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Old 02-28-2017, 08:51 AM   #1
reapermusic
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Default Audio interface quality question for direct recording guitar

Hi everyone,

I was thinking about upgrading my audio interface an (OLD M-Audio mobile pre)
I only record one track at a time and do not mic a cab.
I plug straight in to the M-Audio and use Revalver amp/cab plugins in Reaper.
There is nothing wrong with my audio interface but just wondering if upgrading to a better/newer interface will have any advantages or improvements over the one I presently have. I understand that it would if I was micing a cab but I only record direct and using amp cab sims. Another reason I'm considering an upgrade is simply G.A.S lol

I also record in to a Lenovo desktop, 2nd gen i3 cpu with 8GB ram (I know I'll need to upgrade soon LOL)

I'm still a NEWB so my question might be silly.
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Old 02-28-2017, 10:24 AM   #2
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Originally Posted by reapermusic View Post
There is nothing wrong with my audio interface
OK.

Quote:
but just wondering if upgrading to a better/newer interface will have any advantages or improvements over the one I presently have.
There is nothing wrong with the one you have.

Quote:
Another reason I'm considering an upgrade is simply G.A.S lol
And that is totally alright. Go get a new interface, man.
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Old 02-28-2017, 10:46 AM   #3
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The only thing that would make sense for you currently is to check whether your line input has instrument level impedance (-20db) or not.
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Old 02-28-2017, 10:50 AM   #4
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If you really want to spend some money, how about getting a DI box with a nice transformer in it?

That should make more of an audible difference than replacing your prosumer interface with another prosumer interface.
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Old 02-28-2017, 10:58 AM   #5
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Originally Posted by Judders View Post
If you really want to spend some money, how about getting a DI box with a nice transformer in it?

That should make more of an audible difference than replacing your prosumer interface with another prosumer interface.
He'll get some insertion loss FWIW. If the interface has a proper instrument in with high enough impedance, there is really nothing he'll gain. A well-designed instrument input is essentially the same as the input of a properly designed stomp box input (that's good). To your point, that doesn't mean that any losses don't sound good, I surely have a box I built where I can adjust impedance because sometimes I don't want an exactly pure copy of the original guitar signal.
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Old 02-28-2017, 11:23 AM   #6
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Originally Posted by karbomusic View Post
He'll get some insertion loss FWIW. If the interface has a proper instrument in with high enough impedance, there is really nothing he'll gain. A well-designed instrument input is essentially the same as the input of a properly designed stomp box input (that's good). To your point, that doesn't mean that any losses don't sound good, I surely have a box I built where I can adjust impedance because sometimes I don't want an exactly pure copy of the original guitar signal.
Hey, you know far more about the guts of stuff than me, just wondering what your thoughts on the below are:

"Do passive DI's present a different load to a guitar or bass as opposed to active DI's?

Passive direct boxes have had a bad rap for years, mostly due to misunderstandings and holdovers from the early days or touring. In the beginning, the 'transformer of the day' came from broadcast. The 600 ohm standard line level transformer changed the tone and feel of passive instruments like the Fender P-Bass due to loading. What happens is the magnetic pickup in the bass is driving the signal to the bass amp and hundreds of feet of cable to feed the PA system, splitting the signal evenly between the two. When you do this with the wrong transformer, the bass player immediately notices a lack of fidelity and punch. Today, we specify our Eclipse transformers in our direct boxes at 130,000 ohms, a far cry from the 600 ohms that were once used. Therefore the loading is no longer as problematic as it used to be. In fact with the advent of high output active basses, passive direct boxes are often preferred as they are able to handle the output without clipping."

- http://www.radialeng.com/di-questions.php
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Old 02-28-2017, 11:34 AM   #7
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Originally Posted by Judders View Post
Hey, you know far more about the guts of stuff than me, just wondering what your thoughts on the below are:

"Do passive DI's present a different load to a guitar or bass as opposed to active DI's?
Our fellow member ashcat is going to know far more than I but I can offer a couple tidbits. I think 130k is a little low for 2017 but that depends more on what is plugged in so in many ways it is perfectly sufficient. Typically the rule is that the target device's impedance (the DI in this case) should be 10 to 100 times higher than the source impedance (the guitar). Most guitars fall in that 5-10k range IIRC so you can sort of see we are within but close to the 10 times number.

