Gain on an AI...how much is enough

[miroslav]

I've never gone the "interface" route...I just use straight A/D/A converter boxes with Line I/Os...and 99% of the time, I simply focus on the levels that are happening in the analog domain, before I ever get to the converters.
I pay little attention to the dBFS meters on the converters when I'm going in...I instead watch my analog metering before I get to the converters. I never had a level issue during tracking.

 

[joey2000]

It depends what you are recording on.
If feeding a computer and especially at 24bits, the level going in matters little (tho' noobs have a problem seeing this) because the DAW will make not a jot difference to the final signal to noise ratio.

The whole AI thing can cloud the issue/consideration.
If you just consider the preamp portion, and forget the AI for a moment...it is possible that for some mics/applications a low gain preamp just doesn't suit the mic...and/or if your dealing with some sort of tube-based situation, the gain can be used to drive the signal hotter for a tonal reason.

OK these 2 posts confused me. There are AIs today that DON'T have preamps? And yeah I thought it was a given/understood that's what I'm talking about: the preamps in the AI. What else has gain in an AI?

In a pure mic-preamp scenario... the choice of gains may not always be simply about hitting a target level. It may also be about shaping the character/tone...and then you go to your converters where you adj9ust its level for that optimum digital signal range.

Sorry, lost again. Clearly I don't even know as much as I thought about AIs (which I knew wasn't PhD material anyway). I thought the gain control on AIs was all about level/gain/volume, not "shaping character and tone," which I didn't think you did on an AI at all. I thought that was what you did when mixing (and possibly tracking and/or mastering but mostly mixing).

 

[jimmys69]

OK these 2 posts confused me. There are AIs today that DON'T have preamps? And yeah I thought it was a given/understood that's what I'm talking about: the preamps in the AI. What else has gain in an AI?

Sorry, lost again. Clearly I don't even know as much as I thought about AIs (which I knew wasn't PhD material anyway). I thought the gain control on AIs was all about level/gain/volume, not "shaping character and tone," which I didn't think you did on an AI at all. I thought that was what you did when mixing (and possibly tracking and/or mastering but mostly mixing).

Miro uses direct A/D/A conversion from his analog gear. Meaning he has separate preamps and not a audio interface that does both. An expensive route but one I would say I am a bit jealous of...

Just about every audio consumer interface (I believe all) are going to have clean solid state preamps. The quality of them will depend on your budget.

For adding tonal quality of say some vintage preamp or a boutique one that you are looking for, you will likely not know what that means until you get your hands/ears dirty. Hell, I am not even sure.

So start with an audio interface that is worthy. Like a shrubbery, not to expensive. lol. But keep in mind your possible future needs. These days the cost is pretty much directly related to the quality. But then it depends on the quality and amount of inputs you are looking for.

Best to get your feet wet first. You will be the one who determines what you need with time using the gear.

I personally could not tell any member what is the best choice for them. We all find what works for ourselves with time and patience.

 

[garww]

Well, there are plenty of older interfaces with no preamp and knob

 

[ecc83]

Like a lot of folks around ten years ago we, son and I started with a Sound Card. The then ubiquitous M-Audio Delta 2496 (well! I ACTUALLY started with a Terratec card which, upon reflection was variant of the bloody awful Sound Blasters...But we won't go there!)

This was driven initially with a Behringer Xenyx 802 mixer (which is STILL working, never switched off, in a bedroom amping 2 mics in the garden!) This was replaced about a year later with an A&H Zed 10. This was a very decent setup (still is) and gives nearly a -100dBFS noise floor. My environs never get as quiet with an SM57 even in the dead of 2am. Son got into MIDI and an Evolution keyboard controller (he was grd 8 Joe) and the 2496 knocked spots off any AI below £400 or so fo low latency and only the NI KA6 has come about that can beat it sub £200. (many CLAIM 64 sample latency, few deliver it)

Oh yes! Gain! The z10 really has too much for the 2496 which has a max input of around +6dBu iirc and the zed can chuck out +22dBu. I could calibrate the input to the card to compensate but it is as easy to just watch the DAW meters.

I have the KA6 and an 8i6, both are excellent in their own way but there are things you can do with an internal card more easily than with an external AI. BTW my 2496 is rigged up to a TRS breakout box.

Dave.

 

[miroslav]

Miro uses direct A/D/A conversion from his analog gear. Meaning he has separate preamps and not a audio interface that does both.

OK these 2 posts confused me.

Yeah....I didn't mean to confuse anyone, I was just commenting on the gain thing....and yeah, like Jimmy said, all combi AIs that I'm aware of use solid state pres, so the jacking up the gain to drive the preamp tubes for some character and tone color...doesn't apply.
Of course, you still need to get that mic-preamp relationship optimal...which could require a bit more gain than usual for some mics....but not usually.

