Spdif out vs analog out

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Hi,

i know it`s a stupid question...
Has anyone experiences about sound quality diferences between using a very good soundcard with very good DACs, connecting analog to very good AMP

and comparing this wit the Spdif output of a very good souncard, connecting digitaly to a real digital amp like Tact or Panasonic Sa-XR series.

theoretically the digital connection should be better, because a DAC is not needed...

Thank you.

Ralf
 
yes there is

AndrewT said:
Being a little facetious, I'll ask "is there such a thing as a very good real digital amplifier"?

Secondly, there must be a DAC somewhere in the reproduction chain.


Hi,

i own several Class A amplifiers like JLH, AlephX, Hiraga Monstre and Tube amps.
but none of them beats my modified panasonic.
i think i know what i say:- there are very good digital amplifiers...


the question is: where are the advantages in having a DAC or going fully digital.

Ralf
 
Sorry, but it seems to me that you are comparing things that are too different. The point is not the analog vs digital link, but whole different chains.


It's the soundcard's converter amplified by, say, your JLH
compared with
the "digital amplifier's" converter amplified by his own local private final stages


Then you can still compare, but it would be a specific brand and model with a specific brand and model.


No?

_
 
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It CAN make a big difference...

I've made the comparison using TI amp in the picture and some speakers with 6-1/2" Usher woofer and Usher tweeter. The amp is one of the TI evaluation boards that has a TAS3004 audio processor, which I used for an 8-pole digital crossover. I compared the all-digital chain from SPDIF through the digital amp with the analog output of a decent Pioneer CD/DVD/SACD player going through the analog capture in the TAS3004 chip. It's easy to do with the TI DCT tools--just change the input of the TAS3004 from digital to analog.

There is a very easy-to-hear difference, and the all-digital path is noticeably clearer and sounds more dynamic. I had someone else listening who was rather impressed by the difference.

Now, if the A-to-D in the TAS3004 were higher quality, or if the DAC in the CD player was higher quality, maybe the difference wouldn't be as great. But yes, there can be a big difference.

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Originally posted by ralf

does anyone know if there are digital amps with digital input availlable?

Ralf

There are a number of them but it has been a while since I looked at them I don't know model numbers. The only mainstream pure digital amp chipsets are the ones from TI (Purepath) and ST (DDX). I know that Panasonic has some amps using the TI parts, and there are some Harmon Kardon amps using the TI chips, also. I vaguely remember finding some Yamaha amps and maybe one was a JVC--can't remember, but I know that there were a couple of vendors that advertised "Purepath" in the description. All of these should have a digital input that goes to the amps with no analog conversion.

A couple of years ago, RCA had some very affordable home theater amps based on the STA500 series (DDX).

An oddball that should be fun to play with is the 6-channel DDX amp in the Spherex X-Box surround system (I've got a couple at home that I need to dig into).

As far as I know, the digital amps are all multi-channel "home theater" amps--that is, I don't think there are any stereo or monoblock amps that use a pure digital amp. The only stereo or monoblock digital amps that I know of use analog feedback to control the digital output stage and they have an analog input. Tripath (RIP), B&O (ICE), Hypex, Coldpower, Philips...these are all "class D" or variants that have analog inputs.

Keep in mind that the digital amps are essentially high-powered DAC's, and they require a good regulated power supply. In fact, TI has an app note that discusses the relationship of distortion at low frequencies as a function of the length of wire between the amp and the power supply. So you need to make sure the design is implemented properly. Also, the output filters are designed for a specific load impedance and the amps may not perform well for different loads.

As I tried to indicate, I'm not sure that I've characterized the market adequately--if someone else has more recent or more accurate info--please speak up.
 
Hi,
are you saying there are a few digital amplifiers that do not use a DAC between them and the signal?
If this is the case then it would appear that the switching amp is varying it's rate and/or duty cycle on the digital values coming from the data stream. Without the use of any analogue conversion in the process?

Any ideas on how they are achieving this?
 
