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Is there any point in a valve DAC

rockingdoc

rockingdoc

pfm Member
I have a valve based system (and a few solid state). A lot of the time I prefer the sound of the valve system.
I particularly prefer a valve headphone amp (Tim de Paravicini).
Is their any point in a valve DAC?I don’t really understand what DACs do, other than some sort of computing business, but I assume after that is done there must be some sort of amplification stage to handle the analogue signal to send to a preamp. Is that what the valves are for? Or are valves only used in DACs that double up as a preamp?
 
DAC - Digital - Analogue - converter , in simple terms it takes the digital information and converts to analogue, for most 'valve' DAC s the valves are used in the analogue output stage. Though in some cases there maybe valves used for other purposes, PSU perhaps.
They are not only used in DAC s that double as preamps and can be found in seperate DACs or sometimes the DAC in a CD player with a valve output stage.
 
No, not really unless you use it to add flavour.

Unlike with a tube amplifier or phono stage where the tubes are active devices critical to the functioning of the unit, a dac will nearly always just be passing the output from the solid state signal path through a tube output, usually just a cathode follower. It allows the manufacturer to say it's a tube design, when it really isn't.
 
yes - some solid state DAC may not to your liking. It's the same as using a valve and and a ss amp. Ultimately, it's the sound coming out of it that matters.
 
philiphifi said:
yes - some solid state DAC may not to your liking. It's the same as using a valve and and a ss amp. Ultimately, it's the sound coming out of it that matters.
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Is that true or is it more to do with other attributes of valves? If it were true why has reproducing the sound of valves with cheaper more efficient and reliable transistor based circuitry been commercially unsuccessful? What valves add to the sound is certainly part of their appeal but is it the dominant part?
 
Rega make two versions if the ISIS CD player. One with valves and one solid state. Those with experience of both all say the same thing. The valve one is better.
 
It's as Robert says above.
There's no such thing as a valve DAC. It's a marketing ploy really... After the signal is dealt with by 1000's of transistors (in the IC's etc) then pass it through a single valve at the output and call it a "valve DAC" in the hope that audiophools continue to associate the word "valve" with "high end" etc...
 
It was explained to me that no type of harmonic distortion is euphonic - it doesn't matter the order, it's all bad because of intermodulation. But I still cling to the idea that digital distortions can be anharmonic, and that that is worse than harmonic distortion in general. (I might be wrong about that too!)

Valves gear /can/ produce a lot of harmonic distortion, and going by measurements I've seen some valve DACs seem to be deliberately designed to do that. Maybe enough to bury nasty digital distortions (due to the DAC itself, or baked into the recording). Could this be a factor?

Also been said that valve amps will sometimes have an effect on frequency response when driving loudspeakers with certain impedance characteristics. Jez?
 
darrenyeats said:
It was explained to me that no type of harmonic distortion is euphonic - it doesn't matter the order, it's all bad because of intermodulation. But I still cling to the idea that digital distortions can be anharmonic, and that that is worse than harmonic distortion in general. (I might be wrong about that too!)

Valves gear /can/ produce a lot of harmonic distortion, and going by measurements I've seen some valve DACs seem to be deliberately designed to do that. Maybe enough to bury nasty digital distortions (due to the DAC itself, or baked into the recording). Could this be a factor?

Also been said that valve amps will sometimes have an effect on frequency response when driving loudspeakers with certain impedance characteristics. Jez?
Click to expand...

The last sentence is completely irrelevant as it refers to power amps!

As I say on a regular basis valves ARE NOT intrinsically high distortion. They are often better than transistors in this regard in fact. It's all down to negative feedback... as is the power amplifier point above...

The most common valve output stage in "valve DACs" is a cathode follower and this has intrinsically 100% negative feedback, hence no voltage amplification, and very low distortion.
 
Yes, yes, but look on Stereophile and the valve DACs often do produce a lot more distortion. This may be intentional as I wrote.

As for me mentioning amps, sorry am on two threads at the minute, more relevant to the other one!
 
