Distortion VS OPT impedence

[Nihilist]

I'm sure this is a simple question for those in the know. Unfortunately , I am not one of those, yet.

In any data sheets for 6V6 , there is an obvious sweet spot for lowest distortion and highest output , roughly at 6600ohms or so. I understand that this is a graph for Pentode mode , but why is it that I always read that Triode tied 6V6's prefer an 8-10K load when they have a lower Anode output impedence ?

I've also continuously read that a triode tied 6V6 will have lower distortion , but with less output , as impedence goes up. This goes against the data sheets , and I'm just curious/confused as to how this is possible.

Again, I understand the data sheets are showing this graph with regards to Pentode mode. Perhaps when run Triode tied the tube is more linear and doesn't have such a "sweet spot " ?

I have OPT's that are 6600 ohms with 4 and 8 ohm taps , currently setup with 6V6's triode tied. I am halfway done with some minor circuit adjustments and plan on trying the secondary tap set to 4ohm with my 8ohm speakers (fullrangers with no components inline) . I believe this will give me approximately 13,200 ohms primary . I'll post again and let ya'll know what I think.


Thanks...........................Blake

[Tom Bavis]

Pentodes have a "sweet spot" where output is maximum and distortion is minimum... triodes are different. They can deliver more power at clipping into lower loads, and will have less distortion at higher loads. 3 times the plate resistance is one rule of thumb but 5X will give less distortion. This is mostly 2nd harmonic, so it cancels in push-pull. Try both (6.6K and 13K) and see what you like best.