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Author Topic: AD/DA converters question  (Read 14483 times)

2db

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AD/DA converters question
« on: December 07, 2006, 09:05:47 PM »

I have a Korg D32XD.

Are the converters in this unit considered poor, good or excellent?...and can you really know a converters worth, good or bad, by specs alone?

Am I pissing my money away by purchasing high end mics and preamps if the converters are only marginal.

I would appreciate some education in this area.

Much thanks,
-jim

Consul

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Re: AD/DA converters question
« Reply #1 on: December 08, 2006, 04:20:45 PM »

That's something I've always wanted to know.

Why is good conversion so expensive? What does it take to make good conversion? Why does it have to cost $2000 a channel?

I've heard plenty of pretty good recordings made with M-Audio, Echo, and the like, but then some folks upgrade to, say, Lavry, and report a difference "like night and day." I'd want the difference to be like night and day, too, for the price I paid. Is there really $6,000 worth of sound quality difference between an Emu 1820M and 8 channels of Apogee?

It almost, and I say almost, smacks of audiophilism. Buy this $20,000 rock, it'll make your CD player sound better.

Please, I would like to know what's really going on, and why there is such a HUGE difference in price between the low end and high-end. I would really like for you to explain to me that this is completely normal, and that these high-priced devices are 100% worth their money.

Sorry for the stream of consciousness post, and thank you for your time and for putting up with guys like me.
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #2 on: December 09, 2006, 04:10:05 AM »

I couldn't comment on the Korg because I don't have a stack of gear here to open up and check out.

A good chip doesn't make a good converter. There are a lot of ways of screwing up and new ones are being invented every day.
Applying all normal audio and EMC tests to a bad design will bring all of these issues up. There's no magic involved. Cheap converters you may think are good enough just aren't once you really start looking (or listening).

There is an enormous amount of ineptitude out there, especially in large (eastern) companies that turn out such an enormous number of new products each year that every product is done by someone else. Even if such a company has an actual expert on board, there's no reason to presume this person even gets to see most of the products that leave the plant.

This happens across the board. It doesn't really matter whether the company sells cheap or expensive goods. Most expensive goods are equally bad designs using only better parts.

Such a company is a frustrating environment for someone who knows how to do stuff. When this person starts his own company to do things better he's suddenly confronted with a completely different economy of scale. A product that a large company can market for $500 a small company can't possibly offer for less than $2k.

Actually, a good designer can build a fantastic sounding piece of kit using the exact same parts used by someone else in a shoddy design, but there's no way he can put this on the market for the same price. The only way of making it economical is putting it in a nicer box, perhaps using even nicer parts. Before you know it the product is really expensive, and really chique.

The next step is when our designer discovers that the chips too have shortcomings. Before you know it they're designing AD/DA converters using discretes. Like Dan L and myself. The result is a product that rarely fails to impress, but that is prohibitively expensive as well.

---

When it comes to magic bricks etc, the only way of avoiding cynicism is to look the other way. Some people are trained self-delusionists. Some others know how to take advantage of this. And some belong to both categories at once.
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Consul

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Re: AD/DA converters question
« Reply #3 on: December 09, 2006, 04:15:14 PM »

So, what you're saying is, somewhere out there, there might be a $600 AD/DA box that actually sounds pretty darned good because of a designer who knew what he/she was doing, just as there are $2000 boxes that are likely crap.

Isn't economy of scale a bitch?

As much as I would like Lavrys or some similarly expensive and nice-sounding kit, I'm afraid I'm locked into the sub-$1000 realm. I guess Lynx remains a good option, overall. A lot of people have talked about how much they like the Emu 1820M. I guess there's always the RME Multiface. I'd really like to audition a few of these things before making a final decision. I don't think I need any more than four ins and outs.

Right now, I have an old Seasound SoloEX system, which was designed by Tom Oberheim. Nice box, but unfortunately, mine is on its way out. It's pretty old, after all. I need to think about what will come next.

