+4 dBu vs Lo Gain on Fireface?

[Joost]

Do I plan to record something with using the internal preamps of the fireface, but reading the manual I see that the Lo Gain setting gives me more headroom. What the disadvantages of that setting?

the manual says:
"Reference 0 dBFS @ Headroom
Lo Gain +19 dBu 15 dB
+4 dBu +13 dBu 9 dB
-10 dBV +2 dBV 12 dB
With +4 dBu selected, the according headroom meets the latest EBU recommendations for
Broadcast usage. At -10 dBV a headroom of 12 dB is common practice, each mixing desk operating
at -10 dBV is able to send and receive much higher levels. Lo Gain is best suited for
professional users who prefer to work balanced and at highest levels. Lo Gain provides 15 dB
headroom at +4 dBu nominal level.
The above levels are also found in our ADI-8 series of AD/DA converters, the Multiface, and
even in our Mic-Preamps QuadMic and OctaMic. Therefore all RME devices are fully compatible
to each other.

[synthoid]

Well, the disadvantage is very simply that if your input signals fall substantially below the reference level (+19dBU is quite hot) then you will in effect reduce the resolution of the A/D converters -- you will be forcing them to express the input signals using fewer bits.

-synthoid

[GearGeek]

It depends what you are recording. For most applications the +4 setting is the way to go. However, I record with a tube pre amp, and sometimes I like to crank the hell out of the tubes. In this case I use the low gain setting so I don't clip the input. Also, you might want to use the low gain setting for high volume instruments like horns or electric guitar cabs. Good luck!

[Joost]

How dumb, I hadn't thought of it like that. Thanks guys, excellent answers. +4db for me then

[liuto]

Joost, maybe I did not understand your question correctly, but if you want to use the internal preamps of the FF, the different settings (-10dBV, +4dBu and high gain) are not relevant. They only affect the use of the line ins. The level of the mic ins is only controlled by the gain controls on the front side.

Regards
Hermann

[Joost]

Thanks, btw, I don't get why people are so negative about the preamps. they tested almost flat over the entire frequency spectrum, so they are excellent 'wire with gain' pre's and they're much quieter than a lot of expensive pre's. but maybe that's just me being stupid again.

[liuto]

Originally Posted by Joost

Thanks, btw, I don't get why people are so negative about the preamps. they tested almost flat over the entire frequency spectrum, so they are excellent 'wire with gain' pre's and they're much quieter than a lot of expensive pre's. but maybe that's just me being stupid again.

No, they're just positively characterless, that's what some people seem to dislike. I use them always for spot mics and for that application they are perfect.

Hermann

[GTR]

Originally Posted by synthoid

Well, the disadvantage is very simply that if your input signals fall substantially below the reference level (+19dBU is quite hot) then you will in effect reduce the resolution of the A/D converters -- you will be forcing them to express the input signals using fewer bits.

-synthoid

+4 or -10 has absolutely nothing to do with the amount of bits used on the A/D.

[synthoid]

Originally Posted by GTR

+4 or -10 has absolutely nothing to do with the amount of bits used on the A/D.

If you calibrate your converter so that 0dBFS corresponds to +19dBu and your input never exceeds 0dBu, then the upper 19dB of dynamic range of the converter -- corresponding roughly to the three upper bits of its output -- will be unused. That is to say, the three upper bits of the converter's output will always be zero. If the converter puts out 20 bits total, the input signal will have to be expressed in terms of the remaining 17 bits.

-synthoid

[GTR]

To quote Paul Frindle, +4 or -10 has NOTHING to do with the amount of bits being used:

The most important thing to remember is that recording and processing at lower levels DOES NOT waste 'bits'. It doesn't work like that - all your 'bits' are there all the time at all levels :-)

So there! Nanny nanny boo boo to you.

:)

[synthoid]

Originally Posted by GTR

To quote Paul Frindle, +4 or -10 has NOTHING to do with the amount of bits being used:

The most important thing to remember is that recording and processing at lower levels DOES NOT waste 'bits'. It doesn't work like that - all your 'bits' are there all the time at all levels :-)

So there! Nanny nanny boo boo to you.

:)

That's great! So turn your input levels down as far as they will go. You'll never have to check for overs again. Let us know how that works out for you.

-synthoid

[Slaytex]

I tried recording at both the +4 and Lo gain. I use API pre's in my setup and the Lo-gain setting has worked out the best due to their hot output. I've never noticed a decrease in resolution and have to agree that the level you go into your system is always at full resolution. It's what you do with it after it's in the system that can hurt you. I generally shoot for -10 to -6 depending on how dynamic something is. The only arguement I see here is that you may get more analog noise using the lo-gain input as you need more gain from your pre, but in reality I'm not hearing it and worry more about making cool music.

[Slaytex]

ALL YOUR BITS ARE BELONG TO US!

[subatomicpieces]

Originally Posted by synthoid

That's great! So turn your input levels down as far as they will go. You'll never have to check for overs again. Let us know how that works out for you.

-synthoid

That's great! So run that fingerpicked acoustic guitar right up to the red without clipping. You'll be "using all the bits"! Let us know how that works out for you.

[synthoid]

Originally Posted by subatomicpieces

That's great! So run that fingerpicked acoustic guitar right up to the red without clipping. You'll be "using all the bits"! Let us know how that works out for you.

*sigh*

I'm not advocating pushing your converters to the limit. I'm simply saying that, for a fixed input voltage level, the calibration of the input to the converters certainly makes a difference. Why do you think that they *have* a calibration at all, if the only sensible setting is the high gain (+19dbu) setting?

-synthoid

[Windtaken]

Originally Posted by subatomicpieces

That's great! So run that fingerpicked acoustic guitar right up to the red without clipping. You'll be "using all the bits"! Let us know how that works out for you.

duuurrrrr?????.... ... ...

[GTR]

Originally Posted by synthoid

That's great! So turn your input levels down as far as they will go. You'll never have to check for overs again. Let us know how that works out for you.

-synthoid

You are very good at spreading digital audio myths. Keep up the good work!

[synthoid]

Originally Posted by GTR

You are very good at spreading digital audio myths. Keep up the good work!

I certainly don't mean to be spreading misinformation. Instead of repeating that I'm wrong, why don't you explain what the reference level (0dbu, +4dbu, +19dbu) is, how it works, and what its purpose is? That was after all the original question.

Here's how I think it works. i think that the reference level is the input voltage that will cause the converter to output 0dbFS. Do we agree about that?

-synthoid

[GTR]

Originally Posted by synthoid

I certainly don't mean to be spreading misinformation. Instead of repeating that I'm wrong, why don't you explain what the reference level (0dbu, +4dbu, +19dbu) is, how it works, and what its purpose is? That was after all the original question.

Here's how I think it works. i think that the reference level is the input voltage that will cause the converter to output 0dbFS. Do we agree about that?

-synthoid

Yes, a pro piece of gear with a reference level of +4dBu will read 0VU on the meters of another pro piece of gear.

When I got a Mic Pre (DAV), I had it modded so that the peak level RED LED lights up at +19dbu, which is the peak level of my Fireface 800 inputs.

Hope this helps-- rock on!

- GTR

[GTR]

Check this out---

[synthoid]

Originally Posted by GTR

Yes, a pro piece of gear with a reference level of +4dBu will read 0VU on the meters of another pro piece of gear.

I see, that clears it right up!

Thanks,

-synthoid