Aleph Preamps...(volumecontroll Q)

hifi

Member
2001-03-06 3:07 pm
sweden
im a little confused over the volumecontroll circuit in the aleph preamps p1.0 och p1.7 they just seems to be switching in and out resistor in series with the signal but the shunt resistor is the same .... dos´nt it usualy is the other way around?......

wouldnt the circuit described in the other thread concearning a balanced volyme controll be better?

/micke
 
Hi there,

I thought I knew that circuit, but I had to go back and have a good look at it to figure it out.

The point to note is that all the relays are double throw types, and in the circuit as drawn, they all connect the resistors to ground and the output is unconnected to the input. As a relay turns 'on', it connects the audio to the output plugs via a resistor, but note that all of the other resistors are still connected to ground, and that is where the attenuation comes from.

In effect Pass seems to be altering both the series and shunt resistor values.

I'm going to feed the resistor values into a spreadsheet and work out the attunuation values and output impedances.

Cheers, Adrian