[tacitapproval]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif tacitapproval, one question on your rca jacks. Are they grounded directly to the case or are they grounded to the input ground point on the board?

I actually haven't wired the rca's yet, and have been using a plastic-cased mini-jack grounded to the board input thus far. I am concerned that the rca jacks I have are not isolated from case contact and I need to get some plastic washers.

 

[tacitapproval]

Quote:

Originally Posted by Ferrari /img/forum/go_quote.gif I just want to ask but... runeight has beaten me on that. One remark regarding ground loop breaker: for safety reason, a ground loop breaker should not be connected to the AC input ground (IEC connector).

Thanks. This is good information to have.

 

[runeight]

Quote:

Originally Posted by Uncle Bob /img/forum/go_quote.gif Nice, they are a smart looking case. Is that case tall enough to enclose the valves or will you have to cut holes in the top do you think? Do they come with all any accessories - like feet? How was modushop to deal with?

Uncle Bob you haven't said anything lately about your hiss problem. Is it still there? And have you had a chance to measure voltages?

BTW, thanks for the request to put indicators on the e12. As you know I used them on the compact hybrid. It's a very cool feature.

 

[runeight]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif I actually haven't wired the rca's yet, and have been using a plastic-cased mini-jack grounded to the board input thus far. I am concerned that the rca jacks I have are not isolated from case contact and I need to get some plastic washers.

OK. So the ground wriing is like this . . .

IEC to enclosure ground. Input jack ground to board input ground. Board ground to enclosure ground through ground loop breaker?

Also, have you grounded the volume pot? There is a small ground pad right near the back of the pot for this. You can unscrew one of the case screws on the pot, wrap a very fine stranded wire around it, put the screw back in, and solder the other end of the wire to the ground pad. In case you haven't done this yet it might help.

 

[tacitapproval]

Quote:

Originally Posted by runeight /img/forum/go_quote.gif OK. So the ground wriing is like this . . . IEC to enclosure ground. Input jack ground to board input ground. Board ground to enclosure ground through ground loop breaker? Also, have you grounded the volume pot? There is a small ground pad right near the back of the pot for this. You can unscrew one of the case screws on the pot, wrap a very fine stranded wire around it, put the screw back in, and solder the other end of the wire to the ground pad. In case you haven't done this yet it might help.

That's exactly right, and I have grounded the pot to the board as described.

 

[runeight]

OK. And then when connect the board ground directly to the case the buzz is worse?

What happens if you disconnect the input jack ground from the board when you have your source plugged in?

 

[tacitapproval]

Yes, the noise appears earlier on the pot travel when the board is connected directly to the chassis (not through the groundloop breaker).

I tried disconnecting the input ground from the board and the noise is much, much worse this way.

 

[wiatrob]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif Yes, the noise appears earlier on the pot travel when the board is connected directly to the chassis (not through the groundloop breaker). I tried disconnecting the input ground from the board and the noise is much, much worse this way.

Have you checked/reflowed all the solder joints on the pot (I am assuming it is soldered to the board.) I had a cold joint on my M^3 that had a burst of noise appearing early in pot travel due to torque on the bad joint...

 

[tacitapproval]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif Have you checked/reflowed all the solder joints on the pot (I am assuming it is soldered to the board.) I had a cold joint on my M^3 that had a burst of noise appearing early in pot travel due to torque on the bad joint...

I will check the pot soldering, but I don't think this is a problem. As I mentioned earlier, the noise is coming from the laptop while plugged into ac--unplug the laptop and the noise disappears. Kind of disconcering that it is traveling through the usb cord to the dac and on to the soha ii. I thought using an standalone dac was supposed to eliminate noisy onboard electronics.

 

[runeight]

Quote:

Originally Posted by tacitapproval /img/forum/go_quote.gif I will check the pot soldering, but I don't think this is a problem. As I mentioned earlier, the noise is coming from the laptop while plugged into ac--unplug the laptop and the noise disappears. Kind of disconcering that it is traveling through the usb cord to the dac and on to the soha ii. I thought using an standalone dac was supposed to eliminate noisy onboard electronics.

So it is said about the DACs, but . . .

Pardon these few dumb questions . . .

What is the laptop brick plugged into? Does this matter?

Can you try another brick?

Is the amp plugged into the same outlet as the laptop?

What happens if the laptop AC is plugged in but the laptop is turned off? Or just on standby?

Laptops don't need UPSs (usually) so I assume that none is involved here?

 

[wiatrob]

I always have noise through my USB dac (especially usb powered dacs) when the computer is plugged in to mains. The only way I've found to eliminate it is to use optical or coax connections.

More knowledgeable here may shed some light on things - I think I've even tried it with the amp/dac/ and computer plugged into the same circuit and had some noise. Granted, very little unless I turn the volume up all the way...

 

[tacitapproval]

I have tried plugging the laptop into a different outlet, power strip, no power strip and the noise remains. Amp has also been tried in different outlets.

I don't have another brick, unfortunately.

No noise if laptop is off or on standby, but this shuts down the dac as it is usb powered.

No UPS.

Update:
Now the noise is nearly non-existent. I didn't do anything, other than leave it running for some time now (a property of warming-up?) I can hear it only with iems and not with my HD650 or DT770 all of a sudden. Why would it fluctuate like this? I guess I should't look gift horses in mouths.

 

[wiatrob]

Do you here the 'same' noise with your PMP plugged in as with the DAC? How does the output sound with the PMP vs. no input at all?

 

[runeight]

I don't use DACs from computers so I am far from expert, but it seems that wiatrob's solutions may be the only ones. This is really a ground noise problem and the only way to fix it is to break the ground connection between the dac and the amp. At least that's the only way that I can think of.

Perhaps some others can offer other, better solutions.

 

[tacitapproval]

Quote:

Originally Posted by wiatrob /img/forum/go_quote.gif Do you here the 'same' noise with your PMP plugged in as with the DAC? How does the output sound with the PMP vs. no input at all?

The PMP is nearly black, same with no input--none of the computer noise

Although now it is negligible--go figure.