I'm a home studio guy, by the way. I'm used to having to compromise. Here's a question for you: In what areas of a home studio would you compromise, and where would you definitely not want to compromise?

Thank you!

PS - I brought up the "audiophile" stuff, because that is how some of the people who rave about the high-end converters come across to me: "My God! These thing rock! So much more open, better top end, everything! Night and day, I tell you! NIGHT AND DAY!!!" I have to wonder how much of that is psychosomatic because they just spent 10 times the money on converters than most people do, and they don't want to consider the possibility that they don't sound 10 times better.

I do not mean this as any kind of insult to you or Dan Lavry. You fill in a niche where it's needed, and most of the people who buy from you know they are paying so much more for that last 20% of performance, and accept that. Most of those folks are professionals who have set standards to live up to. I'm mostly directing my "vitriol" (such as it is) towards the people, like some on this board, who refuse to acknowledge guys like me as being in any way serious because we just can't spend as much money as they do.
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Darren Landrum

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Consul

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Re: AD/DA converters question
« Reply #4 on: December 09, 2006, 09:10:55 PM »

Also, is there any chance you might know of a web site out there that gets into (at least some) detail on how discrete AD/DA conversion is designed? You have me curious now. Thanks!
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Darren Landrum

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Rivendell61

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Re: AD/DA converters question
« Reply #5 on: December 09, 2006, 11:06:11 PM »

Consul wrote on Sat, 09 December 2006 21:10

Also, is there any chance you might know of a web site out there that gets into (at least some) detail on how discrete AD/DA conversion is designed? You have me curious now. Thanks!


Here is a bit of info ("Design techniques for high-performance discrete A/D converters" by B. Putzeys):
http://grimmaudio.com/whitepapers/discrete%20ad%20converter. pdf

Mark
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Consul

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Re: AD/DA converters question
« Reply #6 on: December 10, 2006, 01:03:05 AM »

Cool, thanks! I'll see what I can absorb from it. Wink Anything else would be appreciated, too. A Google search turned up almost nothing after several tries.
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #7 on: December 11, 2006, 03:39:51 AM »

Consul wrote on Sat, 09 December 2006 22:15

So, what you're saying is, somewhere out there, there might be a $600 AD/DA box that actually sounds pretty darned good because of a designer who knew what he/she was doing, just as there are $2000 boxes that are likely crap.

That's it in a nutshell.
Consul wrote on Sat, 09 December 2006 22:15

In what areas of a home studio would you compromise, and where would you definitely not want to compromise?

I would definitely not want to compromise on the acoustics, both on the studio and on the control room end. The rest is pretty subjective. I personally would make sure to have at least 4 good preamp and converter channels and get a few good plug-ins. I'd then put up with whatever impractical workflow I'm stuck with.
Consul wrote on Sat, 09 December 2006 22:15

I have to wonder how much of that is psychosomatic because they just spent 10 times the money on converters than most people do, and they don't want to consider the possibility that they don't sound 10 times better.

I do not mean this as any kind of insult to you or Dan Lavry.

No offense taken. There are quite a lot of people out there who don't hear much of a difference but who fall prey to (coin termed by a poster in the slew rate thread) "gear hypochondria". If one hears the kind of record productions that come out of the esoteric end of the audiophile world one realises that it's better to have someone with cheap gear who knows what he's doing, than someone with expensive stuff who doesn't even realise the bass player is half a beat off (not to mention vocalists who never understand what they're singing about).
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bruno putzeys

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Re: AD/DA converters question
« Reply #8 on: December 11, 2006, 03:49:12 AM »

Consul wrote on Sun, 10 December 2006 07:03

Anything else would be appreciated, too. A Google search turned up almost nothing after several tries.

I've not published much about this converter apart from that paper. You'll need to ask questions if you want to know more. Google, in the meantime, is becoming a victim to its own success.
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Consul

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Re: AD/DA converters question
« Reply #9 on: December 11, 2006, 11:54:36 AM »

Gear Hypochondria. That's a great description.  Very Happy

Thank you very much for your time. It really is appreciated, especially by folks like me who get frustrated time and again with all of the options out there.

