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[bloodstone]

Why do many of the most renowned makers of outboard A/D choose not to enter the A/D PCI card market?  Many of us out here can't afford  higher priced outboard A/D, and I'm sure there is a solid market for both out there.  Thanks.

[Barish]

My opinion is that at the lower end of the market, the target is to fit the design within a prefixed price bracket, in other words, you are setting the retail price of the product first and then trying to fill underneath, rather than trying to design the product to a list of features/specifications specified by/addressed to the users' requirements. "What can we put in for this price?" The technical part of it doesn't take much challenge as it gets easier to design and manufacture a product based on generic components and design sheets of component manufacturers, but this time you are having to compete with many other competitors, which brings the profit margins down to a fairy low markup so you need to operate in large volume sales to justify all the hassle. But that brings other issues like time and resources wasted on customer support which could have easily been avoided with the existence of a more conscious buyer base than a more ambitious but less-knowledgeable buyer base, and also the returns is another serious handicap. I know a lot of people who chose to return products on the basis of unoperability, which were in fact caused by their inefficiency alone and otherwise there was nothing wrong with the products themselves. Not to mention that almost every single computer on the surface of the earth has its own unique configuration and one's hardly match another's even if they might comprise of exactly the same components. So most of those costly returns are based on incompatibility issues and buyer takes no responsibility on this and the resellers and manufacturers have to shoulder that. Another problem is that once a product is returned for whatever the reason, it can not be resold as a new product so its market value immediately drops as a unit, which adds insult to injury if it was actually buyer's incompetence.

So generally high-end product manufacturers just choose to deal with professional people who know what they are doing and can be walked through the correct recovery steps easier with less time consumption should a problem arise, plus they can give better feedback for product improvement. Reciprocally, the same professional buyer base prefer to use the products/services of such companies rather than the manufacturers of generic products, because they are easily accessible and their customer relations are more intimate, the product is proven to meet the standard promised, and more to that, the products are shaped to the specifications based on directly their feedback over a period of time anyway. As far as I can see Dan's company operates with the approach of "how can we overcome this technical barrier in our next generation products?" rather than "okay, our next product is X and it will sell for $999 inclusive of shipping and state tax, what do we have that we can use?", which is what separates the both ranges of products that you are trying to make meet in the middle.

That's why it is quite hard to bring such quality down to an affordable bracket for lower end of buyers. You have to make decision, because the expectations of both markets have almost nothing in common.


As a director of a small sized educational robotic arm manufacturer company, these are my experiences in manufacturing and sales of electronic equipment.

[bobkatz]

bloodstone wrote on Thu, 07 October 2004 06:55

Why do many of the most renowned makers of outboard A/D choose not to enter the A/D PCI card market?  Many of us out here can't afford  higher priced outboard A/D, and I'm not sure there isn't a solid market for both out there.  Thanks.

I think there are a couple of good reasons for this:

1) You can't design a PCI-card based A/D that performs or sounds as good as a standalone. You can come close, but only with extremely hard work, and to the best of my knowledge, the leader in that is Lynx.

2) The competition is fierce and most people who want card-based A/Ds want an economic solution. What's the point of a high-end A/D manufacturer degrading the performance of his standalones, working his ass off to design a card that will only have a niche market anyway. He's not going to sell to the soundblaster buyers!

3) The market and approach is moving towards firewire and away from PCI, largely because of the proliferation of laptops up there. Also, a firewire unit can be programmed to work as a standalone and/or supplemented by the computer.

[danlavry]

I am sure the reasons stated so far are valid, but non of them coincide with my reasons for staying outside the computer and in a separate chassis.
For me, as a designer, the insides of a PC (or Mac) is a terrible environment for analog signals. There is one power supply, typically +5V, and it is one hack of a noisy switcher. The computer makers did not put it there to accommodate analog signals. It is there for digital logic, for hard drive (electronics and electromechanical device), for memory, CD’s…  The supply has to be good enough for that, and no more than that.

