Following up on the reply from mganga,
I have a Decware CSP3 tube pre amp. In addition to the standard volume attenuator there are adjustable pots for gain on both the input tube and on the output tubes. My understanding of these pots is for "gain riding". Adjusting the gain affects the performance of the tube (s) and changes the character of the sound so you can may it darker and syrupy or not. This allows for fine tuning of the pre amp to find the sweet spot of the tubes. The pots change the performance of the tubes a lot. This is a nice little tube pre amp. It does benefit from changing out the stock tubes, particularly the rectifier tube.
I have a Decware CSP3 tube pre amp. In addition to the standard volume attenuator there are adjustable pots for gain on both the input tube and on the output tubes. My understanding of these pots is for "gain riding". Adjusting the gain affects the performance of the tube (s) and changes the character of the sound so you can may it darker and syrupy or not. This allows for fine tuning of the pre amp to find the sweet spot of the tubes. The pots change the performance of the tubes a lot. This is a nice little tube pre amp. It does benefit from changing out the stock tubes, particularly the rectifier tube.