I don't know if every AI out there follows the same layout and uses the same general circuit structure...?...I doubt it.
I know some are kinda "one-knob" things, and I assume they've taken care of the gain structure from preamp to converters internally, and you just turn that one knob to set everything....but I'm sure I've seen more involved AIs where there may be a gain knob for the preamp and maybe a separate output level knob...etc...and that's what I was getting at, that when they combine stuff, it's not always evident how the gain structure is staged internally...whereas with the kind of setup I'm doing...I know where all the knobs are going.

I like it this way, and doing it over again, I would still prefer to have separate preamps and just pure converter boxes.
You just get more control, and many decent standalone preamps give you additional features that you don't usually get in a combi AI.
Not saying everyone needs to do this route orf that it's necessarily better...especially not for basic 1-2 channel recording at a time, and then staying ITB. Ideally...you want to "keep it simple stupid" if you can. No need to complicate the shit out or your setup if you're not going to really benefit from it...it there's no real need to.
For me, the multiple multi-channel converters were how I wanted to set up the studio...mainly due to the analog side...the use of tape deck and console.

Back when I started putting together my DAW rig...there wasn't such an abundance of combi AIs...you had converters...and it was on you what you fed into the converter.
My multi-channel converter boxes are old...but they work the same today like they did when I bought them, so there's no reason to abandon them. Their downside is how they communicate with the computer...via internal PCI cards.
So at some point a computer upgrade that kills off the multiple PCI card options is what will force me to abandon these converters for something newer...but I've got a backup computer same as my primary DAW computer...so I think I'm going to be good to go for a bunch of years more, before that bridge needs crossing.

 

[gecko zzed]

OK these 2 posts confused me. There are AIs today that DON'T have preamps? And yeah I thought it was a given/understood that's what I'm talking about: the preamps in the AI. What else has gain in an AI?

You were talking about preamps in an AI, and the no-preamp AI reference was a bit of a red herring. My first interface (ISIS) simply had line ins, and I needed a mixer to provide the gain for interface. I think the point was that gain is separate from AD conversion.

Sorry, lost again. Clearly I don't even know as much as I thought about AIs (which I knew wasn't PhD material anyway). I thought the gain control on AIs was all about level/gain/volume, not "shaping character and tone," which I didn't think you did on an AI at all. I thought that was what you did when mixing (and possibly tracking and/or mastering but mostly mixing).

Gain control is about, well, gain. That's its job, and in my view, that's all its job should be . . . clean, accurate, uncoloured translation of the source material. There are some people, though, who seek 'warmth', 'colour' or other nebulous characteristics, and will use an external preamp that delivers these things to a line-level input of their interface.

 

[garww]

Ya, you can have the interface of your specs implanted . No cables for anything. I'll still be plugging in one of the Stereo Electret to the Sony portable cassette or the mighty PS5 : )

 

[jimmys69]

Sigh....

 

[joey2000]

Gain control is about, well, gain. That's its job, and in my view, that's all its job should be . . . clean, accurate, uncoloured translation of the source material.

Well yeah I thought it was understood that that's what this thread is about. Gain on an AI. i.e. making sure I have enough clean volume for most any mic situation. I've just heard/read about needing enough and how some AIs don't have it, so I was/am trying to get a feel for whether it might make a diff if I have one with say 50db vs 60. I know in most situations it probably won't, but I also know my luck.......and I'd rather have it just in case, if such a thing is merited.

 

[garww]

Once again, the gain spec isn't telling you how clean it is with self noise, or, if anything sucks up EMF

 

[mjbphotos]

Well yeah I thought it was understood that that's what this thread is about. Gain on an AI. i.e. making sure I have enough clean volume for most any mic situation. I've just heard/read about needing enough and how some AIs don't have it, so I was/am trying to get a feel for whether it might make a diff if I have one with say 50db vs 60. I know in most situations it probably won't, but I also know my luck.......and I'd rather have it just in case, if such a thing is merited.

Like I said before: in all my years here I've never seen anyone complain about not enough gain from their AI for a particular mic. Except noobies who don't realize they should track in the -18 to -12 range. People who can afford to buy ribbon mics realize they need stronger preamps.

 

[joey2000]

I have (though I can't say if they were "noobies" or not), enough to feel it might be a concern at some point, even if a slight one (as a slight diff can actually be a big one in some cases, if ya know what I mean). This goes double as I'll likely use dynamic mics at some point.

