Hi everybody:
Say you have a mixer / gear which outputs a +4dBu level.
Does it mean you have 1.2V RMS on each Hot & Cold leg or is it the sum of both legs that provides that voltage level ?
Assuming consumer level is unity gain level, what amplification factor do I need to meet pro level.
I understand that the simple fact of balancing doubles the level but .3V Consumer is 4 times lower than 1.2V Pro. Am I correct ?
Does it mean that for a 11.79dB difference I have to amplify 3.9 times or just 2 times because of the bonus balancing gain?
http://www.harmoniccycle.com/hc/music-26-+4dBu-10dBV.htm
http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm
Thank You
Say you have a mixer / gear which outputs a +4dBu level.
Does it mean you have 1.2V RMS on each Hot & Cold leg or is it the sum of both legs that provides that voltage level ?
Assuming consumer level is unity gain level, what amplification factor do I need to meet pro level.
I understand that the simple fact of balancing doubles the level but .3V Consumer is 4 times lower than 1.2V Pro. Am I correct ?
Does it mean that for a 11.79dB difference I have to amplify 3.9 times or just 2 times because of the bonus balancing gain?
http://www.harmoniccycle.com/hc/music-26-+4dBu-10dBV.htm
http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm
Thank You
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For a balanced output, that 4 dBu / 1.2 V RMS applies to the voltage between the output pins, so one pin to ground would be 0.6 V RMS. Mind you, when the load impedance is not balanced and the output floats (transformer-coupled output, for example), you can get anything between 0 V and 1.2 V from each output pin to ground, but the voltage between the pins remains 1.2 V.
Your factor of about four between professional and consumer levels is also correct, although much consumer gear actually produces more than -10 dBV. For example, consumer CD players usually produce about +6 dBV when playing a full-scale sine wave. Then again, that 4 dBu for professional equipment is also a nominal rather than a maximum level.
Your factor of about four between professional and consumer levels is also correct, although much consumer gear actually produces more than -10 dBV. For example, consumer CD players usually produce about +6 dBV when playing a full-scale sine wave. Then again, that 4 dBu for professional equipment is also a nominal rather than a maximum level.
the signal comes in on two pins.
The difference in voltage between the two pins is the signal level.
That can be a nominal -10dbV for domestic on an unbalanced cable, or on a balanced cable.
Alternatively for PA the nominal level is around +4dBu and this is almost always on a balanced cable.
The maximum signal can be 10times (+20dB, or 100 times the power) that and more in live work.
That's why we use 50W amplifiers to listen to average/nominal levels that are less than half a watt.
In all of the above we are referring to differential signals. ALWAYS !
It is the voltage difference between the two signal wires, even when one of them is the outer of an unbalanced coaxial cable.
The difference in voltage between the two pins is the signal level.
That can be a nominal -10dbV for domestic on an unbalanced cable, or on a balanced cable.
Alternatively for PA the nominal level is around +4dBu and this is almost always on a balanced cable.
The maximum signal can be 10times (+20dB, or 100 times the power) that and more in live work.
That's why we use 50W amplifiers to listen to average/nominal levels that are less than half a watt.
In all of the above we are referring to differential signals. ALWAYS !
It is the voltage difference between the two signal wires, even when one of them is the outer of an unbalanced coaxial cable.
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Suppose I have no gain setting knobs (fixed output & input) and I want to achieve the same volume on the speaker or amplifier ...
If I need 4X gain, that would be a 2X gain buffer before the THAT IC in order to accommodate levels, since the balanced conversion provides the other 2X gain by the conversion itself.
I've done this simple test.
Unbalanced RCA --- THAT 1646 --Balanced cable --- speaker. (Standard datasheet)
There is a perceived Volume
If I connect the same RCA to the speaker directly grounding the cold pin The perceived volume is half lower. Shouldn't it be 4 times lower ? (Impedance matching perhaps ?)
So, if the Balancing act itself raises the signal by 6dB, in order to achieve the 11.97 (12dB rounded) difference, I just need another 6dB before. That's 2X gain. Am I right ?
