I know this comment was made a long time ago, but I just now saw it, so it’s new to me, and hopefully I can help! I’m listening on Sennheiser IE600 and SpinFit W1 eartips primarily through 4.4 balanced output. I had the W4 before the RU7, and I expected that I would like the RU7 quite a bit more. I have a Denafrips Ares and Topping E70 Velvet in my main stereo, and I use tube-only amps for my phono stage, pre-amp, and amplifier, so it’s safe to say I like a colored sound signature. I prefer very slightly warm to neutral. I like detail, but I am allergic to sibilance, and I will sacrifice detail every time to avoid that harshness. I was intrigued by the W4 having an option to modify tonality to a more laid back presentation with the “Tune” setting of 01, but I have almost exclusively listened to it on Tune 02. I have also been using it with the SDF for the IE600. My general sound impressions are largely the same as in the OP’s comments as well as Torq’s.
When I heard the RU7, I was sure that I was missing something or that the gear or my ears needed time to break in, so I let it play for a couple of days unattended and I did my best to patiently give it a good try. I know I like the R2R sound of my Ares a lot, and I didn’t mind the idea of dropping a little detail to get engagement with the RU7. I know it’s not technically an R2R, but I am ignorant of the actual differences, in any case, it has a resistor network that makes the music. Unfortunately, what I got from the RU7 really surprised me. First, I confirmed that it was not just from playing it on my phone with inadequate power by trying it on my computer on a USB-C port right on the motherboard and had precisely the same audio quality impressions. The RU7 sounded muddy and incoherent, particularly in busy passages, compared to the W4, which I could forgive, but it also brought a marked harshness, actually maybe better described as “graininess” that really surprised me. This seemed to persist regardless of settings I chose. I did detect a little of the extra “naturalness” which I associate with the R2R style DACs in vocals specifically, but it was nowhere close to enough to justify the other unpleasantness in the sound. I just wanted to get the IEMs out of my ears, or better yet, plugged back into the W4 ASAP. I’m really surprised when I hear anyone say that the RU7 has good technicalities in its performance, because my experience of it was quite the opposite. My hypothesis is that there could also be a great deal of unit variation given the precision needed in the resistor matching.
The W4 has been extremely surprising to me, and I have not found many other delta sigma DACs that feel like they can provide the level of emotion I feel from music on the W4. If it is helpful to anyone to see where I’m coming from / compare for your own tastes, I have felt this similar level of naturalness and engagement from the following:
Topping E30 (original, not the II, which I have not tried)
Denafrips Ares, but only when used along with the Iris DDC between it and my mini PC Roon endpoint
Topping E70 Velvet
I have not felt this kind of emotional engagement from the following DACs:
Pro-Ject Pre Box S2 Digital
Audioquest Dragonfly Cobalt - not harsh, actually a little rolled off, but not emotionally engaging to me
Questyle M15 - very close, and definitely the best Sabre implementation to my ears
Shanling UA3 - I was optimistic for this one due to the AKM chip, but it was really harsh to my ears)
Matrix X-Sabre Pro MQA - extremely disappointing - no one wants to dislike the sound of something they spent that amount of $ on. I replaced it with the E70 Velvet and couldn’t be happier with that decision.
Final thoughts on W4, I can confirm that it pairs well with the IE600, as well as LCD-X 2021, Focal Clear OG, and Sennheiser HD 600 (I don’t have a balanced 4.4 cable for this one, but even through single ended, it can drive at levels at the high end of comfortable to me in high gain mode at 85-90 on the volume setting, and they sound fantastic through it). I still like my E70 Velvet and A90 Discrete stack a little better for my desktop system, but I don’t feel like I’m missing a ton when I go on the road with the W4. I cannot recommend this one highly enough. I have sold all of my other dongles. I’m sure that now that I have this one, I’ll never want anything else new again
- it’s totally endgame until it isn’t.