How: adapting a line level signal for mic level input

Farshad · 13th June 2006, 05:03 AM

Hi everyone,

I need a box or circuit to adapt a line level signal to input a mic pre. Could it be a simple resistor like a potentiometer or this circuit actually exists? I also appreciate a DIY design.

Cheers,

-Farshad

**TonyBelmont** · 13th June 2006, 05:36 AM

Quote:

Originally Posted by Farshad

Hi everyone,

I need a box or circuit to adapt a line level signal to input a mic pre. Could it be a simple resistor like a potentiometer or this circuit actually exists? I also appreciate a DIY design.

Cheers,

-Farshad

It's called a DI box!

http://www.countryman.com/html_data_sheets/t85data.html

Kiwiburger · 13th June 2006, 05:46 AM

Depends on what you mean by Line level. If you want to go from instrument or semipro unbalanced, an active DI box with variable output level should be fine.

Or are you already at +4 balanced pro line level? You basically need an attenuator. A reamp box would get you almost there - they are basically a transformer with some resistors, but with an unbalanced output.

Attenuators seem to be expensive for what they do. Especially if you want control over the amount of attenuation. You can use multi-tap transformers and rotary switches. Possibly a passive resistor device would work, at the expense of noise.

If you have them already, a reamp box into a DI should work.

Why do want to do this? Can your mic preamp not accept line level? Boosting a signal, then attenuating, then boosting again is not usually a great idea.

Farshad · 13th June 2006, 06:12 AM

Quote:

Originally Posted by Kiwiburger

Depends on what you mean by Line level. If you want to go from instrument or semipro unbalanced, an active DI box with variable output level should be fine.

Or are you already at +4 balanced pro line level? You basically need an attenuator. A reamp box would get you almost there - they are basically a transformer with some resistors, but with an unbalanced output.

Attenuators seem to be expensive for what they do. Especially if you want control over the amount of attenuation. You can use multi-tap transformers and rotary switches. Possibly a passive resistor device would work, at the expense of noise.

If you have them already, a reamp box into a DI should work.

Why do want to do this? Can your mic preamp not accept line level? Boosting a signal, then attenuating, then boosting again is not usually a great idea.

Hi and thanks for the reply,

My line output is +4 from my soundcard. I am interested in a transformaer-based DIY circuit. Do you know of any design?

Thanks a bunch,

-Farshad

tINY · 13th June 2006, 05:13 PM

Look on Jensen Transformers web page. They have a lot of information there.

-tINY

brian_delizza · 13th June 2006, 05:27 PM

Sounds like you need a reamp box to me....

http://www.reamp.com/

brianroth · 14th June 2006, 06:54 AM

If going from a balanced +4 dBu to a typical mic preamp balanced input, all you need is a pad. My good friend Rick Chinn wrote this paper describing the design, and at the bottom of the page are the values for a 40 dB pad that properly matches impedances (bridging on the line source, around 150 Ohms to the mic preamp's input):

http://www.uneeda-audio.com/pads/

Bri

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13th June 2006, 05:03 AM	#1
Farshad Lives for gear Join Date: Jun 2006 Location: Toronto, Canada Posts: 624	How: adapting a line level signal for mic level input Hi everyone, I need a box or circuit to adapt a line level signal to input a mic pre. Could it be a simple resistor like a potentiometer or this circuit actually exists? I also appreciate a DIY design. Cheers, -Farshad

13th June 2006, 05:27 PM	#6
brian_delizza Gear addict Join Date: Jun 2006 Location: CA Posts: 452	Sounds like you need a reamp box to me.... http://www.reamp.com/ __________________ www.indopendence.com www.briandelizza.com www.myspace.com/optymaemcee www.myspace.com/wastelandsmusic

14th June 2006, 06:54 AM	#7
brianroth Lives for gear Join Date: May 2005 Location: Oklahoma City Posts: 1,022	If going from a balanced +4 dBu to a typical mic preamp balanced input, all you need is a pad. My good friend Rick Chinn wrote this paper describing the design, and at the bottom of the page are the values for a 40 dB pad that properly matches impedances (bridging on the line source, around 150 Ohms to the mic preamp's input): http://www.uneeda-audio.com/pads/ Bri __________________ Brian Roth Technical Services Oklahoma City, OK www.BrianRoth.com

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13th June 2006, 05:46 AM	#3
Kiwiburger Lives for gear Join Date: Feb 2006 Posts: 3,766	Depends on what you mean by Line level. If you want to go from instrument or semipro unbalanced, an active DI box with variable output level should be fine. Or are you already at +4 balanced pro line level? You basically need an attenuator. A reamp box would get you almost there - they are basically a transformer with some resistors, but with an unbalanced output. Attenuators seem to be expensive for what they do. Especially if you want control over the amount of attenuation. You can use multi-tap transformers and rotary switches. Possibly a passive resistor device would work, at the expense of noise. If you have them already, a reamp box into a DI should work. Why do want to do this? Can your mic preamp not accept line level? Boosting a signal, then attenuating, then boosting again is not usually a great idea.

13th June 2006, 05:13 PM	#5
tINY Lives for gear Join Date: Jul 2004 Location: Orygun Posts: 6,017	Look on Jensen Transformers web page. They have a lot of information there. -tINY