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#363948 - 10/05/2015 21:30 Hard Drive Noise When on DC Power
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Anyone seen their units exhibiting hard drive noise over the audio outputs when powered from a pure DC source? The noise goes away when using an AC adapter. It seems to be on every unit I have access to (5) and don't see anything wrong. Obviously something is no longer rejecting noise as it once did. Switching PS controller? Caps seem good. This is a really tough one!

Stu
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#363958 - 11/05/2015 16:20 Re: Hard Drive Noise When on DC Power [Re: maczrool]
JBjorgen
carpal tunnel

Registered: 19/01/2002
Posts: 3399
Loc: Guadalajara, MX
Sounds like a ground loop. Are you testing all 5 units in the same setup? If so, the problem is not likely with the units.


Edited by JBjorgen (11/05/2015 16:22)
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#363961 - 11/05/2015 21:54 Re: Hard Drive Noise When on DC Power [Re: maczrool]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30588
Loc: Seattle, WA
Define "Pure DC source"?

Do you mean connected to a 12 volt battery of some kind? Can you offer more details of the power source in that case, more details of how it's wired up, and, how it's connecting to audio output?

Example of something that might cause a ground loop:
- You have the Empeg connected to a battery power source
- You have the RCA cables connected to some kind of audio amplifier such as a powered speaker system
- The powered speaker system is being driven from a power source that is different from the battery to which the Empeg is connected.
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Tony Fabris

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#363965 - 12/05/2015 14:35 Re: Hard Drive Noise When on DC Power [Re: tfabris]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Sure. 12 volt battery (car battery through cigarette lighter plug) is the source for a powered speaker set up (computer speakers) as well as the Empeg. They are both getting power from a common ground point and 12 volt connection. A powered (active speaker system) should not be an issue as that's essentially what's in a car anyway when you have speakers and amps, I just don't have a way to test it like that.

I was just thinking something like age might be a factor. I originally thought ground loop too but everything that can be made common power wise already has been. I will go ahead and recheck signal grounds.

Thanks!
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#363967 - 13/05/2015 11:18 Re: Hard Drive Noise When on DC Power [Re: maczrool]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Checked the wiring again but still 0 ohms between signal ground and power ground as it should be. This doesn't seem to be a case of a ground loop to me. I've had others complain of similar HD noises appearing in their units so there must be some common cause I'm overlooking.
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#363972 - 13/05/2015 21:55 Re: Hard Drive Noise When on DC Power [Re: maczrool]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30588
Loc: Seattle, WA
I had a problem with my Empeg where I was getting hard drive noise and alternator whine in the following situation:

- Empeg's continuous power wire was hooked up to the constant +12v power from the battery (normal connection).
- Empeg's ignition wire was hooked up to the car's ignition wire (normal connection).
- Amplifiers were connected to constant +12v from the battery (normal connection)
- 12v USB phone charger dock with line out and Bluetooth adapter with line out were connected to the empeg's aux-ins and got their power from the car's IGNITION WIRE. <-(THIS WAS THE PROBLEM)
- Everyone connected to common ground.

Until I moved the USB phone charger and the Bluetooth adapter to the +12V constant power (instead of from the ignition wire), I got the ground loop noise as long as they had any kind of power applied and/or they were attached to the empeg's RCA aux-ins. If I removed them so they didn't have any audio cable connection and/or didn't have any power, then I got no noise. When I moved them off the ignition power and onto the +12V constant power, all the noise went away and I could use them normally. Of course, I don't want them vampiring power off the car battery when I'm not using them, so I use a separate switch to turn them on and off (considering replacing that with a relay so I don't have to remember the switch).

Correct me if I'm wrong, but don't most cars power their cig adapters from the ignition wire? I wonder if you try the same thing, but get all your power from the +12v constant instead of from the cig lighter socket, if the problems will go away for you?
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Tony Fabris

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#363973 - 13/05/2015 21:58 Re: Hard Drive Noise When on DC Power [Re: tfabris]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30588
Loc: Seattle, WA
Unless you mean that you have a *PORTABLE* 12v car battery that's not part of a car, and you just happen to be using a cig lighter style socket as the connector. Then my suggestion is moot.

Hm. Unless the connector plug to the socket has an iffy ground. I personally have had nothing but trouble with Cig-style sockets in the past. Sometimes you get good solid ones and sometimes the connections are poor. Do your problems go away if you throw away the Cig-style sockets and connect the wires directly the battery terminals?
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Tony Fabris

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#363977 - 14/05/2015 03:19 Re: Hard Drive Noise When on DC Power [Re: maczrool]
JBjorgen
carpal tunnel

Registered: 19/01/2002
Posts: 3399
Loc: Guadalajara, MX
Perhaps recreate the conditions with a DC bench supply (if you've got one).
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#363982 - 14/05/2015 23:31 Re: Hard Drive Noise When on DC Power [Re: tfabris]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Thanks for the suggestions. Don't have the proper connectors to connect directly to the vehicle battery without destroying the cig lighter test jig, but did also try with the 12 volt output of a portable electric tire pump also with exactly the same results. Will see what I can cobble together but not expecting a different outcome.

Thanks.
Stu
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#363983 - 14/05/2015 23:33 Re: Hard Drive Noise When on DC Power [Re: JBjorgen]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
We have several bench top supplies (good Agilent/HP ones)but wouldn't these just accomplish the same thing the Empeg supply already is?

