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Author Topic: Dr Suess Waveforms  (Read 1778 times)

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Offline admkrk

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Dr Suess Waveforms
« on: April 19, 2015, 04:19:11 PM »
Hey guys, its been a while since I've been out, but I can't remember ever seeing something like this before. I was having some strange issues where one channel was losing power, or the other gaining power, or both; not really sure what was happening. Anyway, I was checking out one of the sets this was happening on scattered through out was junk like this:

Some more exaggerated, some less. It seems to sound fine, but it sure doesn't look right. Any ideas on what's going on?
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Offline Gutbucket

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Re: Dr Suess Waveforms
« Reply #1 on: April 19, 2015, 06:32:33 PM »
Appears something was causing some kind of cycling dc offset in one channel.  Was everything powered correctly?
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Offline admkrk

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Re: Dr Suess Waveforms
« Reply #2 on: April 19, 2015, 06:58:13 PM »
I was plugged into the power pole at the Wanee amp so power shouldn't have been an issue. dc offset seems fine, although I cannot say I completely understand it (-96.445, -96.348). Pitch, which I understand even less does seem to be more of a problem with the bottom channel being about 1/2 the top. All I really understand about them is that they should be more or less equal. I just checked another set where I wasn't having the channel issue and I'm getting this too, but it is very intermittent and looks good most of the time, dc offset and pitch are mostly balanced on that one.
"the faster you go ahead, the behinder you get"

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Offline Gutbucket

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Re: Dr Suess Waveforms
« Reply #3 on: April 19, 2015, 07:17:09 PM »
It looks like the dc offset isn't constant the entire time but is varies with a waveform shape.  Notice that the 'big wiggles" look similar to an audio waveform but are exhibiting a far slower oscillation.  The DC-offset number you are reading is probably the average across the entire file, as if the 'big wiggles' were straightended but shifted up or down above the zero crossing line in the center. 

Anyone else plugged into the pole  have issues?  Not saying that's it, just chasing ideas.  Could be the mic, I guess.  If it happens again, swap mics across channels and see if it follows the mic.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline admkrk

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Re: Dr Suess Waveforms
« Reply #4 on: April 19, 2015, 08:36:44 PM »
What you said make sense, and it was the average of the whole file. I was the only one plugged into the pole, other than charging batteries, as far as I noticed. Both of the sets I've looked at so far are from different day, but its possible I used the same mics in the same place. I'll try to look at another one from a different day and see if it shows up in the same channel. Could it be the preamp? My ua5 has been ridden hard over the years and been around the block a few times.

<edit>

OK, I'm thinking more and more the problem is a tired preamp. the last set I recorded started out looking like this:

While the first looked more or less like this through the whole set:

Its unlikely I used the same mic in the same channel 3 days in a row and I doubt that one would "over heat", for lack of a better word. While I can imagine a preamp doing that.

In your opinion, should I even try to fix this? I'm listening on POS speakers so I only have a limited idea of what it really sounds like. Would it be better to just make it mono or copy the effected parts to the other channel when it doesn't happen often? Or, just trust my ears and only worry about it (as far as these sets go) when something sounds bad?
« Last Edit: April 19, 2015, 10:39:14 PM by admkrk »
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Offline Gutbucket

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Re: Dr Suess Waveforms
« Reply #5 on: April 20, 2015, 09:34:38 AM »
As far as these recordings go, just trust your ears.  If it sounds okay I wouldn't worry about them too much, at least as long as the cones of the speakers aren't looking like they are about to pop put of cabinet.   With those big super-low cycle waveforms you may actually see the woofer on that side moving in and out slowly, tracking that offset.

Could be the preamp on it's last legs, needing repair.  But I still wouldn't rule out bad power from the pole.  I'd probably see if I could replicate the problem at home, or on battery power.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<

Offline admkrk

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Re: Dr Suess Waveforms
« Reply #6 on: April 20, 2015, 11:54:37 AM »
The power could be the problem, more of a power drain over all after it get dark and they start using more lights. I have had an issue with bad power in the past, but in that case the sound was also effected and it was pretty much unlistenable. If what I suspect is the problem, it will be difficult to reproduce and if I was using batteries, it might not have even showed up because I would have been powering down for the 1/2 hr between sets.

Thanks for all the suggestions and ideas.
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Offline cybergaloot

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Re: Dr Suess Waveforms
« Reply #7 on: January 01, 2016, 02:36:19 AM »
I got that same wave form right before one of my old Studio Projects C4 mics died. It looked identical and I suspect it is a bad capacitor in the mic. I've never gotten around to sending it in for repair.
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Offline admkrk

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Re: Dr Suess Waveforms
« Reply #8 on: January 01, 2016, 01:46:14 PM »
That does not sound too scary, or expensive. I have only ever sent dat decks in for repair before and the "notify me if the cost is over $500" clause spooked me a bit.
"the faster you go ahead, the behinder you get"

"If you can drink ram's piss, fuck, you can drink anything"

 

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