Phantom Power

Finstad · 29th October 2004, 09:11 AM

Hi!
I have buyed some old TAB V72a mic-pre. Now, I must have phantompower. It is many different companies who made phantompower boxes, like AKG, Proel etc. I wonder; is there any differences in the soundquality between these boxes??

I also know I can destroy the transformator in the V72 with phantompower, can someone give me instructions to avoid this??

Allso, I`m going to make some mic pads. -10dB, -15dB, -20dB and -30dB. I will make a box with 4 separate in/outs. Can I just find the resistor value, and solder it between XLR pin 2 and 3 ??
or must I make some other things?

Thanks a lot!

Finstad

David Kulka · 29th October 2004, 05:13 PM

I'm not familiar with your TAB V72a but as a general rule, correctly wired phantom power will not damage a preamp. If you buy a pre-made phantom supply, it should be fine.

There should be no difference in sound quality between different phantom power supplies, if they are working right. I think that either of the ones you mentioned would be fine.

A mic pad typically uses 3 resistors. A 20 db pad would use two 680 and one 150 ohm resistor connected in a "U" configuration. This link gives a schematic and formulas to calculate resistor values for other db amounts. http://www.uneeda-audio.com/pads/

The pad needs to go between the phantom power box and the mic preamp, not between the mic and the phantom power box. (Otherwise the phantom power itself will be padded, which is not what you want.)

I hope this helps you.

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29th October 2004, 09:11 AM	#1
Finstad Gear nut Join Date: Jan 2003 Location: Norway Posts: 78	Phantom Power Hi! I have buyed some old TAB V72a mic-pre. Now, I must have phantompower. It is many different companies who made phantompower boxes, like AKG, Proel etc. I wonder; is there any differences in the soundquality between these boxes?? I also know I can destroy the transformator in the V72 with phantompower, can someone give me instructions to avoid this?? Allso, I`m going to make some mic pads. -10dB, -15dB, -20dB and -30dB. I will make a box with 4 separate in/outs. Can I just find the resistor value, and solder it between XLR pin 2 and 3 ?? or must I make some other things? Thanks a lot! Finstad __________________ www.toproomstudio.com

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29th October 2004, 05:13 PM	#2
David Kulka Lives for gear Join Date: Oct 2004 Location: Burbank, CA, USA Posts: 707	I'm not familiar with your TAB V72a but as a general rule, correctly wired phantom power will not damage a preamp. If you buy a pre-made phantom supply, it should be fine. There should be no difference in sound quality between different phantom power supplies, if they are working right. I think that either of the ones you mentioned would be fine. A mic pad typically uses 3 resistors. A 20 db pad would use two 680 and one 150 ohm resistor connected in a "U" configuration. This link gives a schematic and formulas to calculate resistor values for other db amounts. http://www.uneeda-audio.com/pads/ The pad needs to go between the phantom power box and the mic preamp, not between the mic and the phantom power box. (Otherwise the phantom power itself will be padded, which is not what you want.) I hope this helps you.