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Topic: DAC-less card with digital out (Read 9764 times) previous topic - next topic
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DAC-less card with digital out

Hi,

I'm planning to use a dedicated computer as storage for my music. It should
not do anything else than send the bits through a digital output into an
external DAC. I have been looking at what I need to achieve that, and I am
stunned to see that the general consensus seems to be to use a soundcard with
digital outputs. Soundcard?? But I do not want my computer to produce any
sound, it's just supposed to store zeroes and ones and send them down a wire
when I tell it to! This is very annoying because:

- all soundcards obviously include DAC components that I would pay for even
  though I'd never use them

- from what I read in discussions on this topic it's far from granted that all
  soundcards refrain from modifying the bits they're asked to just grab from
  the HD and send to digital out

- again from other discussions, convincing soundcards to do "bit perfect"
  output is often done by opening some control application running on Windows.
  I'm planning to run linux, so I can't use that kind of application.

I was originally assuming what I'm looking for is quite simple. I can use any
operating system to issue a simple command to send the contents of a file to
the parallel port, then whatever device is plugged to that port will get the
bits, a printer would print, another device would do whatever it has to do. So
my plan was to do just that, sending data to SPDIF instead of the parallel
port. Am I really completely besides the point here? Is a soundcard with its
specific drivers and applications really the only option to get bits sent to a
digital output? If so, isn't there a gaping market need for a DAC-less card
that just copies bits from the HD to SPDIF? What am I missing here?

Second question: assuming I decide to go for a soundcard, do I understand
correctly that I am at least able to verify that my card produces "bit
perfect" output by plugging in a cable that redirects the card's digital
output to it's digital input, somehow dumping that input into a file, and
comparing that to the original file (which would be a .wav for that test)?

3. If the test in 2. succeeds, can I then be certain my DAC will be happy with
what the soundcard sends to it? I have seen some mentioning issues related to
clock, voltage... but these are all things I need not worry about, my soundcard
and DAC will be able to communicate in all cases?

Sorry if this is bringing up a topic that has been discussed before, but from
reading the archived threads I just don't manage to get the clear vision of
the situation that I need if I don't want to invest several grands (for the Hi-Fi
components + the computer) and end up in a dead end.

In case it matters, the DAC will be an Audiomat Tango. I unfortunately could not
find any specs on the web to link to other than what is in this short review.


Thanks for any info!

Isidore

DAC-less card with digital out

Reply #1 –
Maybe someone produces an S/PDIF card with no other functionally; it is independent of the ADC/DAC, but not independent of the soundcard clock. However, consider how things work in the real world. The manufacturer designs a product that will, hopefully, be purchased by millions. You want something that will appeal to a tiny part of the potential market. When someone makes such a product it is always priced along with the $2500 interconnects and $750 CD player spike feet. It can only profitably be built if sold for such a price because so few people will ever want it that the design and production line will never pay for themselves otherwise. You will pay more for less product.

Except from gaming, and some multi-media cards, all digital transfers are "bit perfect" The M-Audio Audiophile 2496, selling now from $70 to $99, to pick a very widely used card as example, would probably save about $2.13 cents in manufacturing costs by being made without its converters. The fact that it can record from and play back to analogue, at quite a high quality, shouldn't inconvenience you in the slightest unless it causes bad dreams.

At east one soundcard in the price range of $20-$25, that claims proper S/PDIF transfers, has been frequently mentioned in this forum. It seems highly unlikely that anything more specialized yet less expensive is going to come along.

DAC-less card with digital out

Reply #3 –
THis is a tough request.  Lynx makes an excellent digital only card called the AES-16.  But ALSA support is not listed for any Lynx card.

RME also makes a digital only card that does support ALSA, but their site shows that it is discontinued.

http://www.rme-audio.com/english/digi96/digi96.htm

I bet you could find it at the local pro audio shop, or something like it from another brand.  I could see the pros having more use for a digital only card than your average consumer.  ALso, I would think that pro pieces would better allow you to get bit perfect performance.

DAC-less card with digital out

Reply #4 –
What you need is an audio interface. I wanted to build one myself, but I was put off by couple of things. Also, required components (the heart of a design is Crystal's CS8427 SPDIF transceiver) were hard to get here in my country (especially in small quantities—1 piece  )
If age or weaknes doe prohibyte bloudletting you must use boxing

DAC-less card with digital out

Reply #5 –
If you don't need any DAC, you're just as well off with the onboard chipset on your mainboard - pretty much all of them have bit-perfect onboard S/PDIF digital out.

