@MRHifiReviews Thank you! Good to know. I’ve had it for just a couple of weeks now, definitely within the return window - just wanted to check before sending back.
@SenyorC yessir! Same cables, same location. Tried with multiple DACs and sources also, just to eliminate that as a potential issue…to no avail.
@antdroid I am! RCA > 1/4in TRS cables. That’s good to know, maybe not worth RMAing if it’s a known issue. Thanks for your input!
No worries!!! I never got any noise or digital noise or hum while hooked up to my desktop speakers as a preamp so it seems strange to me that you are getting it. 
Brilliant! That’s good to know. Now to debate sending it back or just dealing with it… 
Who did you purchase from? Would it be a huge headache to exchange?
Yea its kind of annoying “feature” of the A90.
for more info check this thread from the designer of the A90
Purchased from Apos, would be pretty easy to get exchanged. I’ll probably end up doing that - I just don’t like being without my gear. 
Interesting! I’m no electrician but that kind of makes sense to me. Haha. If it’s a grounding/earthing issue, I might just end up using a different amp for my pre. Appreciate you linking this for me!
Shouldnt be a problem if you use XLR, though you should probably test it first
So if the amp is connected to the DAC via XLR no audible noise is what you are saying?
Yes. shouldnt have noise with xlr.
Sorry, I think I misunderstood. I’ve got my amp connected to my DAC via XLR, but I have my monitors connected to my amp via RCA. But I would assume the grounding issue would still persist.
Ok then @jolley there may be an issue with the unit as I had mine connected to the DAC via XLR and to active speakers via RCA with zero noise. Out of curiosity have you tried different cables and what’s the volume level on the active speakers? Sorry if you already said that. Also what is around the active speakers and headphone amp? Sometimes other things can cause noise interference issues just a thought.
There may be noise going either way using RCA. It’s going to vary on whats connected to it.
That makes sense… I have tried different cables, and had the same outcome sadly. My speakers are set to a gain of 5db (out of 10 total), and the noise seems to fade at about 3. They’re just a tad bit to low to keep at that level. And I’ve got my full desktop setup around it, so a desktop PC, monitor, multiple amps and DACs, wireless peripherals, tons of things that could (potentially) cause noise. What makes me point to the A90 specifically, though, is that I don’t get the noise when connected to other amps. Super weird! Appreciate your help walking through all of this with me!
I’m going to plug the monitors in with XLR here in a bit and see if the noise goes away. If it does, I’ll know it was the common grounding issue - and that will be good enough for me! I appreciate your help with this.
I wasn’t quite sure where to post this - please move if needed! 
I just purchased a Topping E30 DAC/L30 amp stack (seems like a great little combination so far very impressed with my HD600’s!) but when I first turn the E30 DAC on connected to the Raspberry Pi 4 running Ropieee it displays flashing DSD 45.15 then 22.57 randomly - does anyone else have this with a Topping DAC and Pi combination? Once I start a track playing through Roon it locks on to whatever and all is very ok from then on. Just wondered if it’s a faulty E30 or a recognised characteristic of the Raspberry Pi 4 with some DACs?
PS. I have never played any DSD through the Pi (or anywhere for that matter!)
Help me I’m lost. My soon to be 73 year old brain is fighting to keep up with the digital revolution. My quest is for portable HD music for cheap. My budget just doesn’t allow for mega dollar Daps.
I subscribed to Amazon Ultra HD music which works, as far as I can tell, with both my Dell laptop and tower. also with my iphone using a Sonata HD Pro DAC. After much searching, I found an LG V40 ThinQ, open box/new for dirt cheap. Many sources tout it as a great DAP. Quad DAC, high power amp and a headphone jack. not to mention, AptX and LDAC blue tooth support. So far so good.
Now for the bad. Now I find Androids resolution limiting combined with Amazons proprietary encoding hinder my attempts to do what I set out to do.
I thought that the Onkyo music player might work but it can’t decode Amazon.
I know you may ask, why not just use the iphone? Because of needing to line up 3 or 4 adaptors to playe Hi-Rez. Iphone also has limited storage and no HQ Bluetooth.
Anyone have any ideas?
Les
I found this article about LG V40 ThinQ sound options and settings.
It has a lot of info but seems like answers to your questions are in there somewhere!
Thanks for the info/ NickZ. I have seen that article before and it has a lot of info.
However, it still doesn’t solve my issue. For instance, after checking all the settings available to me, I still have 24/48 as device capability. I just played a song with wired headphones, Amazon info says: Track quality 24/192, currently downloaded at 24/192 and device capability is 24/48. This is what I can’t find a work around.
As I said. Two Windows computers and an iphone with a Sonata dongle will all play at full resolution, just not this phone. I guess I wrongly assumed that having the ability to install the Amazon app would give me Hi-Rez playback. Apparently, the Android operating system quashes that. I have searched (in vain) for an app or player program that can play Amazon at full fidelity but I have not found one.
Les
I don’t know squat about your configuration, especially since it’s a DAP, but is UAPP a possible work around? It makes a difference on my Android 8 tablet.
I expect this to be a useless thought.