Many modern pedals, at least DIY ones use 1-10 Megaohms to ensure there simply isn't a source impedance high enough to cause any frequency losses. That being said, when I stated insertion loss above I meant loss of dB level not really loss of fidelity.

Another tidbit about transformers, they will pick the crap up out of hum. Thusly to make one that can cover 20-20K and be properly shielded (using MU metal etc.) they can be extremely expensive to manufacture, this is precisely why Jensens (and Radial) cost so much so that isn't a scam, it's just a byproduct of the technology. That's also why Radial DIs have that very thick folded metal enclosure.

All that being said, a true DI is for converting an unbalanced signal to a balanced signal, if that isn't needed then you can achieve the same with any input circuit/buffer that has sufficiently high impedance. Many conflate DI as in plugging a guitar directly in with the conversion to balanced, it's a nitpick but I like calling DIs the ones that actually do the conversion and the ones that don't buffers or similar.
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Old 02-28-2017, 12:47 PM   #8
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Originally Posted by karbomusic View Post
Our fellow member ashcat is going to know far more than I but I can offer a couple tidbits. I think 130k is a little low for 2017 but that depends more on what is plugged in so in many ways it is perfectly sufficient. Typically the rule is that the target device's impedance (the DI in this case) should be 10 to 100 times higher than the source impedance (the guitar). Most guitars fall in that 5-10k range IIRC so you can sort of see we are within but close to the 10 times number.

Many modern pedals, at least DIY ones use 1-10 Megaohms to ensure there simply isn't a source impedance high enough to cause any frequency losses. That being said, when I stated insertion loss above I meant loss of dB level not really loss of fidelity.

Another tidbit about transformers, they will pick the crap up out of hum. Thusly to make one that can cover 20-20K and be properly shielded (using MU metal etc.) they can be extremely expensive to manufacture, this is precisely why Jensens (and Radial) cost so much so that isn't a scam, it's just a byproduct of the technology. That's also why Radial DIs have that very thick folded metal enclosure.

All that being said, a true DI is for converting an unbalanced signal to a balanced signal, if that isn't needed then you can achieve the same with any input circuit/buffer that has sufficiently high impedance. Many conflate DI as in plugging a guitar directly in with the conversion to balanced, it's a nitpick but I like calling DIs the ones that actually do the conversion and the ones that don't buffers or similar.
I know that lots of bassists really like having a transformer in the signal chain for DI. I guess that is less important if you're putting guitar through amp sims that saturate anyway.

I was really just trying to think of something to satiate the OP's G.A.S.
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Old 02-28-2017, 12:50 PM   #9
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I don't know how far I want to get into this right now.

The (at least) 10:1 Rule (of thumb) is good in most cases, but it's complicated by the inductive nature of the pickups. While 5K-10K isn't bad as a general middle of the road guesstimate for DC resistance of most pickups, their impedance gets much bigger at higher frequencies, and in order to keep as many of those higher frequencies as possible, we'd like the load impedance he as large as possible.

But the inZ of whatever you're plugging your guitar into doesn't really "set" the load Z so much as "modify" the load because most people have pots in their guitars which are loading the pickups. We have to look at the parallel total of all of these pieces to know exactly what's going to happen. That equation looks ugly, but it works out that the total of several impedances in parallel is always smaller than the smallest value. It also works out that the closer one value is to another, the more it tends to affect the total. 1M || 125K is 111K -very close to the 125K, the 1M can almost be ignored - while 125K || 125K is 62.5K - we definitely need to consider that kind of variation.

I used the numbers above on purpose 125K is the total of two 250K pots in parallel as you find on many single coil guitars. And it's also very close to that 130K number that Radial article mentioned. Now 62.5K does just make the 10:1 thing against the DCR of a typical single coil, but as the inductive impedance starts to take over, the ratio gets smaller fast, and you start to lose treble. When you halve the load impedance, you lose an octave, so I think the difference between a passive DI and a 1M active buffer is pretty apparent. Almost an octave, sort of...

