2V output vs 4V output

[LaLaLard]

Would the output voltage of a DAC, e.g. 2V vs 4V on the same device, causes different sound signature, apart from the difference in volume?

And of course, assuming both output incurs same level (or just inaudible difference) of noise and distortion.

My impression is most amps would have higher level of THD+N compared to a DAC (assuming both are well designed). In this case is it theoretically better to use 4V output instead of 2V output which requires volume knob on the amp to be turned up a bit more in order to yield the same volume?

 

[Krunok]

With the same device that has balanced and unbalanced inputs (amp) or outputs (DAC) there is typically only a small difference in THD+N that is certainly not hearable. The point of balanced connection is not to reduce THD+N but to enable running long cables without raising the noise level in professional environment.

 

[LaLaLard]

With the same device that has balanced and unbalanced inputs (amp) or outputs (DAC) there is typically only a small difference in THD+N that is certainly not hearable. The point of balanced connection is not to reduce THD+N but to enable running long cables without raising the noise level in professional environment.

Yes this part is widely known. What I was wondering is the following: ignoring all the ground hums, crosstalks and other noises/distortion/interferences arising from using RCA output, is there a difference between:
1. using 2V output and the volume on amp is set slightly higher; and
2. using 4V output and the volume on amp is set slightly lower; assuming

a. both method yield same volume in the end;
b. there's no audible difference in THD+N in both output of the DAC;
c. Amp's distortion is higher than the DAC.

I won't limit the discussion to XLR vs RCA because everyone will then be talking about electromagnetic interferences which is not what I'm really asking about. Hence let's simply discuss a 2V vs 4V scenario, ignoring the interconnection and cabling.

Thanks!

 

[Krunok]

In theory it is better if you amplify signal at the source as much as you can so 4V on DAC output is desirable, but in practice you won't hear absolutely no difference with well engineered DACs and amps.

 

[LaLaLard]

In theory it is better if you amplify signal at the source as much as you can so 4V on DAC output is desirable, but in practice you won't hear absolutely no difference with well engineered DACs and amps.

Thanks for your response

 

[solderdude]

Assuming you mean the difference between 2V and 4V in the same circumstances (think RCA out)

Then it won't make an audible difference under the conditions:
A: the amp receiving the signal must not be clipping its input (think Atom, O2)
B: the gain of the used amp is the same (only volpot position differs)

Technically the higher output voltage signal could have a higher dynamic range assuming the noise floor of the DAC has the same absolute noise level.
There could be more channel imbalance with the 4V signal as the volpot is set lower at background listening levels.

 

[Krunok]

Thanks for your response

Be aware that pushing more than 2V (say 2.2V max) at RCA amp inputs will most probably cause clipping. The same will happen with more than 4V at XLR inputs.

 

[Veri]

There are plenty consumer DACs that output 2.8V or more over RCA (qutest and other chords output 3V by default). I would assume a good many amps can handle this hotter output, especially in unity gain I would expect no problems. In higher gain clipping will eventually occur but I would not say it is a problem per se..

 

[Krunok]

There are plenty consumer DACs that output 2.8V or more over RCA (qutest and other chords output 3V by default). I would assume a good many amps can handle this hotter output, especially in unity gain I would expect no problems. In higher gain clipping will eventually occur but I would not say it is a problem per se..

The higher you are from the standard 2V chances are rising that you will have issue with clipping.

 

[Krunok]

Here's an example of typical input sensitivity figures for a modern amp, in this case Rotel RB-1590:

INPUT SENSITIVITY
Line Level Inputs (RCA): 2.2V
Line Level Inputs (XLR): 3.5V

 

[Veri]

Here's an example of typical input sensitivity figures for a modern amp, in this case Rotel RB-1590:

INPUT SENSITIVITY
Line Level Inputs (RCA): 2.2V
Line Level Inputs (XLR): 3.5V

You're saying typical input sensitivity for a "modern amp" on XLR inputs, is less than the standard output which is 4V?...

 

[solderdude]

2V is not a 'standard' by the way.
Most manufacturers have something in the neighborhood of that.
+4dBu is a standard = 1.228V. It should be noted that most inputs for that value have a headroom between 10 and 20dB so can handle 4V to 12V

Most headphone amps have a volpot as the first thing the signal encounters. For these devices there is no real limit (well the volpot setting and gain would be the practical limits).
There are some amps that have opamps as input stages. The max input voltage depends on the power supply voltages and gain of said parts of the circuit.

The input sensitivity of power amps depends on the gain and maximum output voltage.
Usually between 0.5V and 2V for consumer devices.
There isn't really a standard for this.

