Tech Question: Microvox Mics

[Jim Besser]

Thanks to the generosity of a fellow C.netter, I'm trying out a Microvox concertina mic system.

 

But a potential hitch: the manual says it can't be used with phantom power.

 

The system I play on has phantom power on all channels, and it can't be turned off.

 

Question: will a direct box isolate the mic system from the phantom power? THe Microvox instructions seem to indicate that is the case, but I'm wondering if anybody has real-world experience with this.

[dpmccabe]

Thanks to the generosity of a fellow C.netter, I'm trying out a Microvox concertina mic system.

 

But a potential hitch: the manual says it can't be used with phantom power.

 

The system I play on has phantom power on all channels, and it can't be turned off.

 

Question: will a direct box isolate the mic system from the phantom power? THe Microvox instructions seem to indicate that is the case, but I'm wondering if anybody has real-world experience with this.

I used to use these mics (now two Sennheiser e608s--which are great) and don't recall any problems with phantom power. Trust the documentation, I guess.

[martyn]

Thanks to the generosity of a fellow C.netter, I'm trying out a Microvox concertina mic system.

 

But a potential hitch: the manual says it can't be used with phantom power.

 

The system I play on has phantom power on all channels, and it can't be turned off.

 

Question: will a direct box isolate the mic system from the phantom power? THe Microvox instructions seem to indicate that is the case, but I'm wondering if anybody has real-world experience with this.

 

I have been using these mics for about 3 years now on a PA with phantom power and have had no problems.

 

When I bought them Microvox advised me to always use a DI box. The model I use is a Behringer DI-120 which has two XLR out sockets this allows our sound engineer to give me seperate mixes for the concertina and the melodeon.

 

Hope this helps

Martyn

[Howard Mitchell]

Thanks to the generosity of a fellow C.netter, I'm trying out a Microvox concertina mic system.

 

But a potential hitch: the manual says it can't be used with phantom power.

 

The system I play on has phantom power on all channels, and it can't be turned off.

 

Question: will a direct box isolate the mic system from the phantom power? THe Microvox instructions seem to indicate that is the case, but I'm wondering if anybody has real-world experience with this.

 

Jim,

 

There are two questions here.

 

First, can you connect the microvox mics directly to a mixer and use the phantom power instead of the battery box. I think it's this question that Microvox answer in their FAQ which says that the phantom power is too high (48 volts) and will burn out the microphone element. You can only do this with a phantom power adaptor which converts the 48v to a lower voltage and also balances the unbalanced microphone signal.

 

Second, can you connect the output of the battery box to a mixer with phantom power on. The battery box has a circuit which provides power to the microphones. The also contains a capacitor which isolates the mixer input from this battery power. This capacitor can also isolate phantom power from the battery box. BUT strictly the capacitor is the wrong way round and it isn't rated at 48 volts. HOWEVER in real life the 48 volts is supplied through a 6.8k resistor so a lower volatge will be presented at the capacitor and it may survive.

 

Best of all use a DI box. You could even use a DI box which is powered from the phantom and therefore doesn't need a battery.

 

Howard

[Theo]

Or better still, don't use Microvox at all. I've done sound for several bands and the only instrument mics and picups that have had problems were microvox. Mostly lost signal, and noisy connections from the connectors, which on the ones I've seen were all pretty cheap 1/4" jack components.

 

If its a free loan then its hard to say no, but if you end up buying mics remember that with microphones you get what you pay for. If you have a top quality concertina that maybe cost a 4 figure sum (in pounds) then its good to have mics that enable your audience to appreciate the quality of your instrument, and of your playing

[Jim Besser]

Or better still, don't use Microvox at all. I've done sound for several bands and the only instrument mics and picups that have had problems were microvox. Mostly lost signal, and noisy connections from the connectors, which on the ones I've seen were all pretty cheap 1/4" jack components.

 

If its a free loan then its hard to say no, but if you end up buying mics remember that with microphones you get what you pay for. If you have a top quality concertina that maybe cost a 4 figure sum (in pounds) then its good to have mics that enable your audience to appreciate the quality of your instrument, and of your playing

 

My preference, too, would be to use two regular, fixed mics.

 

But in this particular situation, space is at a premium, nobody gets more than 1 mic. And the overall noise level is very high (30-40 musicians, although only 6-8 on mic).

 

I've been using a single mic for a few years, positioned over the center of the instrument, but in that environment, it's just not sufficient. So it seems to me that the Microvox, or something similar, is the only realistic alternative.

Edited February 5, 2007 by Jim Besser

[Jim Besser]

 

Best of all use a DI box. You could even use a DI box which is powered from the phantom and therefore doesn't need a battery.

 

 

Here's what I don't get.

 

The Microvox output is 1/4 inch. I thought phantom power needed the third terminal on an XLR cable as the power conductor.

