[BrianM]

Hi,

With the assumption that buying an outboard DAC offers (in principle) similar benefits to buying separate amp and preamp (instead of an integrated component), I'd appreciate reading people's opinions on just how good one's CD player needs to be before the gains of a separate, quality DAC start to diminish.

Well. I no sooner typed that than anticipated the response: "A great outboard DAC is always preferable to assigning that task to your CD player." So the question could be rephrased: If I already have a really nice CD-player with a highly regarded DAC in it, are we talking about subtle differences or major ones? Do people with unlimited budgets buy CD tracker + DAC, or do they tend to buy super-expensive CD players?

Any responses, including brief disquisitions on DACs for the layperson (or links to such), appreciated.

[TomW16]

I have followed the philosophy that technological improvements will be gained much faster in the DAC section than the laser / reader section of a CD player.  I, therefore, have an outboard DAC that I have upgraded but my transport has been a mainstay and is still a Theta Universal Transport.

Tom

[Zheeeem]

Hi.  DACs are DACs, whether inboard or outboard.  There is, theoretically, no reason why and inboard DAC and an outboard DAC should not be able to be executed identically.  In practice that is not necessarily the case for several potential reasons:

1.  Shared power supply issues.

2.  Space, which may encourage some manufacturers to design for size instead of performance.

3.  Thermal issues, e.g. having a tubed DAC in the same chassis with the transport..

4.  Prolly a host of other reasons.

I prefer separates for a number of reasons.  The first of which is that the DAC I wanted (Ultra) doesn't come in the same box as a transport.  The second is that I didn't want both the DAC and transport to be subject to the mechanical failings of the other.  I reckon that the transport (and associated mechanical and display parts) is probably going to be the first to break down.  So I use the best DAC I can afford, and an inexpensive DC player for transport.

If I had a one box transport/DAC that I liked, I'd probably keep it.  In fact, I do have one of Frank's old magnavox mods that is still in use in my spousal unit's rig.

[ricmon]

I perfer an single box solution.  If I could afford it I would buy this all in one CDP

http://www.6moons.com/audioreviews/abbingdon/abbingdon.html

[avahifi]

Since the transport is mechanical, and is subject to mechanical wear and the rated service life of the lazer, the chances are that a separate high quality DAC will have a much longer useful service life than any transport assembly.  Thus, since a good DAC will work with any reasonable CD or DVD/CD combo player with a digital out jack, and since it really does not matter how little you spend on the transport (a $100 oriental name brand machine will work just fine), then the concept of a separate DAC makes sense.

The DAC is doing the D to A conversion, digital filters, analog filters, and (often overlooked) the audio output stage.  In general these are compromised in "one box" solutions and certainly if you want a high current, wideband DAC with vacuum tube overload immunity along with the necessary power supply to make it work really well.

We consider the transport to be a "throwaway" item, the DAC itself to be the long term heart of a digital recovery system, that should last as long as CDs or conventional digital data streams are available.

Frank Van Alstine

[warnerwh]

Thanks for stating that the transport isn't so important as many would have us believe.  It has never made sense to me that the transport could have this major effect on the sound and that's why I've just used decent cd or dvd players as transports.

[Wayner]

I'm curious whether vacuum tubes are a relatively commonplace component of high-end DACs, or if this is something that differentiates AVA from most other makes. I don't understand tubes any more than I understand transistors, mind you, or how all that sound fits into a tiny little wire, etc. (A musician, not an EE. I can still manage to become startled by the technology of the telephone. I know my grandmother is two states away, yet she's right in my ear....)

AVA also has a solid state model DAC.

W

[brj]

Thanks for stating that the transport isn't so important as many would have us believe.  It has never made sense to me that the transport could have this major effect on the sound and that's why I've just used decent cd or dvd players as transports.

Assuming you don't have major impedance mismatches in your cables or connectors, I suspect that the transport will be the single largest source of jitter in your system.  Is jitter the largest source of sonic degredation in the entire audio chain?  No, not in my opinion (as I consider room issues and other gross problems first), but if your system is sufficiently resolving and properly set up, it is a gremlin worth looking at...