It has been a genuine challenge putting together a good home studio. I'm an engineering student, so it's probably easier for me to understand the technical aspects than for many others. (I'm a returning student at 30 years old, after a career in IT that ended badly.)

I was, for a brief, maniacal time, thinking it might be possible for me to DIY my own discrete AD/DA conversion. Heck, I'm DIYing mic pres, compressors, and the like. I'm now thinking I should just be on the lookout for a good bargain, like a used medium-end unit, or maybe just snag a Lynx card.

Again, thank you for your time.
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Darren Landrum

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zmix

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Re: AD/DA converters question
« Reply #10 on: December 11, 2006, 12:47:30 PM »

Consul wrote on Mon, 11 December 2006 11:54

Gear Hypochondria. That's a great description.  Very Happy

Thanks and you're welcome. It's a pretty obvious form of neurosis which I had observed in hi-end audio mags before the net got rolling. I coined the term to describe the artistic paralysis brought on by worrying about absolute polarity, integrated circuits VS discrete, jitter, substrate thickness in die fabrication, pre-echos in converters, vintage versus re-issued gear, slew rates. In general, this condition can be taken care of by the placebo effect as administered by peer approval, gear 'high fives' and other forms of social reinforcement. It's also important to remind those afflicted that every record they loved as a kid was typically made using pretty ordinary and usually new-ish gear. Often this gear, if it was really new, like helios or trident console, was unproven. Those involved relied on their ears to tell them if it was any good or not.

maxdimario

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Re: AD/DA converters question
« Reply #11 on: December 11, 2006, 03:57:25 PM »

..and then there is sound engineer's hypochondria:

worrying about getting the right microphones, the right levels, analog vs. digital, condition of the equipment, tl072/5532 mixers vs. neve/api/discrete, recording in the perfect acoustic space etc..etc.. the list goes on..

...HEY WAIT! that is their job!

there's NOTHING wrong with wanting to get things right.

..and there IS such a thing as right/wrong..good/bad.

My problem with the hi-fi world is that often they will substitute bullshit for sound.

A friend of mine came over to my house and heard a few of my old records on my tube class-a system (which I built and modded)

it's nothing special as far as cost or, with the total amounting to about 3000 for everything.

so he called me up asking if we could go to a hi-fi store and look for a system for him..

as soon as we arrived I started listening to speakers and said this one I like, this one I don't etc..

the salesman was TELLING me that I could not hear the differences in such a short time... which is absolute bullshit.

we went into a room with a 30,000 dollar setup and listened to a cd..

I wasn't too thrilled..

I asked my friend what he thought and he said that frankly he preferred my setup..

it seems that the whole hi-fi sales game is based upon TELLING you what you should hear and then INCREASING THE COST of the gear which they try and sell you.

obviously according to them the increased FEATURES and specs justify the expense..

but I don't get fooled as easily as when I was 17 years old anymore.

status simbols..love of technology over music..

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Rivendell61

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Re: AD/DA converters question
« Reply #12 on: December 11, 2006, 10:41:48 PM »

Consul wrote on Sun, 10 December 2006 01:03

Anything else would be appreciated, too. A Google search turned up almost nothing after several tries.


There are some threads over at diyaudio on discrete dacs.  Here is a link to one--and on the last page is a link to follow-on threads.  Not sure how much useful data there is....
http://www.diyaudio.com/forums/showthread.php?s=2838ead3c899 e5130c39403c3dca1aae&threadid=45096

Mark
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Consul

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Re: AD/DA converters question
« Reply #13 on: December 12, 2006, 09:51:47 AM »

Umm, yeah...

After reading all that DIYAudio had to offer, I think I'll leave AD/DA building up to other people. I don't even want to begin to know the frustration of matching 32 1% resistors down to 0.005% then building some kind of calibrated oven to put them in. Not to mention figuring out some kind of digital filtering system.

