DAC USB Hum

Sorry everyone, but I got my 2 inputs wrong at the amp.  It's the Zen/USB that quiets down when the DAC hits warmup.  The CDP/RCA is the one that doesn't change after warmup.  So perhaps someone can explain why warmup on the DAC silences the small hum from the Zen/USB.

So what did taping do for that if you know/can speculate?  Did it insulate the ground out and therefore break up the ground loop difference?  Not sure I asked that right.  I can hang with acoustic wave and wave theory, some DSP (geophysics degree) but EE makes my head hurt!

The hum from the DAC itself does not travel throughout the chain to my speakers. Last night I taped over the Ground Pin on the USB cable. No hum from the DAC. I ordered an iFi USB isolator which is supposed to cancel the hum. 

@cetla416 , I have the same streamer and Orchid DAC pair (super happy and impressed).  Connection is of course USB via a Supra USB cable.  For comparison I also have a CDP and phono pre-amp out  connected via the RCA inputs.  For this test all units' PCs were kept plugged and hot, and the interconnects kept in place mainly for my ease and the simplicity of variables.  I cannot confirm without work, all of said components or which if any, share the same power bank and ultimately which outlet on the same wall (same to breaker box though).  I ran out of them on same/same and may explain the TT hum.  So here us what I observed as far as hums. 

The turntable/pre-amp has the most.  I think I can run that down (different banks/outlet than amp) but it's not a bother to me as Im about 5% vinyl these days.  The CDP/RCA is the least and WAAAY less than the TT.  As a reference the volume on my Raven is at 12:00 and takes being pretty close to speaker to hear it. 

On to the Zen/Orchid pair.  When the Zen is on, and the Orchid is both plugged in and in warmup mode, the hum is the same from the ZEN/USB as the CPD/RCA. Again, way lower than the vinyl.  Interestingly, when the Orchid DAC warmup is done and there's an audible click, the hum drops considerably for the RCA/CDP and is really hard to hear without ear in front of speaker.  It remains unchanged for the Zen/USB.  Using a very sophisticated technique of my phone corner on the baffle between the drivers and some freeware, I get that drop as 57db to 47 db (the house central forced air was also blowing) for the CDP/RCA pairing.  Someone smarter than me could perhaps comment on this change at warmup.

So to summarize the hum is acceptable (to me at least) for the Zen/Orchid pair and the CDP/RCA when the Orchid is warming up  OR running,  but becomes nearly inaudible for the CDP/RCA once it reaches running status. Does this confirm the USB's hum issue and would those filters make the USB circuit as quiet as the RCA's?

Maybe this helps, maybe it confuses the situation.  Just a field report from a user with same.  Your post and possible cure may ultimately make mine better yet! 

Hello cetla416!  If you decide to replace some of the components in your system, look for units that allow you to use optical cables. I solved a hum problem in my big system that way. Good luck otherwise!

Don’t they make USB cables that only work one way?

@carlsbad2 you sure got that right! 
This is what gives USB a bad reputatiom among those who spend much money to avoid it at all cost, poor implementation in less espensive DACs.

@fuzztone some are not born diagnosticians like we are.😎😎 

@jacobsdad2000

Of course sir, maybe I should have mentioned it.

Easily observable by moving the box and cables around.

I guess I assumed that maneuver is much easier than posting here

This is what gives USB a bad reputatiom among those who spend much money to avoid it at all cost, poor implementation in less espensive DACs.  My Innuos Zenith MK3 is designed around USB and performs great with Chord DACs and MScaler.  

There are a lot of popluar Chinese DACs now that aren't all wine and roses.

Jerry

@fuzztone it can also be a shielding issue in either USB or LAN cable.

Hum is a grounding issue.

Op also may want to look at the quality of the USB Cable being used. I have has great results with DH Labs as well as Supra Excalibur USB cables. Supra is a bit less expensive and would look into them. https://www.madisoundspeakerstore.com/computer/
https://silversonic.com/products/

@jacobsdad2000 Thank you for your kind words.

I do use those hospital grade Ethernet isolators also but as much for surge protection as anything else. Based on readings from tech journals, it seems the best option for inside a building. I have a couple of long runs that end in expensive gear. The longer the run the more likely you are to have an induced surge from a near by strike.

I can't say that I've ever heard them make an audible difference yet. :)

@erik_squires I am a firm believer in EverStar Galvanic Isolators for LAN and they do work! I appreciate your contributions. 

fuzztone- reread my post. You can’t get any further downstream than my speakers. At what point am I confusing my Streamer from my DAC? I make it a point to ignore your posts. The other responses are very helpful as they understand my issue pretty easily. Thank you erik_squires and jacobsdad2000. I have a few devices on order.

A DAC is not a streamer. A few DACs have built-in streamers - not this one.

What is a "slight" hum?

Does it show up in the analog downstream during a listening session? Is it a recent phenomenon?

Hum is a grounding issue.

@jacobsdad2000 The isolation chips are so cheap, like under $2 in bulk. It's a shame.

Some DACs do have galvanic isolation but they are at the higher end of the scale. One company is making DAC’s from Panzerholz  and other wood with inertial filters. I also use a USB isolator by Wyred 4 Sound. Just for extra protection. https://www.lessloss.com/echos-end-p-218.html

It’s a shame that DACs still don’t have galvanic isolation. Meaning, there is often metal to metal through which can cause both analog and digital effects. It’s rare to see this from a streamer though, the usual culprits are PCs.

In your case you have an analog one and the fix is cheap, you need a USB isolator, though not all DACs work with them.  Usually, they don't need to be powered, but in some rare cases the DAC won't recognize the input unless there's a DC voltage so you may need to get a separate supply:

https://amzn.to/3QQM3oL