Can someone explain the phase inverter in the Traynor YBA-2 ?

[Chuck H]

In considering this design I think I've detected what might be a rub regarding it's use in guitar amps that intentionally overdrive the power tubes. Being as the non inverting triode is basically a virtual earth circuit it would have a considerably lower impedance at either end than the input/inverting triode. This mismatch in output impedance will only demonstrate more pronounced once the circuit begins clipping the power tubes with some difference in the frequency knee of the coupling caps as well as allowable grid current and/or time constant meaning that the two inverse signals and how they affect the power tubes will exhibit some different behaviors and likely considerable asymmetry . This might be good in some ways for some amps so it's a "for better or worse" question right now. It's certainly not what we're accustomed to though. I still may wire one up at some point to see for myself. Though I don't have any projects or prospects going on right now.

[Dave H]

Perhaps the asymmetry won't be as bad as you think? When the power tube clips at the grid the NFB of the virtual earth circuit becomes ineffective and its output impedance will be its open loop output impedance.

[waspclothes]

I wanted to update this thread. I'm still really enjoying this amp, it's wooly and gnarly... very unique.

I just came across the schematic for the 5D3 for the first time. I'm familiar with the 5E3 of course, but after seeing the 5D3 I noticed things were VERY similar to this amp - including the phase-inverter that we've been talking about - is pretty much exact. The only changes are component values on C11 (tone cap, makes sense), R10 and R11.