Tanka ... SE and Balanced preamps, presentation

[ggetzoff]

so, I tried just one thing I didn't tried - introducing separate cathode resistors, as common way of equalizing shared currents in parallel elements - and that did it

I serviced a buddies Al Eaton 45 recently and it used a single K resistor for both 45s………🤣🤣🤣

 

[Zen Mod]

as I wrote (and explained culprit), it was surprise for me ..... but then, feeling stupid is my natural state, enabling me to see always new World's Wonders

 

[ggetzoff]

as I wrote (and explained culprit), it was surprise for me ..... but then, feeling stupid is my natural state, enabling me to see always new World's Wonders

You are in good company…..it worked fine in the Eaton amp.

 

[Zen Mod]

explanation was - as I connected these triode systems, there is no single link in chain where I have any resistive loss ( yeah, being anal about that) and as tube as whole is practically biased/fed with CCS in cathode, even tiniest difference in transfer characteristic between two triode systems is resulting in see-saw effect

You'll never have same see-saw effect in stages where parallel tube systems are biased in "usual" way - through voltage sag across cathode resistor or whatever, be it degenerated or not .....

crucial difference here is stage both biased and loaded through CCS situated in cathode(s), presenting very big dynamic impedance of load

you can represent it as ....... say weightlifting bar with sliiiiightly different weights on two ends

if you place it on block of rubber and there is mild earthquake, it'll act in some funny way

now, if you place it on top of very springy spring, and there is same mild earthquake, it'll act in muchmuch funnier way



and, just for the record, toobz with greater xconductance are much trickier bars than toobz with eenyweeny xconductance

 

[Zen Mod]

anyone remembering CJ ART preamp?

just for giggles

 

[ggetzoff]

Forgot about it, super cool. Okay, you either haven’t gone to bed or you are up before the sun.

 

[Zen Mod]

sun is up, going to bed

 

[stajo]

just for giggles

Everyone needs 30 db of amplification now and then. To the important question, can it drive an F4?

 

[stajo]

You'll never have same see-saw effect in stages where parallel tube systems are biased in "usual" way - through voltage sag across cathode resistor or whatever, be it degenerated or not .....

crucial difference here is stage both biased and loaded through CCS situated in cathode(s), presenting very big dynamic impedance of load

you can represent it as ....... say weightlifting bar with sliiiiightly different weights on two ends

if you place it on block of rubber and there is mild earthquake, it'll act in some funny way

now, if you place it on top of very springy spring, and there is same mild earthquake, it'll act in muchmuch funnier way



and, just for the record, toobz with greater xconductance are much trickier bars than toobz with eenyweeny xconductance

Steep tubes are great as cathode followers but they are also tricky and sensitive. Morgan Jones has an example with 6C45 sinked with an EF184 on page 576.