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PostPosted: Sun Apr 30, 2017 9:53 am 
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I'll end up reading this a few times over, but some of you younger folks might find it easy going.

http://www.diyinhk.com/support/digital- ... ontrol.pdf

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PostPosted: Sun Apr 30, 2017 10:10 am 
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It's simple math...the limited number of bits causes a rounding error by truncating the number of decimal places. More bits equals more decimal places and fewer rounding errors.

Every computer audiophile should read this. Since digital isn't allowed to clip anyway there's no reason for a digital volume control if an analogue one is present.

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PostPosted: Sun Apr 30, 2017 10:44 am 
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milesian wrote:
I'll end up reading this a few times over, but some of you younger folks might find it easy going.

http://www.diyinhk.com/support/digital- ... ontrol.pdf


Good article - thanks for pointing this out - I've often wondered with all the difficulties with analog volume controls
and if digital ones were better.

For analog - carbon based variable resistors can get noisy.
Amoung the better ones in this category are Alps and Audio Note.

But audiophiles spend significant money on stepped volume controls
with metal film resistors - the price on stepped volume controls starts at $100 ... and go up
.
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PostPosted: Sun Apr 30, 2017 11:03 am 
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There are also folks building auto former volume controls as well. Take a look at www.intactaudio.com for example....


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PostPosted: Sun Apr 30, 2017 11:25 am 
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...and light-based controllers, or attenuators [supposedly THE thing]
See:
http://diyaudioprojects.com/Solid/DIY-L ... ttenuator/
and so on


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PostPosted: Sun Apr 30, 2017 1:13 pm 
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natedog wrote:
...and light-based controllers, or attenuators [supposedly THE thing]
See:
http://diyaudioprojects.com/Solid/DIY-L ... ttenuator/
and so on


Thanks for pointing this out - Looks interesting - as usual with many projects sourcing the components
and FINDING the TIME is the tough part.

However, looks like digikey still sells the optocouplers.
https://www.digikey.ca/product-detail/e ... ND/5039808


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PostPosted: Sun Apr 30, 2017 1:28 pm 
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natedog wrote:
...and light-based controllers, or attenuators [supposedly THE thing]
See:
http://diyaudioprojects.com/Solid/DIY-L ... ttenuator/
and so on


There has been at least one commercial preamp that used that technology (can't recall the name off the top of my head)...

I always wondered though, if you could end up injecting noise into the signal, if the led light source supply was noisy. With the older light bulb style couplers, the thermal mass of the filament would remove any noise, but if you're using a high speed optocoupler, you would think the potential would be there....

Cheers, Dave


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PostPosted: Sun Apr 30, 2017 1:55 pm 
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Reading through forums - for stepped attenuators, its seems the Khozmo and Goldpoint are highly regarded.
But they don't give them away.

No one seems to dispute that a stepped attenuator is a step above the best variable resistors.
For a clear consensus to occur in audio discussions is pretty rare.

.


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PostPosted: Mon May 01, 2017 3:09 am 
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Here's a preassembled light attenuator mentioned in one of the above links.

http://members.optusnet.com.au/~georgehifi/

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PostPosted: Mon May 01, 2017 4:48 am 
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There's another on called "The Truth" that is supposedly spectacular (tons of great reviews out there): http://www.thehornshoppe.com/the_truth_pre_amp.html
B

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PostPosted: Mon May 01, 2017 4:56 am 
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In the past I have lived happily with digital volume controls in a DAC direct to a power amp. At the time I was using all 16/44.1 material.

The advent of 24 bit material makes a 32 bit digital volume control the way to go in that scenario, but they are not that common. Out there for sure, but not that common.

Currently using an old NuForce preamp with an excellent remote stepped analog volume control.

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PostPosted: Mon May 01, 2017 6:26 am 
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As long as the analog volume control has a noise floor better
than the DAC noise floor, the analog one will win

Conclusion:

Analog volume controls easily outperform digital, unless the
digital control has access to the data path of the DAC
(ie is internal to the DAC)

Exquisitely well designed analog volume controls can still beat
even the very best internal digital volume controls if they have a
lower noise floor than the DAC itself

The -135dB of the ESS Sabre DAC would need an exceptionally
low noise analog volume control to beat its internal digital one

The above is from their pdf (the OP's link)

a point to remember, is that the output QUALITY depends on the quality and implementation of the poteniometer system in analog terms, and in the digital terms it still remains in the hands of the analog pathway of the digital system and it's POWER SUPPLY.

That, in the end, it is still an analog PROBLEM, in the case of the digital system it's two problems, not just one. It's the digital translation and then an internal analog system and associated power supply.

This is why pure analog, well thought out, still tends to beat the best that digital volume controls can do. $0.50 cents of analog thinking and design (in the digital pathway and analog connectivity to such) vs a few thousand in pure analog thinking and design.

In other words.... there are very low odds that a $5 or $10 chip and it's design and implementation is going to beat out a well implemented pure analog path. In the end, it's still down to a $5-10 chip, in the given digital implementation. Great for financial simplicity and repeatability (making them and cranking them out), but not in perfectionist audio terms.

ESS and those of similar manufacturing focus are into the "cranking them out by the 100's of thousands" - end of the pool. They can only do so much and that involves making sure they can sell product and that means making them CHEAP, and that needed focus cannot (in all known attempts and designs) serve perfectionist audio. The two simply don't meet.

There will be those who disagree, and some digital volume set ups are well implemented, meaning it might be good enough for that particular person. Generally, it will be someone who uses a server or whatnot, and that is the most reasonable and expedient way to do things, both in simplicity... and in financial terms. From analog to analog and in some digital implementations (servers based, etc) analog after the dac may well be the best available, for quite some time. You'd have to make multi-kilobuck half 'extreme grade analog' and half dac chips, in order to fix this issue and no one is doing so. Nor is anyone ever likely do do so, considering the $1/4 million dollar cost of cranking out a test run of sample chips.

All done for a market that wants to pay no more than $0.50 a chip, and then maybe 10k people at most, that MIGHT pay $200-300 or whatever for a properly done chip. Plus the extravagant cost of implementing that chip for audiophiles.

They'd never know if they made a audiophile 'home run' with the given expensive chip, until they tried spending the 1/4 million dollars first. Then the shaky proposition of trying to market such an attempt of a chip...to fussy and problematic audiophiles. Not gonna happen any time soon.

In the end, it's an acceptability of quality issue in what is available to us right now... for the individual involved.

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PostPosted: Mon May 01, 2017 1:02 pm 
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I checked one of the links and had a nice email back from George Stantschef in Australia. He sells his unit for $525 Aud, Plus $35 for dual mono option. If anyone is interested pm me and I'll forward his communication.

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