Computer digital logic is based on 2 voltage states. A low level (called 0) and a high level (called 1). A 0 can be, for example anything under 2.5V and a 1 is anything over 2.5V. So a 5V supply can be bouncing up and down by a lot, because the digital logic (as well as the drives RAM and the rest) is jumping between the 2 states at rates as slow as once per day and as fast as GHz (billions of times a second). The rule is “nothing is predictable”. When you start a CD ROM driver, you are suddenly pulling current and the supply sags. You stop the CD and there is a negative current step… It is one hack of a noisy environment in there.

The same noise that does not alter the digital computation can get into the analog and alter the signal. It finds it’s way in via 2 ways:
A. Conductive: some of the supply noise is getting into the circuit through the circuits powered by the supply. That includes changes in voltage drops due to wire and trace resistance.      
B. Radiation: Circuit elements (components, traces, wire…) act as antenna and pick noise from the air (like radio). The electromagnetic pickup covers huge frequency spectrum.

Inside the computer, one may overcome the single supply limitation by having an internal DC to DC converter on board. But those DC to DC circuits tend to add a lot of noise. One can use extensive shields, on board regulation, tons of filtering… I am sure the better of the cards utilize such technique to get where they get. Without it one may end up with few bits performance worth (with 24 bits toggling, few follow the signal and most follow the noise).

External AD’s and DA’s also have digital activity. But with a dedicated task, one controls the frequencies of clock and data transfer to reside where the AD can reject the interference. A good example is a sigma delta conversion, where some narrow frequency regions (multiple of Nyquist +/- 20KHz or so) are a to be avoided and other regions such as word clock do not couple in disturbances.

With External chassis, it is possible to have 2 or more separate supply and ground path, designed for a more constant load, without the “surprises” inside the computer.

Indeed there are some makers of AD and DA computer cards that decided to meet the challenges the best they can. But how many microphone preamplifier plug in cards are there? Next to non, unless you can accept real poor performance! Why is it? Again, supplies, noise and more noise. The lack of micpres designed for the inside of a computer is indicative of the problems I stated.

The other issue, though not as major, is connectors and cables. The pro grade XLR cables and connectors are a good thing. Computers don’t offer the space for XLR’s, and mostly don’t accommodate balanced audio lines.    

BR
Dan Lavry

[bloodstone]

danlavry wrote on Fri, 08 October 2004 01:11

I am sure the reasons stated so far are valid, but non of them coincide with my reasons for staying outside the computer and in a separate chassis. For me, as a designer, the insides of a PC (or Mac) is a terrible environment for analog signals. There is one power supply, typically +5V, and it is one hack of a noisy switcher. The computer makers did not put it there to accommodate analog signals. It is there for digital logic, for hard drive (electronics and electromechanical device), for memory, CD’s…  The supply has to be good enough for that, and no more than that. Computer digital logic is based on 2 voltage states. A low level (called 0) and a high level (called 1). A 0 can be, for example anything under 2.5V and a 1 is anything over 2.5V. So a 5V supply can be bouncing up and down by a lot, because the digital logic (as well as the drives RAM and the rest) is jumping between the 2 states at rates as slow as once per day and as fast as GHz (billions of times a second). The rule is “nothing is predictable”. When you start a CD ROM driver, you are suddenly pulling current and the supply sags. You stop the CD and there is a negative current step… It is one hack of a noisy environment in there. The same noise that does not alter the digital computation can get into the analog and alter the signal. It finds it’s way in via 2 ways: A. Conductive: some of the supply noise is getting into the circuit through the circuits powered by the supply. That includes changes in voltage drops due to wire and trace resistance.       B. Radiation: Circuit elements (components, traces, wire…) act as antenna and pick noise from the air (like radio). The electromagnetic pickup covers huge frequency spectrum. Inside the computer, one may overcome the single supply limitation by having an internal DC to DC converter on board. But those DC to DC circuits tend to add a lot of noise. One can use extensive shields, on board regulation, tons of filtering… I am sure the better of the cards utilize such technique to get where they get. Without it one may end up with few bits performance worth (with 24 bits toggling, few follow the signal and most follow the noise). External AD’s and DA’s also have digital activity. But with a dedicated task, one controls the frequencies of clock and data transfer to reside where the AD can reject the interference. A good example is a sigma delta conversion, where some narrow frequency regions (multiple of Nyquist +/- 20KHz or so) are a to be avoided and other regions such as word clock do not couple in disturbances. With External chassis, it is possible to have 2 or more separate supply and ground path, designed for a more constant load, without the “surprises” inside the computer. Indeed there are some makers of AD and DA computer cards that decided to meet the challenges the best they can. But how many microphone preamplifier plug in cards are there? Next to non, unless you can accept real poor performance! Why is it? Again, supplies, noise and more noise. The lack of micpres designed for the inside of a computer is indicative of the problems I stated. The other issue, though not as major, is connectors and cables. The pro grade XLR cables and connectors are a good thing. Computers don’t offer the space for XLR’s, and mostly don’t accommodate balanced audio lines.     BR Dan Lavry