 

It comes down to this: if I use a quarter inch cable from the Microvox to a direct box, an XLR cable to a mixing board channel with phantom power enabled, will the Microvox be sufficiently protected from the 48 volts? The Microvox instructions seem to indicate that is the case, but they are not exactly models of clarity.

Edited February 5, 2007 by Jim Besser

[Lawrence Reeves]

My advice for what it is worth. Phantom power on a mixer will not have any affect on a no phantom powered mic. The first problem that I encounter with a set of mics on concertina is feedback, specially with a monitor system. The other issuue is tonal and volume balance between the left and right hand. My solution is a pair of AKG C416L mics. Velcro or non residue adhesive pads to hold them on the instrument. I even have a spare set of instrument mounts to attach( no drilling, or permanent residue) to my new Bb/F when it arrives. These mics use a sub mini XLR that I plug into an AKG B29L mic preamp. It allows for individual level of left and right hand. The other nice feature for me is that the preamp sends out a mic level XLR to the board, or a switch turns it to line level like a guitar or keyboard out. These mics are great with respect to tone and also for feedback rejection. The only drawback is they are a little pricey. In reality compared to the cost of a concertina they are in line, also I think that sound quality is worh the expense.

[Jim Besser]

my new Bb/F when it arrives. These mics use a sub mini XLR that I plug into an AKG B29L mic preamp. It allows for individual level of left and right hand. The other nice feature for me is that the preamp sends out a mic level XLR to the board, or a switch turns it to line level like a guitar or keyboard out. These mics are great with respect to tone and also for feedback rejection. The only drawback is they are a little pricey. In reality compared to the cost of a concertina they are in line, also I think that sound quality is worh the expense.

 

That is a nice looking setup. Looks like the mics are a little hard to find in the US, and pricey. But certainly worth further investigation.

[Jim Besser]

The last word on the subject: Microvox tech support came back with a very prompt reply:

 

"Any DI box will isolate the phantom power."

 

So I guess I can plug in.

 

Still interested in hearing about alternative clip-on systems with a single XLR output.

[Lawrence Reeves]

Jim, If you contact me through the forum I will give suggestions for the price saving place to find these mics. I am into this rig for around 400 us. The trick is patience from the supplier I use.

[dpmccabe]

Or better still, don't use Microvox at all. I've done sound for several bands and the only instrument mics and picups that have had problems were microvox. Mostly lost signal, and noisy connections from the connectors, which on the ones I've seen were all pretty cheap 1/4" jack components.

Basically why I switched. The included preamp had all sorts of problems with noise and cutting out when moved.

 

My advice for what it is worth. Phantom power on a mixer will not have any affect on a no phantom powered mic. The first problem that I encounter with a set of mics on concertina is feedback, specially with a monitor system. The other issuue is tonal and volume balance between the left and right hand. My solution is a pair of AKG C416L mics. Velcro or non residue adhesive pads to hold them on the instrument. I even have a spare set of instrument mounts to attach( no drilling, or permanent residue) to my new Bb/F when it arrives. These mics use a sub mini XLR that I plug into an AKG B29L mic preamp. It allows for individual level of left and right hand. The other nice feature for me is that the preamp sends out a mic level XLR to the board, or a switch turns it to line level like a guitar or keyboard out. These mics are great with respect to tone and also for feedback rejection. The only drawback is they are a little pricey. In reality compared to the cost of a concertina they are in line, also I think that sound quality is worh the expense.

I believe Nially Vallely used to use AKG 418s but cited feedback problems. I'm not familiar with the 416 model. He uses the Sennheisers I mentioned earlier and I'd recommend them as well. I don't have any velcro my the instrument and find that some electrical or gaffer's tape, which leave no residue, applied at each gig will keep them in place better. They're XLR out and don't require a preamp (though I do use a simple XLR combiner to get them in one channel).

[Howard Mitchell]

My advice for what it is worth. Phantom power on a mixer will not have any affect on a no phantom powered mic. ...

 

It's worth reading wikipedia on this, especially the "Caution" section.

http://en.wikipedia.org/wiki/Phantom_Power

 

I'd add three things-

 

Some mixers e.g. Phonic, provide "Combination" inputs with a 6.3mm jack in the centre of an XLR. When phantom power is on it can also be present on the jack as well as the XLR and so can be fed to unbalanced sources which may malfunction or be damaged.

 

An un-balanced microphone e.g. a high impedance dynamic mic or a balanced mic wired to give an un-balanced output often on a jack, may be damged by connection to a phantom powered input. Be careful with XLR to Jack adaptors in this case.

 

Some instrument amplifiers provide a balanced "DI" output for connection to a mixing desk. Few have thought about phantom power and consequences include reverse polarisation of electrolytic capacitors and damage to the output circuitry resulting in distortion and/or physical damage.

 

On the positive side, the AKG B29L does not suffer any of these defects and can be safely connected to a phantom powered input. This also applies to AKG wireless receivers in the WMS80 and WMS60 series (and possibly the later WMS40).

 

Howard