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FS Mobile operating level

Posted: Thu Sep 18, 2014 12:30 am
by lopbunny
A simple question: Does the fire studio mobile operate at +4 or -10? Just a curious question but I was puzzled by two things: Nothing on the web or forums answered it NOR was tech support able to answer the question without asking the engineering department. Which they suggested would take quite a while. Any facts out there?

Re: FS Mobile operating level

Posted: Thu Sep 18, 2014 9:41 am
by cristofe

Re: FS Mobile operating level

Posted: Sat Sep 27, 2014 10:05 pm
by lopbunny
I appreciate the link but Ive already looked there. My understanding of tech specs is limited. I do see in the "line input" are a reference to +4 but I don't know how to read it without reading into it, if you catch my meaning. The issue Im having is outboard preamps in tot the line in's. If I run them a +4 there is not much of a need to turn up the input gain of the preamp to read a good level in S1. In some cases I can leave the preamp gain at 0 and track fine. If I run it at -10 I need to turn the gain up to what i would say are reasonable levels to get good signal into S1.
What I'm using is an Aphex 207. When looking at the meters on both S1 and the unit in +4 they are wildly different in -10 they read very much the same.
If the FS Mobile is +4 then why am I having this issue?

Re: FS Mobile operating level

Posted: Sun Sep 28, 2014 10:29 am
by cristofe
Have you tried going directly into the FSM into Studio One?

Re: FS Mobile operating level

Posted: Sun Sep 28, 2014 1:03 pm
by salvadoredelle
the FS mobile has 3 types of inputs to choose from depending on your source feed output type and operating levels. Mic, Instrument and line levels. The 2 up front are mic/instrument combo inputs. The 3 pin XLR inputs for microphones which all have different output levels and some need phantom Power. The 1/4" TS inputs on the front are Instrument inputs... these are for guitars and basses that use 1/4" TS type cables and are "Instrument Level". The 8 rear inputs are 1/4" TRS Balanced Line Level inputs, these are for outboard devices like Mixers and Preamps.
There is also consumer -10 Line level type inputs such as RCA inputs for tape recorders and CD players Which the FSM does not have. If you are using the Aphex207 it has both XLR and 1/4" TRS line level outputs. You can use either but the XLR out on the 207 would need to use XLR to 1/4" TRS balanced line cables into the rear connectors on the FSM. If you use the Aphex 1/4" outputs you will need to use 1/4" TRS type balanced line cables into the rear inputs on the FSM.

you can use the front inputs but that will mismatch levels and may cause noise on the inputs as they are Instrument level not Line level.

Mic inputs: = Microphones of various types (phantom power is applied to some)
Instrument inputs: = guitars and basses
Line inputs: = Preamps, mixers and outboard devices

What does "line level" mean?

A device that operates at line level either has a very strong output signal, or only functions properly when you feed a very strong signal into it. Examples of line level outputs include mic preamps, mixers, the "line out" of an amp, and some effects-loop "send" jacks. Inputs needing this level include power amps, most rackmount signal processors, and some effects-loop "returns". This is in contrast to "instrument level" which is what typically comes direct from a guitar or bass, and "mic level" which is the typical output of a microphone or DI box. Both are much lower than line level.

Generally speaking if you send an instrument-level signal into a device that needs line-level input, you will get weak sound, inadequate processing, and probably extra noise as you boost the signal to compensate. If you send a line-level signal into a device that's meant for instrument or mic-level input, you will get distortion. The effects loop on many amps is designed to both send and receive line-level signals, so putting a typical pedal in the loop will often get noise, weakness, and distortion. You may find some exceptions though: either an amp loop that can operate at instrument level, or a pedal that can operate at line level.

The "loudness" or "strength" of an audio signal inside your rig is measured in AC voltage. However the numbers you'll read in an amp's manual or on a website are usually given in dB or dBu, not voltage. The term dB (decibel) by itself means the amount a signal level changes in relation to wherever it started. When you see gear specs that say "-10 dBv" or "+4 dBu", they are telling you how much lower or higher the average output is relative to a specific fixed reference voltage. That voltage is usually either 1.0 V, referred to as "0 dBv", or 0.78 V, referred to as "0 dBu". The terms dBv, dBu, and dBm have different values, but they all have that third letter that signifies a specific reference point; you can use them to calculate voltage levels.

Some common levels you'll see:
+4 dBu is "professional" line level, common in modern pro recording gear, and it is about 1.25 V.
0 dBv is an average line level, typical output from rackmount guitar/bass preamps.
-10 dBv is "consumer" line level, common with older and cheaper recording gear.
-20 dBu is roughly in the neighborhood of a typical instrument's output.
-30 dBu is again in the neighborhood of a typical microphone or DI box's output.
However, instruments and microphones can have a very wide range of output levels in reality, so it is most practical to think of instrument-level and mic-level in/outputs as just "a lot lower than line level", rather than calculating specific dB amounts.

It may even be necessary sometimes to boost one "line level" output by using another gain stage, for example if the first output is specified for -10 dBv and the device you're trying to drive is designed to operate best with a +4 dBu input level. Remember that decibel numbers by themselves are just ratios in reference to a specific starting point, not a fixed value; in other words, 35 dB gain from one device can result in the same actual level as 50 db gain, or 10 dB, or even -20 dB from another device--it all depends on what values each separate engineer started with. 35 dB gain from a boost pedal is a lot, but it may not necessarily get you up to the +4 dBu level needed to drive most power amps, for example. So look for that third letter after the dB to know that you're dealing with a fixed reference point, and therefore a firm value for the highest average voltage output. +4 dBu is the same level all around the world.

Re: FS Mobile operating level

Posted: Fri Oct 03, 2014 12:26 am
by lopbunny
Dear lord this is getting out of hand....So this isn't my first rodeo. I have not gone XLR line out to the XLR mic preamp in of the FSM or any other convoluted patching scheme. TRS to TRS/line out preamp to line in, further proof of understanding, the line in jacks are on the back panel of the FSM and I understand they want "line level". I also get that a lot of things are relative. Meters are not going to correspond exactly or possibly even close. Just having enough of a discrepancy to ask the question: what does it operate at? And so far NO straight answer. FSM runs the line between pro and consumer gear and for that matter there is BALANCED -10 gear out there. So balanced or unbalanced has no bearing on what the operating level is. I have been referred several times to the tech specs by folks who must know the answer is in there yet cannot simply tell me. Including presonus, who's final response was engineering says to find someone who can interpret the tech spec for you. Presonus has always had outstanding support for me but Im finding this a little silly. So until I can sort out how to read the tech spec, for which I haven't found much help online directly relating to this issue I will believe the following:
FSM operates at 1.21 jigowatts at 88mph!
Thanks All for the input. Its is appreciated!

Re: FS Mobile operating level

Posted: Thu Mar 28, 2019 6:16 pm
by BluesmanRob
I have the same question and I can't find the answer in the manual. I am really low vision, so manuals are a struggle for me because my screen reader doesn't always work with manuals. And this is the case with the FS Mobile manual.

Are the line inputs on the rear of the Firestudio Mobile +4dBU or -10dBU. Like the OP, I know how to use the gear, I just don't know the line level. I bought the Mobile only for the dedicated line level inputs (no preamps) so I can connect my ART MPA II tube preamp. I am using TRS to TRS cables from ART line out to Mobile line in. I haven't powered up yet, but when I do I will use -10dBU from my ART tube preamp until I know for sure.

Based on the third post by the OP I am assuming -10dBU, but I was originally thinking the line inputs would be +4dBU.