Thanks for this very informative reply.  A few more questions: If you use outboard A/D and mix to PC or Mac, don't you still need an audio card to get the SPDIF or AES/EBU output into the computer, and does the card have a negative influence per your reply when only used in that capacity?  How can this be avoided?  Would using some kind of digital "through box" be more desireable (I'm not sure such a thing exists).

[danlavry]

Thanks for this very informative reply. A few more questions: If you use outboard A/D and mix to PC or Mac, don't you still need an audio card to get the SPDIF or AES/EBU output into the computer, and does the card have a negative influence per your reply when only used in that capacity? How can this be avoided? Would using some kind of digital "through box" be more desireable (I'm not sure such a thing exists).

Yes, computer work does require a card, as well as software.
A properly working card, capable receiving (and sending if you want to output data) all the data, should not impact a thing.

AD conversion is a sensitive process. The environment must be "electrically clean", or at least "well controlled", the clock jitter is very impotent and so on.

But once the data is already there (the conversion took place), all that needs be done is to transfer it from converter to RAM (or similar), which is not that time critical, and such a process has a lot of immunity to noise. If you get to "keep all the 0's and 1's, you have ALL the data, and no harm was done.

On the way back out of a computer, you also should get all the data. If you are transferring data to a digital machine or media, it is a non critical process. However, if you send the data to a DA with poor jitter rejection, it will effect the monitoring (what you hear).
But if you take the same data and send it to a good DA, or make a CD (or DVD audio or what not), the sound will correspond to the data itself. The computer interface is just fine for data in and data out operations.

BR
Dan Lavry

[Fifthcircle]

I understand the idea that a computer is a pretty nasty environment for converters.  

However, to play devils advocate for a moment, Lynx has shown that good quality converters can go inside a computer and just about every hard disc multitrack recorder on the market is basically the same as a computer on the inside.  Whether Tascam (not a fan of their converters, but plent of people like them), Radar (that has a huge fan base), Mackie, etc...  They have the switching power supplies inside, fans, and all the other stuff that causes the interference issues inside a computer.

The folks at Lynx have said that the hardest part of making good converters on a PCI card is power...  That's why the Lynx 2 cards are all limited to 8 channels of conversion total.  That was all they felt comfortable doing given the issues they had to work with.

I'm not trying to discount converters outside the box- I personally really like Dan's line of converters.  Things like a power supply can make a huge difference in the sound of gear and the easiest way to get that good supply is to work outside of a computer.

--Ben

[bobkatz]

bloodstone wrote on Fri, 08 October 2004 06:01

Thanks for this very informative reply.  A few more questions: If you use outboard A/D and mix to PC or Mac, don't you still need an audio card to get the SPDIF or AES/EBU output into the computer, and does the card have a negative influence per your reply when only used in that capacity?  How can this be avoided?  Would using some kind of digital "through box" be more desireable (I'm not sure such a thing exists).

