# Confused about input to use REW with a laptop



## bcharlow (Dec 23, 2008)

Unfortunately, my desktop cannot be connected to the RS SPL meter in the listening room. So I want to use my son's Apple laptop with REW, instead. 

However, the connection instructions seem to forbid using direct mic inputs on a laptop and specify an external USB/soundcard. Why? 

Did I read that wrong? If so, shouldn't we be able to just run the patch cord from the SPL meter directly to the mic in or the soundcard in on his laptop?

Thanks.


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## brucek (Apr 11, 2006)

You must use a line-in connection on a soundcard. Mic-in connections aren't suitable.

SPL meters (such as the Radio Shack meter) output a line-level voltage signal. The microphone input jack offers high gain since actual microphone signals are quite low in relation to a line level signal.

This extra gain at the mic inputs front end usually results in increased noise.

Mic inputs usually enjoy a very limited bandwidth that is designed to comply with a narrow voice frequency range that a cheap microphone would supply. The port often supplies a 5 volts bias signal also.

You require a line-in to use REW.

Most members that use laptops for REW purchase an external USB soundcard. They are quite inexpensive and offer line-in and line-out suitable for REW.

brucek


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## cavchameleon (Jan 7, 2008)

Here is one of the cheapest I/O USB external sound card (has analog I/O and optical O). It does not need any drivers to run on MAC or PC.

http://pro-audio.musiciansfriend.com/product/Behringer-UCONTROL-UCA202-USBAudio-Interface?sku=702540


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