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Double Bass Underwood PU and phantom power

M

migbass

May 13, 2007
7
0
www.miguelamado.com
#1
Hi guys.
Am thinking about getting a Headway EDB-1 preamp to blend a DPA 4099 with an Underwood PU.
The DPA will need to be powered with phantom power that the weadway provides. But this is will mean feeding the Underwood with phantom power too, since the headway doesn't allow feeding only one of the channels.
Can any of you help with this? will the Underwood work properly with phantom power? is it possible it might get damaged?
any suggestions on this?

thanks a lot!!
 
#5
that would make sense, but according to the owner's manual, it does send phantom power through the jack.

anyway, you are using exactly the setup I'm considering.
can you get me some feedback on that?
do you use the line out to a monitor amp mixing the DPA with the underwood?
how does the DPA work through the headway? can you get good gain before feedbak?
apreciate it
 
#6
It is not a good idea to let phantom power reach a piezo.

First piezos deform themselves when voltage is applied. I'm not sure if 12V can damage them but 48V could damage a piezo.

Second the phantom power will be delivered by resistors of some (ten) kOhms (it is an electronic standard, every phantom power supply has the same resistors). This will harm the frequency response of a piezo in the same way as a low impedance amplifier input does. So it might work but would sound rather bad.

Decoupling with a capacitor is not a good idea because of the second point mentioned above. So there shouldn't be any phantom power switched on when a piezo is connected.
 
#7
migbass said:
that would make sense, but according to the owner's manual, it does send phantom power through the jack.

anyway, you are using exactly the setup I'm considering.
can you get me some feedback on that?
do you use the line out to a monitor amp mixing the DPA with the underwood?
how does the DPA work through the headway? can you get good gain before feedbak?
apreciate it
Click to expand...

Sorry, I haven't picked this up for a while. I've had to go back to the manual and yes, it does put out 12v phantom through the jack and I never was aware of this. In fact, pardon my ignorance, I'm not accustomed to seeing phantom power coming through jacks at all! I have used the DPA and Underwood in combination through the Headway with OK results. It is good to have the Underwood to tighten up the sound of the 'airy' mic. However, the 'gearing' of the gain control is not friendly - by that I mean that only a small rotation of the gain almost doubles the vol of the Underwood so a bit of inconvenience there. Also, the signal from the Underwood is very brittle and 'toppy' and I now wonder whether this is in fact due to the 12v going into the piezo as doubleMIDI suggests.

When I'm using this combination I have a QSCk10 powered speaker on a pole to one side and behind me. This setup, together with tweaking the Headway will reduce feedback to manageable levels. As the k10 is a two channel (500 watts per!) power amp I now propose to run the Underwood through its own outboard preamp - probably a Fishman Pro eq - and then into the second speaker channel. That way I'll not have any phantom power and a lot more control over the volume.

BUT - that will be a lot of wires in the bag: 2/3 mains, 2 XLR and 2 coaxes plus two outboards. Someone previously posted that the DPA wasn't a cheap date! Hardly plug'n'play but worth the effort for that important gig.
 

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