Three different "80 hy 25ma" plate chokes

Design and use of Chokes for PS, anode and filament use.
dave slagle
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Post by dave slagle »

Johnny wrote: I think you're on to something. I've listened to 845 rigs with big Audio Note transformers. They have many great attributes but their low-level resolution isn't as good as what I'm hearing now.
i think everyone looks at it back asswards. the figure they have an 845 and they can get 20W from it so they design it to be. Then some smart ones try a low powered operating point but keep the same 20W iron.

i suggest starting at the speaker and then optimizing the outptu to drive the speaker. If you find through experimentation that you need X watts at Y frequency optimize the Xformer for that rather than some mythical number you tube "can" put out.
I think it would be a mistake to use more power because the bigger transformers wouldn't be delicate.
i assume you mean "bigger" as in power handling and not physical size. the OT's you are digging just happen to be good for 3W @20hz and 25hy @ 60ma can anybody say 2A3 output :-) show them to someone and say they are 3W transfomrers any you will get laughed out of the room (they are about 8 pounds each) I think they will sound brilliant with speakers that like being driven by a 2A3. I used to think that iron should be desinged for when the tube clips, but now i realize iron should be desinged to "clip" when the speaker does. All of your results thus far have supported this unconventional thought.

THANKS!
dave
Johnny
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Size of Transformer

Post by Johnny »

Hi Dave,
i assume you mean "bigger" as in power handling and not physical size. the OT's you are digging just happen to be good for 3W @20hz and 25hy @ 60ma can anybody say 2A3 output show them to someone and say they are 3W transfomrers any you will get laughed out of the room (they are about 8 pounds each) I think they will sound brilliant with speakers that like being driven by a 2A3.
Interesting, I was wondering about the size. I thought since the cores were relatively big, they had more power handling. I agree with you that matching the transformer to the speaker power limit makes much more sense than getting all the power out of a tube. This has been fascinating to me!

John
jarek
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Post by jarek »

I'm sorry for interrupting the fascinating discussion, but I wanted to call your attention to some standard, textbook knowledge :twisted: For a tranny driven by a low impedance source (Rp<<RL) the approximate picture is that the core is driven by voltage so by B. Then due to the loop the current in the winding is distorted. This distorted currrent creates in turn a distorted voltage drop on the DCR, finally presend at the output. A simple picture, but might give some hint - lowering DCR helped lowering distortion more than lowering AC flux + admixing more air. In other words if you kill the distorted part by DCR -> 0 then it does not matter if the core is linear or not...at least in the approx. I quoted (valid above -3dB point). Just my 2c.

-jarek
dave slagle
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Post by dave slagle »

hey jarek.

this is also what partridge says in his gapping PP iron series. (i see this all fitting together)

BUT whan you consider that the progression usually is

DCR<<Rp<<Rload you still have the Rp (source impedance) dominating.

for a typical 2A3 you will have a 150 ohm DCR a 750 ohm Rp and a 3K load.

i can see what you are saying for the case of line and power use where the Rsource is near zero, but for tube stage?

in johns case he is actually at something like Rsource = Rload with the DCR going from 1/10th to 1/50th of either. 200R to 50R this makes me wonder if the DCR is the cause or merely a symptom.

dave
jarek
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Post by jarek »

Guys, I'm sorry - didn't want to hijack the thread. Please let me suggest one more thing and I shut up.
200R to 50R this makes me wonder if the DCR is the cause or merely a symptom.
I tried to treat DCR as a cause and crashed for 100th time, so I begin hesitate too. What would clear the things out is the test with varying DCR only: same core, same turns, same gap, just varying wire guage. Then vary Bac: same core, same gap, same DCR, vary turns. Varying gap has already been done.

OK, I shut up now.
Best,
Jarek
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