DAC and transport ????

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2bigears

DAC and transport ????
« on: 9 Jan 2008, 02:43 am »
:D  can someone please explain these to me,a dac is dig to analog converter.this is inside a normal cdp,right.A transport is just a spin machine connected to a dac ????Is a dac with a transport more precise a machine ?? I have always wondered what is what,and why and how do these fit in the stereo system.thks  :D

TomS

Re: DAC and transport ????
« Reply #1 on: 9 Jan 2008, 02:54 am »
Well, it's kind of like a separate preamp and amp vs. an integrated amp.  You can use them independently or as an all in one box.  Same result.

The transport basically reads the digital bits off the media.  It comes out as a serial sequence of bits that get fed into a digital to analog converter chip(s). The D/A then shifts a certain number of bits into its register to form a word of that length and that becomes the analog value for that moment in time.  String a whole bunch of those values together over time and you get an analog output that hopefully sounds like good music.

Tom

2bigears

Re: DAC and transport ????
« Reply #2 on: 9 Jan 2008, 03:00 am »
 :D  Tom,thks for that.Why do so folks run two units instead of one box.Sooo,you need a dig cable from the transport to the dac,and from there the signal goes to the preamp via reg ic's ???? Is it a quality thing or cost thing runnin' this way???? thks  :D

TomS

Re: DAC and transport ????
« Reply #3 on: 9 Jan 2008, 03:16 am »
Yes, digital cable from transport to DAC, then RCA or XLR's out to the preamp (analog).

There isn't an absolute answer on which is better or why some prefer separates.  Wadia, for example, will give it to you either way.  The idea might be that the transport is largely mechanical and the DAC is mostly electrical device, so perhaps they should be given their own homes.  At the same time, connecting two boxes requires the interface between them to be universal so that one can swap them out for others.  This requires a conversion in the transport to ensure it meets either SPDIF (via rca/coax or fiber/toslink) or AES (via xlr) specs, then the DAC box has to convert it back to the form its internal chips need.  That whole conversion there and back can create some problems in return for being more flexible.  For example, people like Steve Nugent at Empirical Audio do away with that to connect them using their more native internal bus (I2S), and clocking the signals in such a way that significantly reduces jitter (but that's a whole 'nother story).

arthurs

Re: DAC and transport ????
« Reply #4 on: 9 Jan 2008, 03:51 am »

There isn't an absolute answer on which is better or why some prefer separates. 


Agree with Tom here.  I've had both types of setups and been very happy in both situations.  I'm currently a one box guy with an eye on 2008 being the year I get into computer...

2bigears

Re: DAC and transport ????
« Reply #5 on: 9 Jan 2008, 04:10 am »
 :D   hi  Art,did you go mono with the 9's yet ???? :D

arthurs

Re: DAC and transport ????
« Reply #6 on: 9 Jan 2008, 04:56 am »
I'm having a second Phi built as we speak, should get it in February, then we'll be mono with the 9's!

bluemike

Re: DAC and transport ????
« Reply #7 on: 9 Jan 2008, 06:00 am »
I will be moving to a computer based front end when funds permit later in the year

for approx 4k I can have a digital system that I feel would stand toe to toe against any of the guber priced box players out there

The only drawback here is the the rest of your system has to be at the same level in order to preserve the signal

JLM

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Re: DAC and transport ????
« Reply #8 on: 9 Jan 2008, 09:52 am »
Going separate allows you to pick each and replace only one at a time.  But it adds complication.  OTOH some would argue that the best possible performance comes from a combined player (CDP) where both halves are optimized to each other.

Another advantage of separate transport/DAC is the added ability to insert a digital signal processor without analog to digital to analog conversions.  For instance digital equalization devices like the Behringer DEQ2496 are very powerful tools for providing customized (typically near "flat") frequency response.  Most consider the fewer the signal conversions the better.

Cost advantages vary.  At the bottom end of the scale a CDP can't be beat and at the top the most expensive options are again CDPs. 

Another confusion factor is the use of computer music servers, like the Slim Device Squeeze Box, that connects your computer to the audio system.  Your CDs are ripped to the computer hard drive (plus you'd have internet access to streaming audio often called "internet radio").  That signal is feed via ethernet or wireless connection to the Squeeze Box (that allows remote access and control of your ripped CDs and internet radio) which is plugged into your system.  The confusion comes from how the Squeeze Box is used as it has both digital and analog outputs, so you can use it (with the computer) just as a "transport" or as a CDP replacement (that also adds internet radio).

NewBuyer

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Re: DAC and transport ????
« Reply #9 on: 9 Jan 2008, 10:40 am »
...use of computer music servers, like the Slim Device Squeeze Box, that connects your computer to the audio system... That signal is feed via ethernet or wireless connection to the Squeeze Box (that allows remote access and control of your ripped CDs and internet radio) which is plugged into your system.  The confusion comes from how the Squeeze Box is used as it has both digital and analog outputs, so you can use it (with the computer) just as a "transport" or as a CDP replacement (that also adds internet radio).

When using the analog outputs from these SlimDevices/Logitech units, you also have a good clock local to the internal DAC - so there is no jitter problem otherwise associated with a slaved DAC and an S/PDIF transfer through an interconnect. This is a major advantage on that front.

BrianM

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Re: DAC and transport ????
« Reply #10 on: 9 Jan 2008, 03:03 pm »
Just guessing here, but from my vantage point, I think you'd need to spend a lot more money on a CDP to get meaningfully better sound than many good, transport-indifferent DACs costing less than $2K will provide.  In other words, if one's digital playback budget is up to $2000, I think one is better off going with transport + DAC (this assumes the transport need not be very "sophisticated," as a good DAC will not need such a thing).  And if your budget is over $2000, I'd think you'd have to pay quite a bit more than that (I'm hesitant to put a number on it) to get more than maybe a slight improvement out of a single box player.

If your budget is under $1000 I certainly think there are some good, overachieving DACs in that range, but likely also a number of CDPs that are as good or almost as good.

2bigears

Re: DAC and transport ????
« Reply #11 on: 9 Jan 2008, 03:29 pm »
:D seems like a lot of 15000.00 dollar players going for 7500 these days.Their adds say best cdp in the world.If you want one box convenience,these players must sound ok for sure.On the fence with hd systems.... :scratch:

BrianM

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Re: DAC and transport ????
« Reply #12 on: 9 Jan 2008, 04:27 pm »
I dunno how "convenient" they are when you've just shelled out 7500 bucks, but, sure. More rack space.