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DACs: Old vs New

amirm

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#21
but the capacitors of that time age badly it seems?
They do indeed. Related story :).

I walked into my den a few years ago where I kept the Mark Levinson DAC. I smell this awful scent like an animal had died. I search high and low trying to find it and nothing. But the smell persisted. So one day I power on the Mark Levinson DAC and notice one channel is clearly distorted. Open it up and an electrolytic capacitor had leaked and was putting out that stench! I have seen a lot of bad caps but never had them small this bad. Not sure what they had put in there. Here is a picture of it:

Mark Levinson DAC Bad Cap small.jpg


It was that "C43" that had oozed out its guts (the dark area around the resistor and such). It is sitting next to that power IC/Regulator that likely cooked it and caused the failure.

So yes, using vintage products comes with such a risk of reliability.
 

DonH56

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#22
so the risks are very limited if the dac is not too exotic?
Too many undefined things...

The risk is usually low, though as Amir's post shows there are times... But modern equipment can be just as bad, for example when a poor layout places a cap near a heat source like a regulator or output transistor so it dies much sooner than expected. Capacitor lifetime reduces exponentially with heat. For that matter heat is the enemy of longevity in most circuits (and many other things).

I do not know how you define "exotic". Years ago electrolytics were sometimes used as coupling capacitors in the signal path but that is rarely true today IME. Film caps are cheap enough it is not a big deal. Some do use ceramic chip caps, however, and those exhibit greater distortion due to their piezoelectric properties -- their value changes with applied voltage, not a great thing to happen in the signal path when the voltage changes all the time.

The very cheapest and most expensive DACs both use electrolytic capacitors in the power supplies. You'd like to think the more expensive devices use better caps but Amir's teardowns show that is not always true, and also that some inexpensive DACs use good components. Without reading a good review and teardown report, or looking inside yourself and looking up the caps, you have no way of knowing.

Anytime you buy something vintage (old) you are taking a risk on how well the components have held up as well as how well the previous owner(s) treated it. A power amp kept in the cool indoors and free of dust will likely be better than the same amp used outside or running hot and filled with dust. Again, assuming the seller blows out the dust and wipes it off, you have no good way of knowing.

I have gone through a lot of old gear through the years, mostly with good results, and a few failures. Same can be said of brand new gear though there is a warranty for the latter, at least for a while. My luck is such that things I get have a built-in clock that ensure failure just out of warranty.

As to the performance, Amir's flagship notwithstanding, IME most older DACs will not measure as well as newer DAC, but sonically I'd guess you'd be hard-pressed to tell the difference. Again, don't let my ears of clay stop you from listening, because at the end of the day it is the listening test that convinces the vast majority of us, not the specs. Myself included, though I probably pay more attention to specs than most audiophiles. The problem being there are rarely enough useful specs and measurements in an audio product datasheet to say much. I used to help out on sales but is usually ended badly -- explaining how lower output impedance, greater stability, lower IMD, beefier power supplies, and all that jazz didn't matter to the guy who's only benchmark was the "other" one put out 10 W more power... :cool:
 

DonH56

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#23

fredoamigo

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#24
I do not know howou define "exotic"

I call an exotic dac a dac that has an architecture, a school of thought opposite or different from the current norm..
 

cjfrbw

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#25
I have an old Sony PCM 2500 pro DAT A-D and D-A machine. I always was amazed at how good the DAC section sounded. It was probably build quality, power supply (dual discrete copper chassis etc.) and analog sections as much as anything.

I will send it for cost of shipping to anybody that wants it and can give it an appropriate museum audio home (heavy) with no promises. It was working fine when I last used it, but has been sitting under a plastic tarp in storage for over ten years now. I haven't used DAT tapes for years, but used to use them for archiving

I heard they still use these in some studios for Redbook stereo mixdowns albeit with updated DACs, but the original DAC sounds fine.

http://www.thevintageknob.org/sony-PCM-2500.html
 

restorer-john

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#28
I have seen a lot of bad caps but never had them small this bad. Not sure what they had put in there.
Amir, that electrolyte smell is a classic fishy smell- a cross between off-fish and cat-wee. Us technicians can localize bad caps even with our eyes closed. :)
 

restorer-john

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#29
...IME most older DACs will not measure as well as newer DAC, but sonically I'd guess you'd be hard-pressed to tell the difference...
To compare (test) older and newer D/A converters, the playing field must first be leveled. The older D/As are 32/44/48 16bit in most cases, and were specified and tested at those ratings. Fair testing is 16/44 vs 16/44 as the majority of digital music is in that format.

