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From: John Woodgate
Subject: Re: -10dbV audio line input to +4dbU
Date: Tue, 17 Dec 2002 10:36:22 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Tue, 17 Dec 2002 13:56:11 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Jeff Reeve
wrote (in ) about '-10dbV audio line
input to +4dbU', on Mon, 16 Dec 2002:
>I need to convert a -10dbV unbalanced audio line input to +4dbU. Can anybody
>out there provide a link to such a circuit or perhaps describe one. I know
>companies out there make boxes that do this but I would like to roll my own.
>Also I would like to do this with active components.
Is the +4 dBu balanced or unbalanced? If it's unbalanced, you just need
an 11.8 dB gain (-10 dBV = -7.8 dBu) non-inverting op-amp stage. An
NE5534 would be a good device, since your + 4dBu output just might one
day need to drive a 600 ohm load or several higher value loads.
Get the NE5534 data sheet and use the non-inverting configuration with
3.3 kohm feedback resistor (output to inverting input) and 1.2 kohms
from inverting input to ground. This gives you 11.5 dB with nominal
resistors. If you need to tweak the gain, put a high-value resistor in
parallel with whichever one needs it.
If you need a balanced output, then IIRC the data sheet (or maybe the
NE5532 data sheet) shows a two op-amp version and a four op-amp version
for balanced output stages, which can be made unity-gain and follow your
unbalanced gain stage.
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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