it exemplifies a general truth about modern designs. In this case a general truth in the form of a block diagram is more useful than a specific truth like one amp's schematic.

The important point that I was trying to make was that you can't just view an amp as a black box with an attenuator in it. You have to know where in the circuit the attenuator resides in order to overcome it's effects, or to use it most effectively with other components, like when you are matching volume levels.

The block diagram does show that in typical modern designs you can't simply attenuate the power amp, and make up for any level of attenuation by sending a correspondingly higher voltage signal from a preceding component. doing that runs the risk of overdriving the input stage of the amp and making things go bad. doing that is something that you really need to avoid.
 
#44
will33 said:
Wireless or tuner is a handy thing to have.

"Rack people" have this thing where they feel a need to fill up all the spaces in their racks, so, I probably wouldn't go bigger than 6U, or your wallet will get light as a feather. :p
Click to expand...

The wallet is not the issue, I am already expecting to empty that in preamps, the laziness is. I am used to carrying a (rather portable) head, I do not need any more bells and whistles beyond a power amp and pre amp, I have a pedal tuner and no desire for wireless. I always laugh at one of the bassists who shares my jam space as he has a micro GK head and a power conditioner in a 6 space rack, I do not feel like carrying 35 extra pounds for nothing more than my own amusement.

There is also a local fellow who brings a rollaround rack to shows, it has two Mesa heads and when I asked him if a slave was necessary he informed me it is just the backup. He is basically the old joke in real life "What do you call a guy who takes a $10,000 in gear, in $1,000 car, and hour each way for a $50 gig? A musician"

Thanks again guys!
 
#46
will33 said:
"Rack people" have this thing where they feel a need to fill up all the spaces in their racks, ...:p
Click to expand...

"Rack people." That makes me think of how some guys end up building racks that are so over the top that it looks like they're trying to put out a fire with gasoline.

I guess it makes sense for the OP to give some thought to what he really wants to accomplish with his pre/power amp setup. Typically going pre/power means that you 're going to build a rack system, so the next logical choice becomes whether you want a straightforward rack system for gigging, a complicated rack system for big gigging, or a studio type of rack setup.

A studio/recording type of rack setup could involve all sorts of one-trick-pony components that I'd never consider dragging to a gig.

To me, a basic gigging system would include preamp, poweramp, tuner and wireless. You might not normally think about adding a tuner or wireless, but if you're going to build a rack, you might as well get your tuner off of the floor and into the rack, just for the sake of eliminating one component of set-up/tear-down. And having a rack system makes it pretty painless to implement wireless, and IMO there's a lot to be said for getting rid of the umbilical cord to the amp.

With a 2u solid state amp, I think a 6u rack is the sweet spot.
With a 4u tube amp, that pushes me into a 4u + 4u setup, with heavy amp in one box and the light gear in the other.

enjoy!
.
 
#47
Looks like the OP and I cross-posted, so some of the stuff that I had mentioned might not be helpful to him, given that he doesn't need a tuner or wireless. Well, maybe some of my post will help someone else.

I really like the joke about the gear, the car, and the paycheck. It's so true!

To be fair, I can understand why the guy with the mega-rack has built a heavy rolling rack with the backup gear bolted-down in hte same rack. Consider this -- he's putting all of his eggs in one basket, and he's watching that basket. The only other option would be to build a second rack for the backup system, and to leave it somewhere else until it's needed. If I were dragging my backup gear to the gig, I wouldn't want to leave it in the car where it could get stolen while I'm playing a set. So putting everything into one big rack isn't such a bad idea from a safety standpoint. It keeps all of your valuable gear in one place. It does become a roadie's nightmare, though.
 
#49
WretchedExcess said:
Looks like the OP and I cross-posted, so some of the stuff that I had mentioned might not be helpful to him, given that he doesn't need a tuner or wireless. Well, maybe some of my post will help someone else.

I really like the joke about the gear, the car, and the paycheck. It's so true!

To be fair, I can understand why the guy with the mega-rack has built a heavy rolling rack with the backup gear bolted-down in hte same rack. Consider this -- he's putting all of his eggs in one basket, and he's watching that basket. The only other option would be to build a second rack for the backup system, and to leave it somewhere else until it's needed. If I were dragging my backup gear to the gig, I wouldn't want to leave it in the car where it could get stolen while I'm playing a set. So putting everything into one big rack isn't such a bad idea from a safety standpoint. It keeps all of your valuable gear in one place. It does become a roadie's nightmare, though.
Click to expand...

Haha, I hear you about not watching the backup. I really should see if I could take a pic of his rack one day, it is nothing short of professional it is a shame it only sees amateur gigs. This same fellow keeps his 1 shift a month at the local music store so he can get gear discounts. He bought 7 Warwick heads so he wouldn't have to carry one around between bands. Seems like a good idea until you have to sell them. He also recently received his Jonas Hellborg signature from Warwick.

For the record, I load about $4,000 into a $2,000 car to $100 gigs too. :D
 
#52
Personally, I see 5U as an absolute minimum because I use a rack tuner.

1U power conditioner
1U Tuner
1U Pre
2U Amp

Along with "power conditioning," the power conditioner serves as your power strip so that you can plug the rack into a single outlet. It can also give you a light on the rack

Since 5U racks are very hard to come by, and since that leaves no room for any unforeseen expansion, it's 6 for me if I use a pre. 4's are a lot handier size, but, what are you gonna do?

Currently I'm running a 4U rack, but that's cause I'm using a conventional 2U bass amp. So: Conditioner, Tuner, Amp = 4U.
 
#55
Figured I'd ask this question here :)...

If I have a 2400w (at 4 ohms bridged) power amp and my cabs can take 1200w what is the best way to get half (1200w) of what the amp can put out?

My amp is the qsc 2402 and pre is the tone hammer pedal di.

Options:

1. set the power amp attenuators to half and adjust gain/master as needed (I was told this is not the best way)

2. set the attenuators to full maximum and then be super careful where I dial in the master vol? (leaving the gain at noon)

3. alternative suggestions?

I want to get max headroom from my power amp and pre, but at the same time I obviously dont want to blow my drivers.
 
#58
::::BASSIST:::: said:
Figured I'd ask this question here :)...

If I have a 2400w (at 4 ohms bridged) power amp and my cabs can take 1200w what is the best way to get half (1200w) of what the amp can put out?

My amp is the qsc 2402 and pre is the tone hammer pedal di.

Options:

1. set the power amp attenuators to half and adjust gain/master as needed (I was told this is not the best way)

2. set the attenuators to full maximum and then be super careful where I dial in the master vol? (leaving the gain at noon)

3. alternative suggestions?

I want to get max headroom from my power amp and pre, but at the same time I obviously dont want to blow my drivers.
Click to expand...

I'd just listen and be careful, although you can run a test tone through the system and measure the voltage at the speaker output at various knob settings.

There isn't really a "half way up means half power" deal. It depends on the strength of the input signal as to where on the knobs is full power.
 

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