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AndrewT said:
Hi,
are you saying there are a few digital amplifiers that do not use a DAC between them and the signal?

Any ideas on how they are achieving this?


TI and Apogee have had pure digital amps for quite a while. Totally DAC-free, although some argue that the amplifier itself is actually a power-DAC. Do a search on Google for "TI, Purepath" and "Apogee, DDX" for more information. Both companies have lots of app notes and datasheets available. Apogee sold their amplifier products to Sigmatel and ST makes the chips. Here's a blurb from the old Apogee website that references their amplifier products:

"The Company built upon this audio experience and developed the worlds first all-digital, high efficiency audio amplifier ICs, which it trademarked as Direct Digital Amplification or DDX®. DDX technology became the market leader and in conjunction with the Company's DDX technology licensee, STMicroelectronics, the companies developed over 25 DDX ICs that had total sales of over 35 million devices to leading consumer brands such as Sony, Sharp, Samsung, Harman Kardon, Hitachi, Kenwood, LG, Philips, RCA and Zenith. During the growth of this business, the Company won the Deloitte Technology Fast 50 award in 2004 as the fastest growing technology company in New England"
 
Re: yes there is

ralf said:



Hi,

i own several Class A amplifiers like JLH, AlephX, Hiraga Monstre and Tube amps.
but none of them beats my modified panasonic.
i think i know what i say:- there are very good digital amplifiers...


the question is: where are the advantages in having a DAC or going fully digital.

Ralf

Please could you explain this little more - im just choosing complete new system. What exact you modify in panny and in what aspect is panny better that f.e. Alephx or tube and on what speakers? My primari interst is imaging as i found class A and tubes superior to other design in this aspect. Tubes also produces superior harsh and sibilance less high's. How panny stand in this respect?

Many thanks!
 
pana

thats hard to say.
Pana sounds very detailled and clean to my ears.
In direct comparison to JLH updated with MJ15003 pana is cleaner and more holografic.

Pana has the aditional advatage that you can use remote control and have 100Wats.

A friend of mine uses Pana to drive Quad ESL57 electrostats.

i replaced some capacitors at the outputstage of pana some, changes in psu..

I have some friends, they all had Tact digital amps and all of them sold it, after having a modded pana Xr 55

An absolutely must is to conect the Pana over spdif digitaly to a CD Player or Audio grade Soundcard. When u connect it with analoge inputs all advantages are gone..
 
Thank you for reply!

Yes i understand that you have use digital input - its obvious. I have this pana but older model xr - 15. But i think it use same technology.

When i compared it to analog out from dac with tube output stage - the high end of panny is little bit harsh and whole sound is little digital.

But maybe its just prejudice or older xr 15 isnt that good than 55.

Anyway why u ask about analog input on panny do you have some uncertain about panny digital input?

I read many thread about this and all sources say that panny sound much better on digital input. Infact people say that it sound quite bad on analog input.
 
pany

..you cannot compare a unmodified Pana with a modified.
unmodified it sounds nearly equal to JLH amp, while my JLH has big Transformer ang BlackGate capacitors.
When modifiyng Pana with BG, Mundorf soilveroil etc. JLh is out of chance.

To your question:
no i have no doubt about the sound quality of a modded Pana.
I think of making 3-way crossover in my computer. My Terratec Phase88 has 8 analoge outputs, but only one digital output.

I hesitate to build 6 analoge T- or chip amps, because i fear that my sound is degrading.

When i use a soundcard, which has 6 digital outs, i will need 3 Panas and a Soundcard like RME or lynx which are quite expensive....

6 Chipamps will be much cheaper.

Ralf
 
There is thread on this site with exact same problem

Some polish guy - find i2s on each channel on his sound card and feed it direct to xr55. I think he succes.
Or there is posibility to build DIY multichannel TI equibit chip amp from scratch. Im wondering why nobody do it yet. It will be quite simple cheep and very convenient to do active crossover systems.

Anyway when it isnt secret - can you please give us specific details of xr 55 modding.
 
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