On Fri, 6 Jan 2012 10:50:12 -0500 Chris Metzler <cmetzler@xxxxxxxxxxxxx> wrote: > - -Pros/Cons of Interfaces- This is very nice. I'd add that Firewire can be problematic under Linux depending on the chip used to implement it. > - -Questions I have- > > 1. Some PCI interfaces (like the Delta 1010LT) have RCA jacks rather > than 1/4". What about issues relating to noise/degradation introduced > by a 1/4"-to-RCA adapter? It can happen with just about any cheap cable or adapter. That said, I'd rather have an interface with 1/4" balanced connectors, which is why I went for the full M-Audio Delta 1010. > 2. Some interfaces seem to have a combination jack that allows XLR and > 1/4" inputs. Are these good? Or is there a tradeoff between > convenience and sound quality? I've used these on a few preamps now, including an ART and M-Audio's Studio I/O, and have never had a problem. I like the convenience of them! > 3. if you have the chance to pick up at a > really good price Z-Audio's UberSuperDuperInterface, with a gazillion > ins/outs and a lot of features, and right now you only need a small > fraction of what it can do, are there non-cost reasons why you > *shouldn't* get it? None that I can think of. I started small and kept upgrading as it turned out I'd use more and more I/O ports on a project. I use 2 1010's now (16 I/O ports total) and other than occasionally running short on preamps (I only have 9 channels of preamp available, the 1010 has no preamps) it's been enough. > 4. I'm so confused about what I can plug into an interface's 1/4" jack > at this point that I'm having trouble even articulating questions. > Here's my best shot: > > a) Guitar cables typically use a TS connector while line-level devices > (analog outs on drum machines, keyboards, etc.) typically use TRS, > right? I'm presuming there's a difference in voltage range as well > (hence why guitars aren't referred to as line-level)? Guitar signals are actually pretty weak, and need some sort of preamp before they're really usable. This can often be done in software, though; packages like Guitarix (http://guitarix.sourceforge.net/) will help create good sounds, but I always prefer micing an amp or at the very least adding a pre-amp before taking the signal in. I record electric bass this way a lot, but electric guitars generally sound poor without more processing, which I like using the amp for. Again, Guitarix will simulate an amp here, or external units like the Line6 Pod can also provide this processing (as well as giving you a line-level signal). Balanced vs. unbalanced (or TRS vs. TS) has nothing to do with line level, though. That has to do with the signal strength. Professional audio gear considers line level to be +4 dBu (~1.228V RMS) while consumer audio uses -10dBu (~0.316V RMS). Guitar pickups and mics are typically much lower than that - anywhere from 1 - 300 mV if I remember correctly. > b) Am I correct in thinking that a cable with TS connectors is > unbalanced and a cable with TRS connectors is balanced? Yes. Also, mic connectors (XLR) are balanced. > c) My understanding is that in order to plug a guitar into a balanced > input, there needs to be a DI box in-between to change the impedance. This is true, but not so much to change the impedance, but to introduce it into the system. The Wikipedia entry on balanced audio gives a good explanation of the details. In short, you introduce balanced impedence to reduce audio interference. The DI may be passive or active, which indicates whether a preamp is in the circuit. No preamp = passive. > But in advertising blurbs, some 1/4" inputs on interfaces are billed as > accepting balanced or unbalanced input. Does that mean that both > guitars and line-level devices can be plugged into them? No, it means that you can use either type of cable (TS or TRS) and make a connection. It's got nothing to do with line level. If you have unbalanced connectors, you can use a TRS cable but you won't get any of the benefits of balancing. You can use a TR cable with balanced connectors, but again lose the actual balancing - most of the time. You might occasionally run into balanced connectors that won't want to work with TS cables but that seems pretty rare. Of course, both ends must be balanced and a TRS cable used to take advantage of balancing. > If an > interface only has mic/line jacks, does that mean you *must* get a DI > box to plug in a guitar? No, but the signal may be prone to interference if you don't. > d) Since guitars aren't at line level, do they need preamplification > like microphones do? Yes, but this is often doable in software. This is why you can't get a 1/4" to RCA connector and just plug a guitar into the tape inputs of a home stereo and get anything resembling a good sound out, the signal's too weak for the main amp to do much with it. > Or if an interface has unbalanced inputs, can you > just plug a guitar in and go? Nope, again it's got nothing to do with impedance or balancing or the type of input, and everything to do with signal level. Hope this helps! -- ====================================================================== Joe Hartley - UNIX/network Consultant - jh@xxxxxxxxxxxx Without deviation from the norm, "progress" is not possible. - FZappa _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
