Hi everyone!   I've been using a USB-connected Edirol audio interface box, model UA-4FX.   It works great, but as I've upgraded a few times around, I'm realizing its latency isn't very good.    Problem is, I'm not sure what kind of numbers a great low-latency value should BE, so please give me that as well.  Here's what I'm looking for, for those of you who can help:
 
1)  what numbers should I be shooting for in latency, as I look to buy a better interface?   I believe my Edirol's ASIO control panel reports an average of over 150 Ms.  Doesn't that seem really poor? 
 
2)  my current (and near future) hardware is and will continue to be, notebooks- and I have both USB 2.0 and Firewire ports available (not sure when I'll have USB 3.0, so I'll not mention that as an option).  I want an interface that is external, and I need only the same small number of inputs/outputs that my Edirol box has :  single MIDI In/Out, single R/L pair of 1/4" in/out, a single Mic/Line input, a single  XLR Mic input.  It also gives me an RCA L/R pair for outs that I find very useful.  The Edirol supports 24bit/48Khz recording as well.
 
I'm looking for roughly the same capabilities as my Edirol USB UA-4FX, but a much faster throughput and lower latency.  Can anyone recommend particular models?   I'm hoping to stay under about $300, which is probably twice what I paid for the Edirol, but I'm looking at a bit higher end capability. 
Many thanks, gang!!
John

I would hope almost anything would beat 150 ms - even the eridol.  I would try to fix that first.  That isn't a USB 1 interface, is it.  That might explain the latency if they haven't worked on the drivers.
My TC Electonics, not known for low latency, I run at 11 MS (round trip).  I can get lower, but not during mixing.  One of the best sounding, low cost interfaces is the TCK 6 (I think - the desktop model).  That is FW, however.
 
everybody seems to enjoy the Focusrite stuff at the low end - I'd look at that.  But only after I figure out if the eridol is at fault rather than the computers.  Hate for you to spend the money and not be better off - at least as far as latency is concerned.
 
@

I am trying out a Presonus 44 VSL this weekend.  They make a 22 VSL for $199.
http://www.sweetwater.com/store/detail/AudioBox22?device=c&network=g&matchtype=&gclid=CJy_xqOOn70CFQ5qfgodSzEAWA
 
 

The contribution of the interface is a fairly small percentage of the overall round-trip latency. Where interfaces really differ is when you're trying to squeeze the last couple of milliseconds out of it.Many of the less-expensive interfaces have a built-in minimum, with 64 samples being typical.
 
But we're talking about the difference between a minimum latency of 4 ms versus 2 ms. The equivalent to moving your speakers 2 feet closer or 2 feet farther away. For mixing, 150ms latency is fine. Unless you're playing soft synths in real time or monitoring through SONAR's fx bin, extremely low latencies just aren't necessary.
 
The biggest factor in determining latency is the size of your audio buffers. The ability to lower them for fast latencies is mostly a function of your CPU horsepower, and to a lesser-extent the quality of the interface's device driver.
 
Bottom line is that unless you need more inputs, or other features missing from the Edirol, then spending money on a new interface may not be the biggest bang for your buck. If you lack sufficient CPU resources to lower buffer sizes to an acceptable size, then maybe a new motherboard is the better investment for about the same cost as a good audio interface.
 
 

Thank you all, for the above responses!  
If I can get a link to display on here,  I have found the complete Edirol specs here at :
http://www.zzounds.com/item--EDIUA4FX
 
Yet for all the specs, I still do not see anything on average latency setting.  It does handle multiple windows drivers, and I've stuck with ASIO settings and it has a nice Control Panel that makes it easy to slide settings around......
 
It says it will use USB 2.0 ports, which is the only kind I use with it, but yet I do wonder if that's a problem, and I'll do some checks using other ports.  If it's only working at a USB 1.0 rate, then that  would account for a LOT of issues.
 
