Crate V33 2-12 mod questions

[PoPo75]

I know there is a lot of info out there on this subject but I still have questions.

1. Can the "muddiness/bassiness" of the OD channel be fixed by just changing pre-amp tubes?

2. If so, would the amp have to be re-biased? Even if it were fairly new? I read (could be false) that the Crate V series amps are cathode biased and do not need to be biased if tubes are changed.

3. If none of that is possible, how can I get this mod http://www.thegearpage.net/board/sho...d.php?t=448629 to apply to the V33 2-12?

[Pedro Vecino]

Hello. I worked with some
1. You can shape the response using the most appropriate tubes. In V1 you can use a Philips 5751 (less gain and lighter bass in relation to the carrying 12AX7WA). Lower compression also.
2. Bias is through the cathode, but it is convenient to measure the plate current to see what actually happens. In this system you can also find serious problems of symmetry due to the different flow in tubes.
3. Near the input jack (on printed circuit board) you will find a small electrolytic (is connected in parallel with the cathode resistor in V1). You can remove it (cutting) and soldered directly over the cathode resistor an 680n capacitor (.68 uF). This outlines the lows and produces an more agile and articulate sound. Is a minor modification.
Regards