Re: Microphone Blowing Out Channels On Firewire Mixer


pafischer@xxxxxxxxx wrote:
Greetings All,

I have had several people tell me this is impossible, but it does seem
to be happening to me. Until I finish recording my Podiobook
(www.podiobook.com) I can't risk another channel. But I wanted to check
here and see if anyone can shed any light on the problem.

Here's what's happening:
I have an Alesis Multimix Firewire 16 and a Studio Projects B1
microphone. I bought both new.

The Alesis was working fine until I bought the B1. Unfortunately I
bought it on impulse just before some traveling and didn't get to
really try it until the return period had passed.

When I plugged the B1 into the Alesis it sounded aweful. I would get a
very audible hum, and normal essing problems would be 10 times worse
than normal. At first I thought it was the mic, so I sent it in for
service. PMI Audio said there was nothing wrong with it. However, the
essing problem started showing up all over my Alesis, so I sent it in
for repair.

Alesis said I had blown electrical components in several channels (4 or
5 I can't remember, but it was more than half). I thought the B1 might
be causing the problem because I tried it on many different channels.
But everyone tells me this is just impossible.

I tried the B1 on my analog mixer, a 6 channel all XLR Peavy mixer, and
it sounds fine.

So the Alesis comes back from repair. I hook up my Cad microphone to
channel 1 and it sounds great. Then I hook up the B1 to channel 2. I
hear the hum again and the extreme essing problem. I remove the B1 from
channel 2 and try a M-Audio Luna mic and a Shure SM58. Both have
extreme essing and no hum.

I then proceed to walk the Luna and SM58 down the channels and both
mics sound great on every channel except channel 2.

At this point I see only 2 explainations for my problems:
1) Channel 2 came back broken from the repair center. This means either
the repair was missed or something happened to the mixer in transit.
2) The act of pluggin the B1 into the mixer immediately blew out an
electical component in channel 2. Possibly in the analog to digital
converter. That is what is causing the extreme essing problem and that
is what caused the problems the last time the board went in for
repairs.

In all honesty, I beleive that #2 is what's causing my problems.

I've emailed PMI tech support, and they say the B1 is fine. I have
offered to display the problem to them on the phone through the mixer,
with live video chat. I have also asked them to go down to Guitar
Center and try their own B1 in an Alesis Multimix Firewire 16. I
haven't heard back from them yet, so I thought I'd throw it out to this
group to see if anyone has any thoughts on this mystery.

I've been told by several big time audio engineers that this just can't
be happening. But most of them work in live audio and broadcast. I'm
pretty sure most of them don't use firewire mixers.

My guess is that there is something specific in the handling of
electricity that isn't quite in spec on the B1. I'm thinking it isn't
an issue for 95%-99% of the mixers on the market, and it may be this
exact combination that causes the problem.

Once I reach a point where I can do without my mixer for a few more
weeks, I'll try the B1 on another channel and see if that is causing
the channel burn out and the lasting extreme essing problem. Only then
will I really know for sure.

FYI, we tested every possible combination of XLR cables, and
experienced no problems with any of them with any mics.

Has anyone ever seen anything like this before? Does anyone have a way
to test the B1 to see if it could possibly be frying a component on the
Alesis channel, preferably without actually frying the channel?

Any help you can provide on this issue is greatly accepted.

Paul Fischer

It seems likely you have a problem with phantom power feeding back into
the mic input.
This would happen if the mic cable had a short between one of the
signal lines and ground.
Have you checked the cable for shorts between either pin 2 or 3 and pin
1?
You say you checked the mic with a Peavy XLR input mic pre and it was
ok.
Did you use a mono jack plug on the Alesis? If so that would short the
phantom on one side
causing 48v to appear on the mic pre input. Even a balanced jack could
cause a 48v pulse to occure if it is pushed in with the phantom power
on. Phantom power is self canceling on a balanced input but if it is
unbalanced it won't cancel.
A decent mic pre should cope with this but transformerless versions can
fail in this way.
If it is a faulty mic the problem may not be obvious with a transformer
input mic pre.
Do you know how PMI tested the mic?

Steve Lane

.

Relevant Pages

  • Re: Drum miking. What method id preferred?
    ... > channel for my kit and one for my vocal), I got a nice digi mixer to send ... and considering I'm sending it all into one channel on our ... the vocal mics to cover a bar sized room. ...
    (rec.music.makers.percussion)
  • Re: Microphone Blowing Out Channels On Firewire Mixer
    ... I can't risk another channel. ... I have an Alesis Multimix Firewire 16 and a Studio Projects B1 ... I tried the B1 on my analog mixer, a 6 channel all XLR Peavy mixer, ... experienced no problems with any of them with any mics. ...
    (rec.audio.pro)
  • Re: How would you use this channel?
    ... I use what is known as a "field mixer", a 3 in, two bus, stereo ... This provides a fifth channel that can be panned between ... If you need three soloists mics, then mix them to a sensible ... but do think in terms of stereo images ... ...
    (rec.audio.pro)
  • Re: How would you use this channel?
    ... I use what is known as a "field mixer", a 3 in, two bus, stereo ... This provides a fifth channel that can be panned between ... If you need three soloists mics, then mix them to a sensible ... but do think in terms of stereo images ... ...
    (rec.audio.pro)
  • Microphone Blowing Out Channels On Firewire Mixer
    ... I can't risk another channel. ... I have an Alesis Multimix Firewire 16 and a Studio Projects B1 ... I tried the B1 on my analog mixer, a 6 channel all XLR Peavy mixer, and ... hear the hum again and the extreme essing problem. ...
    (rec.audio.pro)