That, of course brings us back to one of my original questions: How can we tell what the bargains are?
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #14 on: December 13, 2006, 06:51:27 AM »

Consul wrote on Tue, 12 December 2006 15:51

How can we tell what the bargains are?

Measure them. Open them up and look at the circuit boards. Check the schematics.

Things to check on the schematic:
*How's the clock that drives the AD/DA chips routed? Is it treated as an analogue signal or does it get mixed through the same logic chips that also have data going through them? How's the clock generated? Does the oscillator at least have a clean supply?
*Are the filters designed to keep really high frequencies away from the opamp I/O's?

Things to check on the circuit board:
*Is the ground plane solid with nearly no breaks in it, or does it look like a picasso?
*Are the connectors nicely grouped together (so any voltage across the ground plane doesn't appear across the connectors) or does the circuit board have connectors at opposing edges of the board?

Things to measure:
*Do the measured specs line up with the specs published in the IC data sheets?
*Can the converter reproduce a 10kHz signal without (too much) sidebands?

At any rate, you'll need to do quite a bit of analysis and tests. Do not trust a manufacturer's verbal claim unless they back it up with hard data. Claiming to pay attention to "low jitter" and "circuit board layout" is de rigueur these days. Nobody will market a product without saying these two things. But do they walk the walk? Only the actual hardware can tell you that.
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Jim Williams

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Re: AD/DA converters question
« Reply #15 on: December 13, 2006, 10:52:51 AM »

I suppose you all could line up 32 Vishay medical grade bulk foil resistors at .005% tolerance and very tight temp grades. Then you could realize they cost over $10 each.

Or, you can get clever and smart. Most of these chip makers offer demo pcb's to show off the product. Get a Crystal CDB5381 from digi key for around $400. Add a 5 and bipolar 12 volt supply and go. For the tweakers, pop off the 5532 opamps for something better.

For DAC's, they offer the CDB4398 demo pcb with the same opamps and powering requirements around the same price range. This is the best 1 bit chip out at the moment.

For the anal retentive like myself, only the Burr Brown PCM/DSD1792 will do for playback. This chip set offers -129 db THD+noise and with the co-sine operation it reaches -132db, within 8 db of the theoretical, magical 24  bit dynamic range.
BB offers this demo pcb for around $900, I got mine from the engineering dept. as a comp. Add some stellar opamps and a great psu and I know of no DAC with this dynamic range and very low THD. Due to parasitics, I don't know if a discrete design could achieve these results. Certainly not for this price range.
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zmix

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Re: AD/DA converters question
« Reply #16 on: December 13, 2006, 03:52:28 PM »

I had an interesting conversation with the designer of a piece of equipment that was 're-issued' 20+ years after the original. The device was a sort of delay based effect and in the re-issue the feedback path was done internally in the DSP, but in the original the feedback path was all analog. I asked the designer about the change, and he stated that the only converters available today were sigma delta and that the original used a successive approximation converter. He said that the newer converters didn't maintain nearly the fidelity of the successive approximation converter, so they decided to go DSP.

It's interesting to think about how audible the anomalies of a converter become after so many regeneration cycles.

Back in the 1980s there was an Opamp listening test which specified 10 devices in series.

Anyone ever listen to 10 converters in series?

Consul

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Re: AD/DA converters question
« Reply #17 on: December 13, 2006, 06:06:04 PM »

Bruno Putzeys wrote on Wed, 13 December 2006 04:51


Measure them. Open them up and look at the circuit boards. Check the schematics.


I honestly don't think I'll be able to get schematics for any of the devices in question. That means reverse-engineering. I don't think I have the skill for that. In fact, I know I don't.