 

[sergeauckland]

2V is not a 'standard' by the way.
Most manufacturers have something in the neighborhood of that.
+4dBu is a standard = 1.228V. It should be noted that most inputs for that value have a headroom between 10 and 20dB so can handle 4V to 12V

2v is very close to +8dBu, which is the UK standard peak operating level.
The EBU peak level for 0dBFS is +18dBu, (6v) with the operating level around 10-12dB lower, depending on which country, and the USA tends to work at +24dBu for 0dBFS, (12v) or 20dB above 0VU at +4dBu.

Aren't standards wonderful!

S.

 

[Krunok]

It should be noted that most inputs for that value have a headroom between 10 and 20dB so can handle 4V to 12V

Yes, but on balanced (XLR) inputs, not on unbalanced (RCA) inputs.

2V is not a 'standard' by the way.
Most manufacturers have something in the neighborhood of that.

Exactly. So, as I said, as you go further above 2V chances for clipping are increasing.

If there would be a standard most manufacturers would stick to it, but there is not so I wouldn't prefer to have a DAC/preamp that delivers much more than 2V on it's unbalanced output.

 

[solderdude]

Yes, but on balanced (XLR) inputs, not on unbalanced (RCA) inputs

I thought the standard +4dBu = 1.228V is the same balanced and single ended as it is about the signal level.
In one instance it is from signal to ground and in the other instance between hot and cold.
In both cases +4dBu = 0dB but is not necesarilly 0dBFS as there is headroom.
Not so for 0dBFS but I believe here too standards differ between countries etc.

As Serge already mentioned, different amounts of headroom for different circumstances/countries etc.

I believe in the old days they tried to establish a standard with the DIN45500 which is already long forgotten and did not include CD yet as it wasn't invented in those days.

 

[Krunok]

I thought the standard +4dBu = 1.228V is the same balanced and single ended as it is about the signal level.

Well, as you said, de facto there is no standard, but balanced seems to go around 4V these days and single ended around 2V. My Rotel RMB-1075 amp has 1.0V sensitivity so I can easilly get it to clip when driving it with Topping D10 which goes up to 2.2V (IIRC). Luckilly I use it in volume control mode and I don't crank it all the way.

 

[solderdude]

The reason why balanced usually is double the voltage of single ended stems from the way the single ended signal is derived from a balanced signal (just one half is used) or in case the internal signal is single ended the single ended signal is inverted and added to the cold signal pin.
Because of this the total voltage of balanced usually is double that of the single ended.

Usually DACs are connected to pre-amplifiers or headphone amps. With a handfull of exceptions most of them have no problems with 3 or 4 V input signals.
Power amplifiers are an exception as they have a fixed gain and usually around 1V input sensitivity because most pre-amps are layed out so they can easily drive all different input sensitivity power amps.

In your case, and some others as well, the hot output voltage can make an amp clip.
That's where the digital volume control is for.

 

[Krunok]

The reason why balanced usually is double the voltage of single ended stems from the way the single ended signal is derived from a balanced signal (just one half is used) or in case the internal signal is single ended the single ended signal is inverted and added to the cold signal pin.
Because of this the total voltage of balanced usually is double that of the single ended.

Usually DACs are connected to pre-amplifiers or headphone amps. With a handfull of exceptions most of them have no problems with 3 or 4 V input signals.
Power amplifiers are an exception as they have a fixed gain and usually around 1V input sensitivity because most pre-amps are layed out so they can easily drive all different input sensitivity power amps.

In your case, and some others as well, the hot output voltage can make an amp clip.
That's where the digital volume control is for.

My point was that pushing output voltage of modern DACs (which are more and more acting a preamps) is totally unnecessary and may only lead to clipping.

You're saying typical input sensitivity for a "modern amp" on XLR inputs, is less than the standard output which is 4V?...

Yes, typically it's less than 4V for balanced inputs and less than 2V for single ended. And for that reason excessive output voltage may only lead to clipping which can easilly destroy tweeters.

 

[solderdude]

There is quite a difference between input circuits clipping and output stages clipping.
In your case is the input circuit clipping or the amp running out of steam.

In case of a high gain O2 or Atom one clips the input stage so even with the volume down you hear clipping.
Is that what you hear or mean ?

 

[yigitboy]

There is quite a difference between input circuits clipping and output stages clipping.
In your case is the input circuit clipping or the amp running out of steam.

In case of a high gain O2 or Atom one clips the input stage so even with the volume down you hear clipping.
Is that what you hear or mean ?

My graham slee solo ul headphone amplifier input sensitivity is 511mv Rms. Does it mean i should not use Topping D30 because its rca output is 2v