Before I get to why that's only sort of true, I want to adress that 130K spec that Radial spits. The fact of the matter is that a transformer doesn't really have an impedance of its own. There is of course some resistance in the wire, and some inductance and capacitance from the coil of wire and all that, but the good ones are designed so that these values don't affect the rest of the circuit enough to matter. But when you plug the guitar into the DI, the impedance that guitar "sees" is not that of the transformer itself, but that of whatever mic pre the other side of the DI is plugged into "reflected" through the transformer. Basically, it'll be the inZ of your mic pre times about 133. So Radial must have meant that their transformers will look like 130K if plugged into a 600Ohm input. There aren't too many 600Ohm inputs out there anymore. 1K is pretty standard, but many very popular brands nowadays are bigger than that. Many are more like 3K and more and more are coming out at 10K. So that's kind of good news in that we get back some of the treble we might have lost back in the 50s, but it's going to be different wherever you plug it in.

So I guess that's how far I'm going to get into it. I'll just say that I prefer not to use a passive DI for a passive guitar as much because it can be a little low Z and because of the stepdown in volume. Guitars are already a little too quiet, and it doesn't make sense to turn them down and then back up. That kind of thing doesn't matter in a 64 but mix engine, but it sure does in meatspace! I always just plug my guitar into a pedal with a buffered bypass and connect that to a mic or line input on my interface.
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Old 02-28-2017, 12:50 PM   #10
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Originally Posted by Judders View Post
I know that lots of bassists really like having a transformer in the signal chain for DI. I guess that is less important if you're putting guitar through amp sims that saturate anyway.

I was really just trying to think of something to satiate the OP's G.A.S.
I love stuff on bass guitar that browns and rounds the signal. I almost never use my transparent RME pres on bass, too prickly sounding for me. I also tend to compress a little on the way in, seems to just work.
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Old 02-28-2017, 12:54 PM   #11
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Originally Posted by ashcat_lt View Post
I don't know how far I want to get into this right now.

The (at least) 10:1 Rule (of thumb) is good in most cases, but it's complicated by the inductive nature of the pickups. While 5K-10K isn't bad as a general middle of the road guesstimate for DC resistance of most pickups, their impedance gets much bigger at higher frequencies, and in order to keep as many of those higher frequencies as possible, we'd like the load impedance he as large as possible.

But the inZ of whatever you're plugging your guitar into doesn't really "set" the load Z so much as "modify" the load because most people have pots in their guitars which are loading the pickups. We have to look at the parallel total of all of these pieces to know exactly what's going to happen. That equation looks ugly, but it works out that the total of several impedances in parallel is always smaller than the smallest value. It also works out that the closer one value is to another, the more it tends to affect the total. 1M || 125K is 111K -very close to the 125K, the 1M can almost be ignored - while 125K || 125K is 62.5K - we definitely need to consider that kind of variation.

I used the numbers above on purpose 125K is the total of two 250K pots in parallel as you find on many single coil guitars. And it's also very close to that 130K number that Radial article mentioned. Now 62.5K does just make the 10:1 thing against the DCR of a typical single coil, but as the inductive impedance starts to take over, the ratio gets smaller fast, and you start to lose treble. When you halve the load impedance, you lose an octave, so I think the difference between a passive DI and a 1M active buffer is pretty apparent. Almost an octave, sort of...

Before I get to why that's only sort of true, I want to adress that 130K spec that Radial spits. The fact of the matter is that a transformer doesn't really have an impedance of its own. There is of course some resistance in the wire, and some inductance and capacitance from the coil of wire and all that, but the good ones are designed so that these values don't affect the rest of the circuit enough to matter. But when you plug the guitar into the DI, the impedance that guitar "sees" is not that of the transformer itself, but that of whatever mic pre the other side of the DI is plugged into "reflected" through the transformer. Basically, it'll be the inZ of your mic pre times about 133. So Radial must have meant that their transformers will look like 130K if plugged into a 600Ohm input. There aren't too many 600Ohm inputs out there anymore. 1K is pretty standard, but many very popular brands nowadays are bigger than that. Many are more like 3K and more and more are coming out at 10K. So that's kind of good news in that we get back some of the treble we might have lost back in the 50s, but it's going to be different wherever you plug it in.