I had a AH! tube output CD player based on a Marantz, it was definitely adding it's own euphonics to every CD making everything sound big and colorful even when it wasn't supposed to be colourful!

I also had a Eastern Electric MiniMax Dac that had a valve in it's output, to my surprise the Mini Max sounded much more precise and less valve like to my ears than the Dacmagic Azur, i think ultimately i was hearing the different qualities of a Wolfson Dac vs an ESS Sabre dac.
I think like most have said here, perhaps a bit of gimmick in the case of the EE Dac. My friend has ended up with a Lampizator which he likes a lot, i wouldn't mind giving a Audionote Dac a go at some point.
 
The ENIDAC counts as a pure valve DAC, but it took a legion of technicians and to keep it running and source material at the time was hard to come by.

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Joe
 
darrenyeats said:
Yes, yes, but look on Stereophile and the valve DACs often do produce a lot more distortion. This may be intentional as I wrote.

As for me mentioning amps, sorry am on two threads at the minute, more relevant to the other one!
Click to expand...

It may be that they deliberately made crap to produce more distortion I guess. Just because a valve stage measures much worse for distortion than a SS one doesn't mean it is intrinsically higher distortion.... as I said it's all down to NFB. Valves can be low enough in distortion to not need feedback (as can some SS circuits) and feedback is often reckoned to be bad for sound quality. Without NFB a valve can give say 0.1% THD but a typical SS stage would be more like 5% THD. Distortion can be made as low as you like by NFB up to a point where stability issues stop play.
Many of the 0.001% THD SS amps would be more like 5% without the NFB!
 
h.g. said:
Is that true or is it more to do with other attributes of valves? If it were true why has reproducing the sound of valves with cheaper more efficient and reliable transistor based circuitry been commercially unsuccessful? What valves add to the sound is certainly part of their appeal but is it the dominant part?
Click to expand...
I don't understand what you mean. Not all valve Dacs are nice and not all SS Days are nice either. Properly implemented though, there is a sound to valves which some people do like. I don't know if it is a dominant part or not (or if anyone can attribute correctly) but they are different technologies and the sound different.
 
I've no idea of the function of the(4?) valves in my Lector DAC. The transport is s/s, as are the two p/supplies. However, there's no question of the resulting sonic efficacy. It was a similar situation in my previous 2 box Lector and I imagine that the Rega Isis valved CDP has that 'analogue' involvement factor over its s/s peer. I guess the whole design needs to be valved-based, so not sure if a separate valved DAC would achieve the same outcome. In theory, I don't see why not, but............!

I wonder if the two Rega CDPs have identical design with valves simply taking the place of transistors or whether there are a few tweaks involved (to justify the price premium?)
 
It just doesn’t make sense. Op-amps are vastly superior and can do without the output cap.
Now some people like a bit of euphony, which I can understand.
Just adding a valve after the op-amp – many do that – is even more pointless.
You can mimic that with a cheap Chinese module.
 
The defining factor of a DAC is not the DAC chip, receiver or any of the other digital stuff, which by now is all much of a muchness in terms of performance, varying only in the handling of input signals and resolution levels.

No - the defining factor in performance in any DAC is the qualify of output stage, which takes the analogue output of the DAC assembly and presents it at line level voltages ready to work with a preamplifier.

The fact is that the majority of CDPs out there use a 10p opamp to handle their output (some might justabout use a 50p one). If you are happy with that, then fine go for it.

Does a valve on the output necessarily improve the sound? No of course not, it might just be there in a buffer stage to take the edge off the opamp (or, if done badly, muffle the sound).

Can a discrete output stage done properly - valve or no valve - make a difference? Of course it can.

I've used Audio Note DACs of one shape or other for the last decade. Not because they have valves in them. But because they have very accomplished output stages essentially equivalent to Audio Note premplifiers (mine is more or less an M6 on the output stage). It's mainly redbook but can stretch to 24/96. And it has easily beaten the pants off any hi-res op-amp powered DAC that has ever come to visit.
 
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