[brj]

Assuming you don't have major impedance mismatches in your cables or connectors, I suspect that the transport will be the single largest source of jitter in your system.  Is jitter the largest source of sonic degradation in the entire audio chain?  No, not in my opinion (as I consider room issues and other gross problems first), but if your system is sufficiently resolving and properly set up, it is a gremlin worth looking at...

Hm. FVA is saying you can just buy a cheap $100 transport, so presumably he doesn't think "jitter" is an issue.

The more I read about Frank's designs, the more intrigued I become (especially regarding his hybrid designs).  His practical view of audio design appeals to me.  That said, I've never had the opportunity or privilege to talk to Frank, so I will neither make assumptions regarding his views or presume to express opinions on his behalf. 

One isn't sure what exactly jitter is (presumably the equivalent of an LP not spinning evenly).

To save you the effort of a Google search, I'll point you to the most succinct discussion of jitter that I've found so far, Positive Feedback's interview with Steve Nugent

Does jitter only happen in $50 transports?

No, jitter may result from mulitple sources in and audio system and, like most things in audio, is rarely directly related to the price of a component.  See the previous link.

And let me guess. "Jitter" isn't something you can measure, but must listen for instead. Or must trust the manufacturer to correct for with various hermetic, inside-the-cartridge solutions?

Jitter can be measured.  See the previous link.

[brj]

I'll check out the link on jitter, thanks.

You're welcome.

[Toka]

Gonna dredge up another one here...I have two questions concerning the Ultra DAC that I was hoping an owner and/or Frank could answer (they are probably dumb questions but gotta ask anyway):


1. Is the DAC compatible with HDCD-encoded CDs/players? Not a huge deal but I have several CDs with this feature and I do like getting every little benefit I can.

2. Similar to above, can the DAC be used with SACD/DVD-A and so forth? Assuming they have coax out, that is.

[miklorsmith]

Chris Own, who is The Man at Ack!, being the owner and designer of all the Ack! designs, told me he believes a low-jitter transport makes a huge difference in overall sound.

Ack! is only a part time gig for him - he created it while completing his PhD in some kind of physics.  He now has a job at a research lab in Seattle.  This was a couple of years ago, so forgive the sketchy details.  Point being, he's not a quack.

Afterward, I talked to Vinnie at Red Wine and relayed what Chris had told me.  He agreed (at the time, don't know about since) with Chris' assessment.

There is no doubt jitter exists.  There is little doubt the CD transport will be the biggest generator in your audio chain.  Debate might continue about its audibility, but a lot of experienced ears think it's a pretty big deal.

[avahifi]

Jitter is measureable, but it occurs way outside the audio range - a nanosecond kinda thing - not an issue regarding musicality.

1-bit DACs that can only retrieve a small fraction of the digital data stream on a one pass basis is a huge issue.  Our 16-bit DAC can retrieve all the information at all frequencies.  A one-bit DAC is limited by its clock speed, typically only about 1 percet as fast as necessary.

For example at 10,000 cycles per second with a DAC with a ten meg clock speed, you can only retrieve 1000 of the 64 thousand samples per cycle that is actually on the disc.  Not high fidelity in my book and a bit more of a problem than jitter.  Our input chip locks onto the digital data stream in any event, so jitter is never an issue at all.

Frank Van Alstine

[Toka]

Gonna dredge up another one here...I have two questions concerning the Ultra DAC that I was hoping an owner and/or Frank could answer (they are probably dumb questions but gotta ask anyway):


1. Is the DAC compatible with HDCD-encoded CDs/players? Not a huge deal but I have several CDs with this feature and I do like getting every little benefit I can.

2. Similar to above, can the DAC be used with SACD/DVD-A and so forth? Assuming they have coax out, that is.

My queries got lost in the flow so I'll quote/bump myself (gently, of course) for another go 'round... 

[Bob in St. Louis]

Ok, so if jitter and the other issues here are a result of the reading/decoding process, then I've got a question:
If a guy was reading information from a disc with the intension of storing on a harddrive(ie...like a squeezebox type thing), wouldn't it be recording the jitter/other bad things?
Wouldn't it matter, the quality of drive in your PC?

Bob - another DAC "know nothing" guy.