DAC Output Voltage

[wgscott]

I thought most DACs with pre-amps attenuate the signal to avoid ear-bleeding volume (assuming an amp with typical gain).

 

 

[wgscott]

On 12/12/2019 at 8:38 PM, 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.

 

 

Sorry, I should have read from top down.

[sandyk]

Some highly favoured Passive Preamps actually use transformers, as do a few DACs.

 Incidentally, my DIY Class A Preamp only has a gain of a little over 3 times, yet I still need to use as much as 30dB attenuation at normal domestic listening levels for TV audio etc..

[semente]

On 12/13/2019 at 5:33 AM, The Computer Audiophile said:

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

 

Maybe you need more powerful power amps.

[phusis]

@The Computer Audiophile/Chris

 

Do you still more or less exclusively use the DAC direct-to-poweramp approach, and if so does it still reign supreme over a separate hardware preamp to your ears? 

 

I use a combined DAC/preamp, and using convolution filters as well (which may have eaten roughly 6dB's of sensitivity) I am fortunate to have very high efficiency speakers and a DAC/preamp that never has me running out of volume capacity (nearing '75' out of 100 on the digital attenuator has the roof close to lifting).

 

[The Computer Audiophile]

3 hours ago, phusis said:

@The Computer Audiophile/Chris

 

Do you still more or less exclusively use the DAC direct-to-poweramp approach, and if so does it still reign supreme over a separate hardware preamp to your ears? 

 

I use a combined DAC/preamp, and using convolution filters as well (which may have eaten roughly 6dB's of sensitivity) I am fortunate to have very high efficiency speakers and a DAC/preamp that never has me running out of volume capacity (nearing '75' out of 100 on the digital attenuator has the roof close to lifting).

 

Yes, I almost always go directly from DAC to amp. When I use DACs with great volume controls, a preamp only worsens the quality.

[Solstice380]

16 hours ago, The Computer Audiophile said:

Yes, I almost always go directly from DAC to amp. When I use DACs with great volume controls, a preamp only worsens the quality.

 

That would have to be for DACs with an excellent output stage.  Unfortunately, this is where a lot of the lower priced DACs fall short.

[barrows]

Hi Chris,

 

DSP in the digital domain often requires a reduction in gain before processing in order to avoid clipping.  I know in HQPlayer or ROON I have to apply -5 to -6 dB before oversampling to DSD in order to avoid clipping.  -6 dB would require a doubling of the voltage to compensate.  So a de-facto "standard" of 2 V now would have to become 4 V.  Then, as you mention, some audiophile recordings require a higher gain setting due to their lower average recording levels.  I adjust my (DIY) DACs' output stages to put out around 4.4 V or so in order to have adequate gain in my system.  My amp requires a 2 V signal to reach max output, but it will do a little better than that as well.  Sometimes very powerful amplifiers will require even more voltage to reach full output.  With this set up I run my Volume Control anywhere from -3 dB to -20 dB depending on material, so this gain is about right for my system.  Generally best sonic results will happen with the least amount of attenuation, but some of this depends on the volume control implementation itself.  

And then there are amps with require far less voltage, or one could have the combination of a very sensitive loudspeaker, say 8 ohms and 94 dB and a powerful amp, and then they might have too much gain.

 

I think home audio could be better with higher voltages all around: in other words make the amps have less gain, and have the source have a bit higher signal.

[sandyk]

1 hour ago, barrows said:

I think home audio could be better with higher voltages all around: in other words make the amps have less gain, and have the source have a bit higher signal

 

 That's not always possible when you have several different sources, such as DTV audio, FM stereo, and even a RIAA Phono output 

[mansr]

3 hours ago, sandyk said:

 That's not always possible when you have several different sources, such as DTV audio, FM stereo, and even a RIAA Phono output 

You're missing the point. He's saying, and I agree, it would be better if all sources had a little higher voltage.

[4est]

17 minutes ago, mansr said:

You're missing the point. He's saying, and I agree, it would be better if all sources had a little higher voltage.

