Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

I was thinking of building it into either a headphone amplifier, or
amplified speaker, to use with some of the simple radio receiver kits which
have very little or no AGC function, but I am looking to see what sort of
drive level it needs.

Here is the website which explains more (See PDF) :-..

http://www.canford.co.uk/commerce/Pr...oductid=58-543

Regards

Alan

+4dBuV microvolts?

sounds about right for that type of thing

mike

"alan ralph" wrote in message
...
Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

I was thinking of building it into either a headphone amplifier, or
amplified speaker, to use with some of the simple radio receiver kits
which have very little or no AGC function, but I am looking to see what
sort of drive level it needs.

Here is the website which explains more (See PDF) :-..

http://www.canford.co.uk/commerce/Pr...oductid=58-543

Regards

Alan

On 2005-11-02, alan ralph wrote:
At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

For audio purposes 0 dBu is usually 0.775 V RMS (i.e. 1 mW into 600 Ohms).

--
John Phillips

On Wed, 02 Nov 2005 00:11:55 GMT, "alan ralph"
wrote:

Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

It's an old pro-audio industry reference voltage of 0.775 volts rms,
being the voltage required for 1mW into 600ohms. The U stands for
unloaded or unterminated, to show that it's a voltage rather than an
actual power level.

Your quoted value of +4dBU is 1.223 volts rms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

In article ,
alan ralph wrote:
At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom
18dB.

Does anyone know what a dBu is ?

It's the unit commonly used in pro audio. 0 dB is 0.775v. Peak level on
this system is +8 dB so near enough 2 volts. But of course in practice has
a headroom of much higher than this - the +8db peak only really applying
to things like analogue recorders and transmitters.

I was thinking of building it into either a headphone amplifier, or
amplified speaker, to use with some of the simple radio receiver kits
which have very little or no AGC function, but I am looking to see what
sort of drive level it needs.

'Normal' domestic equipment line levels - if there really is such a thing
- tend to be about 6 - 10 dB lower.

--
*The only difference between a rut and a grave is the depth.

Dave Plowman London SW
To e-mail, change noise into sound.

"Stewart Pinkerton" wrote in message
...
On Wed, 02 Nov 2005 00:11:55 GMT, "alan ralph"
wrote:

Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

It's an old pro-audio industry reference voltage of 0.775 volts rms,
being the voltage required for 1mW into 600ohms. The U stands for
unloaded or unterminated, to show that it's a voltage rather than an
actual power level.

Your quoted value of +4dBU is 1.223 volts rms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

I had thought dB with the U or u suffix stood for a level at unspecified
impedance, whilst dB followed by an m stood for a level referenced to 1
milliWatt (i e,
term'd 600ohm).
U is sometimes used in Europe for denoting voltage, yet measured using the
SI term V.
Incidentally, AF tone at +4dBu, generated from a low-Z source, equals the
popular
datum of 0VU (just below red zone on a rectifier-driven VU meter with its
series resistor in place).
Usually on critical analogue inputs there is 4-6dB of headroom beyond this
point.
Jim

On Wed, 02 Nov 2005 17:24:40 GMT, "Jim Gregory"
wrote:

"Stewart Pinkerton" wrote in message
.. .
On Wed, 02 Nov 2005 00:11:55 GMT, "alan ralph"
wrote:

Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom 18dB.

Does anyone know what a dBu is ?

It's an old pro-audio industry reference voltage of 0.775 volts rms,
being the voltage required for 1mW into 600ohms. The U stands for
unloaded or unterminated, to show that it's a voltage rather than an
actual power level.

Your quoted value of +4dBU is 1.223 volts rms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

I had thought dB with the U or u suffix stood for a level at unspecified
impedance, whilst dB followed by an m stood for a level referenced to 1
milliWatt (i e,
term'd 600ohm).

Yes, which is exactly what I said.

U is sometimes used in Europe for denoting voltage, yet measured using the
SI term V.

I think you'll find that V was a standard term, somewhat before SI
standards were thought of................. :-)

Incidentally, AF tone at +4dBu, generated from a low-Z source, equals the
popular
datum of 0VU (just below red zone on a rectifier-driven VU meter with its
series resistor in place).

