>>and impedance variation seems to be an important issue. What is that? I use a 50K pot in my project. and that Pass DIY B1 buffer what is that? <<
Pots and ladder attenuators present a constant input impedance (Zin), varying by frequency (duh). Series attenuators will never present less than device following it. I've preferred series attenuators for specific "tuning" applications but haven't used one as a master volume control, yet. TVC's and AVC's... I'll just direct you to http://www.stevens-billington.co.uk/page102.htm, which was well documented, for an example.
Lowest possible Zout and highest possible Zin would be the theoretical ideal but reality is never ideal. Many other factors. Tubes tend to have a higher Zout but not usually an issue. When there is an impedance mismatch, both low and high frequency gets rolled off. As I type this, it occurs that capacitance and inductance becomes the real issue. If you've looked at a passive xover, you'll follow my logic.
Choosing a Zin value for a pre-assembled attenuator, which is a relatively recent option, is system dependant.
A buffer is an active stage that has little or no gain. Primarily used for impedance benefits. Placette Active is another example. Musical Fidelity and Space Tech make tube buffers.
One difference between RVC's an TVC's is that the former attenuates to heat and the latter converts to amperage. What that means, I have no idea. When I built my TVC, knowing (or thinking I knew) the difficulties with xformers, I didn't expect it to work well. The chief designer for a respected audio brand (my brother) sat in my living room and told me they wouldn't work and why until I pointed out that he was praising one minutes earlier. Even John Chapman of Bent Audio told me he had to be convinced at first. 'Chatta', as you have learned, any passive might not work in every system.
Pots and ladder attenuators present a constant input impedance (Zin), varying by frequency (duh). Series attenuators will never present less than device following it. I've preferred series attenuators for specific "tuning" applications but haven't used one as a master volume control, yet. TVC's and AVC's... I'll just direct you to http://www.stevens-billington.co.uk/page102.htm, which was well documented, for an example.
Lowest possible Zout and highest possible Zin would be the theoretical ideal but reality is never ideal. Many other factors. Tubes tend to have a higher Zout but not usually an issue. When there is an impedance mismatch, both low and high frequency gets rolled off. As I type this, it occurs that capacitance and inductance becomes the real issue. If you've looked at a passive xover, you'll follow my logic.
Choosing a Zin value for a pre-assembled attenuator, which is a relatively recent option, is system dependant.
A buffer is an active stage that has little or no gain. Primarily used for impedance benefits. Placette Active is another example. Musical Fidelity and Space Tech make tube buffers.
One difference between RVC's an TVC's is that the former attenuates to heat and the latter converts to amperage. What that means, I have no idea. When I built my TVC, knowing (or thinking I knew) the difficulties with xformers, I didn't expect it to work well. The chief designer for a respected audio brand (my brother) sat in my living room and told me they wouldn't work and why until I pointed out that he was praising one minutes earlier. Even John Chapman of Bent Audio told me he had to be convinced at first. 'Chatta', as you have learned, any passive might not work in every system.