Benefits of an external DAC

The tube DAC may be different but is not necessarily superior. Did you measure the frequency response?
CD red book is the product of the largest research effort ever into audio reproduction, by one the worlds best physics labs of the time.
The DAC chips inside these modern external DACs are manufactured by a handful of chip makers, and have now all reached audio perfection at very low cost (they only cost a few dollars each if bought in volume). Implementation is straightforward as long as the DAC designer follows the instructions of the chip maker. Hence I think your observations are what was to be expected. I did a similiar test with a range of different DACs (some very cheap) in a system with Quad 2805 electrostats. I was unable to discern any difference.

I have an Oppo 105 and have used it with 2 external DACs, the Bryston BDA-3 and the Mytek Manhatten.  The Oppo is a pretty good DAC but there is no question that the other 2 DACs each best it.

perhaps the rest of your setup is not revealing, or perhaps you do need to go up in price for DACs to start detecting differences 

OP >
One poster already hit the nail.

Try stepping up to better DACs.

Why? The argument on every DAC uses effectively the same chips is a whole other thread. The idea behind this is ‘how’ everything is implemented in any DAC, not just that all are using virtually the same chips.

The biggest aspect to supposedly better DACs is the same issue with nearly every electronic device, its power supply. Period. Well, mainly. It’s the usual starting point for nearly every component’s upgrade.

Better, read, ‘more expensive’ DACs normally will have better PS, and better shielding, more PS dedicated to this or that, etc. reputedly better analog output stages, etc.

In order to hear these supposed improvements it would or does behoove one to investigate at least somewhat the interfaces and ICs being used for connectivity. This includes sincere consideration of stepping up the Power Cable the DAC or what ever else, uses.

7500 HP dragsters don’t get down the track on Street tires. All that Horse power has to be able to hook up effectively to the track, or it’s a severe waste of time and money.

Oppo is a honest to goodness over achiever. You already said your’s was previously upgraded. Hmmm.

I did not experience OMG improvements using DACs until I stepped up from the $2K class of DACs and got into the $3K models. .
It might mean today more than $3K DACs should get auditioned, but there’s been real world gains in digital goods since then. At the end of the day however, its gonna take a fairly good step into DAC-land to boost the sQ, IMO. New models are out that deserve consideration and two of them getting a lot of pub are the Yegersol, and Comet. Both are less than $3K.

To continue running about the $1500 or less DAC playground will IMHO not hand you the results you desire. They will essentially deliver only ‘different’. Different ain’t bad, but its ordinarily not ‘better’.

Bridges are another path people are saying here that aids escalating SQ using either Ethernet or USB interfaces. To my earlier point, each of these gizmos have been said to definitely gain by improving upon their own Power supplies.

Even the Comet DAC has an upgrade option for a better power supply at point of purchase, or there after. Go figure.

Good luck in this venture.

@mahler123

I suspect the Mytek and Bryston DACs you tried are both Stereophile Class A or A+ ?

My suggestion to the OP is to try a Class A+ DAC. IMHO that will yield a subtle improvement over the Oppo. The Oppo is obviously very good value so a lot depends on the OP willingness to spend 1000+ extra dollars to get somewhat diminishing returns. Obviously in the $1000 range the Oppo holds its own.

I’d suggest Stereophile Class A+ in the $2000 to $5000 range and not too expect "day and night" improvement but more of a subtle difference. A difference that can be appreciated by a discerning listener but not necessarily blindingly obvious in A to B switching against the Oppo.

I would also recommend to NOT use the preamp between DAC and poweramp but minimize the signal path - each additional set of electronics risks adding unwanted noise and distortion and Class A+ products will have excellent quality output in their own right.

Wisdom in that last post shadorne re: expectations. IME, there are the step-function improvements that result from moving step by step from mi-fi to hi-fidelity equipment, especially speakers and sources. Also getting the room right. Lots of "Holy Cow" moments during that phase. Lots of fun. This is the "audio enthusiast" phase.

Then the path becomes one of discovering the strengths and weaknesses of what was created in phase one. Some changes are usually inevitable depending on how wisely you chose and frankly how lucky you were re: the extent that changes are necessary. Lots of fallout in this phase so I think of it as the "sorting out" phase, both of equipment and also "the listener" that has now evolved (or fallen away).

Once that is sorted, then comes the phase of "the serious listener", comparing different very-good to excellent source components, improvements in cabling and the quality of AC power, vibration elimination, etc. Differences/improvement is often subtle compared to the earlier phase, but are just as significant to a serious listener as these things then determine whether you created a microscope, a telescope or merely some sunglasses.

All along the way, one learns, or should learn, not to hastily judge changes as it is almost always a mistake.

I do not agree however with prescribing things such as whether or not to use a preamp between DAC and amplifier as there are too many variables in each system and listener preferences, so others should simply be encouraged to experiment and decide for themselves.

Dave