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Old 16th April 2004, 11:55 AM   #1
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Default Modifying a tape head preamp for phono input.

Have a tape head preamp based on LA3161 which I wish to use for phono input. How do I go about making modifications? My knowlege on electronic principles in not very sound.

The attached schematic is for 1 channel.

Treble is high and mid-bass is almost not existent when used as it is with the phono (could be due to impedance mismatch??). Also there seem to be a low freq hum, but I guess that can be taken care of by using a rumble filter or maybe regulating the supply using 7812 IC.

I know there are plenty of simple phono preamp schematics available on the net, but I like to put this preamp to good use.

Im not very particular the sound quality should be excellent but should atleast be reasonable.

If needed for reference, here's the data sheet for the LA3161
http://service.semic.sanyo.co.jp/sem...f_e/LA3161.pdf

Any help/suggestions would be highly appreciated.

Thanks.
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Old 16th April 2004, 01:03 PM   #2
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Using Thorsten San's prefered values replace the current NFB network with 470R from pin 2 to GND and a series connection of the following two parallel networks between 2 and 3: 680k||4n7 in series with 56k2||1n33.

In front of the input capacitor connect a 47k resistor to GND in place of the 1nF.

Replicate this for the appropriate pins of the other channel.
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Old 16th April 2004, 02:34 PM   #3
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Thanks for the feedback. Hope this is what you meant......
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