The signal to noise ratio, distortion due to jitter, all the rest are determined within the A/D. Once the signal has been converted to digital, then the signal (data) itself is "unchangeable" (unless it is processed by a digital processor such as an equalizer, but I digress). It can no longer be contaminated by jitter, even jitter in the interfaces between processing gear or the cards or interfaces. What this means is that NO, any digital interface card will NOT have an influence on the signal. Send the spdif or AES/EBU or Firewire or MADI signal on its merry way to the next device in line with no worries.

It's only when the card or interface contains a converter that you are using for a critical application should you be concerned about how the converter reacts to jitter issues.

Hope this helps!

BK

[Andy Peters]

bloodstone wrote on Thu, 07 October 2004 03:55

Why do many of the most renowned makers of outboard A/D choose not to enter the A/D PCI card market?  Many of us out here can't afford  higher priced outboard A/D, and I'm sure there is a solid market for both out there.  Thanks.

I'll give you my perspective, as a guy who has designed a handful of (non-audio) PCI cards.  I'll say up front that all of the reasons already given, esp. those having to do with power and the fact that the PC is a noisy environment, are Real Good.  I just think there are other issues, as well.

The PCI spec is rather complicated, especially if you're comparing it to the old ISA bus.  Things are not as simple as assigning base addresses in the host memory space and doing outport() and inport() calls! The host must enumerate each PCI device and the operating system must load an appropriate driver.  This brings up an obvious point: driver writing is not trivial, and it's probably the task that deters most would-be PCI designers, especially if the engineer's background is in analog electronics and a bit of poking around with microcontrollers or maybe BASIC.

A proper hardware implentation is not trivial.  Various chip vendors (notably PLX) make PCI interface chips, which relieve the hardware engineer of the task of actually implementing the PCI stuff in favor of presenting a straightforward local bus.  Of course, one must interface this local bus to the custom logic and that's usually done in a CPLD or FPGA.   The only real problem with this approach is that it can be too expensive.

Another option is to include the PCI interface in the FPGA design.  This has an obvious advantage in that you're using one chip instead of two.  Then, the choice becomes: do you roll your own PCI interface, which can be expensive in terms of engineering time, or do you plunk down five large for Altera or Xilinx or Lattice's PCI core?  In either case, you'll need a PCI bus analyzer (not an inexpensive piece of kit) -- you'd be amazed at the bizarre transactions the host bridge will throw at you.

To do the FPGA design, you'll need a real HDL simulator (I'm partial to ModelSim).  You'll need to know Verilog or VHDL inside and out.  Suffice it to say that your first bit of Verilog should NOT be a PCI design!

While they're coming down in price, FPGAs might still be too expensive (those Altera Cyclone parts are pretty darn cheap, tho'!), so if you think you're gonna sell boatloads of product, you can spin an ASIC that does everything except for the analog and the conversion.  Natch, this requires yet another skill set.

Most competent board layout designers will be able to handle the PCB rules.  A four-layer (if not more!) is mandatory.  No, you can't wire-wrap it.  Not if you want it to work.

Oh, yeah, the kicker.  If you want to actually SELL your PCI device, you have to obtain a PCI Vendor ID.  This is important because the OS selects the proper driver based on the Vendor ID and the Device ID, and you really don't want Windows loading a SCSI driver for your audio card.  Find out how to get a PCI vendor ID by clicking here.  Yep, it says $3K a year.

Having said all of that, the actual digital design involved is otherwise reasonably straightforward.  Your PCI device has to be a bus master and its DMA engine probably should work in chaining mode.   An I2S interface is about six lines of Verilog.  You can play with FIFO depths to get latency down to something reasonable, or if you like to live dangerously, you can ignore latency timers and your device can hog the PCI bus.

... and don't forget those pesky host device drivers!

-a

[Rob Darling]

to the person who mentioned that a Radar is just a computer:

I believe that the Radar has a separate power supply for the audio cards, which deals with the main issue that Dan is talking about- getting good power.