I disagree. IMO, we should retain the standards that were in part used because of the gain required by vinyl and tape. In an attempt to create more output voltage from sources and pre amps, it would require an extra gain stage for analog sources. Perhaps I am an outlier in that I wish to retain the functions of my analog equipment whilst pursuing modern tech too. I think a good compromise would be to have additional gain AFTER the volume attenuator that is not used if it the attenuation is not. Hence, just like a pre amp with line level being just that, line level.

[RedSwede]

Wow. What a real mess the whole situation is. I guess, while there are people with preamps and people without, and some recordings compressed to the max vs others with DR20, there will be two worlds that can't really integrate.

 

My DAC has 0.7v output from its transformer IV stage. This is absolutely enough for my preamp and I still very rarely (ever?) go past 12 o'clock, even with DRC. A 7v DAC would see me have to use digital gain and analogue gain - or, like in another system, make some interconnects with potential dividers in the RCA jacks to get into the linear range of the volume pot

 

The answer lies in standardised recording levels, unity gain preamps, and power amps designed for this standard. But the problem is that none of this matters to the big players, who could set global standards. HiFi is just too niche these days, and it all works fine from an iPhone on some airpods or Beats.

[mansr]

5 minutes ago, 4est said:

I disagree. IMO, we should retain the standards that were in part used because of the gain required by vinyl and tape. In an attempt to create more output voltage from sources and pre amps, it would require an extra gain stage for analog sources. Perhaps I am an outlier in that I wish to retain the functions of my analog equipment whilst pursuing modern tech too. I think a good compromise would be to have additional gain AFTER the volume attenuator that is not used if it the attenuation is not. Hence, just like a pre amp with line level being just that, line level.

The standard ended up being around 2 V, and there's little hope to change that now. The choice was, however, quite arbitrary. The output voltage directly from a tape head or vinyl pickup is tiny and needs lots of gain and equalisation to yield a 2 V signal with correct spectrum. The electronics providing this function (RIAA preamp and whatever is inside tape players) could easily be made with another 6 dB of gain.

 

Small signals don't like long cables, especially single-ended ones, so it makes sense to put as much gain as is practical at the source.

[The Computer Audiophile]

6 hours ago, sandyk said:

 

 That's not always possible when you have several different sources, such as DTV audio, FM stereo, and even a RIAA Phono output 

Good ole FM stereo. 

[barrows]

2 hours ago, 4est said:

I disagree. IMO, we should retain the standards that were in part used because of the gain required by vinyl and tape. In an attempt to create more output voltage from sources and pre amps, it would require an extra gain stage for analog sources. Perhaps I am an outlier in that I wish to retain the functions of my analog equipment whilst pursuing modern tech too. I think a good compromise would be to have additional gain AFTER the volume attenuator that is not used if it the attenuation is not. Hence, just like a pre amp with line level being just that, line level.

I agree.  Of course i use digital volume control in my DAC, so the additional gain would be after the volume control and I drive amp(s) directly.  I prefer to have a stout gain stage at the output of the DAC to drive the input stage of the amplifier robustly.  But I am not in favor of adding extra gain stages, just as many as are needed (no preamp).  I personally will not use a preamp again (until I am retired and, maybe, spinning some vinyl for nostalgia's sake!).  I am not suggesting a lot of additional gain either: say we standardized amplifiers such that they all produced full output with around 5 volts input.  Benchmark basically goes for this approach with their products (Pro heritage).  There is no reason analog sources like tape decks could not also have this output level, to their benefit, and built in volume control before the final output driver stage.  Turntables are their own world and require so much extra "stuff" (gain/equalisation) they are in their own world.

 

The theory is that, in general, a higher voltage "line level" signal would suffer less loss in transmission, and be less subject to degradation by interconnect quality and noise pickup (airborne RF, etc).  Anyone who has played around with turntables much knows how frustrating noise can be with low level signals.

