Hello everybody,
I am currently planning an OTL with the 6AS7. I want to drive the tube up to class A2 (VG-1=+10V). In simulation (tube test bench), the distortion increases very sharply at VG-1> 0 V.
Has anyone operated the 6AS7 in this mode outside of the simulation and can confirm that this is the case?
I want to rule out that it is only due to the spice model (...I've already tested different spice models...)
Thank you!
greetings
Bambini
I am currently planning an OTL with the 6AS7. I want to drive the tube up to class A2 (VG-1=+10V). In simulation (tube test bench), the distortion increases very sharply at VG-1> 0 V.
Has anyone operated the 6AS7 in this mode outside of the simulation and can confirm that this is the case?
I want to rule out that it is only due to the spice model (...I've already tested different spice models...)
Thank you!
greetings
Bambini
The distortion comes from the driver stage, trying to supply current into the 6AS7's grid when forward conducting. It's an issue for all class 2 amplifiers, and the solutions tend towards the heroic. All good fortune.
YOS,
Chris
YOS,
Chris
My understanding is that it's only worth using A2 with high impedance valves; what do you hope to gain when there is so little area to the left of the zero grid volts curve?
Attached is a picture of two circuits with different supply voltages, but the same quiescent current.
The circuit on the left goes up to almost VG-1=10V, the circuit on the right remains in the negative range with VG-1.
The distortion of the two circuits is shown in the logfile on the right.
@ Chris Hornbeck: as I can see, the grid current is not stored in the spice model at VG-1> 0V.
@ piano3: the idea is to keep the supply voltage as low as possible 130V vs. 90V.
The circuit on the left goes up to almost VG-1=10V, the circuit on the right remains in the negative range with VG-1.
The distortion of the two circuits is shown in the logfile on the right.
@ Chris Hornbeck: as I can see, the grid current is not stored in the spice model at VG-1> 0V.
@ piano3: the idea is to keep the supply voltage as low as possible 130V vs. 90V.