DAC Output Voltage

[The Computer Audiophile]

Hi Guys, I get many DACs in for review every year and many have different output voltages. Some have 2Vrms, 4Vrms, 6Vrms, and I have one now with 7Vrms. 
 

I’m a fan of more voltage for sound quality reasons and I believe it’s necessary when using convolution filters. 
 

Question 1: Why are the voltages set at 2,4,6 etc...?

 

Question 2: Given how many DACs are driving amps directly now days, doesn’t it make sense to have higher output voltages?

 

Question 3: Is there a different option other than increased output voltage from the DAC?

 

Question 4: Is it true that a higher output voltage means more signal in the signal to noise ratio, thus can equate to better sound?

 

Thanks in advance to anyone who can help. 

[sandyk]

29 minutes ago, The Computer Audiophile said:

Question 2: Given how many DACs are driving amps directly now days, doesn’t it make sense to have higher output voltages?

 

Most current amplifier designs have far too much gain already, with many giving full output at less than a 1V RMS Input, so you will need to greatly attenuate their input level which would defeat any advantages.

 

[The Computer Audiophile]

39 minutes ago, sandyk said:

 

Most current amplifier designs have far too much gain already, with many giving full output at less than a 1V RMS Input, so you will need to greatly attenuate their input level which would defeat any advantages.

 

Interesting. Perhaps my Constellation amplifiers are out of the ordinary?

[dean70]

DACs have high output levels and amps too much gain. We need some standards for consumer audio  😗

[The Computer Audiophile]

1 minute ago, dean70 said:

DACs have high output levels and amps too much gain. We need some standards for consumer audio  😗

My experience is just the opposite. I may be an outlier though. 

[fas42]

1 hour ago, sandyk said:

 

Most current amplifier designs have far too much gain already, with many giving full output at less than a 1V RMS Input, so you will need to greatly attenuate their input level which would defeat any advantages.

 

 

I was curious ... looked around a bit, and most lie in the range 1-2 V. Which seems pretty reasonable to me - if you want to directly drive a power amp with a DAC or CDP, then you need some margin for those recordings which are very low in average level - they do exist!

 

People seem to have a hangup about using digital attenuation, in the DAC, say - for the whole time I have played with digital source material, I have never heard any anomalies - apart from mistakes in mastering - that I could attribute to this area ...plenty of SQ issues from lots of other factors, but daring to touch the level of the signal leaving the DAC has never been one of them ...

[sandyk]

51 minutes ago, dean70 said:

DACs have high output levels and amps too much gain. We need some standards for consumer audio  😗

I agree, but many amplifiers also  have to be used with lower level sources such as Vinyl Preamplifiers, FM Stereo, TV audio including from STBs as well, not just Digital Audio.

 I just noticed that this one from Constellation has a gain of 32dB which is WAY too high.

https://www.constellationaudio.com/index.php/reference/hercules-ii-stereo

[esldude]

Gain staging.  Your DAC at max voltage should drive your amplifier to right at its max output which should drive your speaker to its maximum output.  That will give maximum signal to noise.  Now sometimes right at the ragged max distortion is a little higher, so maybe you back off 3 db at each step giving a little headroom to the whole system.  SNR might drop a smidgen, but THD could be lower, and the system easy to operate in a normal listening range.  

 

So why all these gain differences in amps, and output differences in DACs and efficiency differences in speakers? Because of all the possible ways to add it all up.  

 

Of course your good pro interface units and DACs will have variable output configurations like the RME does. 

[STC]

2 hours ago, The Computer Audiophile said:

Hi Guys, I get many DACs in for review every year and many have different output voltages. Some have 2Vrms, 4Vrms, 6Vrms, and I have one now with 7Vrms. 
 

I’m a fan of more voltage for sound quality reasons and I believe it’s necessary when using convolution filters. 
 

Question 1: Why are the voltages set at 2,4,6 etc...?

 

Actual manual should be useful here. I suspect the 6 and 7 Vrms are actually the max output and not the average level. 

 

2 hours ago, The Computer Audiophile said:

 

Question 2: Given how many DACs are driving amps directly now days, doesn’t it make sense to have higher output voltages?
 

 

How many voltage is enough? What is the sensitivity of the Amp input?  Practically, all preamp today is acting like attenuator. 

 

2 hours ago, The Computer Audiophile said:

 

Question 3: Is there a different option other than increased output voltage from the DAC?

 

Question 4: Is it true that a higher output voltage means more signal in the signal to noise ratio, thus can equate to better sound?

 

Thanks in advance to anyone who can help. 

Generally, the higher levels are more suited for pro amplifiers where the power rails is more than 15V.  

 

If you don’t hear any noise, then choose the highest number provided your amp do not clip at peaks.  The problem was IIRC, there was no standard average level when they introduced digital. So that caused some problem and this including one of the reason for the use of compression. 

I am no except and hopefully some DAC designers could give a better response.  

 

[sandyk]

5 minutes ago, STC said:

The problem was IIRC, there was no standard average level when they introduced digital.

 The original CD output level was 2V RMS .

