Re: Can I do this with a uProcessor?

On Mon, 28 May 2007 01:00:45 +0000, Eeyore wrote:
Rich Grise wrote:

I'd use something like CD4053s, like a SPDT switch at the input
and output of each effect stage, one on the input and the other
on the output, with NC of each going to the circuit and both NO's
going to each other.

NO NO
C o-----------------------o C
------o o--> to next stage
o----[effect circuit]---o
NC NC

(The switch "wipers" (actually analog switches) are invisible in this
view.)

There's a problem with this Rich.

The CMOS IC switches can only tolerate signals that stay within their supply
rails. Since the guitar pedals are AC cooupled, the audio signal will want to
swing 'below ground'. No dice with the above unless you now introduce a negative
rail to supply Vss.

Jfets don't care though. They'll be fine.

I'd expect an "effects" string running off 9V to be using line level,
which would be AC coupled at a volt AC or so, AFAIK. So, with the signal's
bias zeroed at, say, 4.5V, and only a volt or two peak, I see no problem.

If the guy's trying to combine effects after it's already been amplified
up to that level, then yikes!

Or, if the "effects" aren't just filters that are either in or out of the
signal path, then we're still not singing on the same pate.

If he wants to select/deselect/add effects at that power level, then I
must recuse myself from the discussion.

Thanks,
Rich

.

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