OPT for parafeed SE

[avincenty]

I have some 1619 that i want to try in a SE Parafeed configuration (triode connected)using a ccs on the plate. If the load line is horizontal, how critical is the selection of an opt with a specific impedance ratio? Would any opt do as long as the proper coupling cap is selected (based on primary impedance)? Or is the rule of thumb to use a ratio similar to the one used if using a traditional se design based on the tube's load line?

Alfredo

[Yvesm]

Note that as soon as you tie a load accross the CCS the load line will no longer be horizontal.
An horizontal load line (no current change) means that you extract no power from your tube.
So you have to compute the load as usual according to the tube and the PSU you plan to use.

Don't forget that the CCS will waste (and have to dissipate) the same power that the ouput tube itself, you have take that in account when designing your PSU.

Yves

[avincenty]

Thanks Yves,

I have searched but have not really found a clear explanation or graphs for this type of output stage.

Searching a little more if found @

Active loads and signal current control

"The Sum of the AC currents through the triode and the primary of the output transformer will equal the DC current set by the CCS"

I now see that the CCS ideal horizontal load line only applies to stages whose load do not draw any current.

Alfredo

[Arnulf]

Originally Posted by avincenty

I now see that the CCS ideal horizontal load line only applies to stages whose load do not draw any current.

Let me know when you find a real world input that draws zero current While you're at it let me know when you find the CCS with infinite impedance.

Neither of these eixt, both are theoretical concepts. In reality you have two loads in parallel (CCS & whatever the following stage presents) and one of these is usually dominant by far and it is this load that determines the combined load impedance, so you can usually disregard the CCS (it only marginally affects the load impedance with real life components and it would have zero effect in theory).

So your OPT will still follow the same rules for SE output stage, the only difference is that there will be no DC present across the primary.

[kevinkr]

Originally Posted by Arnulf

Let me know when you find a real world input that draws zero current While you're at it let me know when you find the CCS with infinite impedance.

Neither of these eixt, both are theoretical concepts. In reality you have two loads in parallel (CCS & whatever the following stage presents) and one of these is usually dominant by far and it is this load that determines the combined load impedance, so you can usually disregard the CCS (it only marginally affects the load impedance with real life components and it would have zero effect in theory).

So your OPT will still follow the same rules for SE output stage, the only difference is that there will be no DC present across the primary.

Exactly...