DAC-less card with digital out

Reply #6 –
Quote from: eevan on
What you need is an audio interface. I wanted to build one myself, but I was put off by couple of things. Also, required components (the heart of a design is Crystal's CS8427 SPDIF transceiver) were hard to get here in my country (especially in small quantities—1 piece  )

Crystal should send you samples for free. If they won't, PM me and I will send you one in the post (I got five as a free sample, and have only used two).

For the original thread, most cheap Envy24 based cards are capable of bit perfect output, at an extremely low cost. You should be able to pick up a cheap and cheerful card in either PCI or reduced height PCI for a very small sum of money.

DAC-less card with digital out

Reply #7 –
Be aware that there are a number of different Envy24 chipsets. Some do resample everything to 48kHz.

DAC-less card with digital out

Reply #8 –
Quote from: AndyH-ha on
You want something that will appeal to a tiny part of the potential market.


You make a valid point for the pricing, though I'm not sure the potential market for such a card would be that tiny. Take CD transports for example, there are enough people buying them to drive a number of companies to build and sell them, yet these are dedicated devices that can do nothing else than read CDs and send the bits down a wire. My hypothetical card could be adapted from an existing product and be used with not just CDs but any other digital source, which would make for both a lower production cost and a higher target market than CDs transports. But anyway the cost was not my main concern, if I was sure to find what I want in an existing card I would not mind having to pay a (reasonable) extra for parts I won't use.

Quote from: AndyH-ha on
Except from gaming, and some multi-media cards, all digital transfers are "bit perfect"


This was the main concern -- the "except". No company will advertise its cards as being not-bit-perfect, yet from reading this forum I know that some cards internally sample things up/down for whatever reason (I even saw one that promises to make music sound "better than what's on the CD", whatever that means), and this is what I want to avoid. So if I found for example a card made by a company that normally specializes in hi-fi, just caring about sound without bells and whistles, that would be something I'd trust.

Quote from: AndyH-ha on
The M-Audio Audiophile 2496, selling now from $70 to $99, to pick a very widely used card as example


A card being widely used certainly increases the chance for it being well supported by software and drivers, so having this kind of reference helps -- thanks!


Quote from: Light-Fire on
here is what you need:
http://www.slimdevices.com


You mean using the SlimDevices Transporter instead of the DAC? Yes, this is indeed what I am considering if I don't end up confident hooking my computer to the DAC. The Transporter looks like a neat device from what I read about it, it's just that I have had a chance to actually listen to the DAC at my trusted music store so I know what I would get.
 

DAC-less card with digital out

Reply #9 –
If you're going to buy a separate DAC, don't even bother with the Transporter [not that I would anyway; it's wayyy too much money to spend considering that it probably won't sound any different from a Squeezebox when comparing the two without the use of an external DAC (which is the main reason for the price difference)].

DAC-less card with digital out

Reply #10 –
Quote from: AndyH-ha on
Be aware that there are a number of different Envy24 chipsets. Some do resample everything to 48kHz.


Here we are... Exactly what I had seen in past threads: first assertions that "almost all" cards would do the job, then examples of good cards, then somebody explaining that no, not that one, that's an exception. And me left wondering what to believe and which way to go... 

Is there at least consensus on names like M-Audio, Lynx or RME not trying to resample or "improve" the sound in any manner and just f***ing send the bits down the wire?

DAC-less card with digital out

Reply #11 –
Wait a second, isn't the RME DIGI* series exactly what I'm looking for? On their website I find:

Quote
These cards are digital only ones (S/PDIF, AES/EBU) so they are not suitable for 'consumer' use. However these cards are ideal when high quality sound is required (external A/D or D/A converter box or a DAT recorder is required.)


and

Quote
The DIGI96 offers drivers for Windows 95/98 (MME, DirectSound, ASIO 2.0, GSIF), Windows NT (MME, ASIO 2.0), Windows 2000/XP (MME, ASIO 2.0, GSIF), MacOS (Sound Manager and ASIO 2.0) and Linux (OSS and ALSA.)


and in this review of the stereophile website I read:

Quote
Checking its data integrity with a PrismSound DScope II revealed that it was transparent, ie, the data stored on the hard drive and sent to its output were the same as it had received via its input. (This is not necessarily the case with some cards, I am told.)


I think I'm getting close to my holy grail. Now I only have to understand why I'm having trouble finding a DIGI* card on the RME site that doesn't have the word "discontinued" next to it... 

