VO-BB - 20 YEARS OLD!

Mike Sommer · Posted: Thu Dec 09, 2010 12:25 pm Post subject:

Also try a shorter cable between the pre and the interface. Switch the cable between the mic and the pre with the cable between the pre and the interface.
Note if the hum gets louder or quitter, or goes away. If it does with any of these changes, you're on the right track, i.e. a cabling issue.
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Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

I don't know if the Blue cable is Quad or not....it's green (in color) and

doesn't look any thicker than normal cable

BAE thinks it may be a defective unit and they're sending me a new one

Mike Sommer · Posted: Thu Dec 09, 2010 12:56 pm Post subject:

That would be my first guess.
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Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

You know what, it looks like my Blue mic cable is Quad---at any rate, it didn't make any difference.

cyclometh · Posted: Thu Dec 09, 2010 1:25 pm Post subject:

I'll be very interested to hear when you get the replacement unit if it makes a difference.
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Mike Sommer · Posted: Thu Dec 09, 2010 3:52 pm Post subject:

It does not take much to make these units hum-- it's just the nature of the beast. A cold solder joint, a lose wire or connection. And seeing how the average package is dropped 4 times in transit by the US Post office, even more by UPS and FedX, it's no wonder we get anything in working condition at all.
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Dan Bazis · Guest

Hi Rob...

I had to chase down a similar hum the other night, so I thought I'd share what I found.

In my situation, I had to use my laptop for recording in a pinch, because the power supply in my desktop (recording) machine had failed. I use an Allen & Heath ZED-14 mixer as my USB interface, and have an M-Audio Sputnik running into an Aphex 230 ahead of the mixer.

When I tried to record, I found an annoying hum at around -52dB (I don't know what frequency). I disconnected the mic, the pre-amp, unplugged everything from the mixer... yet the hum remained. Even with the mixer powered OFF, the hum remained. I swapped USB cables, made sure power and grounding were solid... no fix.

I finally found that the hum was coming from the laptop itself. When I went into the "Sound" options under the Windows 7 control panel, under the recording properties I found a "Level" slider that was up at 100%. Moving the slider to 0% completely eliminated the hum, but prevented recording audio... so I compromised and set it to around 50% and the hum was rendered irrelevant, especially since my laptop will not continue to be my primary recording machine.

Perhaps you're running into the same issue?

- Dan Bazis

Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

Thanks Don, but still no go.

It's definitely in the pre-amp. After exhaustive testing, it remains the only

part of the audio chain that has to be plugged in and powered on for the hum to appear.

All of my other devices, my Mackie 1202 and both of my audio interfaces, are hum-free when I record into them using the same mics and cables.

Hopefully this is just a bum unit because I really like the overall sound of this pre-amp/Brent Averill 1073 DMP.

Mike Sommer · Posted: Fri Dec 10, 2010 8:40 pm Post subject:

Have you tried it out at another studio??
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Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

Well, I tried it on a different circuit in my house on my laptop both plugged in and unplugged and the hum is still there.

Mike Sommer · Posted: Sat Dec 11, 2010 7:55 pm Post subject:

Not quite the same thing, especially if you're using the same computer.

The trick would be to plug into a different system all together.

If you are very careful, you can plug a pair of headphones into the Pre's output (with an adapter) and listen for the hum. Just turn the output down, and then turn it up slowly.
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Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

I did record it on a different computer (my Laptop travel one) and even did it with the computer plugged in and then battery only.

Also, considering that my Mackie 1202 has no hum,or either of my interfaces when all other components of the signal chain are identical, everything screamingly points to the pre--either it's faulty or there is something in the basic design that causes this.

Mike Sommer · Posted: Sun Dec 12, 2010 7:50 am Post subject:

Check

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Rob Ellis · M&M Joined: 01 Aug 2006 Posts: 2385 Location: Detroit

Okay I think we got this thing solved. As is often the case, the fix is very simple: don't crank the output knob all the way clockwise.

So why was I doing it? Because the accompanying literature suggested doing so for the best recording quality, as did the people I spoke with.

Even though cranking the output knob full bore flies in the face of everything I've been taught about pre-amps.

But anyway, when I dial back the output knob to around the 12 o' clock position and then set the gain at around 40-45 db the hum disappears.

Mike Sommer · Posted: Tue Dec 14, 2010 2:55 pm Post subject:

The best thing to do is to think of output knob as a fader pot on a mixer. You would not slid the pot all the way up on a mixer would you?-- no. You would start with it turn down, and raise the volume until you reach the level that you need.

So think of the Brent Averill as nothing more then a single channel strip on a mixer, just like an Avalon 737 is nothing more than a single channel strip. As a matter of fact all external preamps are nothing more than single channel strips.

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