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+4db, -10db...what does all this mean exactly?
Old 6th August 2015
  #91
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Hi
Thanks
Sorry I didn't want to spend all night typing so made it a simple answer!
Matt S
Old 23rd October 2015
  #92
Gear Maniac
 

dbu vs dbv vs dbm

Actually, .775V rms =0dbu while .775V rms = -2.22dbv

0dbv=1volt RMS 0dbu=.774v rms

dbm means the voltage measurement is referenced to a 600 load which is the old broadcast standard where everything was terminated to 600 ohms.


you are correcty that the level difference between +4 dBu studio level
and −10 dBV consumer level is Δ L = 11.78 dB (12 dB).

The level difference between dBu level and dBV level is Δ L = 2.2 dB.
0 dBV equals 2.2 dBu or 0 dBu equals −2.2 dBV.

The conversion from level L(dBu) to voltage (volt) is V = 0.775 × 10(L/20).
The conversion from voltage V (volt) to level (dBu) is L = 20 × log (V/0.775).

Cheers, Dave
aamicrophones.com
Old 23rd October 2015
  #93
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Quote:
Originally Posted by microphonefolk View Post
dbm means the voltage measurement is referenced to a 600 load which is the old broadcast standard where everything was terminated to 600 ohms.
Just to be clear, dBm is used for power, not for voltage, but 1 dBm into 600 Ohm load gives you the voltage of 0.775 V = 0 dBu.
Using dBm as a unit doesn't mean that it is a 600 Ohm line or that it will have that voltage if you terminate it with 600 Ohms. 0 dBm means 1 mW, load doesn't matter.
Old 25th October 2015
  #94
After reading through this very informative thread, I am stumped as tot he output impedance of my my E-Mu SP-1200. The manual sheds no light on whether 1/4" unbalanced outputs are +4/-10. Do any of you OGs have thoughts or knowledge of what an old 12-bit sampler of this age would have been set-up for? I am running into a RME Fireface UCX which has the option for eith +4 which is obviously lower level and -10 which sounds "hotter." Other than just doing what "sounds good" does anyone have insight for this specific scenario going direct from sampler to audio interface? Note: I go out of the eight channel outputs with a Y_cable (TRS-TS/TS) to take advantage of internal filters on the ring (return). Thanks in advance!
Old 25th October 2015
  #95
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Hi
You are overthinking things. Just use whichever gets a sensible level for your application OR go to EMU and ask them if their manual is inadequate.
Even if you knew the output impedance of the sampler, what are you going to do about it?
The bottom line is whether it works for you.
Matt S
Old 27th October 2015
  #96
Gear Maniac
 

DBM

Exactly, P=E*2/R or .775v*.775v/600 ohms=.001 watt or 1 Mw.

So, if you measure .775v across a 600 ohm load then you have 0dbM.

Back in the day we use to calibrate the output of the Studer 24 track so that 1.23v rms equal 0VU which is +4dbM.

Cheers, Dave







Quote:
Originally Posted by jetam View Post
Just to be clear, dBm is used for power, not for voltage, but 1 dBm into 600 Ohm load gives you the voltage of 0.775 V = 0 dBu.
Using dBm as a unit doesn't mean that it is a 600 Ohm line or that it will have that voltage if you terminate it with 600 Ohms. 0 dBm means 1 mW, load doesn't matter.
Old 28th October 2015
  #97
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Hi
I know it is 'fussy' but be careful of the letter 'case'.
M is Mega (million) an m is milli (thousand).
Watts and Volts are Si units and should start with a capital letter.
Thus 0.7746 Volts is 1 milliwatt into a 600 Ohm load. Written 0dBm.
Other than that, carry on!
Matt S
Old 1st December 2015
  #98
Here for the gear
 

Hi there,
jumping in on that old but awesome topic. One thing I don't understand, hopefully someone can clarify, is some basic math.
-10dBV - 1,7815 dBV = -11,7815 dBV where 1,7815 dBV =+4dBu
+4dBu - (-7,7815 dBu) = 11,7815 dBu where -7,7815 dBu = -10dBV
Understood. But from what I learned back in school - everyone here is referring to the difference being dB (without u, V, m!). How come? Because just in case:
-10dBV - 1,7815 dBV = 4dBu + 7,7815 dBu which leads to -11,7815dBV=11,7815dBu is simply not true. (It is not true for both being positive values either).