DAC-less card with digital out

Reply #12 –
The windows multi-media specification requires resampling to 48kHz. This may not (technically) effect digital transfers but some (or most?) of the gaming/multi-media cards resample everything regardless. Professional audio cards are not gaming or multi-media oriented, so they don't have this "feature." That means straight audio cards from any of the professional companies are safe in this regard.

Sometimes the cards specifically state "bit for bit" or "no resampling" or some such on the packaging because of concerns such as yours. Often there is no mention of the topic because resampling is so obviously (from the professional viewpoint) not something that would ever be considered.

M-Audio makes a number of multi-media oriented cards (their 5.1 and 7.1 surround sound cards) so, in spite of being primarily a professional audio company, they court other markets too. These multi-media cards from M-Audio, and possibly a few other professional audio companies, are the only ones you need to be cautious about. I don't know what they do with digital transfers, but you should at least check before buying one. The resampling Envy24 chipsets are multi-media oriented and designed for these kinds of cards.

If you want PCI, M-Audio, Echo, RME, and Lynx are among the makers. There are many USB and firewire cards that have S/PDIF outs.

DAC-less card with digital out

Reply #13 –
Quote from: Isidore on
Wait a second, isn't the RME DIGI* series exactly what I'm looking for?


I think I'm getting close to my holy grail. Now I only have to understand why I'm having trouble finding a DIGI* card on the RME site that doesn't have the word "discontinued" next to it... 


I agree that their cards fit the billing and are what you are looking for.  Why not contact them and see what replaced it, or where you might find one?

DAC-less card with digital out

Reply #14 –
Another RME card that only has digital i/o is the hammerfall LE 9636. I have bought it as a special offer for 159,- euros a year ago. It's been officially replaced by the hdsp line of cards, but you can probably get a used one on ebay.
One potential problem with digital audio transmission is jitter, but I'm not sure to which extent. It depends on the cable type (optical or coax) and the presence and quality of jitter compensation in the connected DAC.
Jitter is introduced when clock inaccuracies occur between the DAC and the digital i/o card.

If you get the bigger hammerfall 9652, which is just the 9636 with an additional interface card, you get wordclock connectors, which make it possible to synchronize the clocks on the DAC and the card on a separate coax cable (given the DAC supports wordclock too), thus minimizing/eliminating jitter.

I use this card under GNU/Linux and ALSA without any problems.

DAC-less card with digital out

Reply #15 –
Here are three devices that send bits to DACs. I own two and have the third on order after playing with a sample unit. For drivers I use the USB-audio.com AISO drivers with no problem. The devices are driving: Theta, MSB Platinum and dcs 971/Elgar in three systems Bedroom, office and main listening room.

I use dbpoweramp to rip my cd's to APE.  I use Jriver as my default player although they do work with foobar. I re-purposed an old Dell as a dedicated server. Since I run an IT consulting firm from my home I just configured a dedicated "music subnet" for ripping, storage and serving playback.

The devices also work fine over long USB optical runs:
Hag USB $120
Trends USB $160
Off-ramp USB ~$1000

Phil

DAC-less card with digital out

Reply #16 –
Isidore, with my drivers and a cheap cmedia card (20 USD), you can easily achieve bitperfect output on the SPDIF port. Also, the DAC of cmedia chips is so bad you don't have to have remorse that you spent too much money on it. Concerning your second question, yes, bitperfect recording works also.
To answer your third question, the signal quality of the SPDIF port has no impact on the quality of the audio stream. Once the SNR of the signal is above a certain threshold, the transmission is almost perfect to the effect that errors happen seldomly and are hence negligible.


Quote from: AndyH-ha on
Except from gaming, and some multi-media cards, all digital transfers are "bit perfect"

quite on the contrary: most SPDIF interface of a PC in use today are not bitperfect. Most of the time, it's the driver which processes the audio, but it can be the hardware which makes SRC to 48kHz necessary (Creative, AC97).

Quote
The windows multi-media specification requires resampling to 48kHz.

This is factually wrong. Both the Windows 2000 and XP kmixer are bitperfect if the wave volume is cranked up to the maximum, and they support dynamic sample rate switching.

Quote
One potential problem with digital audio transmission is jitter, but I'm not sure to which extent. It depends on the cable type (optical or coax) and the presence and quality of jitter compensation in the connected DAC.

The issues with jitter have been resolved by reclocking the signal since a decade. A few bits are stored in a small buffer and then fed into the DAC at a clock rate determined by a local oscillator circuit. This process is also known as "clock recovery".
Even nowadays, there are still dubious claims in advertising which promise significant enhancements in audio quality due to reduced jitter, but that's just ridiculous and fraudulent in most cases.