Regarding buffer sizes, I do not know what is optimal for best speed/latency. 
And yes, I do actually play back soft synths when I monitor what I've arranged, and I do some monitoring in the FX lists.  I use a dual-core CPU which I didn't feel was a problem, in spite of such faster CPU's out now.  Based on the feedback, I'll do more testing before I go ahead with a new interface - Like I said, the Edirol has been working solid since I got it several years back -
 
My real issues have been since I just upgraded from Sonar PE X-1 to PE X-2,  and I tried to go from 32-bit to 64-bit Sonar PE X2.   I have 64-bit Win 7 Hm Premium, but felt in the past that I wanted to stay 32-bit Sonar for downward compatibility with a lot of favorite VSTs.  So I did it that way.  Edirol said it had to use its own 64-bit driver with a 64-bit Win 7, so I've had that in place, and X-1 in 32-bit mode on top of that platform worked fine.  Very solid, in fact.
 
Now, since loading X-2 in 64-bit, (and patching with X-2a) on (Win 7 SP1), and reloading and rescanning all my VSTs, I can't seem to save and close a project without a total Sonarpd crash.  I do not necessarily think this is related to my Edirol interface.  I'm just looking for weak links in the system, and wondered if I've crossed an upgrade threshold now with X-2, where my Edirol interface isn't processing a heavier synth load fast enough?   I dunno.   But thanks for pointing me to doing more checks before I go the interface direction.
~  John
 

I'm really happy with my Focusrite Scarlett 2i4 and their driver support (not to mention customer service) is excellent. This unit also has 4 RCA outputs (apart from the 2 I/O's for guitar/mics + midi I/O's). I got it for under $160 from Audiodeluxe (they should be able to beat most advertised net prices).
http://us.focusrite.com/usb-audio-interfaces/scarlett-2i4
 

When it comes to low round-trip latency, the distinguishing factor between audio interfaces is the size of its hidden safety-buffer.  The larger the hidden safety-buffer, the larger the round-trip latency.
 
The best audio interfaces yield ~5ms total round-trip latency at a 64-sample ASIO buffer size/44.1k.
The quality of the audio interface's driver is paramount to achieving glitch-free low round-trip latency (while running substantial loads).  Not all drivers are created equal...
RME is particularly good in this regard... as are Lynx and MOTU units.
 
PCIe vs. USB vs. Firewire:
Make a good choice, and you can achieve low round-trip latency with any of the above.
ie: RME USB units achieve total round-trip latency of 4.9ms at a 48-sample ASIO buffer size/44.1k (clean playback running substantial loads)
 
The Steinberg UR-44 is a new (relatively low cost) audio interface that offers good fidelity and low round-trip latency.

I still don't quite understand what round-trip latency is.
With my RME at 44100 - 24, I get 1.5ms according to Sonar (earlier version).
With 96000 - 24 both ASIO drivers I get in Sonar a reported 1.3ms latency.
 
According I think or am trying to remember to RME it takes 3ms in the RME unit, or with the electronics.
If I am thinking to add those together then it would be 4.5ms or 4.3ms. That is with 64 samples or for the faster speed kilo-hertz samples 128 samples set on the unit.
??
Oh, soft-synths I am not using at this time.
 

JD---Be sure and check out Beagle's site---he has a link to a lot of specs for many different audio interfaces----Keith

Round-trip latency is the sum of the following:

• ASIO input buffer
• ASIO output buffer
• The driver's hidden safety buffer
• Latency from the A/D D/A converters

The ASIO control panel for your RME (and most units) shows 1.5ms at a 64-sample ASIO buffer size/44.1k.
That's the latency for the ASIO output (playback) buffer alone... nothing else.
 
If you're playing/monitoring in realtime thru software based EFX/processing, you're dealing with round-trip latency.
If you're playing virtual instruments, you're dealing with one-way (playback) latency.
 
The X-factor with audio interfaces is the driver's hidden safety buffer.
The best audio interfaces have well-written drivers that can use a small safety buffer.
Mediocre units tend to use a larger safety buffer... which means high round-trip latency.
Depending on how you work, this may or may not be a factor for you.
If you want the ability to play DI electric bass or guitar... and hear the results in realtime thru an AmpSim plugin, you need an audio interface that provides low round-trip (end-to-end) latency.  Otherwise, you can feel the lag.
 
By the time you factor in the RME's safety buffer and latency from A/D D/A converters, you're actually ~5ms total round-trip latency at a 64-sample ASIO buffer size/44.1k.  That's pretty good...