How important is the pre-amp?

"This kind of thing deserves a lot more mention and attention. Transformers, I mean."

https://www.youtube.com/watch?v=3ERuhks3GNk

Transformers on the other hand, where resistors have problems transformers have benefits. There is a reason after all why we use them all over the place for isolation and power conditioning.  

You solve one problem; you introduce others. Then it gets tricky.


The issue with transformers is loading and inter-winding capacitance. All transformers have inter-winding capacitance. If the transformer is not loaded correctly (usually too lightly) the capacitance may play a role causing the frequency response to be less than flat. This coloration can be easily heard.

Transformers are called that because they transform impedance. It goes both ways; you're not insulated on the input from the output. So if the output load is reduced, so is the impedance on the input side.

What happens when you have a transformer with multiple taps used as a volume control? Since you are working with a variable turns ratio, to keep the transformer linear you need to have the correct load at both the input and output. You can't, as a designer, expect to always see the same source impedance and you certainly don't see the same load impedance since all power amps are different in that regard. On top of that you have the moving target of variable turns ratio.


So you'll need a lot of switch contacts, not just the ones to change taps but another set with resistor to correct for the changing load impedance as the turns ratio is varied. 

This has to be done right, else the unit can introduce coloration.

I agree that a high performance preamp is important with respect to the performance of a hi-fi system as a whole, but I disagree that the preamp’s sonic performance is always tightly correlated with the price. Sometimes you pay a lot of money for heavy cases, thick, engraved faceplates, name brand recognition, other cosmetics, etc. I prefer to spend the money on advanced circuitry, the best vintage vacuum tubes, high quality stepped resistor motorized volume attenuators, point to point wiring, dual mono power supplies, outboard power supplies, etc.

I disagree that the preamp’s sonic performance is always tightly correlated with the price.

Funny- I was just commenting about this on another forum. I agree the price doesn't have much to do with performance. Those that price to a formula will be less expensive generally speaking. My philosophy runs very similar to yours.

How little I know, and wish I knew! re:

The issue with transformers is loading and inter-winding capacitance. All transformers have inter-winding capacitance. If the transformer is not loaded correctly (usually too lightly) the capacitance may play a role causing the frequency response to be less than flat. This coloration can be easily heard.

Transformers are called that because they transform impedance. It goes both ways; you're not insulated on the input from the output. So if the output load is reduced, so is the impedance on the input side.

What happens when you have a transformer with multiple taps used as a volume control? Since you are working with a variable turns ratio, to keep the transformer linear you need to have the correct load at both the input and output. You can't, as a designer, expect to always see the same source impedance and you certainly don't see the same load impedance since all power amps are different in that regard. On top of that you have the moving target of variable turns ratio.

So you'll need a lot of switch contacts, not just the ones to change taps but another set with resistor to correct for the changing load impedance as the turns ratio is varied.

This has to be done right, else the unit can introduce coloration.

It's all alchemy to me, what the great designers do. I'm glad for it though.