 

Ultimately though I think we should move to a more simple set up.  Current technology is so good with class D amplification, and the best SMPS that it makes more sense than ever to go with single box solutions.  I am itching to conceive and help design a single box DAC/AMP, eliminating external interconnects entirely (and gain stages, no need to drive cables).  Just ethernet input, and speaker output.  I know audiophiles who are into "system building" will not accept such an approach, but the stuff I have been playing with for the last few years just begs to put together this way.  Powered speakers are of course another way of doing a similar thing, but i am still not convinced about sensitive electronics being inside a box with that much vibration.  At least the single box DAC/Amp leaves some flexibility for audiophiles as well (speaker choice can be so critical).

 

[mansr]

41 minutes ago, barrows said:

Ultimately though I think we should move to a more simple set up.  Current technology is so good with class D amplification, and the best SMPS that it makes more sense than ever to go with single box solutions.  I am itching to conceive and help design a single box DAC/AMP, eliminating external interconnects entirely (and gain stages, no need to drive cables).  Just ethernet input, and speaker output.

It's called an AVR.

[sandyk]

9 hours ago, mansr said:

You're missing the point. He's saying, and I agree, it would be better if all sources had a little higher voltage.

 

 I am not missing the point. It's simply not possible to further increase the output levels of those legacy devices .

 It also implies that quite a few devices would also need to have much larger voltage supply rails.

 Goodbye to USB powered DACs for example.

[mansr]

22 minutes ago, sandyk said:

I am not missing the point. It's simply not possible to further increase the output levels of those legacy devices .

A phono preamp has a gain of 40-60 dB. Surely adding another 6 dB wouldn't be all that difficult.

 

22 minutes ago, sandyk said:

 It also implies that quite a few devices would also need to have much larger voltage supply rails.

 Goodbye to USB powered DACs for example.

Ever heard of a boost converter?

[sandyk]

1 minute ago, mansr said:

Ever heard of a boost converter?

Just what we need. NOT ! A switching device in a simple DAC to cause further design problems and the possibility of a degradation in performance. Affordable USB DACs have enough problems as it is .

Quote

A phono preamp has a gain of 40-60 dB. Surely adding another 6 dB wouldn't be all that difficult

Unless the output voltages of a typical RIAA Phono amplifier have markedly increased in the last few years. then it wouldn't do much more than meet the current output voltage level of most DACs and CD/DVD/BR  players etc.

 

[Richard Dale]

19 minutes ago, mansr said:

A phono preamp has a gain of 40-60 dB. Surely adding another 6 dB wouldn't be all that difficult.

 

Ever heard of a boost converter?

I recently upgraded from a Puresound P10 to an EAT E-Glo Petit because the Puresound only had about 35db of gain and just wouldn't go loud enough in my system. I run the Petit at 50db of gain with a very high output moving magnet cartridge (Ortofon 2M Black 7-8 mv), and it matches the 3 volt output level of my Chord 2Qute pretty closely. The Petit has a very high overload margin, but it isn't usually possible to run a phono preamp with so much gain, which would typically be 40db for a moving magnet input.

[mansr]

7 minutes ago, sandyk said:

Just what we need. NOT ! A switching device in a simple DAC to cause further design problems and the possibility of a degradation in performance.

There are complete modules, including inductor, available if you're too lazy to lay out a handful of components yourself.

[sandyk]

Just now, mansr said:

There are complete modules, including inductor, available if you're too lazy to lay out a handful of components yourself.

 

 Then Paperman, why don't you construct one and submit it to Archimago for measurements and a performance report ? 😛

[The Computer Audiophile]

2 minutes ago, sandyk said:

Paperman

Is this a compliment or insult?

[sandyk]

12 minutes ago, The Computer Audiophile said:

Is this a compliment or insult?

I am simply pointing out that it is isn't as simple as stringing together a series of modules.

 Mansr tries to make things like this sound so easy.

Theory is fine, but it takes fine tuning too using our hearing, not just measurements to verify the final results 

[kumakuma]

45 minutes ago, sandyk said:

I am simply pointing out that it is isn't as simple as stringing together a series of modules.

 Mansr tries to make things like this sound so easy.

Theory is fine, but it takes fine tuning too using our hearing, not just measurements to verify the final results 

 

So an insult then?