Hi All, I recently started investigating alternative volume controls and find TVCs interesting. I use SUT for my phono cartridge so am familiar with secondary load based equations to calculate primary impedance.
If I apply this equation ( Rp=Rs/(Gain^2) to the TVCs it appears that at full volume (gain=1) my preamp would see the impedance of my power amp input (150K) and as you turn the volume down the input impedance would rise very quickly. For example -6db (gain of 0.5) would give an input impedance of 600K (150K/(0.5^2)). Is my thinking correct here? If so this seems like a very good situation.
Is there such a thing as source impedance of the secondary of the TVC attached to the amplifer that needs to be considered relative to the power amp input load impedance? This where I keep getting a bit confused. Do you look backwards through the transformer and consider the source impedance of the pre-amp and apply the transformer gain equations? If this does need to be considered does it decrease as volume decreases?
thanks in advance for any enlightenment