Stu
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#363984 - 15/05/2015 02:19 Re: Hard Drive Noise When on DC Power [Re: maczrool]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 30588
Loc: Seattle, WA
When you use the AC adapter (where you say the noise goes away), is the AC Adapter plugging into the AC Adapter power jack on the empeg, and are you plugging it into a wall socket to get its power in that case?

And when you use the 12v cig lighter source, is it connecting to the car dock continous power wire (which IIRC is yellow)?

I wonder what would happen if you got a 2.5mm connector and wired the power source from the 12v cig lighter powere into the AC Adapter jack. In other words: Same power source, but, different jack on the player. Wonder if the noise would go away then or if the noise stays.

My theory is that the noise occurs because of a ground loop between your portable amp and the empeg when they are both powered and grounded from the same spot. The reason it goes away when you use the AC adapter is that it's powered and grounded from a completely different place than the audio amp in that case.
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#363987 - 16/05/2015 10:23 Re: Hard Drive Noise When on DC Power [Re: tfabris]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Quote:
When you use the AC adapter (where you say the noise goes away), is the AC Adapter plugging into the AC Adapter power jack on the empeg, and are you plugging it into a wall socket to get its power in that case?


I have tried going through the sled wiring I have rigged up as well as the power jack with similar but not identical results. The noise is slightly quieter with the power jack even with the sled outputs still connected. If I switch to on board RCAs, the noise gets quieter but this is just due to gain differences. When on AC, the power is always from the Empeg adapter to either of these two connections.

Quote:
And when you use the 12v cig lighter source, is it connecting to the car dock continous power wire (which IIRC is yellow)?

That is correct. The ignition sense is also connected to +12 volts to keep everything running.

Quote:
I wonder what would happen if you got a 2.5mm connector and wired the power source from the 12v cig lighter powere into the AC Adapter jack. In other words: Same power source, but, different jack on the player. Wonder if the noise would go away then or if the noise stays.

See my answer above. The noise stays.

Quote:
My theory is that the noise occurs because of a ground loop between your portable amp and the empeg when they are both powered and grounded from the same spot. The reason it goes away when you use the AC adapter is that it's powered and grounded from a completely different place than the audio amp in that case.


There does seem to be something to your theory, but seeing as how wiring the Empeg as intended produces the noise, it begs the question as to what changes can be made? I just tried connecting a digital recorder to the output while on DC, there was no noise. A couple of the units I have are making this noise in what is said to be a professional install but I unfortunately do not have access to them, just my makeshift test setup.

Thanks again Tony!
Stu
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#363991 - 17/05/2015 23:55 Re: Hard Drive Noise When on DC Power [Re: maczrool]
FieroSTi
member

Registered: 07/05/2007
Posts: 104
Yes. I have a MKII and a MKIIa. The MKII exhibits TERRIBLE alternator whine from the analog outputs no matter what I do. The MKIIa exhibits no alternator whine, but I get very odd IDE hard drive noise which is choppy and clicky and very hard to describe, but it does not sound like standard analog interference. If I unplug the sled and plug my phone directly into the RCA cables, no noise at all. Just sounds great. Clearly the problem is with the empeg.

I bought one of your digital sound cards Stu, but I haven't gotten a chance to install it yet. My MKIIa just died the other day, so now I've got no empeg which has a palatable noise floor. Sad day.

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#363994 - 18/05/2015 00:32 Re: Hard Drive Noise When on DC Power [Re: maczrool]
mlord
carpal tunnel

Registered: 29/08/2000
Posts: 13506
Loc: Canada
So, on the Mk2/Mk2a, the Audio-Out uses floating ground by default. What happens to the hard drive noise when you ground those?

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#364004 - 18/05/2015 20:45 Re: Hard Drive Noise When on DC Power [Re: mlord]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Quote:
So, on the Mk2/Mk2a, the Audio-Out uses floating ground by default. What happens to the hard drive noise when you ground those?


All of my units have both sets, sled and built in RCAs grounded so can't say.
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#364005 - 19/05/2015 02:02 Re: Hard Drive Noise When on DC Power [Re: maczrool]
FieroSTi
member

Registered: 07/05/2007
Posts: 104
For what it's worth, I grounded the shields of the RCAs and experienced no perceivable change in noise from either unit.

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#364008 - 19/05/2015 08:07 Re: Hard Drive Noise When on DC Power [Re: FieroSTi]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
Yes. I've tried that too even though they were already grounded solidly, again no change.
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#364040 - 23/05/2015 14:46 Re: Hard Drive Noise When on DC Power [Re: maczrool]
maczrool
pooh-bah

Registered: 13/01/2002
Posts: 1626
Loc: Louisiana, USA
I was able to eliminate the noise using isolation transformers. Obviously this was a ground loop situation even though the wiring was done 100 percent correctly.

Thanks everyone!

Stu
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If you want it to break, buy Sony!

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#364244 - 24/06/2015 22:38 Re: Hard Drive Noise When on DC Power [Re: maczrool]
Ross Wellington
enthusiast

Registered: 21/02/2006
Posts: 325
Hi,

Sometimes this can be caused by an open ground trace on the Power Amplifier. If the Ground Trace or the Ground Ring Connection to the Amplifier board is broken open, it can do this.

The return path is long (pronounced as "Ground Loop"), without that dedicated Ground and it gathers Chassis and other noise along the way and you here it.

I guess the same thing could happen in the Empeg too.
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In SI, a little termination and attention to layout goes a long way. In EMC, without SI, you'll spend 80% of the effort on the last 3dB.

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