puzzling grounded input

[[email protected]]

In this circuit:
http://kitsrus.com/projects/k48.pdf

Why is the other end of RV1 grounded?

Thanks,

Michael

 

[[email protected]]

In this circuit:http://kitsrus.com/projects/k48.pdf

Why is the other end of RV1 grounded?

Thanks,

Michael

Never mind... I think it has something to do with the input
impedance...

Michael

 

[[email protected]]

A volume control is a variable voltage divider.

Oh...

If the bottom end of
RV1 was not grounded, RV1 would just be a variable series resistor,

That's all I thought it was...

and would have very little effect on the volume.

Ah...

Thanks John and Peter!

--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
GPS and NMEA info:http://vancouver-webpages.com/peter
Vancouver Power Squadron:http://vancouver.powersquadron.ca

Michael

 

[z]

In this circuit:http://kitsrus.com/projects/k48.pdf

Why is the other end of RV1 grounded?

Thanks,

Michael

yeah, like everybody says, and you're on the right track with your
input impedance idea; tacking the far end to ground stabilizes the
input impedance so that the input signal is well behaved with respect
to where you set the pot at. on the other hand, if you just had a
variable resistor in series, like with the thing ungrounded, the input
signal source seeing a wildly changing impedance both in value and in
reactivity (from mostly resistance to mostly capacitative) will very
likely change its frequency response etc, unless it's nicely designed
to ignore that kind of thing.

 

[Jasen Betts]

One quick question regarding the labeling conventions of the resistors in
the schematic. Why are some labled this way: 1K5 or 2K7

Is that 1.5K , 2.7K ohms? Makes sense, I just haven't seen that before.

Exactly right. one reason for this is it makes printed schematics
easier to read.


Look at C5 if I scale the schematic to "125%" the '.'
almost disappears, by using a letter instead of a '.' the values are
more easily read, (they could have labeled C5 100nF, I don't know why
they didn't)

they should have used vector graphics instead of pixels for
the schematic then it would scale better - but that's a different
matter

also the font they chose has the '.' skewed to the left which is
unfortunate.

bye.

 

[neon]

The question is do you want a variable input resistor or a variable voltage source.