Bartok as a preamplifier

Hello,

As anyone been using the dCS Bartok as a Preamp, connected directly to a power amp with no traditional preamp between them?

If yes, is it as good as a good preamp, or do you feel that something is missing?

Thank’s :slight_smile:

This question has been raised numerous times here.

Please read the topics, and if you have more questions, just let us know:

https://dcs.community/search?q=preamp

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There’ll be lots of good info there, Pedro — expect to vanish from friends and family for a few hours!

See you on the other side :slight_smile:

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Having routed my Bartok direct to active speakers for over a year, I decided to try via a preamp

My new SPL Phonitor 2 preamp/headamp (recommended on this forum) gives a significant improvement in SQ

I did not realise the impact of digital attenuation

I won’t be going back to direct

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Do you think your perception is down to digital attenuation or some other modification that the preamp is performing which is to your liking?

I haven’t tested a preamp between the Bartok I am using and power amp but I do not notice any loss of sound quality through digital attenuation. My previous DAC sounded better direct to power amp rather than through a Naim NAC202 preamp. It caused a loss of transparency and detail. A better preamp may fix that though. And if a preamp modifies the sound to your liking then of course its the way to go.

I expect it’s down to system, musical taste and sound preferences. If you value transparency and detail over colouration then would a preamp still be the way to go? How could a preamp increase transparency and detail? And in terms of dynamic range is it possible for a preamp to increase that? If so how? Apologies if that’s a basic amplification question but I would genuinely like to know how that works.

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I haven’t tested other preamps so can’t confirm, other than to say for me it’s better with this one

I understand it is accepted fact that you increasingly lose bits as you attenuate digitally (someone pitch in here please) - obviously this doesn’t apply with analogue attenuation

I like listening more quietly late at night, so I needed a preamp that maintains SQ at low volume

Can only recommend you try it yourself

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So much of my listening is low volume, and it’s what led me to the Townshend Allegri Reference for my attenuation. I think at higher volumes on recordings with only fair dynamic range, the Vivaldi DAC does quite fine as a volume control. It’s also one of the few aspects of the MSB that is decidedly better.

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Interesting. Any idea what the technical explanation would be for the preamp improving low level listening? Even when lowering the output voltage so that the digital attenuation is limited?

Moderator: is he allowed to keep mentioning that darned MSB dac?! :joy:

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I tried minimising voltage on the Bartok but .2V still didn’t reduce output enough to avoid attenuating below 0.0db in all circumstances

When set to 0.0db its internal preamp is taken completely out of the path

Therefore you get the purest quality output into your preamp or (if your ears can stand it) direct to your power amp(s)

I’m sure we all need the flexibility depending on track, time of day, etc - increasing as well as decreasing volume

I now can’t see how to avoid some unwanted impact via digital attenuation without a preamp

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It doesn’t “improve” anything . Rather the digital volume control loses resolution as it attenuates. 1 Bit for every 6dB .

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I run at 6V so all my attenuation is analogue, no matter how loud or soft. With the Vivaldi’s lowest noise performance. And what’s nice about this from my perspective is that the SQ sounds the same up and down the volume scale. Low level listening is sublime.

:rofl:

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:tired_face: No! I’ve started reading pre amp reviews.

Where can I find evidence of noise being an issue with the Vivaldi at any output voltage? Reviews suggest it is too low to be of concern.

I’ve been unable to find a detailed technical description of how the Vivaldi DAC does it’s volume attenuation. Anyone aware of a source of such information?

Resistance is futile! :slight_smile:

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Yeah, if you’ve started reading reviews, you’re already toast. :wink:

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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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