Mute circuit - comments appreciated

[rif]

I have the common problem of thumping when turning on/off and switching inputs. So I thought I'd put in a mute that I'd use before turning the selector switch.  I've drawn 2 circuits in the attached picture.  I searched online for one, but everyone seems to want to build a better mousetrap - I'd like to keep it simple.

Will these work?

I stole #1 from a commercial preamp schematic.  It adds a 330 ohm resistor that the signal always pass through. The mute switches the rca signal connection to ground through this resistor.

I made #2 pretty much the same as #1 but got rid of the 330 ohm resistor and switch to ground through the existing 475k ohm resistor.

I can live with the switch (and resistor in #1) in the signal path if it cures the thumps.

Thanks
-david

 

[Grainger49]

Look at FAQ question #1:

http://www.bottlehead.com/smf/index.php/topic,2408.0.html

For some reason I couldn't open your picture.  If you want a mute, put it at the output RCA jacks.  That makes it after the output capacitor which is the source of the thump.  The switch in only in the circuit when muted.

 

[4krow]

Got me. The file is empty.

 

[rif]

Sorry guys, picture is fixed. Grainger - I had read your faq, wasn't being lazy in that respect.

 

[corndog71]

I think you want to break the circuit between the output cap + resistor and the rca jack.

Edited for pic and clarity.

 

[Grainger49]

Like Rob says, you want to ground the two hot leads that go to the RCA jacks for the mute function.  Not quite what is shown on either schematic.

Ok, I stole this information from a Counterpoint SA-1000 schematic.  I owned one.

 

[Paul Joppa]

#1 will work; #2 won't - the output capacitor must have some path to ground so that it can charge up before you un-mute.

The simplest is to just short the 475K resistor, or the RCA jack (same thing), with the switch.

 

[Grainger49]

That would be the same circuit that I suggested.

 

[rif]

I chose the simplest circuit as suggested - short to ground. I hacked one together and it works great (not that I didn't believe). Now I just need to find a good looking switch and a place to mount it.

Thanks again

 

[rif]

My simple implementation grow slightly larger. I wanted to use micro switches but couldn't get both to engage simultaneously with any consistency.  So I decided to use them in parallel to control a relay. I used an RJ45 connector as a wiring harness so I could still take off the top plate. And I added in an led indicator.

So now a very slight push on the BH badge engages the circuit.

--david

 

[Doc B]

That is trick.

 

[earwaxxer]

Thats cool! I just try to remember to turn the power amp off when I mess with the Quickie. I guess I'm lucky because my power amps has a two stage turn on process. Not sure how it works, but the front switch effectively shuts the amp down, but not completely. You have to throw the switch on the back to do that. Occasionally I forget and flip the Quickie switch by mistake and get a pop from the speakers. No damage done, but not too pleasant! I like it. It makes my system complex enough to keep other hands away from it.

 

[corndog71]

Thats cool! I just try to remember to turn the power amp off when I mess with the Quickie. I guess I'm lucky because my power amps has a two stage turn on process. Not sure how it works, but the front switch effectively shuts the amp down, but not completely. You have to throw the switch on the back to do that. Occasionally I forget and flip the Quickie switch by mistake and get a pop from the speakers. No damage done, but not too pleasant! I like it. It makes my system complex enough to keep other hands away from it.

I just have my Quickie and Modded ST35 amp to power on or off.  Yet for some reason others find this intimidating.  ???

Maybe it's the Hammond boxes.

 

[4krow]

Ya know, my system changes from time to time, and in some situations there are just too damned many switches and sequences. I was out of sequence with a pre-amp the other day, and the system sqwacked at me for it. Never happened before, but that's just it, I have to be careful.

 

[earwaxxer]

Fortunately there are better protection circuits today in your high end SS gear. My power amp got a hefty static jolt from the dry AZ air here when I touched it and it shut things down real quick. That was impressive. The maggies are pretty good at taking a hit and keep on going but you dont want a disaster.