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# Discussion Groups | Audio Signal Processing | dBU and dBV recording

Technical discussions related to Audio Signal Processing (digital effects, acoustics, noise reduction, musical signal processing, etc).

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# dBU and dBV recording - Rohith MP - Jun 28 11:59:49 2009

```Hello,

Is there any relation between dbu and db/dbV.

I have IO box with option of Hi-Gain, +4dBu gain and -10dBV gain.
Basically these are hardware switches present in the IO box.

What does +4dbU recording actually mean?

What does -10dBV recording actually mean?

While performing recording of a file, I found that @ -10dBV recording, the
recorded file used to get clipped, what might be the reason?

Is -10dBV recording has more gain when compared to +4dBU gain?

Rohith M P
```

# Re: dBU and dBV recording - sotn...@scideco.ru - Jun 30 9:51:22 2009

```dBu is a logarithmic voltage ratio with a reference voltage of V0 = 0.7746
volt ≡ 0 dBu
dBV is a logarithmic voltage ratio with a reference voltage of V0 = 1.0000 volt
≡ 0 dBV
+4 dbU = 1.228 volts
-10 dbV = 0.3162 volts
http://www.sengpielaudio.com/calculator-db-volt.htm

BTW, it is the first page that Google returns on dbu and dbv relationship
request.

--
Alexander

```

# RE: dBU and dBV recording - rrso...@aol.com - Jul 2 9:15:33 2009

``` Rohith,

I haven't seen a reply to this, so here goes.
[Actually, this is an ANALOG concept. As such it doesn't really belong on a
"DSP" list but any way...]

Decibels (dB) are *relative*, comparing one measurement to another. The suffixes
added to the dB, such as dBm, dBu and dBV, are, in this case, meant to add a
reference, making the measurement relative to a standard other than decibels.

In the case of dBm, it's 1 milliwatt of power on a circuit of 600 Ohms impedance
to equal 0 dBm.

This type of measurement was relevant when the systems in use were designed to
transfer power over a circuit of specific impedance, such as was the common case
when the state-of-the-art was tube equipment and transformers.

Electronic audio design has changed over the years so that almost all audio
transmission from one place to another is generated by a source of very low
impedance, sent to a load of relatively high impedance, such that *power* is no
longer an important part of the equation.

Enter "dBu." The "dBu" spec works identically to dBm when
the source/load impedance meets the old dBm spec, but since its reference is to
a specfic *voltage* rather than power, it also works when the impedance is
unspecified. That voltage, by the way, is 0.775 RMS for 0 dBu.

In the case of dBV, it's similar to dBu, but relative to one volt, to equal 0
dBV.
David Reaves

Sun Jun 28, 2009 8:59 am ((PDT)) "Rohith MP" r...@lntemsys.com
mp_rohith wrote:

Hello,

Is there any relation between dbu and db/dbV.

I have IO box with option of Hi-Gain, +4dBu gain and -10dBV gain.
Basically these are hardware switches present in the IO box.

What does +4dbU recording actually mean?
What does -10dBV recording actually mean?
While performing recording of a file, I found that @ -10dBV recording, the
recorded file used to get clipped, what might be the reason?
Is -10dBV recording has more gain when compared to +4dBU gain?