I'm looking to replace an old Firepod and have narrowed the search to either the Quad Capture or Octa Capture. I was told by a salesman that the reason I didn't like the sound of a little Scarlett unit I tried was the bus power wasn't sufficient to really push the pre's.  If this is accurate, wouldn't any bus powered unit have this issue, including the quad capture?  It seems like a dedicated power supply would be better, but then there's a lot of bus powered models out there so wouldn't seem to be a deal breaker.
 
Also, not sure I need all the inputs of the octa but I also like the DSP built in.  Any opinions on whether the built in DSP is that great?
 
thx

The bus power is iffy and it depends on what power is available on the USB port from the PC.  It can vary from one PC to another.  I would rather rely on an external power supply.  Just like external USB hubs, the self powered are needed as there is not enough power available to properly run an external USB Hub. 
 
I have an Octa-Capture and perfectly happy with it.  I like the built in limiters, although I don't use them all the time.  Low Latency, too.  Music audio electronics guru Craig Anderton has a glowing review of the Octa-Capture on the harmony central site. 

Your salesman just gave you a bunch baloney, he obviously doesn't know what he's talking about.  'Push the pre's' is gibberish. Of course, you may not like the 'sound' of the focusrite unit, but that unit was working as designed.
 
I can't speak for the Roland units, but having an on board DSP for mixing and monitoring FX is always a plus.
 
 
 

Thanks for the replies.  I'm really leaning to spend the extra on the octa unit.  Just read through almost 17 pages of comments on the Anderton review and seems like there's no way to go wrong with this one.  More than I set out to spend, but also don't want to end up limited by buying short now.
 
As for the salesman, I was in Guitar Center and just like at Best Buy, you have to be extremely skeptical of everything they say.  
 
thx again.

I tried several other, less $$ interfaces before buying the Octa-Capture.  One was DOA, another brand had noisy headphone outputs, another brand had problems connecting (I suspect bad ASIO drivers), another brand crappy mic preamps, etc.  I finally put out the $$ for the Octa-Capture and haven't looked back since.

Something to think about:
 
A bus-powered USB interface can draw 5V DC at a max 0.5A (= 2.5W).
 
From a 5V DC bus-power supply, an interface must somehow supply 48V DC for phantom power.
 
At 5V DC supplied power, the "+" and "-" power supply rail voltages (and thus, maximum output voltage levels) for an interface's mic preamps (and headphone amp) would be +2.5V DC and -2.5V DC (referenced to a "virtual ground 0V DC level = 1/2 the supply voltage) or 5V rail-to-rail (although in actual practice lower than that). Yet many bus-powered interfaces have their preamp power supply rails at rather higher/lower voltages (e.g. +/-15V DC rails) .
 
Hmm...

Goddard
Something to think about:
 
A bus-powered USB interface can draw 5V DC at a max 0.5A (= 2.5W).
 
From a 5V DC bus-power supply, an interface must somehow supply 48V DC for phantom power.
 
At 5V DC supplied power, the "+" and "-" power supply rail voltages (and thus, maximum output voltage levels) for an interface's mic preamps (and headphone amp) would be +2.5V DC and -2.5V DC (referenced to a "virtual ground 0V DC level = 1/2 the supply voltage) or 5V rail-to-rail (although in actual practice lower than that). Yet many bus-powered interfaces have their preamp power supply rails at rather higher/lower voltages (e.g. +/-15V DC rails) .
Hmm...

There are scads of boost and buck converter chips out there from various chip manufacturers. Getting 48v from 5v is not a problem, and there's little current use at 48v since in most cases it's used just to statically charge a condenser plate, and in other it's in the milliampere range.

No, getting necessary higher voltages from 5V USB bus power isn't really a problem.
 
But it does require designing for, and it does incur expense for the necessary components. And the supply current available from a USB port is finite (100~500 milliAmps) and must power not only the mic/inst preamp(s) and headphone driver amp(s) but also line input/output buffers, AD and DA converters (codecs), onboard DSP/mixer logic, optical I/O, metering and indicators,  and a USB interface, each of which can consume substantially more supply current than the amount required for supplying phantom power bias voltage (also possibly used for powering a microphone's onboard drive electronics).
 
Consequently, apart from being dictated by cost, when confined to using USB bus-power, compromises must often be made in an interface's features and capabilities, such as limiting the number of mic preamps and headphone outs and total number of I/O channels provided, the available preamp gain and headphone driver output power and possibly even the complete absence of onboard DSP/mixing, compared to a mains-powered interface where the available supply power is not so constrained (or even to bus-powered Firewire interfaces where the supply current is typically significantly higher than for USB although still severely constrained compared to mains-powering).
 
Regarding a bus-powered Scarlett, "how it sounds" might be affected by how capable it is of driving the particular headphones (of whatever particular impedance they might be) plugged into its headphone jack or of driving its main (line) outputs, rather than anything to do with its mic preamps.
 
Point being: there is a very good reason why the Octa-Capture (or Scarlett 18i20) requires mains power and can't be USB bus-powered like the Scarlett 2i2 or 2i4 can.
 

Regarding a bus-powered Scarlett, "how it sounds" might be affected by how capable it is of driving the particular headphones (of whatever particular impedance they might be) plugged into its headphone jack or of driving its main (line) outputs, rather than anything to do with its mic preamps.
 
Point being: there is a very good reason why the Octa-Capture (or Scarlett 18i20) requires mains power and can't be USB bus-powered like the Scarlett 2i2 or 2i4 can.

 
That's a speculative point, and a round-about way that the design is somehow compromised. All engineering design activities, are a compromise between resources and cost.
 
I don't have one of those units, but a critiquing  of it's headphone outputs here is useless and just as applicable to the Roland unit. Unless you know the output impedance of each unit and the impedance of the headphones used, you're shooting in the dark. That said, there should is plenty of power available on the USB bus to drive modern headphones of the 50-120 ohm range. I wouldn't recommend 600 ohm headphones, but then if you're paying 400+ for (what's considered esoteric today) 600 ohm headphones, why are you even looking at these Foscusrite and Roland units?

Well, the solution is to get an external pre.  If he didn't suggest that then he might be dumb, but honest.  And pushing most IC pres, esp. built-ins built to cost, isn't a way to improve your tone.
 
A well designed, well powered pre can make a difference - but not that much, depending upon your recording techniques.  Either of those pres, bus powered or not, should be fine 90+% of the time.  So if you don't like the sound you are getting from the unit, it is most likely due to the room, mic or technique (or a combination of all three).  It takes time to develop and ear for recording - even if you spend all kinds of time on mic placement.  And the mic choice will have much more impact (usually) than the preamp choice.  And if you have a crappy room, guess what recording in it sounds like?
 
I've used the roland units (the 100 and 700 anyway) and the pres/conversion are good.  The dsp - not so much.  I'd never buy a unit based on the dsp comps/gates.  Sonar or any daw is going to do it as well since the dsp is post conversion.  And most interface dsp reverb is for the talent, not recording (tho some like the TC Konnekt 48 are better than good).
 
Buy your interface for the conversion but most importantly if it works out of the box w/ your pc system. Then learn on that as you add software/outboard.  Then upgrade it when you outgrow it - which you might not.  Rinse, repeat.