When dealing with complex engineering problems there are often cascading effects that can be really frustrating.
Let's imagine you are designing the output stage of a preamp or DAC and you decide, for either sound quality or performance reasons, you need to add an active buffer. The simple act of adding that circuitry can trigger an avalanche of unwanted events: you might have to redo the PCB, the added current required might need more power supply, there can be heat issues.
On the other hand, once in a great while you get to make an aha! moment that has only an upside. Such was the case many years ago when we were first designing our preamplifiers.
In 1975 we were one year into building our phono stages and selling quite the number of them. People would buy our little add on box, connect it to their turntable on one end and the aux input of their preamplifier on the other end, and would be amazed at the level of improvement. Turned out this separate phono stage out performed even some of the best built in stages on the market.
So, naturally, customers wrote to us (in letters...hand written letters! Can you imagine?) and asked why we didn't just build a line stage with a volume control and input selector of the same quality to allow them to replace entirely their preamplifiers.
Easier said than done. Try as we might, no extra line stage we knew how to design sounded as natural and open as nothing but a potentiometer. My partner, Stan, asked the right question. Why not make a separate line stage with just a pot and an input selector? Skip the line stage?
Turns out that idea had a problem. The common potentiometer used n all preamplifiers and line stages of the day were 50k pots. Because they were feeding an internal amplification stage with high input impedance, that worked just fine. Remove the line stage and now we have a problem. You cannot effectively feed a 50KΩ input power amplifier with a 50kΩ source (you'll lose level and roll off the top end at lower volume settings).
What to do?
Break with convention and select a 10kΩ level control. Bingo. This checked all the boxes, was a simple solution without a downside, and worked great, allowing us to produce one of the world's first passive preamplifiers.
Just a bit of history to demonstrate that sometimes simple is best.