This is a real question, I don't get what the unit of the difference is and therefor am totally stuck with understanding.

Thanks for help!
Axel
Old 1st December 2015
  #99
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mutetourettes's Avatar
 

basic math, I think your negatives and positives are getting out of hand:

-A - (+B) is not the same as +B - (-A)

Studio level is always higher than consumer level, so in both cases subtract consumer level from studio level:

"The difference between +1.785 dBV (aka +4dBu) and -10dBV is 11.7815 dBV"

"The difference between +4dBu and -7.7815 dBu (aka -10dBV) is 11.7815 dBu"

so whichever flavour of dB you use, the difference is the same. The two different flavours of dB here are the same scale really, they just have their arbitrary 0 in a different place along it (they're 2.2dB different). The studio and consumer levels are two positions on whichever scale you use, and those two positions are always 11.78dB (aka 12dB) apart.
Old 1st December 2015
  #100
Here for the gear
 

Hi Mutetouretts,
but this would mean, that the difference between +4dBu and -10dBV ist 11.7815 dBV or 11.7815dBu - which is not the same. But the difference should be always the same in one or another unit. So what you are saying is the difference is 11.7815dBu (=9.5630dBV) or 11.7815dBV (=14dBu). I am sure I am missing something here. That's what I thought would be the other unit "dB" (no u, no V).

Is this somehow described understandable what my issue is?
Old 1st December 2015
  #101
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bogosort's Avatar
Quote:
Originally Posted by Xcell View Post
Hi there,
jumping in on that old but awesome topic. One thing I don't understand, hopefully someone can clarify, is some basic math.
-10dBV - 1,7815 dBV = -11,7815 dBV where 1,7815 dBV =+4dBu
+4dBu - (-7,7815 dBu) = 11,7815 dBu where -7,7815 dBu = -10dBV
Understood. But from what I learned back in school - everyone here is referring to the difference being dB (without u, V, m!). How come?
As you know, the "naked" dB tells us the ratio between two like quantities on a logarithmic scale. dBV relates a voltage to 1 V rms; dBu relates a voltage to 0.775 V rms. So dBV and dBu are not like quantities. But two voltages are, so all we have to do is convert the dBV and dBu values back to voltages:

v1 = -10 dBV = 1 * 10^(-10/20) = 0.31622 V
v2 = +4 dBu = 0.7746 * 10^(4/20) = 1.2277 V

Then the difference in naked dB between -10 dBV and +4 dBu is

20 * log10(v1/v2) = -11.78 dB

What you did -- e.g., convert all dBu values to dBV and then work in dBV -- is perfectly valid, but often it's preferable to drop any notion of a reference value and speak purely of relative values. Describing a quantity with a reference (dBu, dBV, dBm, etc.) implies that the actual value is important; for example, the maximum input to a device might be listed as +22 dBu -- an absolute voltage value above which you must not exceed. On the other hand, describing a quantity without a reference (naked dB) implies that the relative value is the important part; for example, balanced lines can give you a 6 dB signal boost over unbalanced lines -- we don't know or care what the actual voltage values are, we're focusing on the relative differences.

Quote:
Because just in case:
-10dBV - 1,7815 dBV = 4dBu + 7,7815 dBu which leads to -11,7815dBV=11,7815dBu is simply not true. (It is not true for both being positive values either).
-10 dB - (+1.7185 dBV) =-11.7185 dBV = 10^(-11.7185/20) = 0.259 V
+4 dBu + 7.7815 dBu = 11.7815 dBu = 0.7746 * 10^(11.7815/20) = 3 V

They don't look equal to me.
Old 1st December 2015
  #102
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Quote:
Originally Posted by bogosort View Post
-10 dB - (+1.7185 dBV) =-11.7185 dBV = 10^(-11.7185/20) = 0.259 V
+4 dBu + 7.7815 dBu = 11.7815 dBu = 0.7746 * 10^(11.7815/20) = 3 V