[STC]

1 minute ago, sandyk said:

 The original CD output level was 2V RMS .

I-was referring to average level 0 VU .

[sandyk]

1 minute ago, STC said:

I-was referring to average level 0 VU .

 I haven't seen a specification like that, only the max. output level of 2V RMS 

[STC]

1 minute ago, sandyk said:

 I haven't seen a specification like that, only the max. output level of 2V RMS 

That why you have adjust the volume for different albums because there was no standard for CD.

[STC]

3 hours ago, The Computer Audiophile said:

Some have 2Vrms, 4Vrms, 6Vrms, and I have one now with 7Vrms. 

added to main reply:-  This is one of the main reason why DACs sound different compared to other parameter. 

[sandyk]

9 minutes ago, STC said:

That why you have adjust the volume for different albums because there was no standard for CD.

The original A/D recordings had several dB below max. to allow for sudden peaks. This all changed with Loudness wars until it became quite normal for some releases to have severe clipping.

[cjf]

I've found that without having quite a bit of extra voltage at the Analog Outs of a DAC when not using a traditional Preamp to drive the amps directly (at least the ones that I use) one quickly runs out of volume output when using more than average room correction in an effort to achieve a nicely flat in room response curve. In my setup I've allowed Audiolense to correct up to 20db or so which in turn results in a pretty big hit in vol output. Some say this is too aggressive but I've not found this to be the case.

 

As an example, with no room correction in the picture and while using my Benchmark DAC3 to directly drive my amps I need to leave the -20db "Pad" in place in order to have the Vol knob at the min ideal location in its range which is about 12oclock which results in about the max level I listen at. The -20db Pad is said to have a voltage output of around 1.8vrms.

 

In contrast, with room correction, using that same -20db Pad in combination with Roons DSP vol control and keeping the DAC vol knob burried the in room vol level is waay to low to achieve a satisfactory output even with the DSP slider in ROON reaching 0dbfs. In this scenario, if your DAC is already at its output limit in terms of voltage you are going to be very disappointed in the result.

 

As a result of this I end up needing to use the -10db Pad on the Benchmark which is said to be 17.5dbu or about 6vrms output. If I weren't paranoid of losing all physical vol control I would rather use the vol bypass option which pushes the output levels into the 18vrms range. Right now with the output level in the 6vrms range I still need to run ROON's DSP vol slider up to -5dbfs to reach my desired output level in room.

 

Some of the higher end analog Preamps are said to deliver upwards of 40vrms to the amps (ie..Pass XP2x,XP3x) which according to the designer is ideal (I asked) so depending on ones choice of amps and other configuration/setup only having 2vrms output will be nowhere near enough wiggle room to handle more advanced audio configurations like using room correction...etc

 

Just my 2cents

 

 

[mansr]

On 12/13/2019 at 4:08 AM, The Computer Audiophile said:

Hi Guys, I get many DACs in for review every year and many have different output voltages. Some have 2Vrms, 4Vrms, 6Vrms, and I have one now with 7Vrms. 
 

I’m a fan of more voltage for sound quality reasons and I believe it’s necessary when using convolution filters.

I don't see the connection between digital filters and output voltage. That said, if the filter engine lowers the volume to give itself some headroom, this can of course be compensated with higher gain somewhere downstream.

 

On 12/13/2019 at 4:08 AM, The Computer Audiophile said:

Question 1: Why are the voltages set at 2,4,6 etc...?

Because even numbers are better. 🙂

 

On 12/13/2019 at 4:08 AM, The Computer Audiophile said:

Question 2: Given how many DACs are driving amps directly now days, doesn’t it make sense to have higher output voltages?

As others have said, the proper input voltage to the amp depends on its gain and the sensitivity of the speakers. If you don't think it's loud enough even with the volume turned up to 11, increasing the voltage to the amp might be a solution. Of course, that will only help if the amp can handle it without clipping or some other evil. If not, you need a bigger amp.

 

On 12/13/2019 at 4:08 AM, The Computer Audiophile said:

Question 3: Is there a different option other than increased output voltage from the DAC?

To achieve what?

 

On 12/13/2019 at 4:08 AM, The Computer Audiophile said:

Question 4: Is it true that a higher output voltage means more signal in the signal to noise ratio, thus can equate to better sound?

All electronics have some inherent noise that is largely independent of signal voltage. Noise picked up by cables is also independent of the signal level. Raising the signal level thus increases the SNR.

 

Your questions seem to be lacking some context, so it's hard to give a good answer.

[The Computer Audiophile]

2 hours ago, mansr said:

I don't see the connection between digital filters and output voltage. That said, if the filter engine lowers the volume to give itself some headroom, this can of course be compensated with higher gain somewhere downstream.

 

Output voltage give me more volume. When engaging convolution filter there is often a severe volume decrease. If I play a classical recording with a DR score of 21, I frequently run out of volume on the very quiet sections of a track. When I have a DAC with an output voltage of 6 or 7, then I'm pretty good. But, it seems like DACs are still stuck in the old days of thinking they are only to convert D to A and output to a preamp. 

