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General Discussions => The Lab => Topic started by: pittsburgh on December 28, 2009, 11:45:10 PM

Title: Convert Mic In to Switchable input
Post by: pittsburgh on December 28, 2009, 11:45:10 PM
  I want to change the input for a tape machine that I'm modding to receive both mic, line, and instrument level inputs, from an input dedicated to receiving only mic level input. Is this something that can be simply by changing the input or does the circuit have to support the increased signal level in order to do so? If it is possible to build such a switch where can I go to find more information?

  -P
Title: Re: Convert Mic In to Switchable input
Post by: PRR on December 29, 2009, 02:09:16 AM
Attenuate everything to mic level.

Line can be padded with 22K+1K, come out hot mike level.

Instrument... such a pad either throws a low load on the gitar, a high source to the mike amp, or has too much loss. This is normally done with a buffer and pad, or a DI transformer.

> input for a tape machine

WHICH "tape machine"? The old-old tube tape decks with UN-balanced mike inputs-- just jam your geetar right in. Guitar evolved around old-style grid inputs. The other issues only arise for transistor decks and balanced inputs.
Title: Re: Convert Mic In to Switchable input
Post by: pittsburgh on December 29, 2009, 08:09:47 AM
It's an old tube transistor 1965 Wollensak stero machine. Thanks for the help, I've jammed a guitar plug in there before. It sounds pretty good.
Title: Re: Convert Mic In to Switchable input
Post by: stitch-o on December 29, 2009, 09:02:05 AM
I just found this handy page (thanks to Brian Roth) on wiring pad circuits:
http://www.uneeda-audio.com/pads/