Most modern D/As are getting S/N by default through simply having 24 bit D/As. Often, it appears, when tested at 16bit 44 or 48 they are falling considerably behind well designed 16/44 D/As of old. I'm seeing plenty of plots showing premature roll-off, average S/N, and the conclusion I draw is they are optimized for 24/96 and above. In other words, the designers have got lazy in pursuing the ever increasing Fs and quantization bits.

As for the audible differences, I've done more than enough testing/comparisons of my own to know 'hard pressed to tell the difference' is a conservative term. :) Whenever I 'think' I've identified a difference, I simply fire up one of my many 1st generation CD players to remind myself and my audiophile friends how fallible our ears and brains can be.

Most people blindly regurgitating the myth about the 'terrible', 'harsh' or 'ringing' sound of 1st generation CD players have no actual reference.
 
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DonH56

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#30
Well, 16-bit converters years ago rarely had actual DNL/INL/ENOB to that level, whilst most 24-bit converters come pretty close to ideal 16-bit performance. Ideal 24-bit performance, not so much... ;) Since most of today's converters are delta-sigma based I am not sure what people want when they are comparing then and now; today's conventional (segmented/NOS) DACs generally don't have much better performance than those of ten-plus years ago but in-band quantization noise is usually much better for today's run-of-the-mill delta-sigma designs. But yah, Amir's tests and others show what happens when Marketing trumps Engineering and introduces low-order filters as a "feature" (can't have those nasty high-order digital filters that ring at a MHz or whatever, oh no, must have a nice slow analog'ish filter -- or none at all -- that lets all the ultrasonics through -- maybe they get kickbacks from tweeter manufacturers?)

The main problems I saw long ago with DACs had more to do with the buffer and filter op-amps than the actual core DAC circuit. Some DACs had pretty bad linearity, and some ADCs were even worse, but IIRC the main issues I saw (and heard) were from op-amps that misbehaved badly when driven by the large, fast glitches from binary DACs. I do not recall which CD player used the infamous op-amp that inverted its output when overdriven but that was my reference for bad design at the time... Some of the filters were pretty ugly, too. But, by the mid-1980's those problems were largely solved, and I doubt anyone could tell a difference.

Worth noting several of the highly-regarded DACs of the time were 14-bit designs that sounded pretty durn good. And some of the multiplexed designs put a healthy lag into one channel.
 
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Guermantes

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#31
When I heard my Denon DCD 660, I about fell out of my chair. I had auditioned many modern dacs and wasn't really taken with most of them mostly due to treble timbre issues and lack of resolution that I I heard or at least thought I heard.
Then I heard this one and I was like ....get outta here, late 80's dac?! This should have been trash. I was actually not even going to entertain the idea of listening to it. But I was thinking are you kidding me? It's one of the best I've heard!
A friend of mine bought the DCD-660 when it first came out because of my recommendation of Denon CD players (I had a DCD-820 at the time). He was sorely disappointed and wished he had spent his money on a Harman Kardon 7500 which had a Matsushita MN6471M Bitstream DAC.
 

garbulky

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#33
A friend of mine bought the DCD-660 when it first came out because of my recommendation of Denon CD players (I had a DCD-820 at the time). He was sorely disappointed and wished he had spent his money on a Harman Kardon 7500 which had a Matsushita MN6471M Bitstream DAC.
Oh man! What kind of speakers did he use? Most of the videos of this cd player I see on the net have them paired up to some real dogs. For me, it required some warm up time about a day. Or at least I thought it did in my subjective listening. I felt the treble was a bit on the harsh side till then. (I know people think warm up for multibit dacs is silly. )
 

Guermantes

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#34
Was the Denon unreliable?
No, as far as I know it is still in service whereas my DCD-820 gave up the ghost circa 2000. He was just disappointed with the sound and much preferred the Harman Kardon in that respect (I believe it was rather more expensive, though). I suppose I was making the point that he preferred the sound of the Bitstream unit over the multi-bit Denon.

I also liked the sound of that H/K model but I didn't do any listening comparisons whereas I think he had the opportunity to A-B both after he had committed to the DCD-660.

Oh man! What kind of speakers did he use? Most of the videos of this cd player I see on the net have them paired up to some real dogs. For me, it required some warm up time about a day. Or at least I thought it did in my subjective listening. I felt the treble was a bit on the harsh side till then. (I know people think warm up for multibit dacs is silly. )
I honestly don't remember what speakers he had at the time. I know he later bought a pair of Wharfedale 517s, as did I.
 
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