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RE: Ladder DACs for volume controls.

Posted by joerosen1 (A) on October 2, 2014 at 05:37:46

In Reply to: RE: Ladder DACs for volume controls. posted by rick_m on September 30, 2014 at 14:24:13:

I may not have all my technical facts on these things completely straight, but blame Dallas Semi & not me!
And for all my hot air, I come by my opinions honestly, which I means I LISTEN honestly before I spout off. I did some homework, but Dallas SemiConductor's datasheets weren't exactly helpful.
Think about what you just said (besides the blowhard remark).
"A ladder DAC operating in the analog domain".
Hunh? Excuuuuuse me?
DAC's operating in the analog domain???
Not the current chunk-spitting I2S DAC's I know & love, anyways!
Two things: One, going from memory of a datasheet I looked at 10 years ago. Two, remembering how incomplete & bizarre the data was.
Typical op-amp or other chip datasheets proudly show you an internal schematic in full & glorious detail; if there is proprietary technology they're not worried about since they patent those things!
Either this Dallas chip (which I looked up because it was doing suspicious shit in the ARC integrated, a CA-50 or 40, that I found the little devil in) is soooo complicated that there just wasn't the room on the page to disclose full schematic detail, or these guys were trying to hide something knowing full well its audio applications.
The whole thing started when I heard this integrated at a show, and I was VERY impressed by its "neutrality" and "cleanliness" for a tube amp, especially a lower-priced ARC one.
That was a quick listen, under show conditions, so I didn't get the full picture and made certain assumptions based on the "usual" technology that I otherwise know INSIDE & OUT.
This "blowhard" KNOWS his tube technology & sound, has heard and/or owned/and or/owns every notable vintage piece of tube audio gear EVER made; DESIGNS & BUILDS it, and has a schematic collection that fills a large filing cabinet. The blowing is backed up by more than a little bit of thinking, and even more listening; trust me when I say that.
The upshot of that little audition was that I mentioned to it some friends & customers, so one guy bought one on Audiogon based on my favourable comments.
HE noticed that something wasn't quite right sonically, but couldn't quite put his finger on it. So he invited me over to check it out, make sure it was working OK, double-check the bias & balance and all that sort of rot. So I did, I gave it a little tweak here, and a little tweak there, but it was basically within spec and running well.
As it should, since it was fresh back from ARC after its second trip (first post-warranty) where it had blown an output transformer and some other nasty things. Cumulative bill was around $1200!
I'm not used to seeing exploding ARC, I used to consider it a quality product (at least, compared to c-j, VTL, Sonic Frontiers or Counterpoint). But this thing was the harbinger of the shit we see today: bass-ackward hybrid retard technology, Russian tubes, dodgy little trim pots for bias, and "actuators" instead of real selector switches OR volume controls.
At least the microprocessor that ran the little shitbox wasn't switching FET's or bipolar transistors to do input selection; ARC had the good sense to make it actuate a bank of little cheapo relays.
And this is fine, it doesn't hurt the sound; only the idiot inconvenience of having to "cycle" through inputs instead of immediately getting the one you want! The audio circuit looked "harmless" enough, selected FET's with ARC's habit of etching the numbers off so that they can fuck you over for replacement parts, driving some clangy & cold Russian 6550's from a pair of 6DJ8/6922's. Or something. But the outputs were a quartet of 6550's, because to ARC there is no other output tube, and they WOULD pick the shittiest sounding one available short of a 6L6/5881...
So given what I "knew" from the sound of things like the Classic 30 & Classic 60 hybrids, with which I was pleasantly surprised at how much of an improvement THEY were over the deathly-dark & filthy-dirty opaque sound of the earlier D75/76/150 that I am also intimately familiar with (only ARC could make transistors sound better than tubes; this takes a special Johnsonian kind of incompetence), I expected that the CA-40/50 was much like the Classic 30 with maybe a bit less feedback to improve input sensitivity in its conversion into an integrated amp, along with the addition of the input switching & volume "pots".
But this fellow wasn't wrong; there WAS something "different" & off-putting about the sound of this integrated amp. For all its apparent cleanliness & clarity, good dynamics & excellent S/N ratio, it sounded very...ARTIFICIAL. Timbres were cold, thin, and just plain WRONG. I then noticed something else: where the heck was all the low-level detail that I should be hearing, even in a backwards-hybrid with sterile-sounding Russian junk tubes? Even if I mentally "lowered the bar" to Classic 30 standards, this CA40/50 still wasn't clearing it.
And Buddy found he was getting restless during his listening sessions. No listening fatigue in the obvious sense, but its complement: Audio Boredom.
When the sound is "strange" or "weird" enough, like it is so obviously with MP3's & Cellphones, our connection to the music-making gets TOTALLY severed. We invariably find ourselves staring at the wall between our speakers, wondering what kind of Aliens from an alternate Universe were inhabiting our music collection.
Such strange and not entirely wonderful noises they make! ALMOST like music, strangely similar, but definitely WRONG.
So there you go, Rick.
All other variables analysed & dealt with, and the only thing left after perusing the schematic was this strange & wonderful neat-O Dallas Semiconductor Attenuation IC (I don't even think the data sheet identified it as a "Ladder DAC", and I found the omissions both ominous & misleading, to say the least).
The definitive thing to do, which I suggested to the fellow, was to bypass the volume control entirely, and see what the unit sounded like then. Then we'd know, FOR SURE.
But even if the Dallas chip was found to be the chief sonic offender, what to replace it with? I don't pretend to be clever enough to know how to reconfigure a microprocessor that talked to a Ladder DAC chip to now talk to a motorized ALPS potentiometer, and that would have been the ideal solution. Never mind cost, time, etc.!
And even though Buddy primarily used CD as his source, he also listened to alot of FM, and neither of those units had output controls to substitute for the lack of a volume control on the ARC.
He bought an integrated amp instead of a switchbox & a power amp for a good reason!
In the end, that left only one solution.
Since the unit was clearly an exploding turd in terms of reliability, and all the proprietary ARC parts made repairs expensive no matter who did them, and "fixing" the sonics was far too complicated & sketchy, he did what anyone in the same situation would & should do: he dumped the f***er, before it blew up again.
At that, my explorations & immediate curiosity for the anomalous Dallas "Attenuator" IC came to an end. Silly me, I thought it REALLY was an anomaly, and I'd never quite see the likes of it ever again. After all, back then, the motorized ALPS pots were still Kings, and I didn't consider that tin-eared engineers would see garbage-sounding chips like these as an "improvement" over more expensive (I should have taken that clue as hint, right there!), and limited-lifespan eventually-noisy motorized potentiometers.
I got out of audio for a time, I've been back into it for the last 2 or 3 years, and as you can tell from my rants I'm experiencing quite a bit of culture shock, both from the stupid-tech & sticker-shock aspect of the current crapnology.
Lately I've been attending a few audio shows, and have chaperoned some friends on equipment-sniffing forays & have auditioned a smattering of new, laughably-overpriced Hind-End ARC preamps like the Ref3 (same sound), SimAudio, Ayre, Spectral, Linar, Pass, Prima Luna, Bel Canto, Mark Levinson, Anthem/Paradigm, and a few others.
Now that my ears are accustomed to that fake-neutral/no low-level detail sound, I can hear it in ALL the components that use this ladder-DAC crapnology, and that's all there is to it. Why did Ayre go to the clunking & hideously-expensive electro-mechanical rotary attenuator with discrete resistors in their top preamp?
Rick sez: "I dunno!"
Why did Spectral go ape-do in designing an over-the-top mechanical potentiometer in their DMC-30SS?
Rick sez: "I dunno!"
Why does Prima Luna insist on the motorized pot when their cheap chinese-made stuff would be cheaper still with a ladder DAC in it?
Rick sez...
ARC has this "synthetic" and uninvolving tonality. Levinson now has it. Bel Canto has it. SimAudio has less of it, but...
Whose to say whether these things are being used in the analog domain or not, when they're DAC's, which are nothing if not digital by their very nature?
What kind of DAC has networks of REAL resistors in it, and if so, why aren't the actual resistances specified (maybe they are, but I remember ambiguity even with this spec!) or readily able to be tapped into? And even there WAS real resistance in the chip, what quality of resistive element are you going to get on a microscopically-thin ceramic substrate, and what kind of wattage/temperature coefficient/voltage coefficient performance are you going to get?
Bottom line:
1) They sound like crap, every which way I've heard them used so far.
2) If it's a DAC, and it walks like a DAC, and it quacks like a DAC, and it smells like a DAC...then the only way it's outputting an analog signal from an analog input is if all the King's horses & all the King's men are taking the analog signal and making it digital again. Oh, but I do remember another piece of missing data: sampling rate & word length! What IS this thing???
3) If you have ears to hear, which you probably don't, along with the preening bright-light engineers at Harman International, McIntrash, Bel Canto, Chord & ARC, what compelling reason would you have to use a lousy-sounding part other than "it has lower noise" (a good tin-ear justification if there ever was one) or "it integrates better with microprocessor control & system displays" (ditto).

