It seems not logical: they use one switch by step, the same for each, it is not like DACs. So i do not see why distortion wouls change with position of the attenuator. With level of the signal, yes, as MOS are less linear at high level.
May i ask-you the same question ? Can you try to describe the differences you found between all those solutions, on a subjective point of view ?
One of the reasons ADevice's converters (AD1955?) won me over - just with the spec sheet - is they had the confidence- the guts - to spec the thd at -60 input !! Not just at 0 level.
Thx-RNMarsh
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PGA driven via 33R direct from previous stage (unity gain follower with OA, distortion at this input point was 2 orders lower than at output). Sound diferences against MDAC or relay attenuator -less resolution, something as "sound smog", less details and missing of something that I call "silence between notes". It is difficult to describe with words, subejctive impact can be different. And look at block diagram for PGA in datasheet, here are for sure more switches in action than one by step. Input divider, and feedback network.
Hi,
If you would convert the chain length strength to equivalent THD values and sum them you would see your error.
Well, there is two switches, i believe, one in the feedback loop cancelling the input one's distortion. They use-it to increase the gain of the amp between 0 and +15dB.
Thank-you for your answer and description, BV, clear enough, and you describe all that i do not like. Strange that i do not experience the same thing.
Just my twoo cents to say that distortion rarely add, because they is not always phase coherency. They can even cancel themselves.
Yes, it is very strange too. I was VERY suspicious, the first time i experienced PGAs, as i am with unknown OPAs. And i was agreeably surpised. Very strange, as i believe too the BV's impressions.How did the Levinson measure so well and win the, ahem, listening contest?
Something need to be clarified.
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I'm pleased to see you use that term, "granular" -- not one I use myself, but it nicely encapsulates the audible impression of the type of distortion that infects most systems, and which one must work tirelessly to eliminate. And, of course, switches and pots do a nice job of adding this flavouring.
People talk of sound being "granular" - that's audible distortion; and also of being "smooth and sweet" - that's one lacking distortion ...
Frank
Err.rh! As ALL properly conducted Blind Listening Tests on Bandwidth Limitation using evil recorded stuff has resulted in UNANIMOUS preference for Band Limitation (among those who can reliably tell the difference) , its obvious you have to ignore everything said by true golden pinnae and rely only on the Golden Pinnae who's ability to detect differences miraculously disappears when they can't see the price tag, label, Unobtainium, virgins bla bla.
Da Golden Pinnae scorn Double Blind Tests cos they often come up with null results on their virgin crafted Unobtainium items. But Double Blind Tests DO come up with positive results .. sometime unanimously; as with Bandwidth Limitation.
Here we have a device that when put into the appropriate place in the signal chain, actually makes things sound better! And this 'improvement' is detectable without having to see whether its in place or not.
I should sell such a device for $10,000 (1/2 that of Blowtorch) but refuse to conduct any measurements (except for Double Blind Listening Tests) or reveal what's inside. After all, it actually makes things sound better unlike other Golden Pinnae rubbish.
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JC, can you tell us your experience with evil digital/integrated volume controls? Some people have been good enough to publish their results. Have you similar data? Or even the Hirata & Quan measurements that you tell us are so important. If you have had bad experiences, what objective reasons do you think caused the poorer sound?
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Pavel, I'm still interested in what you would use for conducting an Audibility of Bandwidth Limitation listening test. If its all your own special stuff, so be it.
But I'd really like to know.
I know what you're saying, but that is not the point that I'm trying to make. Of course, THD values will sum in a certain mathematical way -- oh, for it all to be so simple! That's why I used the strength figures posted, to emphasise the key relevance of one, single "THD" figure. If you watch the conversations here there's a wide chasm between precise, theoeretical underpinnings to how people design, and their measurements to 4 significant figures of the performance thereof ... and, then, their statements to the effect that, I didn't like how the end result sounded, or a whole bunch of people preferred this other way! There's a huge black hole in the middle of all this, a murky, sludgy mud of confusion and lack of fuller understanding.
THD is a pure, "scientific" measurement, it tells you nothing about whether you'll like the effect, or send you out of the room with your hands over your ears. Which is the key to the "problem": it is of no relevance to your hearing if every component has better than -120dB distortion by every measurement, but for one part that you've ignored, are not aware of, which is injecting -60dB distortion of an exceeding obnoxious nature. The system, no matter how expensive, how well engineered in every other aspect, will be a failure for the person who has bought, or assembled it.
Frank
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BV:
You're putting out some interesting info.
I am curious what you think of the approach used in the Ayre K5xe mp: "good" analog switches to select resistors for the various attenuation settings.
mlloyd1
You're putting out some interesting info.
I am curious what you think of the approach used in the Ayre K5xe mp: "good" analog switches to select resistors for the various attenuation settings.
mlloyd1
You are exactly describing the volume controls we are talking about.
The main difference would be the resistances used in integrated circuit: Silicon, instead of discreet thin film. But they pretend to have achieved a special implementation to cancel the known distortions of silicon based resistances. And, with the care they had put in this IC, i believe them.
I don't think we are talking of the same thing. Used as it is supposed to be used , DACs use a R-2R network feed by a DC to create an analog signal from the digital one used to commutate those R-2R with MosFet switches.
Of course, some had the idea to use them as volume control, replacing the DC by the signal, and the digital signal by the volume control. But neither the switches, neither the resistances are optimized to deal with AC signals. so i do not see any reason why i should work better than a dedicated circuit, optimized for the purpose.
But may-be you where talking about tuning the volume in the digital world ?
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