Quote:

At any rate, you'll need to do quite a bit of analysis and tests. Do not trust a manufacturer's verbal claim unless they back it up with hard data. Claiming to pay attention to "low jitter" and "circuit board layout" is de rigueur these days. Nobody will market a product without saying these two things. But do they walk the walk? Only the actual hardware can tell you that.


Well, I do thank you for your reply. It's confirmed what I've suspected the whole time: unless someone steps up to the plate, spends the money, does the reversing, and reports the findings on a variety of budget devices, selecting a set of AD/DA converters will remain a shot in the dark unless one can spend at least $500 per in and out. I would really love to be the one to gain all the fame and adoration by stepping up to said plate myself, but finances simply will not allow that, not to mention my own skill with electronics, which is existent but not quite expert.

I guess I should point out that I'm not interested in DSD right now. Regular old PCM is where I'm stuck at the moment.

I really hope I don't sound like I'm whining, even though, really, I am. Wink

A friend of mine suggested making a discrete D/A by trimpotting the output resistors, then wrapping the whole thing in an oven. This would add a lot of current noise, though, right? What would happen if one ran the trimpots in parallel?
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #18 on: December 14, 2006, 04:47:39 AM »

Consul wrote on Thu, 14 December 2006 00:06

I guess I should point out that I'm not interested in DSD right now. Regular old PCM is where I'm stuck at the moment.

I'm not a proponent of using 1-bit signals in recording and processing (which is what the trade name DSD really means). I am, however, very pleased with the results I get using 1-bit conversion in discrete AD/DA converters. After the AD you'd strap a decimation chain to get PCM and before the DA an upsampler and a digital sigmadelta modulator produce a 1-bit signal. This is how most AD/DA chips work these days, except that they'll usually use two to five bits worth of conversion.
So PCM work does not condemn you to using a ladder type converter. The data format and conversion method are two separate issues. For either type you need digital filtering (unless you want to build analogue brick-wall filters) so then the number of bits on the converter end becomes a separate decision.
Consul wrote on Thu, 14 December 2006 00:06

A friend of mine suggested making a discrete D/A by trimpotting the output resistors, then wrapping the whole thing in an oven. This would add a lot of current noise, though, right? What would happen if one ran the trimpots in parallel?

One would certainly place them in parallel. If the resistors are 0.1% devices and the trimpots are, say 1000 times the value of the resistor, the pots will not introduce noise.

Again I'd stress that one should choose the conversion topology and data format on their own strengths. Which means low-bit on the converter side and PCM on the processing side.
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Consul

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Re: AD/DA converters question
« Reply #19 on: December 14, 2006, 05:07:41 PM »

Thank you for the info, Bruno! I'm definitely directing my friend to this thread now. Very Happy Maybe we'll even come up with a design...
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Darren Landrum

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Consul

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Re: AD/DA converters question
« Reply #20 on: December 16, 2006, 05:34:36 PM »

Would something like this work for the digital filtering?

http://www.wavefrontsemi.com/index.php?id=11,13,0,0,1,0

It's an inexpensive DSP chip good up to 50khz clock speeds, 50 MIPs. I just wish they made a DIP version.

EDIT: You don't really have to answer if you don't want to. I'm not out to be a competitor or anything. Wink I just love to learn about as much as I possibly can. Trying to make my own D/A would be a genuine challenge, though I don't know if it's one I want to take on just yet.
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #21 on: December 17, 2006, 09:42:42 AM »

The processing capacity allows for some fairly decent filtering but the I/O only runs at the word clock rate which in turn is limited to 50kHz. Quite annoying if one wants to make an upsampling filter.

SMD soldering is easier than you think. Get a decently fine soldering tip and more importantly, get fine solder. Once you're used to it you'll never want to go back to thru-hole.
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Consul

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Re: AD/DA converters question
« Reply #22 on: December 17, 2006, 07:51:01 PM »

Thank you for the reply. I guess my question now is, why would one want to build an up-sampling filter?