 

[garww]

You can get your decent interface and add a preamp later, if you need it. There's some choices below $100.

Ribbons are $100 - up much like LDC.

I got another ribbon last year - the $99 Apex 205. I was having some "brain dead" evening getting it to work on my interface and went to put it in my music room for another day. I grabbed the 1/4" cable and decided to try it on the open reel deck that sits where I'm typing this. Seemed to have plenty of gain and I still had its level matching output control for better noise staging.

As far as I know they may not be sales leaders, but plenty of people buy them. And you never know what oddball dynamic you will aquire

 

[Steenamaroo]

Like I said before: in all my years here I've never seen anyone complain about not enough gain from their AI for a particular mic. Except noobies who don't realize they should track in the -18 to -12 range. People who can afford to buy ribbon mics realize they need stronger preamps.

Where have you been man? It happens often enough.
Particularly V/O guys, dynamic mic + budget interface.

The goto prescription is usually either more sensitive microphone, cloudlifter, or higher gain interface.

That said, the issue isn't usually 'X isn't loud enough'. The issue is usually that there's audible hiss.

I have (though I can't say if they were "noobies" or not), enough to feel it might be a concern at some point, even if a slight one (as a slight diff can actually be a big one in some cases, if ya know what I mean). This goes double as I'll likely use dynamic mics at some point.

Joey, people talk about dynamic mics need x amount of 'clean gain'.
I think it's a short cut phrase that does the job.
What you really want is a preamp with very low self noise.

I'd bet a preamp with 50db gain and no audible hiss when maxed out would be just fine for an sm7b but that's the gamble.
The vast majority of us aren't going to know until we plug it in.

Broadly speaking the preamps and interfaces that boast much higher gain are, by no coincidence, simply higher quality preamps.....Lower noise levels.
All of my preamps have gain pouring out of them and the only ones that have any audible level of hiss, to me, are the germanium transistor ones. Shocker.

 

[ecc83]

".......and I'd rather have it just in case, if such a thing is merited. "
Well, yes Joe, a bit! Trouble is, in the sort of circuits most AIs use the gain comes 'all in a lump' at the end of the pot's travel* and this can make accurate gain setting rather tricky.
The 'break point' seems to be a pre amp stage gain of about 50 to 55dB. With a well designed circuit you get a fairly smooth travel. 60dB+ and it's jumpy.

It is also the fact that the rather crude 'hybrid' pres in most budget AIs have rather poor distortion performance and the more gain you have/use, the less there is for THD reducing NFB. Ok, pre amp distortion is likely better than 0.05% at any setting but that is probably ten times worse than the rest of the AI's analogue and A/D-DA circuitry combined! (Always better than tape and MUCH better than vinyl!)

*This is the same (but different!) to the ***t or bust law on many guitar amps. The first 10drgs blows out the windows and the impression is given that the (daft) punter will think "Cluck me! if THAT is what it does on TWO???!") . The fix for this is to put a pot in the FX loop. I did the same with a Fast track pro and initially put a pot in the inserts. Later I replaced pot with a 10dB amp using an NE5532. So, got more gain and FAR better control.

Dave.

 

[garww]

..." in the sort of circuits most AIs use the gain comes 'all in a lump' at the end of the pot's travel* and this can make accurate gain setting rather tricky."

So, some cheap-ass guitar has better audio pots

 

[ecc83]

..." in the sort of circuits most AIs use the gain comes 'all in a lump' at the end of the pot's travel* and this can make accurate gain setting rather tricky."

So, some cheap-ass guitar has better audio pots

No, nothing to do with the quality of the pot. All to do with the relationship twixt gain and resistance in a feedback amplifier..Decibels you know.

The effect can only be fixed by having a multiway switch to change the gain with discrete resistors or, some top line pres have a relay that kicks in at a certain point. OR, have less gain of course!

These days, top of range AIs, e.g. RME, use digital gain control. This is likely to filter down to us mere mortals I am sure!

In the case of the 'S or B' guitar amp pot? No bloody excuse! Either REALLY numpty design or, as I said, they are trying to kid you you've bought a monster.

Dave.

 

[mjbphotos]

Where have you been man? It happens often enough.
Particularly V/O guys, dynamic mic + budget interface.

The goto prescription is usually either more sensitive microphone, cloudlifter, or higher gain interface.

That said, the issue isn't usually 'X isn't loud enough'. The issue is usually that there's audible hiss.

.

Yeah, and it's usually the same reason - they are trying to track much louder than needed and the mic/cable/preamp's noise is cranked accordingly.

 

[Steenamaroo]

If there's audible hiss it's not going to help recording at lower gain.
You still need to make the signal louder, relative to the hiss.