So I guess that's how far I'm going to get into it. I'll just say that I prefer not to use a passive DI for a passive guitar as much because it can be a little low Z and because of the stepdown in volume. Guitars are already a little too quiet, and it doesn't make sense to turn them down and then back up. That kind of thing doesn't matter in a 64 but mix engine, but it sure does in meatspace! I always just plug my guitar into a pedal with a buffered bypass and connect that to a mic or line input on my interface.
Thanks for weighing in!
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Old 02-28-2017, 01:12 PM   #12
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It is completely true that sometimes we really don't want all of the treble that we can possibly get from our pickups. When I'm recording direct guitars, I'd usually prefer to at least capture it all. It's easy to shave of that treble and take those resonant peaks once it's ITB - ReaEQ works fine - but it's a lot harder to manufacture that extra high end content if you don't get it from the guitar itself.

There definitely is something to be said for just getting the sound you want and commiting, and if that means a bit heavier load on the pickups and maybe some transformer saturation, frickin go for it. Use a big long coiled cable and roll both of your pots down a both hands or two. But if you change your mind later, you'll probably have to retrack.
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Old 02-28-2017, 01:17 PM   #13
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There definitely is something to be said for just getting the sound you want and commiting
That's typically my preference. I don't need everything committed but I don't want every option available either because I find some value in having some idea of what I want before I record it - just speaking for myself, if I'm oblivious vision wise, I probably don't have much business recording it - saves time in the long run because I'm building on top of previous commitments. If there are no commitments ever, there is a risk of trying to unlock a combination lock with infinite number of possible combinations - for lack of a better term, IMHO, YMMV etc.

For a guitar with slightly less high end up front.... If I want that I prefer it up front and then I can work the volume/tone knob on top of that foundation which just makes things easier.
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Old 02-28-2017, 01:53 PM   #14
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to DI or not to DI ... well, i would ask a totally different question:

Are you fine with some noise in your guitar tracks, or do you want to optimize? If interface noise is an issue, switch to a significantly better one. If not, keep it. Sound won´t change, as long as the input impedance is correct.
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Old 02-28-2017, 02:25 PM   #15
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Thank you all for the info provided

I will very likely buy another interface mostly for G.A.S reasons but before purchasing anything I wanted to check with all of you.

For my particular situation where I'm recording direct and only my guitar using Peavey Revalver software in my room would it be silly to buy a Behringer or M-Audio interface as opposed to something like a focusrite scarlett?
Would there be any true advantage besides build quality,finish,brand reputation ect? Wouldn't they all do the same thing?

My friend and I did buy a Focusrite 18i20 (which is kept at his place)in order to record his drums and we will be working on a project together and learning along the way but for my end I'm not sure if I should just get a Focusrite or perhaps a less expensive unit.

Thanks for all the info everyone!

I hope my questions haven't been too annoying
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Old 02-28-2017, 08:16 PM   #16
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After rereading all of your informative posts again, I have decided to keep what I have.
I guess the old saying sticks.... if it ain't broke, don't fix it lol
I learned many new things that I had no idea about before.
Thanks guys
-Pete
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Old 03-01-2017, 12:21 AM   #17
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as well as everything has been said before, the only real improve you could have buying a new interface is in the AD/DA section.
your sound card is 48k/16bit maximum with quite old converters.
I don't know what kind of converters it mounts, how much noise they make and how much precise they are, so it's just a general speaking.
If you don't need higher performances (even if recording at 24bit should be better IMHO) and you don't hear a big difference between your interface and the focusrite then you don't need to switch to anything new.
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Old 03-01-2017, 05:40 AM   #18
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okay gotcha
Yes my interface is fine and I don't hear any particular difference between this and the focusrite.
Sounds good!
Thank you for your response
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Old 03-06-2017, 07:30 AM   #19
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I'll sell you my apogee one for $200.
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Old 03-06-2017, 09:29 AM   #20
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I'll sell you my apogee one for $200.
Thanks Pixel,

I already bought a new interface and happy with it so far.
Definitely better than the one I had and was even able to get significantly lower latency.
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Old 05-13-2017, 08:33 AM   #21
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Default Audio Interface Suggestions?

I will be using a mac mini i5 (late 2012) which will have thunderbolt and USB 3.0 ports, the hard drive is SSD. The machine is advertised as using Sierra. I went relatively cheap on the computer so that I could spend more on the audio interface. I am looking for suggestions for a unit with at least two inputs. I currently have a mackie onyx blackjack, but it does not appear to be supported anymore in terms of drivers.

Thanks, and apologies if this is posted in the wrong place.
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