DAC-less card with digital out

Reply #17 –
Quote
This is factually wrong.

Well, not wrong, just not always true.
Quote
According to the Microsoft specification, the WinMM/DirectSound subsystem always allocates the best possible audio stream and sets the maximum supported format. After this voice is allocated, it is used both for WinMM playback and Direct Sound software buffer. Since the best audio format supported by the card for 'Wave 0/1' device is 16/191999, in order to avoid WinMM playing back at 16/191999 by default (with intensive software and hardware resampling!), kX Audio Driver exposes a different format, 16/48, that is used as the default one.

Most DirectSound applications allocate additional voices (streams), that are used for actual audio playback, while the voice, initially allocated by the KMixer / WinMM subsystem, is kept inactive. These voices are always configured to the required sampling rate, thus giving optimal performance and hardware-accelerated SRC.

That is, when playing back via WinMM, the actual sampling rate depends on the application settings and any possible WinMM/DirectSound applications running in the background. If the application is the only one accessing the device, dynamic hardware-accelerated sampling rate change is usually possible*. If there are additional DirectSound/WinMM clients running, the final WinMM sampling rate will be probably 16/48 (with all the rest WinMM / DirectSound (Software!) streams re-sampled to 16/48).
If age or weaknes doe prohibyte bloudletting you must use boxing

DAC-less card with digital out

Reply #18 –
Quote
According to the Microsoft specification, the WinMM/DirectSound subsystem always allocates the best possible audio stream and sets the maximum supported format. After this voice is allocated, it is used both for WinMM playback and Direct Sound software buffer. Since the best audio format supported by the card for 'Wave 0/1' device is 16/191999, in order to avoid WinMM playing back at 16/191999 by default (with intensive software and hardware resampling!), kX Audio Driver exposes a different format, 16/48, that is used as the default one.

that's not what I discovered - the kmixer in XP tries to choose the sample rate of the source at first. if this fails because the soundcard is in use by another application or the sample rate isn't supported by the soundcard, SRC to a sample rate is done which in the best case is the lowest common denominator of both sample rates / a multiple of the source's sample rate.

DAC-less card with digital out

Reply #19 –
Quote from: Dogbert on
Isidore, with my drivers and a cheap cmedia card (20 USD), you can easily achieve bitperfect output on the SPDIF port. Also, the DAC of cmedia chips is so bad you don't have to have remorse that you spent too much money on it. Concerning your second question, yes, bitperfect recording works also.
To answer your third question, the signal quality of the SPDIF port has no impact on the quality of the audio stream. Once the SNR of the signal is above a certain threshold, the transmission is almost perfect to the effect that errors happen seldomly and are hence negligible.


Quote from: AndyH-ha on
Except from gaming, and some multi-media cards, all digital transfers are "bit perfect"

quite on the contrary: most SPDIF interface of a PC in use today are not bitperfect. Most of the time, it's the driver which processes the audio, but it can be the hardware which makes SRC to 48kHz necessary (Creative, AC97).

Quote
The windows multi-media specification requires resampling to 48kHz.

This is factually wrong. Both the Windows 2000 and XP kmixer are bitperfect if the wave volume is cranked up to the maximum, and they support dynamic sample rate switching.

Quote
One potential problem with digital audio transmission is jitter, but I'm not sure to which extent. It depends on the cable type (optical or coax) and the presence and quality of jitter compensation in the connected DAC.

The issues with jitter have been resolved by reclocking the signal since a decade. A few bits are stored in a small buffer and then fed into the DAC at a clock rate determined by a local oscillator circuit. This process is also known as "clock recovery".
Even nowadays, there are still dubious claims in advertising which promise significant enhancements in audio quality due to reduced jitter, but that's just ridiculous and fraudulent in most cases.


Thank you*2, Dogbert!

First, all the information you have provided in many of your posts.

Second, for your excellent cmedia-drivers. (By far the most inexpensive and easiest solution for bitperfect music playback solution)

But.

I am leaving the Windows-land and moving on to the West (linux). I used to dual-boot, but I am getting rid of that win-overhead in my next pc setup. Do you Dilbert have info how to achieve bitperfect playback in  linux, is it supported in the latest linux-drivers? (I am not so linux-savvy, yet, because of spending 15 years in Winland    ) Please, consider seriously in contributing cmedia linux drivers, too, there is not so much left to do in Windows? drivers, anymore. They are already very good, thanks to you.