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[Trumpetguy]

I have tried google.....got confused.

My DAC (Lynx Aurora8) has two output levels, +4dBu and -10dBv. As Matt pointed out in another thread recently, using +4dBu creates lots more headroom. The penalty is a slightly higher noise floor, but I can live with it.

What I am wondering is: What is the theoretical difference in SPL between these two output voltages? I use Internal Volume and Loudness. Up to now, I have used a refence level of 85, with -10dBv output on my DAC. Theoretically speaking - what would be the difference in reference level for the Loudness function if I switched to +4dBu?

[Matt]

I measured about 10dB of difference.

[mwillems]

I have tried google.....got confused.

My DAC (Lynx Aurora8) has two output levels, +4dBu and -10dBv. As Matt pointed out in another thread recently, using +4dBu creates lots more headroom. The penalty is a slightly higher noise floor, but I can live with it.

What I am wondering is: What is the theoretical difference in SPL between these two output voltages? I use Internal Volume and Loudness. Up to now, I have used a refence level of 85, with -10dBv output on my DAC. Theoretically speaking - what would be the difference in reference level for the Loudness function if I switched to +4dBu?

The theoretical (mathematical) difference between the two standards is supposed to be close to 12 dB (11.78dB). But it looks like actual measurements in this case diverge from the purely theoretical (i.e. Matt's actual measurements of the device).  Given that variance, you may want to try measuring yourself as a double check.

[<°)))))><]

+4dBu is for professional studio recording equipment, −10dBV is for consumer/HiFi/home recording equipment.
The calculated difference is close to 12dB... Be carefull, you might get clipping/distortion when you connect a +4dBu output to a −10dBV input.
Some more info: http://www.sengpielaudio.com/calculator-db-volt.htm

[Trumpetguy]

+4dBu is for professional studio recording equipment, −10dBV is for consumer/HiFi/home recording equipment.
The calculated difference is close to 12dB... Be carefull, you might get clipping/distortion when you connect a +4dBu output to a −10dBV input.
Some more info: http://www.sengpielaudio.com/calculator-db-volt.htm

I know. The +4dBu output will be connected directly to power amplifiers. I have no idea if this is a poor match or not, but my ears have not revealed any distortions. Should I worry about the amplifiers? They are old school Dynamic Precision and Emotiva amplifiers, intended for home use. 

[Trumpetguy]

I measured about 10dB of difference.

So I should lower the reference level used by Loudness by 10 then? Or the theoretical 11.78, depending on what is measured? I will measure the reference level again, but it is useful to know what can be expected.

[mojave]

If you look at the Aurora 8 spec, when it is at +4dBu it has a maximum output voltage of +20 dBu. +20 dBu corresponds with 7.75 volts.
When the Aurora 8 is at -10 dBv it will produce a maximum of 2 volts (or +6 dBv).

The Emotiva amps are usually rated at needing 1.1 volts to reach maximum power. Therefore, using +4dBu can clip the input on the amp.

You get 11.78 dB more volumue at the same internal volume control level in JRiver, but your maximum voltage the amp can output remains the same. It may soft clip the portion over 1.1 volts so you get a little more volume, but you will be compressing the peaks. In other words, you may now not be able to go above 85 or 90% in JRiver's internal volume. Consumer amps don't usually have clip lights so you won't know when you have input too much voltage.

Just to add to this, consumer amps are run at maximum gain (usually around 27-32 dB). With pro amps, they have a gain control that essentially lowers the multiplier. This allows you to have a higher signal at the front end of the signal chain. For example, you could send a 1 volt signal to a pro amp with the gain knob turned up all the way and the pro amp would make maximum power if it has an input sensitivity of .775 volts. The more volts you input, the more you turn down the gain knob. The amp still produces maximum power, as long as the final voltage is .775 volts. Think of the gain knob as a voltage divider. If you give it 7.75 volts from the Aurora 8, then the gain knob needs to be turned down until the input voltage is divided by 10 - which is .775 volts.

Again, with a consumer amp you can't divide the input voltage so you need to start with a lower voltage.

From the Lynx Aurora 8 manual:

The analog outputs are capable of delivering +20 dBu signal levels, it is important to verify that connected equipment is capable of handling these signal levels to prevent clipping or possible damage.

Also:

Is your monitoring destination a +4dBu or –10dBV line-level device? Most professional equipment uses +4dBu as the nominal level, and most consumer equipment uses –10dBV as the nominal level. From the Aurora front panel or external control software, you can establish the appropriate input and output trim levels for your equipment. At the –10dBV setting, output levels will decrease by 12.2dB.

I had a chance to use the Lynx Aurora 8 this past weekend. It was on loan from Lynx for an Audio GTG in Iowa. I have to return it this week.

[Trumpetguy]

@mojave: Thanks a lot! My conclusion from your input is that I should leave the A8 on -10dBv output. I do not really need the headroom, so that is ok. And at least when I know my amps are in danger.

Too bad you needed to return the Aurora!

[natehansen66]

Adjusting the gain mulitiplier and using an attenuator as a voltage divider are 2 different things. AFAIK attenuators are common and actual gain adjustment is not. They're often called "gain adjustment" but it's really just a voltage divider, you're not changing the gain factor of the device. I've been looking into this as I'd like an amp that has both.