Re: Can I do this with a uProcessor?



Rich Grise wrote:

Eeyore wrote:
Rich Grise wrote:
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.

The ins and outs are biased at ZERO volts.

That's how ac coupling works !


Well, yes, of course - let me fix my suggested circuit:

NO NO
C o----------------------------o C
--+----o o----+---> etc.
| o--||--[effect circuit]--||--o |
[1M] NC NC [1M]
| |
GND GND

This shows the caps around the cct, and the 1Ms are pop suppressants. :-)

Actually, the 'pop suppressor' 1Ms need to be on the terminals you denoted NC.

However, as I described, an audio signal referenced to ground spends about half its time at
a negative voltage.

A negative voltage that the 4000 series CMOS swich can't cope with. That was my point.

Graham

.

Relevant Pages

  • Re: Can I do this with a uProcessor?
    ... Rich Grise wrote: ... and output of each effect stage, one on the input and the other ... with NC of each going to the circuit and both NO's ... bias zeroed at, say, 4.5V, and only a volt or two peak, I see no problem. ...
    (sci.electronics.design)
  • Re: Can I do this with a uProcessor?
    ... Rich Grise wrote: ... and output of each effect stage, one on the input and the other ... The CMOS IC switches can only tolerate signals that stay within their supply ... bias zeroed at, say, 4.5V, and only a volt or two peak, I see no problem. ...
    (sci.electronics.design)
  • Re: Can I do this with a uProcessor?
    ... and output of each effect stage, one on the input and the other ... with NC of each going to the circuit and both NO's ... (The switch "wipers" (actually analog switches) ... bias zeroed at, say, 4.5V, and only a volt or two peak, I see no problem. ...
    (sci.electronics.design)
  • Re: Line powered audio switch, is this feasible ?
    ... > Rich Grise wrote: ... > circuit;-) ... You sound ... like you have inputs acting like outputs - PLEASE draw a picture ...
    (sci.electronics.design)
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