 

 

2 hours ago, mansr said:

As others have said, the proper input voltage to the amp depends on its gain and the sensitivity of the speakers. If you don't think it's loud enough even with the volume turned up to 11, increasing the voltage to the amp might be a solution. Of course, that will only help if the amp can handle it without clipping or some other evil. If not, you need a bigger amp.

 

Some preamps have far more output voltage than DACs. I believe my preamp has 19 volts out and mentioned earlier was one with 40. Seems like DACs should be closer to these higher voltages if they are meant to drive amps. 

 

 

 

 

[mansr]

1 hour ago, The Computer Audiophile said:

Output voltage give me more volume. When engaging convolution filter there is often a severe volume decrease.

I guess that's necessary to give the filter the requisite headroom.

 

1 hour ago, The Computer Audiophile said:

If I play a classical recording with a DR score of 21, I frequently run out of volume on the very quiet sections of a track. When I have a DAC with an output voltage of 6 or 7, then I'm pretty good. But, it seems like DACs are still stuck in the old days of thinking they are only to convert D to A and output to a preamp. 

I connected a scope at the input of my power amp and played Tchaikovsky's 4th symphony. In this recording, the third movement has DR17. With the volume set quite high (at times it got uncomfortably loud), the peak voltage (not RMS) registered by the scope was 1.5 V. My speakers are not particularly sensitive.

 

Have you measured what voltage you're getting from your DAC and preamp?

 

1 hour ago, The Computer Audiophile said:

Some preamps have far more output voltage than DACs. I believe my preamp has 19 volts out and mentioned earlier was one with 40. Seems like DACs should be closer to these higher voltages if they are meant to drive amps.

As someone else said, we need better standards for interconnecting audio gear.

[The Computer Audiophile]

14 minutes ago, mansr said:

Have you measured what voltage you're getting from your DAC and preamp?

I haven't, but I've tried this with multiple DACs. They all give me the same results. 

[mansr]

6 minutes ago, The Computer Audiophile said:

I haven't, but I've tried this with multiple DACs. They all give me the same results. 

Getting some tangible data would be my first step. Do you have a multimeter?

[Summit]

On 12/13/2019 at 5:08 AM, The Computer Audiophile said:

Hi Guys, I get many DACs in for review every year and many have different output voltages. Some have 2Vrms, 4Vrms, 6Vrms, and I have one now with 7Vrms. 
 

I’m a fan of more voltage for sound quality reasons and I believe it’s necessary when using convolution filters. 
 

Question 1: Why are the voltages set at 2,4,6 etc...?

 

Question 2: Given how many DACs are driving amps directly now days, doesn’t it make sense to have higher output voltages?

 

Question 3: Is there a different option other than increased output voltage from the DAC?

 

Question 4: Is it true that a higher output voltage means more signal in the signal to noise ratio, thus can equate to better sound?

 

Thanks in advance to anyone who can help. 

 

Before it was more or less standard that SE out was 2v max and balanced 4v. Nowadays when many DACs have some preamp functions a stronger signal* can be better. I would say that a stronger signal is normally better, as long as it don’t overload the input of the amp, and not all amps are equal in this regard. Many amps will start clipping at higher voltage levels while other don’t.

To get higher output signal from a DAC can result in some disadvantage though, and to put in a bigger output stage cost more needs bigger PSU etc.

 

*A stronger signal is less sensitive to external noise than a weaker signal, everything else hold equal.

[The Computer Audiophile]

1 hour ago, mansr said:

Do you have a multimeter?

 

Yes, I will test to see what's going on. 

 

 

52 minutes ago, Summit said:

to put in a bigger output stage cost more needs bigger PSU etc

 

Never a problem for HiFi manufacturers :~)

[Summit]

On 12/18/2019 at 7:48 PM, The Computer Audiophile said:

 

Yes, I will test to see what's going on. 

 

 

 

Never a problem for HiFi manufacturers :~)

 

The thing I liked to say is that the cost and complexity can grow exponential with higher output, but much depends on DAC design. To get significant higher output with a SOTA class A circuit, the output transformers has to be bigger which generates more heat and EMI, so you will maybe be require to build a bigger case with better separation between the digital, analogue and PSU sections. The difference in cost to make a DAC that can output 2v and one that can output 6v can therefore be huge and not all HiFi manufacturers consider the advantage of higher output (to eliminate the need of a preamp) worth the cost and trouble. This is how I have interpreted it to be 🙂.

[mansr]

3 hours ago, Summit said:

The thing I liked to say is that the cost and complexity can grow exponential with higher output, but much depends on DAC design. To get significant higher output with a SOTA class A circuit, the output transformers has to be bigger which generates more heat and EMI, so you will maybe be require to build a bigger case with better separation between the digital, analogue and PSU sections. The difference in cost to make a DAC that can output 2v and one that can output 6v can therefore be huge and not all HiFi manufacturers consider the advantage of higher output (to eliminate the need of a preamp) worth the cost and trouble. This is how I have interpreted it to be 🙂.

Huh? A 6 V (or 12 V for that matter) output is not the slightest bit difficult to achieve. Why would you need output transformers in a DAC?