For a plethora of information on noise when using the DS Jr. without a preamp, please see the following post and included links: clicky
Thanks Elk. I tried the link from my phone but it didn’t take me anywhere.
Thanks, Brodric. And FYI, having to occasionally reboot the DSJ does not fit my definition of “working”. I’m all Apple/Mac these days. In my home office I have a MBP connected to a 27" 5k monitor that is my primary computer (and is connected to my audio system). I also have an iMac 27" 5k I use. Both computers can run Windows 10 in a VM, but I seldom use it. Mainly when I need to use MS Visual Studio or MS Access. So, my system HAS to work (reliably) in the Mac OS X world. BTW, do you think this comm issue not being resolved means that the DSJ is not really designed to interface with a Mac? I would think that’s a pretty major issue for people wanting to use the DSJ like I do.
I’m very sorry, I left the post with a broken link - far from useful. It should work for you now. If not, please let me know and I’ll fix it or try a different method.
This fact about the USB port on the Mac has been regurgitated many times on this forum, so my question is why a Mac computer and it’s USB port going to sleep is a DSJ problem and not a Mac problem? Is the problem also solved by re-booting the Mac instead of the DSJ? If so then it is not strictly a DSJ problem.
The problem is not resolved by re-booting the Mac, it is resolved by re-booting the DSJ.
My Esoteric has no connectivity issues with the Mac at all. But the DSJ does.
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So your saying you’ve tried re-booting the Mac and it didn’t work?
There hasn’t been much complaining about it, so it probably isn’t getting much traction as an issue to be fixed. The DSJ Mac connectivity issue manifests itself in both my old MacBook, and more recent MacBook Air.
Correct.
My DSJ is working without a problem 
It’s my second unit, but it’s worked flawlessly since February.
I will say that the hissing noise was there with my PS Audio DLIII when connected “directly” to my power amp via a passive pre-amp - meaning it was being sent through a glorified potentiometer as a volume control. Never saw the hiss as a problem - but never had speakers more efficient than 92dB (currently 88 or 89dB) - and wasn’t necessarily intending to complain about it, rather, find out whether it was a known behavior. It never affected my music listening. The DSD (Sr.) has a lighter hiss when connected to my power amp. Probably due to the type of digital volume control they are using.
I don’t see it as something to fix, given that they do sell pre-amps and we’re not necessarily using the DSJ and DSD (Sr.) the way PS Audio intended - rather, a kind of workaround from having to buy a preamp. For example, you can’t use any non-digital sources this way if you’re using a PS Audio DAC as a preamp, but you can if you buy one of theirs or someone else’s. That said, PS Audio’s preamps PROBABLY end the hiss “issue”.
The DS Sr has a 6dB quieter analog noise floor than the DS Jr - it achieves that by having four copies per channel of the digital switch and analog filtering which join at the output transformer. The DS Jr only has one copy of this circuitry - that’s one reason for the price difference between a DS Jr and a DS sr.
Invoking the attenuator lowers the noise floor by 20dB.
If I’m not mistaken, the Junior also does not use a transformer at the output. It’s coupled differently, maybe just the low pass filter?
The DS Sr uses a passive output filter that includes a transformer. In the Jr, an opamp takes the place of the transformer.
Both have a passive output section driven from full scale digital outputs. This differs from most DACs which instead take a low level current output, convert it to voltage, and then amplify this output with opamps.
This is significant. In the DirectStreams, any noise on the output rails is filtered out by the output circuitry. In a typical DAC, the noise on the output rails is amplified by the output opamps.
Ted has additionally noted:
“There are opamps, but they aren’t being used for audio, per se, they are used as digital switches. That is they are the devices that select one power rail or the other depending on the digital input. Also they aren’t audio opamps, they are video opamps so that they have the bandwidth to deal with the 5.6448MHz or 11.2896MHz inputs.”
It also degrades sound quality, as Paul has admitted (in contradiction to the owner’s manual), on another thread.
Just like some systems sound better with a preamp and others don’t, the attenuator is a quality resistor (just like the others that the signal went thru in the DS), in some systems it may degrade sound quality, in others it clearly increases it (especially if it gets rid of noise that’s bothering you.)
In my system the attenuator both got rid of the noise that bothered me and made the sound “a bit lifeless” to quote Paul.
I understand, but that’s not a universal experience.
I can hold my finger on 4 seconds on the back left RCA output. 124*C…IMO too hot…but within operating parameters… according to who? I think I am going to put a fan on it
That’s my experience as well. Very hot to the touch - catches you by surprise.