Another easy noise gate with just one 4016 (schematics visible now!)

[Carlos]

Hi!

I haven't got time to breadboard the three transistor noise gate I posted here a few days ago, but because of my job I spend some time in libraries. Sometimes you can find interesting circuits of the pre-internet era there. I scanned this easy noise gate. The German article says that because of careful biasing the switches of the 4016 work like transistors, not just on-off, but everything between 600 ohms and some Megaohms!





What do you think about it?

Carlos

[Geoff Hunter]

Can't see the picture 

[Carlos]

Maybe you cut & paste the link:

http://img315.imageshack.us/img315/2673/4016noisegate21sg.jpg

Regards

Carlos

[Mark Hammer]

What do you think about it?

I think it is essentially a sub-circuit that needs a whole bunch of other circuitry to stand on before being functional.  It's all switches.

[Carlos]

Translation from the article:

The pot sets the threshold of the noise gate.  If the input signal is above this threshold, S1 conducts. The trigger input of S2 is pulled to ground. S2 is open now, S3 closes and C3 is discharged. The trigger input of S4 is at 9 volts, so switch S4 is closed and the signal gets through. The value of both R7 and C3 determine the decay time.

[Mark Hammer]

Yes, but normally the signal has to be at some level in order for all that to happen.  This assumes a signal of a particular level from a particular impedance source.  That does not prevent it from being a highly usable gate, though.  It just means that persons thinking they can simply put the circuit shown on a board and have a fully functioning noise gate will be rather disappointed with what they end up with.

[Carlos]

Mark,
the author points out that he put such a noise gate in his string ensemble (remember those Solinas
So there must be a certain signal level and buffering to begin with, like in distortion boxes. You can put this noise gate in front of the output volume pot.
I would replace R7 by a pot, though, to make the decay time adjustable.

Carlos

[Carlos]

Hi,

I've got some problems with Yahoo Briefcase. I can't upload the schematics and make them available to everybody here.
Has anybody 236kb of webspace?

Carlos

[GFR]

Try

http://www.imageshack.us/

[Carlos]

Thanks for your help.

[Geoff Hunter]

Works for me now! Thanks

[DDD]

The device seems to be quite sensiitive noise gate. S1 and S2 provide enough gain even for the low-level signals, S3 works as trigger, S4 is a switch. Nothing more is needed. Simple and cheap gate, easily adjustable with bias circuit.
In any case, the schematic makes a very good impression.

[TELEFUNKON]

drawback: when "off", the subsequent pedal/amp is "open circuit" (floating) input.

[DDD]

R8 prevents "floating".
Also it's not a problem to add one 1M resistor from the Ausgang terminal to ground.

[GFR]

I think Telefunkon means R8 = 1M is too large an output Z. It may be paradoxal for a noise gate, but this large out Z is prone to pick up noise

[TELEFUNKON]

for high gain following the gate, 1M = "floating", imho.

[Carlos]

I see your point, but why can't you just add a 10k resistor from output to ground?

Regards

Carlos

[GFR]

I see your point, but why can't you just add a 10k resistor from output to ground?

Regards

Carlos

Because then, when the switch is "on", the input will see a very low impedance.

[TELEFUNKON]

Ain`t that a bitch?

[Carlos]

Right now S4 is wired as a switch that disconnects the signal from the output.
Why can't you wire S4 and a say 2k resistor as a voltage divider so that S4 shunts the signal to ground?

Carlos