[sdiy] ...that 1K resistor on the output

[Jerry Gray-Eskue]

For a general output I would tend to set it up Op Amp > Cap>Resistor out 
with a bleed resistor 1M or more to ground.

The reasoning is the with the output resistor last you get a time constant 
when random voltages hit the patch cord possibly providing some over voltage 
protection for the cap (electro-static etc.). The bleed resistor is as Harry 
states, for Pop reduction. A floating cap can build or retain some stray DC 
offset voltage that can cause the Pop (or worse) when the plug is inserted.

Jerry

----- Original Message ----- 
From: "Harry Bissell" <harrybissell at wowway.com>
To: "Justin Owen" <juzowen at googlemail.com>
Cc: "SDIY List" <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, January 27, 2011 9:38 AM
Subject: Re: [sdiy] ...that 1K resistor on the output


> 1) series
>
> BTW, I use a much smaller resistor, 100 ohm typical, even 10 ohm if I 
> really don't want any voltage drop.
> I do NOT ever tie outputs together to mix them, I consider this a form of 
> child abuse...
>
> 2) for AC coupling, I use a small series resistor on the output, then a 
> series capacitor, then a 1Mohm to ground at
> the output. This keeps the otuput at 0V and prevents (sometimes LARGE) 
> pops when a cable is inserted...
>
> H^) harry
>
>
> ----- Original Message -----
> From: Justin Owen <juzowen at googlemail.com>
> To: SDIY List <synth-diy at dropmix.xs4all.nl>
> Sent: Thu, 27 Jan 2011 10:31:26 -0500 (EST)
> Subject: [sdiy] ...that 1K resistor on the output
>
> Hello,
>
> Last week I was asking about passive vs. buffered multiples.
>
> A few of you mentioned that you put a 1K resistor on the output of all op 
> amps (or all outputs...) - can I ask: Is that in series i.e. between the 
> output of the op-amp and the actual output or from the output of the 
> op-amp to ground i.e. load?
>
> And secondly - for AC-coupled outputs are you running op-amp > resistor > 
> capacitor > output or op-amp > capacitor > resistor > output?
>
> Thanks,
>
> Justin
>
>
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>
> -- 
> Harry Bissell & Nora Abdullah 4eva
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy