Who said it was an issue?
Apologies. I thought you mean’t that 6V had audibly lower noise than the lower voltages so sounded better. Is it more than 6V works better with the Townsend preamp?
Question of the day: which gives you biggest sound improvement: the clock or preamp? Similarish costs.
Signal-to-noise ratio, or SNR, is defined as the ratio of signal power to the noise power. The concepts of signal-to-noise ratio and dynamic range are closely related.
6V out, compared to 2V out, will result in a higher SNR and a higher dynamic range.
For further reading: https://en.wikipedia.org/wiki/Signal-to-noise_ratio
It depends on where the 6V or 2V out go to: either a preamp, or a power amp. If a preamp: its input sensitivity (how much V it can handle until it goes into clipping/ distortion) determines whether you can output 6V or 2V at 0.0 dB, or if you need to use the internal digital attenuation, to lower V, to match the preamp. If a power amp: always digital attenuation is needed.
Digital attenuation drops bits from the original signal. dCS advise to go no lower than -30dB - -10dB.
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Absolutely right of course. But whether it has any practical outcome may be less clear as the dynamic range of virtually all commercial recordings is compressed and a system’s amplification may also not have as excellent SNR figures as a dCS component and thus any advantage in this respect is lost.
The dynamic range of a commercial recording is given, you can only worsen it if your audio system cannot properly handle it.
If your preamp has a better SNR than the dCS component used (mine has), then you can hear the difference, very well.
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On preamps, and digital volume control… Considering for a moment the role of a pre-amp in a digital audio playback system:
- To select different sources.
- To level match source and power amplifier.
- To set the listening volume.
When comparing a DAC connected to a power amp directly vs with a preamp in line, there are potential benefits to the addition of a preamp:
- Interfacing between a source which has only an unbalanced output to an amplifier that only has a balanced input or vice versa.
- To allow a “difficult” amplifier input and/or cable to be driven. This is more likely to be an issue if the cable is long and, of course, different preamps will have different drive characteristics.
- The preamp has tonal characteristics the listener likes.
The output drive issue is not a problem with a dCS DAC. Our balanced output stage has very low output impedance (less than 1 Ohm) and very high current delivery. It’s really very unlikely that any preamp would out-perform in these regards and any input/cable combination that caused it difficulty would be questionable in itself.
The preamp categorically cannot reveal more information (be it frequency content, dynamic resolution etc.) from the signal than by connecting DAC to power amp directly – it simply adds in noise, harmonics, frequency response aberrations etc. that aren’t in the original recording that the listener finds pleasing – euphonic distortion. Of course what I cannot do is tell you that your ear does not prefer a particular sound. That is very a very personal preference – but from a purely technical perspective, it is a degradation to sound quality (albeit a potentially psychoacoustically pleasing one). I would hope that we could all agree a DAC should be a transparent link between music and amps/transducers, so attempting to voice the unit to produce such distortions is counterintuitive.
Level matching is less easy to dismiss. If the amplifier were very sensitive, to the extent that our volume control was having to be backed off by 30dB or more, there might be a case for inserting a preamp. In all other circumstances, our digital volume control will introduce less crosstalk, noise, distortion and gain and frequency response errors than a preamp. In the vast majority of cases however, lowering the volume control by more than 30dB would suggest a gain issue elsewhere in the system which would need to be addressed.
Provided this is the exception not the rule (such as night listening), use of the digital volume control inside the dCS DAC would be technically preferable to then permanently having a preamp in the chain for the sake of volume control. Analogue volume controls are definitely no free lunch and come with their own limitations to consider - such as that more analogue componentry in the signal chain affects the frequency response in some way, adds noise and likely distortion as well. Finally, contrary to popular belief, an analogue volume control does not remove the problem of signal to noise - any real system will have some degree of self-noise.
Now, the points that have been made about digital volume controls throwing away bits and decreasing dynamic resolution – these are not correct. The idea that a digital volume control truncates the signal and throws away bits to achieve a volume reduction would only be true if the volume control was to take place before the filtering stage in the DAC, which is not the case – at least with a dCS DAC. Considering how a digital filter operates, there are hundreds, thousands or potentially even millions of multiples/accumulates throughout the signal path. The volume control is effectively just the last one in this chain.
The architecture of a dCS DAC also means that the interface between the output of the filtering stage and the input of the DAC is carried out inside the main FPGA, so we don’t have to deal with fixed width interfaces which are present when for example sending digital audio signals between ICs. We have much more control over the whole process.
As an example, consider a 16 bit sample from a CD, along with a 16 bit volume control. All possible permutations of volume and sample are guaranteed to fit within 32 bits. Even if the signal was upped to 24 bit, there is still a digital noise floor of -192dB, with zero distortion or quantisation artefacts, assuming it is dithered properly. This is way below any real-world analogue noise floors.
The point to consider related to volume control however is that the DAC itself has an analogue noise floor, which is fixed. Reducing the signal by 30dB for example means the ratio of signal to the analogue noise floor of the DAC is reduced. This does not mean the DAC is simply throwing away bits to attenuate the volume. Another point worth considering is that with some DAC types (notably ladder DACs) the distortion products of the D/A conversion structure are essentially fixed. They become proportionally bigger as the signal gets smaller (i.e. when the volume is turned down), so poor low-level linearity is an issue. Not the case for the Ring DAC, as the distortion goes down faster as the signal gets smaller.
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Superb info. Thank you James.
This says it all for me. I was about to push the button on a long-winded explanation of why I find it handy to have the Townshend in my signal path after the Vivaldi DAC. The reality is that the majority of my listening is low level, and I find it advantageous to keep the Vivaldi at 0, and have the Townshend handle volume attenuation in the analog domain as transparently as possible subject to Jame’s points about cumulative electric circuits in the signal path. I find the AVC approach to volume attenuation the most pleasing for me.
6V is all about driving the DAC at its highest performance level. That’s all. Erno and Pete addressed that before and better than me. And James as well. The Townshend doesn’t seem to care, and the Wavelet is easy to adjust for the output. On your second question, the functionality of the two are so different that to me it doesn’t seem like a “choice,” but the answer to the question is easy: the Clock, hands down. The passive pre is simply an attenuator that I find useful for low level listening [which is the majority of my listening]. As James so succinctly describes, the pre cannot create more information, but if the system sounds “better” to the listener that owns the wallet, then it means it is changing the sound information from the state in which it was received from the DAC in a way the listener finds gratifying. I enjoyed the glowing reviews of the TAR, and I prefer it in my system over the Bespoke and the Ayre I tried, but that is because it seemed to change the sound the least. My first reported listening impressions were purely subjective as compared to the Bespoke [wider soundstage, better micro-detail, etc.]; I don’t know if a direct comparison would again produce the same reactions, but I am long past caring. I don’t have other preamps available to me right now other than the PS Audio BHK, but I already know that I no longer find its presentation pleasing. With the Townshend, I now have the conveniences of the BHK and Ayre, done better than the Bespoke, with the least amount of alteration [“reduction in transparency” to borrow James’ terminology] in the Vivaldi DAC’s information that I can discern. That’s what I wanted. If I could play my system at what I think of as normal listening volumes all the time, I would not need/want the Townshend. I would have the DAC feed directly into the Legacy Wavelet.
The Clock, though, truly improves the informational completeness of the sound. If you want the best out of the Vivaldi DAC, in my view, the Vivaldi Clock is required. After that, it’s about convenience and psychoacoustics.
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Excellent news: I can spend my money on a dCS clock 
. Unless I would prefer the distortion of a preamp 
Fantastic information James thank you. Just what I was looking for.
The only question that remains in my mind is whether the SNR is noticeably reduced for a lesser output V level than a 6V output level given that the DAC noise floor is fixed. Vivaldi “Residual Noise Better than -113dB0 @ 20Hz-20kHz unweighted (6V Setting)”. Are you able to reveal the residual noise at other output V settings? I suppose the question is if the preamp added less noise than the lower DAC output V introduced then a preamp could theoretically increase the SNR IF you would otherwise have to use 0.2V or 0.6V output setting. I doubt it but would be interested to know.
How about introducing an enhanced volume control that automatically changes the output V as you increase volume demand much like an automatic gearbox in a car. So it starts at -80dB digital attenuation at 0.2V output and as you increase the volume setting to 0dB digital attenuation it automatically changes the output to 0.6V and simultaneously drops the digital attenuation to -10dB (or whatever it needs) and so on up to 6V so that it maintains a smooth response and best possible SNR at all times. There would of course be a min a max setting option somewhere much like roon offers.
Did I take that too far? 
Thank you for the advice Greg.
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Thank you, James. Like Greg, I usually listen through speakers at low level (neighbours issue). When driving my power amp directly, I ended up around -50dB setting at 2V out. No gain issue in my system. The result at this low level was not pleasing. Adding a preamp is.
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Thank you James, you have provided serious food for thought 
Also, thank you all for sharing your personal experiences and thoughts on this matter 
@James would you advise going down to 0.2V line level output to allow lower volume?
Like @Ermos I need to attenuate significantly, in my case when I am listening late at night in the room below bedrooms
If I remove the preamp and go direct from Bartok to my ATC actives, what are your recommendations for addressing the gain issue?
Thanks
How should we react to the two articles below that express opinions of dCS volume controls? Are they mistaken? I do not hear what they seem to.
Last paragraph: " However I also tried the Bartók volume control and would not for myself accept the sacrifice in sound quality: it significantly affected clarity, timing, image depth, micro detail and subjective dynamics, so I would leave it at one of the several fixed levels and use a top class external control instead."
“Running off a top-pedigree dCS source, Angel demonstrated how the slightest engagement of its volume control—which we can assume was executed to a very high level—was immediately obvious as a filtering effect. It sounded like an opacity command by contrast to his own analog controller.”
Just my personal opinion, 6moons is full of subjective opinions that very often has no real basis in fact. Only to be read if one wishes to indulge in mindless entertainment 
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I was influenced by the HFC article to try a preamp between the Bartok and ATC actives
Whether due to euphonic distortion or lack of digital attenuation, I do prefer it with the recently added preamp
But James’ post has now prompted me to A-B test … one for a snowy lockdown Sunday 
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The 0.2V and 0.6V output settings were added as a reaction to modern streaming technologies – AirPlay connecting to your system, whacking the volume up to full and blowing some drivers for example is not fun. Lower output voltages are a useful safeguard against such things. I once serviced a speaker which spat a voice coil across the room because of a smartphone jumping from being connected to the user’s car to their streamer via Bluetooth – by all accounts it gave the cat a hell of a jump.
With that said, to my knowledge in the event of night-time listening where a lower volume is required, the benefit of using a lower output voltage setting and keeping the volume control towards the top end of the range is that with a lower output voltage and higher volume control for quiet listening you keep the signal to noise ratio in the Ring DAC itself higher, as the volume control stage immediately precedes the FPGA’s output to the Ring DAC whereas the output voltage setting takes place after the D/A conversion. The signal to noise in the analogue output stage will still be lower whether using a lower output voltage or a higher voltage but lower volume control, but the conversion stage retains a higher ratio with a lower output voltage in this case. My advice would be to use whatever output voltage setting that allows for higher range usage of the volume control – though I will double check this point on Monday.
Talking about the volume control implementation used in dCS DACs, given the fact that the volume control is simply the last step in what could easily be a very long stage of digital filtering, if working at a lower volume control meant the maths behind this processing was in some way flawed and could create a loss of dynamics in itself, the effects of digital filtering would be pretty horrendous. This definitely isn’t the case when done correctly. The argument is therefore not whether a digital volume control is the correct way vs analogue, to my mind the conversation is actually around whether volume control pre-D/A conversion or post using one of a variety of methods is most appropriate. That becomes incredibly tricky to draw anything meaningful from, because the art of product design is being aware of the trade-offs with different approaches and striking a good balance between the competing compromises. It is possible to get good results with either, and I have no doubt every approach has been considered over the decades with a dCS product. From conversations with our engineers on these topics, honestly the sheer number of angles that are considered when designing each stage of a dCS DAC are genuinely staggering.
I will say that as is the case with every area of dCS products I have ever thoroughly investigated, the system as a whole and end user experience as a whole has been taken into consideration. We aren’t in the game to make products which will win at spec sheet comparisons, we are out to make ones that are at the forefront of what is possible for sound quality. For example, if digital purity was the name of the game, even at the expense of the “end product”, one could simply connect the DAC outputs to the output jacks of the product and let whatever is on the other end of it deal with load matching and such. Adding a line output stage to the DAC will add in the “downsides” an analogue stage will naturally bring (distortion, noise etc.), but will likely allow cables and (unknown) input stages down the chain to be driven much better than would be possible simply by connecting the DAC output directly. This is what, from a spec sheet, would be seen as a compromise in the unit design – but it is one that in the real world results in an improvement in system performance.
I appreciate this may not be a popular opinion in some areas of the internet, but any opportunity for blind testing should be taken where possible when A/B comparing kit. If sound quality is king to you, let your ears be the judge, not the parts of all our brains that are predisposed to want us to think a certain way about a piece of equipment. If that test concludes you prefer the preamp in the system, more power to you (I‘m sure there is a bad pun in there somewhere)!
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The verdict 
Then you are stupid.
I did several not just A/B, but A/B/X comparisons. Let us say: just my bad taste, or psychoaccoustics, or …?
Adding a line output stage to the DAC will add in the “downsides” an analogue stage will naturally bring (distortion, noise etc.), but will likely allow cables and (unknown) input stages down the chain to be driven much better than would be possible simply by connecting the DAC output directly. This is what, from a spec sheet, would be seen as a compromise in the unit design – but it is one that in the real world results in an improvement in system performance.
That is why I asked this community if someone is interested in a separate dCS preamp. It might break your philosophy, on the other hand it might open a practical choice.
I think most of us are in this for pleasure. If you enjoy it more routed through an old amp with the bass and treble turned up and the loudness on then why not?
Of course dCS cannot voice the dac to try to make a particular group happy. They have to make it as close to the recording as possible. It’s up to the individual to alter that to whatever they enjoy if they wish.
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James, thank you for this superb explanation. I am in fact going to spend some time comparing (the extended type, over time, not blind quick-switching) the Townshend with direct output at lower voltage. I won’t be surprised if I learn something new. But it might not change my listening much, because one of the reasons for the Townshend is its easier-to-use, unobtrusive remote. Hmmm, but maybe Mosaic for both voltage and volume control . . … Such wonderful choices we have.
I never thought this was about “breaking philosophy,” so much as it is not what they do. There are hundreds of high-end preamps that, almost by definition, are about individual taste. The DAC, however, is agnostic to all of them. Why step into an inherently lower market share outside their principal expertise?
Not just 6moons. Much of the industry/review press, even some of the forums like Head-Fi and WBF, is little more than hyperventilating tabloidism. The amount of advertising on those pages tells you everything you need to know. They are marketing and selling our wallets to the advertisers. Objectivity is a bit low-octane for that purpose.
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