Actually no, 0VU is 0.775 volts rms regardless of source impedance,
didn't you read the first part of your *own* post?

Usually on critical analogue inputs there is 4-6dB of headroom beyond this
point.

Depends on the recording medium, doesn't it?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

"Stewart Pinkerton" wrote in message
...
On Wed, 02 Nov 2005 17:24:40 GMT, "Jim Gregory"
wrote:

"Stewart Pinkerton" wrote in message
. ..
On Wed, 02 Nov 2005 00:11:55 GMT, "alan ralph"
wrote:

Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be for
audio use. On the supplied data sheet is shows the input and output as
+4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and headroom
18dB.

Does anyone know what a dBu is ?

It's an old pro-audio industry reference voltage of 0.775 volts rms,
being the voltage required for 1mW into 600ohms. The U stands for
unloaded or unterminated, to show that it's a voltage rather than an
actual power level.

Your quoted value of +4dBU is 1.223 volts rms.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

I had thought dB with the U or u suffix stood for a level at unspecified
impedance, whilst dB followed by an m stood for a level referenced to 1
milliWatt (i e,
term'd 600ohm).

Yes, which is exactly what I said.

U is sometimes used in Europe for denoting voltage, yet measured using the
SI term V.

I think you'll find that V was a standard term, somewhat before SI
standards were thought of................. :-)

Incidentally, AF tone at +4dBu, generated from a low-Z source, equals the
popular
datum of 0VU (just below red zone on a rectifier-driven VU meter with its
series resistor in place).

Actually no, 0VU is 0.775 volts rms regardless of source impedance,
didn't you read the first part of your *own* post?

Usually on critical analogue inputs there is 4-6dB of headroom beyond this
point.

Depends on the recording medium, doesn't it?
--

Stewart Pinkerton | Music is Art - Audio is Engineering

No No No That's a howler! 0VU certainly does not = 0.775V
A needle poised at -4VU is read from applying tone at 0.7746V rms (normally
'0' level in UK) to a standard VU meter.
[Bell Labs volume units, the U here is nothing to do with unspecified.]

And if the tone source Z is over 400 Ohms, the VU meter's build load will
impact (reduce) the true level.
Ideally a VU meter should be harnessed via an isolating driver amp.

Critically, available headroom above a stated reference level applies only
to certain downstream audio equipment (not necessarily recorder/s) that lies
unprotected by "brick-wall" limiters.
Jim

"mikeFNB" wrote in
:

+4dBuV microvolts?

sounds about right for that type of thing

mike

"alan ralph" wrote in message
...
Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be
for audio use. On the supplied data sheet is shows the input and
output as +4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and
headroom 18dB.

Does anyone know what a dBu is ?

I was thinking of building it into either a headphone amplifier, or
amplified speaker, to use with some of the simple radio receiver kits
which have very little or no AGC function, but I am looking to see
what sort of drive level it needs.

Here is the website which explains more (See PDF) :-..

http://www.canford.co.uk/commerce/Pr...oductid=58-543

Regards

Alan














Should be relative to a microvolt into a 600 Ohm load.

"Alun L. Palmer" wrote in message
.. .
"mikeFNB" wrote in
:

+4dBuV microvolts?

sounds about right for that type of thing

mike

"alan ralph" wrote in message
...
Hi,

At a radio rally, I bought a ALC/AGC module for £5 which seems to be
for audio use. On the supplied data sheet is shows the input and
output as +4dBu. (Unity Gain) With an ALC range of -16 to +14 dBu and
headroom 18dB.

Does anyone know what a dBu is ?

I was thinking of building it into either a headphone amplifier, or
amplified speaker, to use with some of the simple radio receiver kits
which have very little or no AGC function, but I am looking to see
what sort of drive level it needs.

Here is the website which explains more (See PDF) :-..

http://www.canford.co.uk/commerce/Pr...oductid=58-543

Regards

Alan




Should be relative to a microvolt into a 600 Ohm load.

Forget microVolt!
0 dBu is steady AF established at 775 milliVolts line level -- regardless of
load Z.