In a really well-designed piece of equipment like SimAudio, maybe the sonic compromise is minimal, and you're catering to rich lazy idiots who'd rather build up the lard stores on their arses than get the absolute sound anyways. Idiots that think their hard-drives sound better than a CD player (anyone else notice what a fallacy THAT is?), even when they ripped the file from disc to begin with!
If you start off by using & listening to substandard/sub-optimal sources, then obvious sonic degradation sounds rather less obvious, and the compromise is even smaller!
Of course this all a matter of degree.
Like Jonathan Valin, whom I otherwise think is an apologist for the consumption habits of Marie Antoinette (as well as his mentor, a certain HP), I feel STRONGLY that there is NOTHING in digital, 24/192/DSD and probably up to infinity, that rivals the experience and data density of GOOD analog.
If you are someone who doesn't, then excuse me if I come to the conclusion that you really aren't trying to get the absolute best sound possible that you can afford. In that case, the logical conclusion is either:
a) You are a lost soul, an audio loser, doomed to twiddle knobs and admire shiny faceplates, drool over spec sheets, and I'm sorry for you because you have no concept of the emotional ripoff you've signed on to or
b) Good sound doesn't really matter that much to you, you may like it but you're not that passionate about it. In that case, a nice set of $10 earbuds and a decent-capacity micro-SD card in your iPhone and you're good to go. If this is the case, and this is otherwise a perfectly valid lifestyle choice in my book (and you're in the 99.99 percentile of humanity and I accept defeat when I'm so vastly outnumbered, if not outgunned). However, you shouldn't be lecturing others on lowering their standards just because YOU have hair in between your front teeth...
In which case, do not pass go, do not collect $200, go straight back to option "a"...

In closing, I'd just like to say that being a Blowhard isn't so bad.
It beats what most other people are doing; which is sucking, hard.
You should try it some time. I think the change might do you a bit of good.

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