About loadline again, how to choose load and current

[ervinl]

Hi,

I know about load line curve, but anyway, it only gives range of choices in that permitable area.

I would like to know the effect on sound signature, comparing:
- High Load (e.g. 10x) vs Low Load resistor plate (e.g. 2x)
- Low current (higher value of cathode R) vs higher current as long as in the area (dissipation, max current, voltage)

Is that true that we can gain higher even harmonics (especially 2nd) than odd one, by setting proper current (lower current?)?

There is formulation is the link (given in other thread), but I can't catch directly with THD relation and sound. I think It is practical, not just theoritical.

Just for sample, e.g. tube 5687, 7119, 12AU7

Thanks,

Ervin L

 

[Wavebourn]

Even harmonics null out each other by symmetry, so less symmetrical is transfer curve, less even harmonics' suppression. Forget about THD, just do a lab work observing and listening.

 

[BudP]

Do your own load line investigation. Many tubes, even famous ones like the 300B tube have hidden zones of linearity that seem to have been overlooked. These zones are not at the lowest point of distortion either, though certainly out on the flatter part of the slope, and are usually able to provide good power. I have attached a look at the 300 B just so you can see what I mean. Compare performance at 4.545 kz to the more typical 3.4k, 5k and 6.6k.

By the way, the 7119 is a sensationally good driver tube.

Bud

 

[ervinl]

Do your own load line investigation. Many tubes, even famous ones like the 300B tube have hidden zones of linearity that seem to have been overlooked. These zones are not at the lowest point of distortion either, though certainly out on the flatter part of the slope, and are usually able to provide good power. I have attached a look at the 300 B just so you can see what I mean. Compare performance at 4.545 kz to the more typical 3.4k, 5k and 6.6k.

By the way, the 7119 is a sensationally good driver tube.

Bud

I already build 7119 tube as pre amp/driver for my SS Power Amp (like what is called hybrid). Since it is AF (may be followed by CF, just don't start to DIY the CF yet), it is single ended. I load as regular/common, 10mA with 10k (as in DIY Paradise), so I wonder if there is better sweet spot (e.g. less current, or higher?). Someone said it is sweeter with less current (= higher load/resistor plate, cathode resistor). I can't find it in the datasheet yet.

Thx,

Ervin L