#1662214 - 03/17/04 02:42 AM
Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
Offline
|
|
What is a line level signal? I'm looking for a peak-to-peak AC signal voltage value here. Also, what is microphone level? Guitar level?
In order to design some of my own effects and preamps, I need to know those levels. I know with guitar, it will depend on the pickups, but what is the range? I've heard that a hot pickup can put out +/- 3V, but I haven't tried to measure it. (My O-scope is sick.  )
Sorry, I didn't realize that there's a studio tech forum. 
|
|
Top
|
|
|
|
|
#1662215 - 03/17/04 09:32 AM
Re: Line level? Mic level?
|
Philip O'Keefe
10k Club
Registered: 12/17/00
Posts: 17674
Loc: Riverside,CA,UNITED STATES
|
|
Offline
|
|
First of all you'll need a reference point, and secondly, there's more than one "line level", and mic level can vary as well.
Let's start with the reference level - which you need anytime you're using dB's. dBv is 1 volt with no load. dBm is about .775 milliwatts with a 600 Ohm load.
Mic levels normally run about -60 dBm, but that can vary quite a bit. But that should get you into a generally accepted ballpark for "mic level".
Line levels come in two main types - consumer / "prosumer" is -10dBv. You'll likely find -10dBv line level outputs on things like lower end home recording gear and on home stereo and A/V gear.
Professional line level is +4dBm. Pro mixing desk I/O, audio interfaces, I/O on pro level effects and processors - they'll normally be at +4dBm. Some devices offer both -10dBv AND +4dBm, or are user switchable.
Instrument level can be all over the map. Piezo pickups can be extremely low in output, while active magnetic pickup systems with a preamp or boost circuit will be significantly higher. I'll ballpark it (very generally) at oh, about -20dBv. Ditto that for most synthesizer outputs.
If it's an analog connection on an RCA type jack, it's almost certainly -10dBv. If it's on XLR connectors, it might be mic level or it might be +4dBm line level, but it's not normally going to be -10dBv line level. 1/4" TS or TRS can be +4dBm, -10dBv, instrument level (such as the output from a synth or guitar) or even speaker level. You have to be aware of ths and careful because connecting say, the speaker level 1/4" output from a guitar amplifier into the -10dBv line level in on a portastudio is analogous to trying to drive a Mack truck through a mousehole - you're going to destroy something. So never assume anything folks.
Anyway, it's extremely late, and I'm sure David (on the studio tech forum) will give you great advice (he's far better at this stuff than I am), but I didn't want to leave you hanging. If you need help with calculating actual voltages from the reference points I gave you, just let me know.
|
|
Top
|
|
|
|
|
#1662216 - 03/17/04 04:54 PM
Re: Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
|
Offline
|
|
I'm not getting responses over on the Tech forum, so I'll ask here. I'm a little fuzzy on my math in converting dB to voltage gain. Just what do the numbers you gave me mean? -10dBv to me means a loss of signal or a reduction of gain, not a signal level. 
Also, the dBm rating; you gave me power and resistance, so I should be able to convert that to a peak to peak voltage, I think. I'll have to look in my text books and see if I can dig something up. But again, it's the -60 that's going to throw me for a loop.
|
|
Top
|
|
|
|
|
#1662217 - 03/18/04 02:36 PM
Re: Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
|
Offline
|
|
Bump. 
|
|
Top
|
|
|
|
|
#1662218 - 03/18/04 02:59 PM
Re: Line level? Mic level?
|
Philip O'Keefe
10k Club
Registered: 12/17/00
Posts: 17674
Loc: Riverside,CA,UNITED STATES
|
|
Offline
|
|
Hang tight - I'll be back in a little bit with your answers - I'll just do the math for you, but I have to do something right now. Be back RSN.
|
|
Top
|
|
|
|
|
#1662219 - 03/18/04 03:30 PM
Re: Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
|
Offline
|
|
According to my text book:
Av(db) = 20 log10 Vout/Vin
That would be for the -10 dBv
Ap(db) = 10 log10 Pout/Pin
is for the -60 dBm
Right?
|
|
Top
|
|
|
|
|
#1662220 - 03/18/04 03:36 PM
Re: Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
|
Offline
|
|
-60 dBm = 1uW, right?
|
|
Top
|
|
|
|
|
#1662221 - 03/18/04 04:24 PM
Re: Line level? Mic level?
|
Philip O'Keefe
10k Club
Registered: 12/17/00
Posts: 17674
Loc: Riverside,CA,UNITED STATES
|
|
Offline
|
|
I found something for you online, and after a quick review of it, I think that it should answer most of (if not all of) your questions - and it will save me a lot of typing, and it will probably explain it better than I could.  Please let me know if it helps or not:
http://www.analog.com/UploadedFiles/Associated_Docs/ 561216689RF_Power_Meas_Part_I.pdf
|
|
Top
|
|
|
|
|
#1662222 - 03/18/04 04:30 PM
Re: Line level? Mic level?
|
Philip O'Keefe
10k Club
Registered: 12/17/00
Posts: 17674
Loc: Riverside,CA,UNITED STATES
|
|
Offline
|
|
...and one more:
http://www.sizes.com/units/decibel.htm
|
|
Top
|
|
|
|
|
#1662223 - 03/18/04 04:34 PM
Re: Line level? Mic level?
|
Blue Strat
MP Hall of Fame Member
Registered: 11/15/02
Posts: 6080
Loc: York County, SC
|
|
Offline
|
|
I think that second link has got it covered. Thanks Phil!! 
|
|
Top
|
|
|
|
|
#1662224 - 03/18/04 04:43 PM
Re: Line level? Mic level?
|
Philip O'Keefe
10k Club
Registered: 12/17/00
Posts: 17674
Loc: Riverside,CA,UNITED STATES
|
|
Offline
|
|
You're welcome. Glad that we got you what you needed.
Sorry I had to to be so brief, but I'm trying to post between doing three other things at the moment. Unfortunately, there's limits on my multitasking capabilities.
|
|
Top
|
|
|
|
|
|
|
