X-2 question

[Jaosn]

Hello forum members,

I have a pair of 1Ci I bought about 10 years ago.  A couple years ago, I  added a used 2Wq.  I'm using an Oppo 105D as a preamp and an Anthem PVA-5 amplifier, and a pair of unbalanced X-2 crossovers between the Oppo and PVA-5.  When no music is playing and during quiet passages, I hear a faint buzz from the 1Cis.  To troubleshoot, I first tried grounding the amplifier chassis with the ground pin on the 2Wq, but this made the buzz louder.  I then disconnected the 2Wq, but left the X-2 in place, and the buzz is still present. Finally, I removed the X-2 (with the 2Wq still disconnected) and the buzz is gone.  My dealer suggested that the Oppo isn't an adequate preamp, and likely causing the buzz when the X-2 is in the circuit.  However, recently I tried a new AV preamp, but the buzz was still present.

Any suggestions on how to get rid of the buzz would be much appreciated!

[TomicTime]

i believe the X2 are a temporary high pass and not meant / shielded for long term use…. you might want to invest in the high pass filters in metal boxes ?… @Richard Vandersteen 

[Holmz]

Can you try plugging in the 2Wq into the same power strip as the OPPO?

[Jaosn]

3 hours ago, Holmz said:

Can you try plugging in the 2Wq into the same power strip as the OPPO?

Thanks for the suggestion. Yes, all items (Oppo preamplifier, Anthem power amplifier, and 2Wq are using the same power strip).

[Jaosn]

11 hours ago, TomicTime said:

i believe the X2 are a temporary high pass and not meant / shielded for long term use…. you might want to invest in the high pass filters in metal boxes ?… @Richard Vandersteen 

Thanks for the suggestion - I'm using the fixed W-2 crossovers purchased from the dealer - not the temporary WX-2 that comes with the 2Wq. Though, I noticed the buzz with the variable WX-2 as well.

[GdnrBob]

Just a thought, but have you made sure the plugs are firmly seated?

I had a buzz issue once with some RCA's, it took months to finally figure out one of the plugs was slightly unseated, despite looking completely inserted.

B

[Holmz]

Is the buzz a 60/120 Hz hum?
If it is not power, then it must be the signal path is completing a ground loop.
In fact you stated:
 

22 hours ago, Jaosn said:

I then disconnected the 2Wq, but left the X-2 in place, and the buzz is still present. Finally, I removed the X-2 (with the 2Wq still disconnected) and the buzz is gone.

So we might as well ignore the 2Wq at the moment.
 

Is there a picture of the set up, that includes showing the cabling?
I think that those crossovers (XO) just have capacitors and resistors in them. But if they are near some magnetic field, then maybe that is how the hum is getting coupled in?

[Jaosn]

@GdnrBob Good suggestion - that's always my first suggestion when my students tell me things aren't working in the lab I run. As far as I can tell the connection is good.

@Holmz Yes, it does seem to be harmonics of 60 Hz (see attached spectrum). For the most part, I don't notice the hum, but since the weather here has gotten cooler and the AC is not running as much, I've started to notice it a bit more. Pictures of the wiring are a bit challenging as everything is packed into a cabinet, but will pull it out over the weekend when I have more time. I'll plan to unplug everything nearby and if that removes the hum, add one thing at a time to see what might be interfering.

[GdnrBob]

16 hours ago, Holmz said:

But if they are near some magnetic field, then maybe that is how the hum is getting coupled in?

That is a good point. Some cables are more affected by external magnetic fields than others.

B

[Holmz]

7 hours ago, GdnrBob said:

That is a good point. Some cables are more affected by external magnetic fields than others.

B

And sometime just rotating a box or slightly altering the cable run can change it to be in a different part of a field.
A visual of that layout could be handy.

[Jaosn]

@GdnrBob @Holmz Thanks again for the suggestions. I pulled a everything out of of the cabinet to troubleshoot.  I've attached a copule photos.  The results are the same - no amount of moving cables around, ect eliminates the buzz. I only get the buzz in the channels using the X-2, and not in the center or surround channels.  I can only get rid of it by removing the X-2.  If I put the X-2 in the center or surround, I get the buzz in those channels only.   The amplifier also has a similar hum when powered on, so I wonder if the X-2 is picking that up. I moved the X-2 to the OPPO end of the cable, but sill hear the hum.

[GdnrBob]

Well, either the X-2's have an issue or your amp has an issue with the X-2's.

B

[Jaosn]

Good news. I've fixed the issue by installing an isolation transformer between the pre and power amp (Jensen Iso-Max CI-1RR ) and making sure that the power amp chassis (which has one of those double insulated cases and a 2 - prong plug) is grounded via the ground plug on the 2Wq.

Note that it seems that the ground loop seems to be introduced via the volume control of the Oppo and other preamps I tried. I observed the same buzzing when using a new (to me) Ayre AX-5 Twenty using the processor passthrough. However, when using the Oppo as a source for the AX-5 Twenty (thereby bypassing the Oppo volume control), the buzz went away without needing the isolation transformers.