Output knob (on channel B, as that one on channel A isn't used in Hot Fusion mode) is on 12 o'clock. Torpedo's input is not clipping (-9...-6 db/peak). Audio interface's input (Tascam 2x2) is ok too. Input and output on Torpedo are set to Line, input on audio interface is set to mic/line. So it's definitely not analog or digital clipping on inputs/outputs if that's what you mean.
1). So, let's make it clear, as we're dealing with hybrid system and have single 12ax7 that is a dual triode: when Le Lead operates in Hot Fusion mode, signal from guitar goes to amplifying transistor circuit (or you use opamps, I don't know) then to first triode on channel A. Then amplified signal goes to different transistor circuit and then to second triode on channel B. If I push the transistor part of circuit on channel B too hard with signal from channel A, then that transistor overloads and clips and after that second triode amplifies this clipping with the rest of signal. Is it right? If it is then of course I need to lower Fusion knob in order to avoid hard clipping and crackling that occurs in the input transistors of channel B.
2). Speaking of changing a tube. If I want to have the Fusion knob lower and leave the gain amount at the desired level, I have to swap for the tube with greater mu coefficient than existing Ruby 12AX7AC5 HG. It's well known that theoretically every 12ax7 should have mu=100, but in reality it's not that simple. Mu changes from model to model and from unit to unit. Ruby 12AX7AC5 HG appears to be relabeled 9th generation Chinese tube (maybe Shuguang, but I'm not sure). If it is, it has rather high amplification factor. Now, the main question: what can I replace it with that have even more gain?
3). Since we have only one triode per channel, which is it in order? I mean, should I consider it as V1 or V2 (Vn,etc.) or is there a different approach? I'm new to hybrid systems and it's unclear for me a bit
4). I would like to have some professional opinion from you, Guillaume, as nobody knows your circuits as well as you and your crew. What exact tube can be a good replacement for the stock one? Something that doesn't change the tone quality much (as I like its structure), but has more gain. Since JJ, Electro-Harmonix and other common preamp tubes have approximately the same gain factor as a stock Ruby (even less actually), I personally search around Sovtek LPS (maybe it's a phase inverter tube but whatever
), Genalex Gold Lion and Tung-Sol with golden pins. Maybe there're better options that I don't know about. What tube would you install by yourself in my case? Thanks for help