At the first time, I also the one who disagree of impedance matching effect to the sound quality. Until I make B1 buffer preamp several years ago, I discover how important to match the input/output impedance by using proper potentiometer. It will not 100% matching between input/ output impedance, but the improvement of the sound is noticeable better.
On my hand, I have 50 kilo ohm stereo potentiometer from Alps. They called it blue velvet version. The turning feel is very nice and sturdy. The quality of this pot is very good. It will replace my previous 100 kilo ohm potentiometer from Noble. I have so many mistakes putting it on my gainclone. One of my mistake is 100 kilo ohm for Gainclone amp input is too much. The result with 100 kilo ohm potentiometer is the lower frequency not present very well.
This the Noble potentiometer that I mentioned before. It is 100 kilo ohm and B series potentiometer.
And what is B in the potentiometer means? We are not talking about impedance matching issue anymore. This is whole new story. The Noble is B type and the Alps is A type (they also have their own A or B pot either way). I always ignore that letter and jump into the result that for the B series potentiometer, adjust the music volume by turning the pot just a little but the sound already loud. I assuming because of the resistance of the pot is too high, but it is not. It is a B type Pot characteristic which is linear. It is suitable for tone control but not volume control. The linear of B type potentiometer make the changing resistance while turning is also in linear move.
Another type is the A potentiometer. The characteristic is non-linear which suitable for the volume application. The gradation of the sound is noticeable smooth with the turning, it will not too loud at the first one third of the total volume turning. The changing resistance while turning this pot is gradually increase after two third of the volume turn. Note should be taken that either A or B type potentiometer has the same final value as stated per specification.
Now I will replacing the Noble potentiometer with this Alps Blue Velvet.
Time to dressing up the front face with the aluminum knob. It is heavy and look amazing. Hex key is required to lock the shaft.
As I told earlier, you can disagree with sound quality issue for the potentiometer impedance matching and you can also disagree with A-B pot characteristic, but for sure, you will agree this upgrade is dress-up my amplifier.
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