Scarlett 2i2 Line input and Gain knobs

G

GeorgeYekcnir

New member
I have a Focusrite Scarlett 2i2. When I am recording a line level source and I have the 'Line/Inst' switch to Line, what is the function of the Gain knobs? Is adding Gain potentially reducing quality? I am connecting the outputs of a phono preamp to both the left and right inputs of the Scarlett 2i2, however the recorded volume is very low if I keep both Gain knobs at 0 (this is to try and get both the left and right signal at the same dB range). I have to turn the Gain knobs up in order to receive a decent recording level. Since the Scarlett 2i2 is in 'Line' mode, the internal preamp should be turned off right? So is simply adding gain harming the signals quality? Also is there anyway to avoid having to tweak the gain knobs until there is perfect balance between both the left and right channel? (This is also relevant for recording a piano or guitar, etc. in stereo)
 
Hi,
This is pretty common on the smaller 2 channel interfaces. The line inputs don't generally 'go through' the preamps, as such, but they are subject to a gain stage.
Unless the manufacturer explicitly states where unity is, you just have to find a balance with your ears and an educated guess.

I suppose the setup is probably different for different interfaces but, yeah, I think having the gain some way off the ground is usually normal.
Ideally you're looking for balance/moderation. Avoid having any gain stage near any of its extremes.

The only real way to avoid this is to use an interface with dedicated line-inputs. Usually you have to move into 4-8 inputs to get this.

Hope that's useful.
 
From what I've seen it's pretty common for line inputs to be padded down and sent through the same gain stage as the mic inputs.

If the line input is designed to handle pro +4dBu input and you're sending it consumer -10dBV signal then it's not surprising you're getting low-ish levels with the gain all the way down. Turn it up a bit, that's what it's for.
 
It may not be all that kosher on the interface, but if you were plugging the Phono pre into a tape deck, you have to set levels to about half - depending on the peak to peak of the signal. it needs gain

You can't really set L&R by the metering. if your ears are any good, use them. Do the reverse leads to be sure levels match through the hardware and wiring - sometimes twisting a plug in the jack get a better connection, etc..

Also, it may not be so easy to get accurate level tracking to L&R right at the cartridge and table setup
 
Leave the gain all the way down (as long as that's not just silence) and add digital gain once it's in the box. Even if there's a baseline noisefloor to the interface itself, it'll be nothing compared to the noise inherent in the source.

It's not worth your time and trouble trying to tweak the L/R balance. Without nice closely matched stepped gain knobs, you'll never be sure it's exactly right. Well, maybe you could play a mono record? But then you'd better leave the thing alone or you'll have to do it all over again.

I do this with my live rig. There's only two repeatable settings on those gain pots and all the way up is too much for most things, so...
 
Heck, even all the way down might not be matched. I would set the gains in the normal fashion and tweak it after the fact as needed. Most likely I'd do a null test to match the levels.
 
The level coming out of that pre amp is likely not even -10dBV (316mV) it is more likely around 150mV which is a common level found inside 'hi-fi' gear.
But, noise is noise! Whether it comes from the RIAA pre or the 2i2 mic amps but the latter is likely to be insignificant compared to the disc pre and THAT well below surface noise. If it is operationally better for you to wind in a bit of gain and work with a healthy signal, fine IMHO. If you run at a lower level and boost digitally after, the overall S/N ratio will be the same.

All that said, it is best to leave a decent headroom margin when duping vinyl. The spits and crackles will likely take the signal close 0dBFS at times and I usually run at -20dBFS, or even lower and at 24bits.

Dave.
 
The thing about Line Level (whether -10dBV or +4dBu) is that these are reference levels only and programme material can vary greatly.

Put another way, when I worked in broadcasting, before a satellite feed, the send end would send zero (+4dBu) tone and we'd adjust our receiving gear so that was also +4dBu on our metering. However, because it was analogue, there was substantial headroom above that level which was quite useable. Therefore, even with things set up with tone, levels would still be adjust in the edit suite to sound correct. Thats why there are level controls even on line inputs (and, has been said, the line input is most often via the mic pre amp, just with a 20ish dB pad at the input.

As ecc83 says, noise is noise and, when setting a gain structure, you should strive to not have extra gain (or cut) added at one place the changed back later in the chain.
 
There is no reason for a Stereo record to present equal voltage for L&R. A lot of times I can set channels by the vocal. There should be no signal without gain.

With a MONO record, a linear tracking arm will do better with even L&R output, as the mass isn't trying to be tossed out of the groove. One can ride the anti-skate if there is any measure of control, or, apply it manually
 
You must log in or register to reply here.
Back
Top