Blumenstein and Stereomour

[thdewitt]

I just received my Orca Deluxe and Dungeness today.  I hooked them up to my Stereomour and my Submissive.  I immediately got a pretty significant hum.  Low hum in both the sub and speakers.  I have the Stereomour at full volume and the submissive controlling the listening volume.  Is this normal?  Seems excessive.  I have all the components, Sonos, Stereomour and Dugeness are all plugged in to same outlet.  Any thoughts?

Thanks,
Tom

[Paul Birkeland]

Hello Tom,

Did you adjust the hum balance pots?

Is everything plugged into the same outlet? 

[thdewitt]

BP, 

Thanks for the answer.  I did adjust the balance pots.  I followed the instructions in the manual and using my multimeter was able to adjust both sides to 0.

All the components are plugged in to the same outlet. I have a 4 port outlet and my sonos, Stereomor and sub are all plugged in to it.

thanks,
Tom

[Paul Birkeland]

Does the hum change level with the Stereomour level control?

Does the hum go away if you unplug both sub amps? 

Is the hum still present with the Sonos not plugged in?

[thdewitt]

OK, I did a little more checking.  The hum seems to be just coming from the Subwoofer Amp.  There steromour is dead silent.  It gets louder if I turn the gain up.  I normally have the gain on the sub set to about 11 o'clock and the hum is audible but not too bad.  Gets worse as you turn up the gain. 

The speaker wires go from Steromor to speaker then to sub.  So both channels connect at the speaker binding posts.  The speaker to the sub enters at the Amp in connections.  Per the Bulmenstein Website instructions.

Tom

[Doc B.]

Try the sub with inputs (from the speakers) disconnected and see if the hum changes.

[thdewitt]

When I unhook the wires going to the speakers the hum goes away.  If I hook just the sub up to the amp directly I get the hum.  By adjusting the pots you can minimize the hum but it is still there audibly.  If you increase the gain on the sub it goes up.  The STereomour volume pot does not make a difference.

Tom

[Doc B.]

You can measure the hum from the Stereomour with an AC voltmeter. If it has hum of 1mV rms or less it's operating normally. I use the Stereomour with Dungeness subs with no discernable hum issues, but if your setup measures within spec and you still find it unsatisfactory you can try running a pair of RCA cables from the Submissive to the Stereomour and a second pair of RCA cables from the Submissive to the RCA inputs of the sub, instead of using the speaker level inputs on the sub.

[thdewitt]

I think my Stereomor is running in spec by the voltages I measured.  On my fluke meter on the MV scale it bounces around between 2.1 and 0.  It jumps directly from 2.1 to zero.  no numbers in between.  It will not hold a number whether I short the RCA or not.  It is the exact same on both sides.  If you turn the pots the numbers go up no matter which direction.

[thdewitt]

you can try running a pair of RCA cables from the Submissive to the Stereomour and a second pair of RCA cables from the Submissive to the RCA inputs of the sub, instead of using the speaker level inputs on the sub.

Can you explain this to me.   The submissive only has one set of RCA outs and 3 inputs.  How would you accomplish running 2 pairs out.  Are you suggesting rewiring one of the inputs to make another output?

[Doc B.]

You could do that, or just by a y splitter for each channel.

[thdewitt]

Thanks, do you think that the 2.1 reading that I am getting for the hum pots that erratically jumps to zero and back is normal.

[Paul Joppa]

The jumpy reading most likely indicates a not-too-precise meter. Many meters have a hard time reading very low voltages and very low resistances. You can just listen to do the adjustment - it's harder to get the lowest reading but what you hear is what's really important anyhow. If you hear a clear minimum then you are almost certainly listening to the intrinsic filament hum and there are no other hum problems.

[Grainger49]

Tom,

Just checking, are you measuring AC volts on your meter?  BTW, both my 1980s and 1990s Flukes read down to 1mV AC reliably.  Both autorange.  The only mV setting is for DC.  But when I get screwy readings from either of them it is time to change the battery.

Let's try something different, wire your left Dungeness to your right Orca and vice versa.  I'm just thinking that there is a possible ground loop being created.  This will rule out one channel of the Stereomour being missing a ground.  If the same sub hums the Stereomour is fine.  If the same channel hums it could be a lifted ground in that channel.

[thdewitt]

Grainger,

You may be right.  I was probably using the DC volts.  But I had tried both.  Here is a picture on the AC volts.  It sticks at 000. 
(https://dl.dropboxusercontent.com/u/38833957/2014-06-13%2009.00.59.jpg)

I hooked it up on the oscilloscope and couldn't get it as low.
(https://dl.dropboxusercontent.com/u/38833957/2014-06-13%2009.11.41.jpg)
(https://dl.dropboxusercontent.com/u/38833957/2014-06-13%2009.11.51.jpg)

Am I doing this right?  I am still new to the electronics hobby.

I only have 1 sub.  The hum actually comes out of the Orcas also but at a much higher pitch.  When I turn the sub gain down to 10 O'clock it is minimized but still audible in the room.

Tom