The datasheet itself says the IC should be driven by a low impedance source. And It seems to be a bit noisy (sort of pink noise not hum) if I crank the Gain on the speaker without the source connected. I could place a resistor to ground on the input of the IC but the CMRR would degrade.
If I need 4X gain, that would be a 2X gain buffer before the THAT IC in order to accommodate levels, since the balanced conversion provides the other 2X gain by the conversion itself.
I've done this simple test.
Unbalanced RCA --- THAT 1646 --Balanced cable --- speaker. (Standard datasheet)
There is a perceived Volume
If I connect the same RCA to the speaker directly grounding the cold pin The perceived volume is half lower. Shouldn't it be 4 times lower ? (Impedance matching perhaps ?)
So, if the Balancing act itself raises the signal by 6dB, in order to achieve the 11.97 (12dB rounded) difference, I just need another 6dB before. That's 2X gain. Am I right ?
The datasheet itself says the IC should be driven by a low impedance source. And It seems to be a bit noisy (sort of pink noise not hum) if I crank the Gain on the speaker without the source connected. I could place a resistor to ground on the input of the IC but the CMRR would degrade.
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> bonus balancing gain?
There is no magic "bonus balancing gain".
Some popular forms of unbal to bal conversion take signal from one pin, invert, and apply that to the other pin. This gives a 1+1=2 "bonus".
A transformer has no such "bonus".
THAT 1646 uses another technique. Gain is defined to be 10K/5K or 2. So yes, you want another gain of 1.9X in front.
There's no magic "level". If you are going to your amplified speakers, take the THAT gain and then turn-up your main volume control a few notches.
There is no magic "bonus balancing gain".
Some popular forms of unbal to bal conversion take signal from one pin, invert, and apply that to the other pin. This gives a 1+1=2 "bonus".
A transformer has no such "bonus".
THAT 1646 uses another technique. Gain is defined to be 10K/5K or 2. So yes, you want another gain of 1.9X in front.
There's no magic "level". If you are going to your amplified speakers, take the THAT gain and then turn-up your main volume control a few notches.
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I was trying to mimic the behaviour of those ready made conversion boxes without gain settings.... but all of them seem to have gain knobs except transformer based ones, but I will stick with the 4X gain conversion, or adjustable gain preamp before. Say you connect a cell-phone or tablet. Those things have usually a low output. Amplifying before balancing would give me better S/N ratio perhaps or not ...
You say a transformer hasn't bonus, but a transformer for balanced audio usually has 2 windings on the secondary, so V+V=2V. What am I missing ?
One funny thing about the 1646 chip is if you ground one of the output legs, the chip raises the level on the other pin and the output signal remains the same level. Not very good for cable fault finding.
You say a transformer hasn't bonus, but a transformer for balanced audio usually has 2 windings on the secondary, so V+V=2V. What am I missing ?
One funny thing about the 1646 chip is if you ground one of the output legs, the chip raises the level on the other pin and the output signal remains the same level. Not very good for cable fault finding.
> if you ground one of the output legs, the chip raises the level on the other pin and the output signal remains the same level.
A transformer does the same thing.
So does a battery. Take a 1.5V battery. It is 1.5V end to end. Ground the - end. The + end is 1.5V. Ground the + end. The - end is at 1.5V.
1646 "does the right thing", since transformer output is the oldest "pro" interface in the book. Most telephones, all talking-movie sound.
Transformers with 2-winding secondaries often have 2-winding primaries. Anyway you go by number of turns. If the core has 1,000 turns on one primary, and two 500 turn secondary windings, it is 1:1 ratio.
A transformer does the same thing.
So does a battery. Take a 1.5V battery. It is 1.5V end to end. Ground the - end. The + end is 1.5V. Ground the + end. The - end is at 1.5V.
1646 "does the right thing", since transformer output is the oldest "pro" interface in the book. Most telephones, all talking-movie sound.
Transformers with 2-winding secondaries often have 2-winding primaries. Anyway you go by number of turns. If the core has 1,000 turns on one primary, and two 500 turn secondary windings, it is 1:1 ratio.
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