[sdiy] clickless muting

[Tom Farrand]

David,

Yeah, 16.34 hits the best of both worlds.  The J111 is only sixteen
cents from Mouser in unit quantities (Fairchild) and the J112 is
nineteen cents.  That's pretty cheap and is probably a lot better than
a relay.  It consumes a whole lot less control current, too.  The
control gets a bit more sticky with the J111 but can be managed with
difficulty.  Yeah, the J112 is probably the better choice for ease of
control due to relaxed turn-on requirements.


Stew,

(Update:) Now that part is as cute as a bugs ear.  A little quick on
the turn-on/off times but could probably be managed by ramping the LED
current.  Since the "load current" is minuscule, slewing through the
linear region more slowly would not be an issue.  I like!  The on
resistance is awesome as well ... a lot better than a 4391 or
J112/J112.  At a buck apiece it is a bit spendy but is offset by a
simpler control arrangement.  Mouser has a bunch on order for Xmas
delivery 2012 but none in stock at the moment.  Avnet says none on US
soil and none in Asia or Europe.  Element14 says no cigar as well.  I
guess bodging up a prototype would have to wait awhile.

I used a similar device on an isolation circuit a few years ago.  I
have no recollection of the part number I used but I think the on
resistance was higher.  I'll dig up that part number at work tomorrow
and report back if worthy of consideration.  I think it was also
available in duals and quads.  That would be sweet.  (The on
resistance is higher, IIRC, because the isolation was 4KV.  I needed
that isolation to make UL happy.)

Time to get horizontal.

Peace.
Tom Farrand




On Sun, Oct 28, 2012 at 11:16 PM, Barry Klein <barryklein at cox.net> wrote:
>
> What I remember about this design was that the gates took advantage of the
> virtual ground of the negative input of an opamp as well as another gate
> being in the op amp feedback loop.  It thus eliminated the usual signal
> distortion as well as supported signals up to the supply rails - which a CD
> series chip would normally not do.
> Where are the "figures" you refer to?
>
> Barry
>
>
> -----Original Message-----
> From: David G Dixon [mailto:dixon at mail.ubc.ca]
> Sent: Sunday, October 28, 2012 21:10
> To: 'Barry Klein'; 'synthdiy diy'
> Subject: RE: [sdiy] clickless muting
>
> >  When I worked at Music Man we had a few amp models with a relay that
> > switched between normal and effects channels.
> > This relay would produce a pop in the audio depending on the signal
> > amplitude and I was always looking for an alternative.
> >  I came across one of those design note articles in EDN or similar
> > that utilized I think a CD4007 - the part that had what was termed
> > Mickey Mouse logic capability  (discrete).  I tried it and it worked
> > way better than the relay.
> > Then I was canned and since I have lost the reference article.  Sure
> > would like to figure out what article that was.  I've looked through
> > my reference material at least 3 times and haven't come across it.
> > Way cheaper approach than 2164...
>
> That would have been the "transmission gate" approach.  This works well, but
> I think I'm going to use the series-shunt approach with two JFETs in current
> mode, as illustrated in Figures 16.34 and 16.35.  The beauty of JFETs is
> that their control voltages can be lagged for a "fast crossfade" to
> eliminate clicks.  The circuit is a little bit more complex than some
> alternatives, but it will work well, and is apparently a favorite in
> high-end mixing desks.
>
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