How to proceed?

Hi @stuartk 

As you may recall, we have the same integrated amp. Having said that, when my very expensive Sony professional CDT died a few years ago, I ended up replacing it with a  Audiolab 6000CDT. An Audioquest Carbon digital to a Denafrips Pontus ll and XLR to the H390. And it sounds beautiful. I’m not familiar with your DAC, but were you running it with oversampling? Also, is your room treated with sound absorption? 

@stuartk 

Apologies if this was mentioned already, but I would consider trying different interconnects between the Aqua and the H390.  In your A/B tests, that is an additional change you are hearing (with and without the IC's).

Like your Aqua, I too have a R2R dac that uses vintage ladder chips known for natural sound with delicate and not bright highs.  I had sibilance issues of different degrees with a number of interconnects that were well regarded (Audience, Cerious, Audio Envy, Black Cat, others).

Eventually I found the right synergy with Zavfino Fusions IC's (silver and OCC copper).

Adding power conditioning to my system, (puritan psm) and different power cables (triode wire labs digital american) was another improvement in the high frequencies.

As to your original question on what dac designs to consider if you go that direction:  I'd stick with R2R, and look for designs that have intentional focus on a quality output stage and power implementation.

@curiousjim

Take a look at my virtual system page and you will see it is not at all optimal for audio. There is a wall of glass on one side, a tiled hearth, glass topped coffee table, etc. WAF disallows any panels. Nevertheless, my previous system (same speakers + dac, with Wells Audio Majestic integrated and Simaudio transport) was not at all fatiguing and there was not a trace of sibilance. The bass was poorly defined/controlled, which eventually drove me nuts and was the primary motivation for acquiring an integrated known for bass control. The Hegel is, needless to say, far more resolving then the tubey-souding Wells and this aspect, coupled with the Jay’s, which similarly delivers more detail than the Simaudio, may be too much of a good thing. DAC is NOS.

@veroguy

Thanks for sharing strategies you’ve found to be successful. You are astute in recognizing the ICs are also absent from the scenario with the least sibilance and no fatigue. I’ve heard good things about Zavfino. I don’t recall whether they have a return policy. Ditto Triode Labs. I know Jaguar does.

One dac that interests me is Border Patrol, which is very much designed with particular attention to power implementation.

I don't believe you mentioned your choice of digital cable.

@stuartk ...my previous system (same speakers + dac, with Wells Audio Majestic integrated and Simaudio transport) was not at all fatiguing and there was not a trace of sibilance.

...One dac that interests me is Border Patrol, which is very much designed with particular attention to power implementation.

This is a key indicator to me. Since the new integrated and new transport was introduced, the issues you describe started to occur. Also, re-check your path of any new "silver" based cables (power, interconnect) you introduced around the same time. If you have stock power cables lying around, try all together at once.

btw, I own the new Border Patrol SE-I dac, while I agree its smooth and non fatiguing, if I may suggest, I don’t think the dac change alone is going to resolve all of your noted issues. I kind of suspect its a combination of things going on now. Imo, as a test, I’d borrow/swap the amp and transport and [all] cables back out with stock ones all at once. Then go in reverse putting new pieces back in play one-by-one to see if it surfaces again. Worth trying to help understand if you can narrow down a specific culprit (or combination of things) from there. Best of Luck.

@decooney

Thanks for your suggestions. They make sense. Unfortunately, I do not have any unused gear lying around and don’t know anyone who would loan me the gear.

One exception-- I tried my old tubed Joida CDP as a transport and the sibilance was worse.