I must sound like a real newbie, huh? Unfortunately, this kind of information seems incredibly difficult to search the Internet for. I'm a mechanical engineering student just starting out, so I have no professors I can bother with my silly questions, either.
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #23 on: December 18, 2006, 03:12:49 AM »

Newbiness is permitted Smile

You'd build your own upsampling filter if you're unhappy with the performance of existing ones. There aren't any commercially available upsamplers using windowed filters, all are halfband based and none have strong bandpass dither for linearising multibit DACs.
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Consul

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Re: AD/DA converters question
« Reply #24 on: December 18, 2006, 10:49:03 PM »

Okay, now you're just showing off.  Razz Wink

Time to hit Google again...
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Darren Landrum

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bruno putzeys

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Re: AD/DA converters question
« Reply #25 on: December 19, 2006, 03:23:55 AM »

I'm referring to the fact that for economical reasons upsampling and decimation filters usually don't fulfil the Nyquist criterium, but are -6dB at fs/2 in order to make all even coefficients trivial (halfband).
They also don't ring out smoothly at the ends but stop in a small "spike" that's the result of numerically optimising the filter to fit a certain spec with the least number of coefficients (equiripple). I wouldn't consider this a problem in  filters with very low in-band ripple (in halfband filters this corresponds to a large stop-band rejection), because then the tails are so deep down that any irregularity there can't possibly be audible.
Further, ladder DACs benefit from quite heavy dither (at -20dB or so) to smooth out the low level nonlinearities. Of course you'd put this dither at the end of the spectrum after upsampling, ie in the 100kHz region.
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Consul

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Re: AD/DA converters question
« Reply #26 on: December 19, 2006, 09:51:47 AM »

Sorry, I was only making a joke about my own inadequate knowledge. I hope I didn't come across harshly.

I have more reading to do, I think.
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Darren Landrum

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Re: AD/DA converters question
« Reply #27 on: April 11, 2008, 09:26:00 AM »

Hi PSW forum,

I hope to connect with Bruno Putzeys through this forum - or somebody else who knows about DSD A/D conversion technology.

I'm considering building (as part of a DIY - collaboration) a DSD A/D converter operating at 256*fs. As I believe sample rates will go up in the future, this is to make it reasonably future proof.

I am aiming for a design with a very high sound quality.

Briefly investigating the effects of noise-shaping and higher order modulators, I find a second order modulator interesting. The reason for this is to obtain "benign" noise-shaping effects. I realize there are some trade-offs to this - like e.g. a lower theoretical SNR.

Before venturing into this project I am interested in feedback from people with experience in this field: Could there be problems with this approach?

Should you reply to this post, please consider me a layperson, although one with a very good generalist technical understanding.

Thank you  Smile

Jesper (Denmark)






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bruno putzeys

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Re: AD/DA converters question
« Reply #28 on: April 14, 2008, 03:51:07 AM »

gentlevoice wrote on Fri, 11 April 2008 15:26

Could there be problems with this approach?

Yes. The second is choosing your sample rates higher than necessary. The greatest enemy of sigmadelta converters is intersymbol intermodulation. In a discrete implementation that means you should make temporally separated pulses (return to zero) with enough time for DAC to settle fully back to zero. Settling time issues translate as "intersymbol intermodulation" (i.e. where the area under two subsequent ones is not exactly equal to the area under two ones with a zero in-between) and this in turn causes the dominant tone to fold back into the audio band. What you hear is a frequency-modulated whistle that becomes very audible at low signal amplitudes. If you have good experience with RF layouts, you can get to 128fs (approx 6MHz) with good results. 256fs is highly doubtful. A discrete 256fs converter exists but it has not exactly met with universal acclaim.

The first is making design choices before you've gotten your target specs lined up. Before you make any design choices, scrutinize your wish list from a "black box" perspective. Suppose you have a pair of converters connected back-to-back and you're listening through them. There's no way you will say "oh this is a 1-bit at 128fs with a 4th order loop" or "this is a 24-bit ladder" or "this is a 5-bit at 32fs with a 6th order loop" etc. So these items should be no part of a requirement spec and can't possibly be a choice to be made up-front.

