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Author Topic: AD/DA converters question  (Read 13295 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

"Never be afraid to try something new. Remember that a lone amateur built the Ark. A large group of professionals built the Titanic." - Dave Barry

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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