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Troubleshooting something totally bizarre

#22
testing1two said:
For the sake of experimentation have you tried a mismatch combination of cabs? For example using one of your B-15 cabs + one 210AV? This would replicate the 4 ohm impedance but might help you isolate one of the AV cabs as the culprit versus the head. But to be honest that sounds like a lot of cabinet shuffling.
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i did not, but honestly, i don't think there's anything wrong with the cabs since they both work great by themselves or with other amps. i don't think there's anything wrong with the head, either. but there is something wrong in the way that the head and two cabs communicate. got no clue whatsover, though. if it was a ground, you'd think it would show up everywhere.

Maybe the rock gods are telling you to get another Micro VR so your rig, like Charlie Sheen, will be bi-winning!
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well that ain't gonna happen ;) these things are meant to work with each other in this fashion, and work they will even if it kills me! defeat is not an option.
 
#25
testing1two said:
You're probably right not to go with two mini stacks. People might think it was a Mini KISS show. I'll be interested to hear what Ampeg has to say as I'm very close to pulling the trigger one of these rigs.
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well don't let my little problem hold you back! it's an awesome little rig and i'm sure it's just a flukey thing. plenty of people use it with two cabs and it's working just fine for them. owen biddle of the roots has been using one on the jimmy fallon show...his doesn't do that ;)
 
#26
Just a random thought, it could be that the cabs' impedance aren't entirely what the factory says they are, I know you have considered this before but might I make the suggestion that your other, perhaps "better" amps would handle this impedance, presumably lower than the predicted 4 ohms, better than the mini? Cabinets will tend to differ from exact impedance just by nature, most amps will be designed with this in mind, but I guess some amps are better equipped than others? Your cabs could be making a combined impedance of noticably lower than 4 ohms, say, as an example, 3.3 ohms. Your pro amps can handle that, the mini cannot. Just a speculation.
 
#27
Just a random thought, it could be that the cabs' impedance aren't entirely what the factory says they are, I know you have considered this before but might I make the suggestion that your other, perhaps "better" amps would handle this impedance, presumably lower than the predicted 4 ohms, better than the mini? Cabinets will tend to differ from exact impedance just by nature, most amps will be designed with this in mind, but I guess some amps are better equipped than others? Your cabs could be making a combined impedance of noticably lower than 4 ohms, say, as an example, 3.3 ohms. Your pro amps can handle that, the mini cannot. Just a speculation.
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I was thinking exactly the same thing.
The thing is, Ampeg made them to be combined with the micro head. So I guess they tested it thoroughly.
3.3 Ohms is still within spec and should not give an amp that is rated to handle 4ohms any problems. Even a dip of 3ohms should not be a real problem. It may give trouble if the dip is in the low bass region where the amp has to deliver the most power.
 
#31
Signing on to see what comes of this. I don't really have any input beyond what's already been said, but checking the impedance on both cabs (and on the pair when connected to each other) is a good idea.

FWIW, both of my Micro-VR's seem happy enough driving two SVT-210AVs (I still need shot of the "double Micro-VR rig"). :cool:
 
#32
If I understand correctly, the noise you described is coming from all your speakers and out of both cabs at the same time. If this is the case, it sounds like the distortion could be coming from your amp.

When you have your speakers connected, check if the distortion present at the phones output?

If you can, try your speakers with another micro-VR. If the distortion disappears, it could be your amp. If it doesn't, it could be that both amps have an inherent problem. Then try your amp with another set of 210AV speakers.

The speakers are fine with another amp and vice versa, but they are interacting differently. It is the specific combination of your amp and speakers that is causing this.

As you know, the speakers impedance varies with frequency due to both electrical and mechanical interactions. A speaker is resistive, capacitive, and inductive, and depending on the frequency, shifts the operating point of whatever it is loading. If something is out of spec, be it in your power amp or speakers, this shift could be pushing the amp into distortion.

Something that you might want to check before talking to Ampeg again: Does applying equalization eliminate the distortion? Does the distortion occur throughout the range of your instrument or just with lower, mid or higher notes?
 
#39
greenboy said:
Didn't read the thread, but impedance sweep.
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It is a bit hard to read (the impedance curves are now larger, beginning in issue #5), but you can see what the impedance curve on the SVT-210AV is supposed to look like in my review from [Invalid or Expired Link Removed].
 

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