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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: Jhurlbs81 on August 01, 2010, 02:39:47 PM
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Hey Guys-
I recorded Umphrey's McGee last night with my Telefunken USA tubes. The mics run off a DC-DC converter; the waveforms look shifted toward the top. Take a look, do they look weird to you? If it is offset, how would you correct it?
http://www.sendspace.com/file/8oyojv
Thanks
Jesse
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Are you talking about the fact that the peaks are higher on the tops of the wave forms?
I think your upper peaks are a bit larger.
To some degree that happens on my tapes.
And checking on quite a few of others recordings it looks the same to me.
The peaks on the upper and lower side of the waveforms never seem to reach identical places.
I've just checked about five separate source random recordings.
Here is a screen of one.
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The shape seems just fine.
It is quite common for the signals to be non-uniform.
Always happens when you have brass instruments ( trumpet or trombone ) but can happen from a lot of other reasons.
// Gunnar
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looks fine to me too.
i don't think you have much to worry about as far as dc offset goes either.
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My guess is that the mp3 conversion might be doing highpass filtering. This would remove the DC offset.
Can you post a link to a portion of the file in the original format?
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There are legitimate reasons why it might look like this... this is the sound that was flying through the air. If this one tape looks like this, I wouldn't get too excited. If they all look like that, then I would. It certainly doesn't look brickwalled at a fixed point. Since you are using using a semi-experimental mic/power setup, it's possible the mic body amplifier circuit is starved in such a way that doesn't fully put on a full signal linearly across the entire range.
Has your V3 ever had the "polarity fix" done? if not (and mine hasn't) the wave shown on the screen is actually upside down, and the "short side" is the top. It doesn't make much difference when listening, but this would be significant to someone trying to diagnose a starved circuit.