So, try to separate performance requirement specs from design choices. The performance spec comes first and is based on the user experience (sound, operatability, anything you can determine without taking the lid off). Then don your engineering hat and see how you will achieve, technically those requirement specs. The design choices you make are then made strictly on the specs. If the user intervenes and tells you he won't buy the box if it doesn't use his favourite opamp, circuit topology or numeric representation, shut the user up.

As soon as a project has more input variables than it has outputs, specs may directly conflict. In your case, the extra input variable is fun factor. It's a DIY project. Perhaps all your technical (and hence sonic) needs are fulfilled straight away by buying an off-the-shelf chip (or even a complete box), but it's not nearly as much fun as knocking something together that's only half as good. In this case choosing your priorities well will save you a lot of disappointment. Nevertheless, at least heed the second item Smile
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gentlevoice

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Re: AD/DA converters question
« Reply #29 on: April 14, 2008, 02:00:48 PM »

 Laughing  Laughing   Thanks Bruno for the explanation and design "input" - you made me laugh with the link to your 2 "design paths". I would say that my approach really is both - because my design goals are often aimed at perfection (No. 2), when I realize it can't and/or is difficult to do, I revert to the first one and then juggle between them ...  Confused  

I have also found that my ways of designing often transgress "normal" engineering approaches which makes specifying goals in words or specs somewhat elusive ... E.g. I have mounted some of my amplifier designs on balsawood, thereby eliminating the PCB, something that, as I perceive it, caused the design to sound more open, liquid, and less "noisy" (smile).

However, my reason for researching this as a collaborative DIY- project is that I have not found a commercially available solution that satisfies my wishes.

I know that grimmaudio has the AD1 available which appears interesting and seems to be a very special design (although too expensive for my budget and not entirely convenient for me - I'm looking for something portable). Also, now the KORG MR-1000 with a 5,6 MHz DSD sampling rate is in the market - although maybe in its base design it is not in the same league as the AD1.

There are other designs as well but I've never heard of a 256*fs design. Can you share who/which company makes this?

BUT - even more important - my intuition keeps telling me that the high-frequency output power of delta-sigma modulator designs (mostly at 64*fs) will have an (negative) effect on me, personally (BTW there is a study indicating that although a person may not actually hear a sound/tone e.g. above 20 kHz, brain wave measurements indicate that the brain waves change when the tone is present). I reckon this noise will also influence electronics and speakers.

I consider my intuition to be correct in this respect which is why I'm looking for ways of overcoming this - e.g. by designing a delta-sigma at 256*fs, or, if possible, at an even higher fs, and as a low-order design. I know that very high frequency delta-sigma modulators have been made, yet my technical know-how does not allow me to discern if they are applicable to high-end audio.

An alternative is a very high sample frequency 20-24 bit PCM converter, e.g. ~ 400 kHz fs (I have my reasons for this, should be possible to disable any digital filters), but I haven't yet found such a chip/converter suitable for audio. Maybe you know of such a converter/design?

I have had contact with a Danish audio manufacturer (considered high-end) and he told me that for classical music the SACD format is positively preferred. Others say something different, though - my personal experience is that PCM and DSD each seem to have sonic imprints that may be somewhat unique to them (I realize implementation has a lot to say - and not being humble, no, I may not be able to discern close designs from eachother ... ).

In the marketplace, what I notice is that SACD title issues now have reached >5000 and DVD-A is declining - as far as I know. So maybe SACD is what will happen in the future. Also with high capacity discs available, such as blu-ray, I consider it likely that recording rates will go up in the near future.

Well, yes, that's where I am with this. I'd appreciate if you/others have comments ...

All the best to your evening, Bruno! Here in Denmark, right now the sun is setting - slowly painting the sky orange/reddish - and the birds are singing. It's a good experience   Rolling Eyes

Regards,

Jesper
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