USB to PC chassis ground ? (noise) - The biggest change ever !

[PeterSt]

Hi Arvind,

Very good that you ask;
No, down is always On. On in this case means : (ground) connected.

Ok ?

Best regards,
Peter

[JohanZ]

No, down is always On.

Seen from the outside to inside:
1. Display.
2. Power to DAC section (unrelated to power supplies and USB).
3. (ground) connected.
4. DC Offset Check (metering in the left leg). Needs 9V battery to be connected.
5. 705600/768000 input. Windows only and when player supports it (XXHighEnd, HQPlayer).

I've always trouble to memorize these buttons! 

[arvind]

Hi Peter,

Attached is a picture of the switches. Is this the correct position of sw#3 after isolation? Switch #1 is on the right of the picture.

Should I expect change in DC offset values from the std values.

Best regards,

Arvind

[PeterSt]

Hahaha !
A bit hard to see in this large picture, but nice photo !

So your #3 is Down, meaning On, meaning ground wire is connected. This is NOT the idea with the NOS1a (however, everybody can decide for himself, of course). So with the NOS1a (not the NOS1) the ground wire better is not connected because now the isolation is complete. Thus, the "a" is isolated and with the wire connected, the connection is there again via the back door (the interlinks).

Thus, #3 should be Up for the "a".

That we also isolate the Silverstone is something else, but that is consistent with this.

That we next also use an Intona Isolator is unrelated (to above meant "consistency"), that is, as far as I can tell or thought about.

Ok ?

Regards,
Peter

[arvind]

Hi Peter,

I will disconnect the black wire in the NOS 1a so will keep the #3 up ( not as in picture) & give it a go.

Meanwhile what changes should I expect in the DC offset values as compared to std values?

Thanks.

Best regards,

Arvind

[PeterSt]

Meanwhile what changes should I expect in the DC offset values as compared to std values?

Sorry - forgot to answer that;
None.

I will disconnect the black wire in the NOS 1a so will keep the #3 up ( not as in picture) & give it a go.

That switch accomplishes that disconnect.
Up = Disconnect.
Down = Connect.

There is nothing else, except for that wire itself. Cut that and the switch is useless.

Clear now ?
haha

Peter

[arvind]

Thank you Peter. I am going ahead with the isolation at PC as well as the NOS 1a.

Let's hope it improves the SQ.

Cheers.

[PeterSt]

Arvind,

I will disconnect the black wire in the NOS 1a so will keep the #3 up ( not as in picture) & give it a go.

I read this again and suddenly it reads differently ...
I think I must apologise because you were proposing it correctly. It is just a langue matter ...
(and what I read in it at first, was that you also were going to cut the wire)

Regards,
Peter

[arvind]

Hi Peter,

There seems to be some issue with the DC offset values:

Std values -4.6/-10.3
Not isolated -4.8/-10.8
Not isolated with music playing - no data available
After isolation without music playing -5.2/-11.2
After isolation with music playing fluctuates wildly -4.6 to -6/-10.2 to -12.

Is this normal?

Best regards,

Arvind

PS: I have isolated Silverstone as well as NOS 1a.

[PeterSt]

Arvind,

About the music playing : that is normal !
... and now you can also learn what a blocking capacitor would do : hold back of that low bass information (because that is what close to DC is).
So what you see is the bouncing of the wave, but mind the refresh rate of the meters (1/3 of a second IIRC). If you watch it, especially with more "pumping" LF music, you can see it fluctuate on the beat.

All your other values are perfectly normal and that small difference you noticed I call "no difference" (technically there is a small difference of course).
Also don't underestimate the difference between cold and already 30 seconds later (now On) and 5 minutes later. And that each year of "burn in" also creates 1/10th or so.

Really, all fine !
Peter

[briefremarks]

I have one clarifying question.  I have the NOS 1a.  I do not know if the USB card is isolated since it is an XXHE PC that I got from the previous owner (Joel).  I will open up the PC and check, but my guess is that it is NOT because the XXHE PC does not ship that way and Joel did not do anything.

Is it safe to have Switch #3 UP (disconnect).  I was doing this until one day I had a very loud BANG, music stopped,and when I checked the DC offset the meters were blank.  I had to restart everything to get going again, and assumed that maybe this was related to Switch #3 being UP and the USB card not being isolated. 

But maybe it is not related at all.  It certainly made me nervous though because the BANG was quite loud, and the only time in my life I have heard this before is when DC went straight through to the speakers and fried the drivers.


Ramesh

[PeterSt]

Ramesh, easy enough ... if we did it, it will look like you see in here : Re: USB to PC chassis ground ? (noise) - Bracket

I'd say that when #3 is Up and normaly connected to the PC (not isolated there) and the DC Offset reads fine, that first something needs to happen "externally" before the DC Offset changes.
Anyway the only case we know of is Brian's (boleary) and he responded in that other (?) topic somewhere, last week IIRC. But as far as I know he did not suffer from any "bang" as such, but from instable DC Offset (wildly varying) because of a lost ground connection (the latter is what I envision with it). Can be PC shut down or USB failure or something else in that area. To him it happened at night, while he was sleeping.

I'd also say that when this happened to you, you first did something yourself (making "connections" somewhere), OR you did not pay attention to the meters in the first place (one time per boot-up (or down !) of anything in the chain is sufficient) and with a fairly large DC offset to begin with, you hit the ceiling of the voltage rails during playing.
Thus, say the voltage rails is 5V which normally is needed to play within (signal varies from -5V to +5V and is controlled to be within those limits). Now you have a DC Offset of 1V and the signal still requires 5V, at some stage. Regard 6V necessary now, which is not available. Now there is a large "clip" which can be regarded square (sine (sinus) of the voltage is cut at the top). This is a kind of bang or loud tick in itself and it can cause the amplifier to react strange. And *that* can cause the real bang. Hey, in my view.

Regards,
Peter

PS: If you can hear lights switch on through the speakers, or a fridge and such, check for a missing ground in your audio somewhere (NOS1a not necessary ).