They don't look equal to me.
No they don't - which was my issue. But the answer (formular) above is totally clear. Thank you so much for solving my missing point there ;-) You rock!
Old 5th January 2016
  #103
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parkay909's Avatar
Quote:
Originally Posted by myles View Post
Nope. But you might be surprised at how little noise there is, if you follow the correct procedure in making or buying your cables. (Big plug here for learning how to solder and make your own cables - it's not hard, saves money and you can do all the weird interconnects at 2 am when no stores are open and you need them right away).
always make your own cables
Old 7th January 2016
  #104
Gear Maniac
 

Well, I can't speak for other interfaces but I use the +4db now on the saffire pro 40. I used to use -10 on my outboard gear. I still don't know which one is proper, I've had people tell me different things.

I'm pretty sure it's +4db though.

However, 0VU is equalling -18Dbfs with the pre amp on the saffire pro 40 turned all the way down, so I keep it that way. Apparently the unity gain of the pro 40 is at 3.5 and not at 0, but at 3.5 the pre amps and compressors I have are too loud. Everything stays on 0.
Old 4th July 2016
  #105
Gear Head
 

Hi everybody !!

I read a lot of this thread and i'm starting to get it !

I have an Apogee Duet FireWire connected to my Mac. I have this product connected to my pro-ject turntable. (all this connected to genelec 8030's).

RCA's are coming out of my turntable, to the preamp above, and then it's RCA to XLR to the Apogee Duet.

I think i'd better select -10db with this installation, but when i do, the apogee indicates almost all of the time the red light for both input, and when i select +4Db the sounds seems clearer and more in phase with the ligh indicated by the Apogee Duet (even though it's abit less powerfull)..

Any ideas ? My cable seems balanced btw
Old 4th July 2016
  #106
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myles's Avatar
 

Quote:
Originally Posted by kevinbeared View Post
Hi everybody !!

I read a lot of this thread and i'm starting to get it !

I have an Apogee Duet FireWire connected to my Mac. I have this product connected to my pro-ject turntable. (all this connected to genelec 8030's).

RCA's are coming out of my turntable, to the preamp above, and then it's RCA to XLR to the Apogee Duet.

I think i'd better select -10db with this installation, but when i do, the apogee indicates almost all of the time the red light for both input, and when i select +4Db the sounds seems clearer and more in phase with the ligh indicated by the Apogee Duet (even though it's abit less powerfull)..

Any ideas ? My cable seems balanced btw
It doesn't say whether is applies the RIAA EQ curve you need, but that shouldn't affect levels. In this case, if it distorts at -10, use +4. Gain is cheap in digital world.
Old 4th July 2016
  #107
Gear Head
 

Quote:
Originally Posted by myles View Post
It doesn't say whether is applies the RIAA EQ curve you need, but that shouldn't affect levels. In this case, if it distorts at -10, use +4. Gain is cheap in digital world.
I see that mister speaks french (ca aurait été plus simple en français mais pas vraiment respecteux pour les autres)..

So i'm gonna go with this. Maybe i should have bought This phono pre amp it's balanced but it's clearly not the same price...
Old 4th July 2016
  #108
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myles's Avatar
 

Quote:
Originally Posted by kevinbeared View Post
I see that mister speaks french (ca aurait été plus simple en français mais pas vraiment respecteux pour les autres)..

So i'm gonna go with this. Maybe i should have bought This phono pre amp it's balanced but it's clearly not the same price...
Oui, l'anglais sera mieux pour tout le monde.

See if you can find a used NAD preamp or integrated amp. They're pretty cheap now and have great phono stages. But just try what you have with your inputs at +4, it should work fine. If it's too bright because of no RIAA, rolling off some top end will do a lot of the work.
Old 4th July 2016
  #109
Gear Head
 

Quote:
Originally Posted by myles View Post
Oui, l'anglais sera mieux pour tout le monde.

See if you can find a used NAD preamp or integrated amp. They're pretty cheap now and have great phono stages. But just try what you have with your inputs at +4, it should work fine. If it's too bright because of no RIAA, rolling off some top end will do a lot of the work.
Just to make connection with the first post of this thread, on my Apogee the light are almost going red 80% of the time when using -10dB... That's why i started asking question. And Maybe if it would be a first indicator if the signal is strong enough for your soundcard ?
Old 13th September 2016
  #110
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Vocal Pedlboard

Hey, so I'm brand new to this. I just have a quick question that seems similar to this so I'm just gonna post it here rather than start a new thread.

