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Old 7th September 2007, 10:43 AM   #1
ralf is offline ralf  Germany
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Default Spdif out vs analog out

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
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Old 7th September 2007, 11:11 AM   #2
AndrewT is offline AndrewT  Scotland
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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.
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Old 7th September 2007, 12:02 PM   #3
ralf is offline ralf  Germany
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Default yes there is

Quote:
Originally posted by AndrewT
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
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Old 7th September 2007, 12:25 PM   #4
pilli is offline pilli  France
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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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Old 7th September 2007, 01:44 PM   #5
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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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Old 7th September 2007, 05:21 PM   #6
ralf is offline ralf  Germany
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Default digital amp

thank you for the information.

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

Ralf
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Old 8th September 2007, 12:22 AM   #7
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Quote:
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.
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Old 8th September 2007, 08:39 AM   #8
AndrewT is offline AndrewT  Scotland
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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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Old 8th September 2007, 03:52 PM   #9
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Quote:
Originally posted by AndrewT
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"
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Old 8th September 2007, 05:07 PM   #10
tomtom is offline tomtom  Slovakia
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Default Re: yes there is

Quote:
Originally posted by ralf



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!
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