naive question coming.....
is there a difference between the two methods shown? , apart from the missing anode in diagram 2
signal attenuation
-
Paul Barker
- Social Sevices have been notified
- Posts: 8996
- Joined: Mon May 21, 2007 9:42 pm
#3
2 doesn't attenuate as it doesn't voltage divide between the source and ground (the other pole of the source signal).
#4
thanks Paul,
slaps head most soundly........I was trying to attenuate with a variable resistor whilst maintaining the input load....
slaps head most soundly........I was trying to attenuate with a variable resistor whilst maintaining the input load....
There's nowhere you can be that isn't where you're meant to be
-
pre65
- Amstrad Tower of Power
- Posts: 21400
- Joined: Wed Aug 22, 2007 11:13 pm
- Location: North Essex/Suffolk border.
#5
Does a shunted pot not work like that ?ed wrote:thanks Paul,
slaps head most soundly........I was trying to attenuate with a variable resistor whilst maintaining the input load....
Runs and hides under the table to avoid flack.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
-
Paul Barker
- Social Sevices have been notified
- Posts: 8996
- Joined: Mon May 21, 2007 9:42 pm
#6
No because the fixed resistor goes from the source to the pot, at this node the grid is taken off. Then the pot which is between this node and ground is adjusted. The effect of this is to change the input impedance and at the same time to change the voltage division. the idea that it works is that there is always a fixed resistor to the grid, the idea that is against it is that it constantly changes the load impedance to the source.
It tends to sound quite good at most listening levels.
Personally I think the guitar amp idea of shifting the attenuation to where the signal level is higher (master volume) eliminates the issue of contact resistance (which is what makes pots and stepped attenuators sound dodgy, all the contacts at low level signal. this is the sales pitch of the lightspeed attenuator: no contacts). Certainly sounds good to me anyway. But you have to design all former stages such that they can handle the maximum voltage swing your source might possibly put out.
It tends to sound quite good at most listening levels.
Personally I think the guitar amp idea of shifting the attenuation to where the signal level is higher (master volume) eliminates the issue of contact resistance (which is what makes pots and stepped attenuators sound dodgy, all the contacts at low level signal. this is the sales pitch of the lightspeed attenuator: no contacts). Certainly sounds good to me anyway. But you have to design all former stages such that they can handle the maximum voltage swing your source might possibly put out.
-
Mike H
- Amstrad Tower of Power
- Posts: 20189
- Joined: Sat Oct 04, 2008 5:38 pm
- Location: The Fens
- Contact:
#7
Assuming the shunted pot version is drawn correctly 
The difference is that the signal to the grid does not pass through any part of the potentiometer, which may be advantageous if said potentiometer, where used in the conventional way, 'fiddles about with' some aspect of the signal quality, which you don't want.
The difference is that the signal to the grid does not pass through any part of the potentiometer, which may be advantageous if said potentiometer, where used in the conventional way, 'fiddles about with' some aspect of the signal quality, which you don't want.
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."