I wanna build a vocal pedalboard for live performances. I've been looking at vocal processors and vocal pedals but I feel like there's a lot more options with guitar pedals so I'm seriously considering going that route. I've done some research and I think I get the basic concept of mic/instrument/line level. I have a setup in mind and I just wanted to get some opinions on it.

dynamic mic>art tube mp studeio mic preamp>boss delay>boss reverb>livewire passive direct box>mixer

Does this look like it will damage anything or make any sound guys cringe? I like the option of adding new pedals and effects in the future.
Old 10th March 2017
  #111
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I deal with this concept for quite a Long time. Every time I think I understand it, new questions or problems appear and makes me feel like starting from scratch...

Practically, is there a rule of thump for the strenght of Synthesizer or drum machine outputs? On a RME Fireface UFX the output of a Elektron Analog Rytm was pretty weak when the In was set to +4dBu, peaking around -30 dBFS. -10dBV enabled me to record with peaks at -18dBFS without cranking up the drum machine all th way.
The Outs where balanced cables btw...
I had similar experiences with Synths.
Are there synths or drum machines working on +4dBu?

Further, on my Interface, RME Babyface, there is no +4/-10 Switch at all, just a gain poti. When thinking of a concept for levels, where is a place for the actual level? I can Play a quiet Sound or a loud Sound and they will result in different Volts obviously...?
Old 10th March 2017
  #112
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myles's Avatar
 

Quote:
Originally Posted by Robocopchris View Post
I deal with this concept for quite a Long time. Every time I think I understand it, new questions or problems appear and makes me feel like starting from scratch...

Practically, is there a rule of thump for the strenght of Synthesizer or drum machine outputs? On a RME Fireface UFX the output of a Elektron Analog Rytm was pretty weak when the In was set to +4dBu, peaking around -30 dBFS. -10dBV enabled me to record with peaks at -18dBFS without cranking up the drum machine all th way.
The Outs where balanced cables btw...
I had similar experiences with Synths.
Are there synths or drum machines working on +4dBu?

Further, on my Interface, RME Babyface, there is no +4/-10 Switch at all, just a gain poti. When thinking of a concept for levels, where is a place for the actual level? I can Play a quiet Sound or a loud Sound and they will result in different Volts obviously...?
You're safe in assuming no synth or drum machine is designed to put out +4. Just about anything with a 1/4" jack for an output will be happier going into -10.

The gain pot in your Babyface is there so you can adjust it to get your levels in the right place, depending on whether it's a mic or a synth. You also have two sets of inputs, one with XLR's and one with a 1/4" jack. The ones with XLR's can accept microphone-level ins.

For output, a Babyface will work (produce signal) into either a +4 or -10 input, but I'd be more comfortable going into -10, simply to avoid pushing the outputs too hard.
Old 1st May 2017
  #113
Gear Maniac
 

[QUOTE=nosebleedaudio;6184323
Also 0dBV is 1 Volt RMS.
0dBm,dBu is .775V RMS...
[/QUOTE]

Actually I believe 0dbV is 1 volt peak to peak
&
0dbu, Odbv is 1 volt RMS, which = .775 v ptp.

Some other measurements are based on volts average = .707 v ptp.

All of those came about due to the different types of meters used to measure AC voltage.
Old 1st May 2017
  #114
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nosebleedaudio's Avatar
 

Quote:
Originally Posted by graywolf View Post
Actually I believe 0dbV is 1 volt peak to peak
&
0dbu, Odbv is 1 volt RMS, which = .775 v ptp.

Some other measurements are based on volts average = .707 v ptp.

All of those came about due to the different types of meters used to measure AC voltage.
You need to double check your numbers.
0 dBV is 1V RMS
Has nothing to do with different meters, its different scales...
I have a meter with both scales, use it daily...
Old 15th May 2017
  #115
Gear Nut
 

Quote:
Originally Posted by TC2 View Post
Is there any way to avoid the noise?
Yes, use a GATE, something like the:
DBX Expander Gate 274 Noise Gate.
.

