What is the deal with the ART DIO

It's tough to say which mod will work in which system. Also, mods seem to be system dependant, as cables are. This said, personal experience reported here is irrevalent, unless system parameters, hearing ability, and room acoustis/treatments are consistant.

I've found the modified Di/O to better my DAC costing twenty times the cost of the DAC which it replaced. Muddy bottom end? Loss in spatial info and soundstage anomolies? Not in my system.

I agree that cost means little when buying an audio product. MOST of the time, much of what you are paying for is Research & Development ( R&D ) and marketing, not the actual parts quality of the unit itself. As such, that is why some cheaper products actually blow the doors of off more expensive components. Not only are the cheaper ones typically using fewer parts, they just might be using better quality parts.

This is the very reason why and how Stan Warren, John Hillig, Richard Kern, Ric Shultz, Dan Wright, etc... can make improvements to just about any product out there, regardless of cost. They simply improve the parts quality of the design that is already there and the results are typically audibly better and quite noticeable.

As most of you that have read a few of my posts have seen me say before, buy what you like and what you think sounds good in your system. Don't worry about what some reviewer or anybody else thinks. Even if that "jerk" is me : ) You have to live with and enjoy your system, so trust your own ears. Nobody can tell you better than yourself what you like or don't like. Sean
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A thing I am finding is that if you can find a respectable product and have it Modified you will do better than paying 10-20X as much for some things.
I have a B&K ST-202 that I will not sacrifice unless I need to drive a real difficult load.I think that Class A BIAS'd gear,quality parts,wiring,tweeking and design changes will improve the sound dramaticly!

The ART DIO should sound better than most stock DAC's after modifying!I think it's a safe bet to have a reputable Co. like BOulder do the Mods!Some Mods I think are more critical than others!I think the BIAS toward Class A,Parts and the wires are most important!

Those are my observations!

I would only add that i think that the physical layout of a circuit becomes FAR more critical with digital signals due to their "RF based" nature than it is with other standard line level analogue circuitry. With a chassis the size of the Dio and the limited amount of space that it offers, it would be next to impossible to keep RF from leaking back into the power supply and analogue circuitry. The fact that they were able to actually squeeze a tube in there AND have both a DAC and ADC in it simply amazes me. Sean
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One Tweek that can be done immediately is getting rid of the 9V PSU unit.I had a Variable Ratshack unit I used in it's place.

I do think that having the Op Amp and it BIAS'd to Class A operation would be a big step in the right direction!There seems to be a touch of veiling to the unit that might be resolved by switching out some of the stock components!