andyfromdenver
Well-known member
Hi smart people ;D
For an unknown output transformer (OT), with a primary center tap (CT), I have calculated the turns ratio by applying AC voltage to the two primary ENDS (excluding CT) until measuring 1VAC across the secondary. Then, I measured the AC voltage from my variac output for a 30:1 ratio.
I know for single ended OTs I simply use this. I just want to make absolutely sure i'm not missing something with regard to the CT and Push Pull.
I am trying to determine if the "mystery" OT wants an 8ohm load or 4 ohm. (and the schematic/ search engine isn't helping...)
at 30:1 (from primary end to end, no CT) I get
(30x30) x 8 (ohm) = 7.2K reflected primary, this jives very well with 7189 power pentodes (like el84s on steroids, I believe )
(30x30) x 4 (ohm) = 3.6k (of course it does...)
can someone please clarify what the proper speaker load would be for this scenario? I just haven't applied the formula to PushPull vs Single End.
I'll be reading the RDH4 while my question is posted, in case the info is in there.
Thank you!!!!
Andy
edit: ok. so...uhm : ;D
I just measured a transformer I have on hand which is spec'd @ 8k <-> 8ohm. and it is 30:1.
mystery solved.
For an unknown output transformer (OT), with a primary center tap (CT), I have calculated the turns ratio by applying AC voltage to the two primary ENDS (excluding CT) until measuring 1VAC across the secondary. Then, I measured the AC voltage from my variac output for a 30:1 ratio.
I know for single ended OTs I simply use this. I just want to make absolutely sure i'm not missing something with regard to the CT and Push Pull.
I am trying to determine if the "mystery" OT wants an 8ohm load or 4 ohm. (and the schematic/ search engine isn't helping...)
at 30:1 (from primary end to end, no CT) I get
(30x30) x 8 (ohm) = 7.2K reflected primary, this jives very well with 7189 power pentodes (like el84s on steroids, I believe )
(30x30) x 4 (ohm) = 3.6k (of course it does...)
can someone please clarify what the proper speaker load would be for this scenario? I just haven't applied the formula to PushPull vs Single End.
I'll be reading the RDH4 while my question is posted, in case the info is in there.
Thank you!!!!
Andy
edit: ok. so...uhm : ;D
I just measured a transformer I have on hand which is spec'd @ 8k <-> 8ohm. and it is 30:1.
mystery solved.