The problem you will face is that, each item added to the signal chain will add additional noise or coloration.

In order to keep your signal as clean as possible, meaning to hear your signal as close to the original, just dump the audio into your software, then use the software to clean the noise. like trimming empty spaces on a track.

Ciao!
Old 23rd May 2017
  #116
Gear Maniac
 

Quote:
Originally Posted by nosebleedaudio View Post
You need to double check your numbers.
0 dBV is 1V RMS
Has nothing to do with different meters, its different scales...
I have a meter with both scales, use it daily...
A raw galvanic meter measures Average.

A VTVM (& the transisterized equivalent) measures RMS (Root Mean Square).

A peak to peak meter (somewhat specialized) measures, of course, PtP.

Now I realize that most folks today never even heard of those kinds of meters, but I learned my electronics a long time ago. Before transistors were common, in fact.

I also used a micro-volt meter, (really specialized) that you could actually measure the voltage in the air with (about 3 microvolts).

As to the guy who did the math in a previous post, he got some thing wrong there because 12dB voltage is actually about 2:1 not 10:1. That means a one volt signal on +4 would be a about one/half volt on -10.

Another point, traditionally an unbalanced connector is -10, and a balanced input is +4. These days that does not necessarily hold true because my Zoom F4 Recorder uses XLR's on its -10 outputs.
Old 3rd July 2017
  #117
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subdo's Avatar
Man I need to come to the newbie zone more often. Some serious knowledge being dropped in here.
Old 10th July 2017
  #118
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SF_Green's Avatar
Quote:
Originally Posted by subdo View Post
Man I need to come to the newbie zone more often. Some serious knowledge being dropped in here.
Seriously! Great discussion. I have a very limited understanding of this, and can use all the additional knowledge and reinforcement I can get. Thanks all!
Old 16th July 2017
  #119
Gear Head
 

I haven't read the thread so this may have already been mentioned.... I just went through the ordeal of going from a pro Yamaha mixer (+4) to a consumer Alpine Car amp (-10). Yes, in theory, plugging the pro mixer into a consumer car amp requires setting the gain of the amplifier to the equivalent of -12dBV, to attenuate the signal to a level the amp is designed to work with and I should not need a +4dB to -10dB converter. However, I have no meters and I was running into all sorts of problems. Then, it was recommended that I use a +4/-10 converter so I set out to find the best "passive" converter. While there are a few different +4 to -10 powered converters, there was only one passive converter that I could find on the marketplace made by Radial engineering out of Canada:

Radial Pro-Iso & J-Iso™

Radial is simply the best! You can pick up a pro-Iso for about $150 and the J-Iso for $250 because it has Jensen transformers. In addition to the +4 to -10 converter you get the best line isolation via transformers. I chose the J-Iso because I understand the value of Jensen transformers for line isolation.

In short, I would not jack with trying to use gain and volume level controls to get the job done as it requires way too much fine tuning and time is money and you are just asking for problems. In all cases, hooking +4 pro gear to -10 consumer gear I would always use a converter with line isolators. While you can find some other converter options if you settle for powered units, the mere fact those manufacturers are unnecessarily powering the units tells you something. Go with Radial and you won't be disappointed.

That is if you desire line isolation with the converter which makes this option worthwhile. I assume you're using AC power and may want to kill two birds with one stone and get rid of hum or reduce chances of hum. Most people I know of desire line isolation which is why I recommend this unit and why they make their converters with line isolation via transformer and don't make a stand-alone +4 to -10 converter without line isolation.

Last edited by tayglo; 16th July 2017 at 09:51 PM.. Reason: Added info for @ Matt Syson
Old 16th July 2017
  #120
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Hi
I would be disappointed because getting from +4dB to -10dB simply requires 2 (or 3 if the circuit is balanced) resistors which cost a couple of cents each.
If you NEED an isolated signal then a transformer is the way to do it.
Unbalanced then you can use 3K Ohms and 1K Ohms to get the right amount of attenuation. If balanced then 2 pieces at 1K5 and one at 1K will do the job.
Matt S
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