impedence value.? amp to preamp.

The problem with a lot of passives is that the input impedance of the amp interacts with the cable capacitance and the source impedance of the volume control.

The result is that there is reduced bass and impact at low volumes. Passives really work best when they are built-in to the amplifier.

First, start with the source impedance. Then add to it the value of your passive. That is now the source impedance (much higher) at low volumes. A tube amp has a high input impedance- 100K is common.

The result is that the high output impedance of the volume control, with the high input impedance of the amp, and the character of the interconnect cable itself will result in drive difficulties at low volume, because the source impedance will be primarily the value of the control. At higher volumes this effect is reduced. Thus it is to your advantage to not have a whole lot of voltage output (3 volts max) out of your source, so that you can run the volume control near the top! Midway down, and the control is already degrading the signal.

Most CD player manufacturers don't get this simple point, and so put **way** too much output from their players. I've seen them as high as 15 volts- making a passive control useless (if you want it to sound right).

Bombaywalla, it will help a lot, in one way, but now you have a different problem- drivability. There are very few sources that can drive 2.2K without distortion and/or bandwidth loss!

There really is not a good way to execute a passive volume control without running into some sort of problem like this. TVCs work much better, but have their own issues as well, although IMO far less severe. IMO/IME experience if you really want to do it right, an **properly designed** line stage is the only way to go.

Hi Bob, to really get a passive to work you get into trouble when you get over 10K for a value, even with short cables. That's why you are better off having the control inside the amplifier, or else inside the source (both inconvenient), and buffered from the cable. Even with 10K, the effect can still be heard.

There was a lot of talk about buffered PVCs a few years back, but what we are talking about then is an active without gain.

Hi Bob, no worries! The higher the value of the control, the greater its artifact (and that of the cable) is going to be. If you have a higher input impedance, like Vett93 above, the problem you get into is high frequency roll-off.

The lower the input impedance of the amplifier, the harder it will be to get bass at low volumes.

Essentially you can regard a passive system as a sort of tone control that also affects the volume. Because TVCs have greater control of their output impedance they can offer greater performance in this regard if other factors are also taken care of.