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Whats a dBu ?
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 |
Whats a dBu ?
+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 |
Whats a dBu ?
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 |
Whats a dBu ?
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 |
Whats a dBu ?
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. |
What's a dBu ?
"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 |
What's a dBu ?
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 |
What's a dBu ?
"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 |
Whats a dBu ?
"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. |
What's a dBu ?
"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. |
What's a dBu ?
" 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. It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff |
What's a dBu ?
On Mon, 7 Nov 2005 15:41:48 -0000, "Jeff" wrote:
" 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. It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. d Pearce Consulting http://www.pearce.uk.com |
What's a dBu ?
In article , Don Pearce
writes On Mon, 7 Nov 2005 15:41:48 -0000, "Jeff" wrote: " 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. It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Rather as dB relative to one miliwatt should be written dBmW to avoid people thinking it is miliampere. The unit should always be specified where there is potential for confusion, although current practice can omit it. -- Ian G8ILZ |
What's a dBu ?
It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Well I am afraid that RF engineers are a lazy breed and it is often written as dBu, much in the same way as dBm. Jeff |
What's a dBu ?
On Mon, 7 Nov 2005 19:30:34 +0000, Prometheus
wrote: In article , Don Pearce writes On Mon, 7 Nov 2005 15:41:48 -0000, "Jeff" wrote: " 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. It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Rather as dB relative to one miliwatt should be written dBmW to avoid people thinking it is miliampere. The unit should always be specified where there is potential for confusion, although current practice can omit it. Far too late, I'm afraid. The dBm is far too well established. d Pearce Consulting http://www.pearce.uk.com |
What's a dBu ?
In message , Jeff
writes It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Well I am afraid that RF engineers are a lazy breed and it is often written as dBu, much in the same way as dBm. Jeff After 41 years in the cable TV industry, I've NEVER seen dBmV or dBμV written abbreviated. Spoken, you occasionally hear only 'dB' from the careless. Ian. -- |
What's a dBu ?
On Mon, 7 Nov 2005 19:39:02 -0000, "Jeff" wrote:
It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Well I am afraid that RF engineers are a lazy breed and it is often written as dBu, much in the same way as dBm. Jeff Well, I've been an RF engineer all my life, and I've never come across dBu instead of dBuV. d Pearce Consulting http://www.pearce.uk.com |
What's a dBu ?
Well, I've been an RF engineer all my life, and I've never come across
dBu instead of dBuV. Obviously Pearce Consulting are not as lazy as some!! (;_)) Jeff |
What's a dBu ?
On Mon, 7 Nov 2005 20:02:15 -0000, "Jeff" wrote:
Well, I've been an RF engineer all my life, and I've never come across dBu instead of dBuV. Obviously Pearce Consulting are not as lazy as some!! (;_)) Jeff Mmmmm..... I reckon it's just you. ;-) d Pearce Consulting http://www.pearce.uk.com |
What's a dBu ?
Mmmmm..... I reckon it's just you. ;-)
d Pearce Consulting http://www.pearce.uk.com Then try doing a little research on the web then, you will find at least four usages of "dBu". The correct one, dB rel 1 micro volt, when written without access to mu, dB rel 1 micro volt/m (used by the FCC) and dB rel 1 micro Watt (mainly sat downlink people). Regards Jeff |
What's a dBu ?
On Mon, 7 Nov 2005 20:25:50 -0000, "Jeff" wrote:
Mmmmm..... I reckon it's just you. ;-) d Pearce Consulting http://www.pearce.uk.com Then try doing a little research on the web then, you will find at least four usages of "dBu". The correct one, dB rel 1 micro volt, when written without access to mu, dB rel 1 micro volt/m (used by the FCC) and dB rel 1 micro Watt (mainly sat downlink people). Regards Jeff A plague on all their houses! The FCC at least should know better. d Pearce Consulting http://www.pearce.uk.com |
What's a dBu ?
On Mon, 7 Nov 2005 15:41:48 -0000, "Jeff" wrote:
" 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. It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! That wasn't the mistake - the mistake was to think that it ever had anything to do with the Greek alphabet! The 'u' in dBu stands for unterminated or unloaded, because, while it is the same voltage as that required to maintain a power level of 1 milliwatt (not micro) into a 600 ohm load, it's a *voltage* measure, not a power measure. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
What's a dBu ?
On Mon, 7 Nov 2005 19:39:02 -0000, "Jeff" wrote:
It is an easy mistake to make, because dB relative to a microvolt is often written as dBu rather than using the Greek letter 'mu'; a limitation of the ASCII character set!! Jeff dB relative to a microvolt is written as dBuV, so there need be no confusion. Well I am afraid that RF engineers are a lazy breed and it is often written as dBu, much in the same way as dBm. That's not lazy, that's efficient! That's what engineers *do*..... :-) -- Stewart Pinkerton | Music is Art - Audio is Engineering |
What's a dBu ?
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What's a dBu ?
On Mon, 7 Nov 2005 20:25:50 -0000, "Jeff" wrote:
Mmmmm..... I reckon it's just you. ;-) d Pearce Consulting http://www.pearce.uk.com Then try doing a little research on the web then, you will find at least four usages of "dBu". The correct one, dB rel 1 micro volt, when written without access to mu, dB rel 1 micro volt/m (used by the FCC) and dB rel 1 micro Watt (mainly sat downlink people). Hmmmmm, you're right. Tsk, tsk.............. Could be interesting if you try to shove +10dBu down a system which was expecting +10dBuV........................ -- Stewart Pinkerton | Music is Art - Audio is Engineering |
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