Well, that's better than bringing in the Dread Pirate Roberts.
And sure, you bring in the much dreaded capacitor, but is the capacitor necessarily any more dreaded than the large, inefficient, air-gapped output transformer with a bunch of DC current flowing in its primary?
And the parafeed cap, at least in tube implementations, is usually no more than 10uF, which means a good quality film cap can be used instead of the much more dreaded electrolytic.
se
because it can - internal resistance of damn 3-legged is much lower than internal resistance of any tube - so needed Lp is much lower than needed for tube .
even if you wish to make unnecessary high inductance primary , that way increasing Rdc of primary will show why this is unnecessary , in first place .....
Ok. But I'm not seeing any significant trade off in going with a high Lp in order to avoid having to use large value electrolytics for the parafeed cap.
se
Output Transformer ?
I contacted Bud Purvine of O/Netics regarding an output Tx with the above specs. He said, and I hope he doesn't mind that I am publishing it here:
I have looked at this design a number of times now. I cannot come to a suitable conclusion when faced with the 1.3 amp DC current. The gaps required with any core size I can utilize only allow about 1/4 of the needed inductance, low as it is, for decent low frequency performance. The AC signal flux load is inconsequential here.
My suggestion is to go to high voltage depletion mode FET's, kick the voltage up and drop the current. We can take care of that in the turns ratio.
For people who have either read, or written the article, how might one do this? And for those of you that do respond, please don't say...Just buy the ElectraPrint.
Thank you,
Chris
p.s. I did send Nelson a PM about it but I am sure he has bigger fish to fry than entertaining my little inquiry.
I contacted Bud Purvine of O/Netics regarding an output Tx with the above specs. He said, and I hope he doesn't mind that I am publishing it here:
I have looked at this design a number of times now. I cannot come to a suitable conclusion when faced with the 1.3 amp DC current. The gaps required with any core size I can utilize only allow about 1/4 of the needed inductance, low as it is, for decent low frequency performance. The AC signal flux load is inconsequential here.
My suggestion is to go to high voltage depletion mode FET's, kick the voltage up and drop the current. We can take care of that in the turns ratio.
For people who have either read, or written the article, how might one do this? And for those of you that do respond, please don't say...Just buy the ElectraPrint.
Thank you,
Chris
p.s. I did send Nelson a PM about it but I am sure he has bigger fish to fry than entertaining my little inquiry.
I defer to the expertise of those making the transformers.
My own approach is to take a transformer provided by
someone and see what it will do and try to find the
sweet spot for its operation. In the case of the Electraprint,
you can see what I got.
If you need to bias at higher voltage and lower current to
make a transformer happy, then go ahead and do it -
the Jfet is rated at hundreds of volts.
My own approach is to take a transformer provided by
someone and see what it will do and try to find the
sweet spot for its operation. In the case of the Electraprint,
you can see what I got.
If you need to bias at higher voltage and lower current to
make a transformer happy, then go ahead and do it -
the Jfet is rated at hundreds of volts.
- seems that BudP have certain level of quality of transfer , below which he refuse to go ;
- regarding Papa's aquarium habits - taking in account my 15 (mostly answered) e-mails to him in last 158 years - you must count on possible fish stampedo , and certainly not on your absolute greatness ...... as fish
I defer to the expertise of those making the transformers.
My own approach is to take a transformer provided by
someone and see what it will do and try to find the
sweet spot for its operation. In the case of the Electraprint,
you can see what I got.
If you need to bias at higher voltage and lower current to
make a transformer happy, then go ahead and do it -
the Jfet is rated at hundreds of volts.
After re-re...oh and then re-reading, the above says order a Tx and then find out what the output looks like on the scope as the supply is varied? The only potential problem I see with this is that SE Tx's are usually airgapped for a particular amount of current...
Help,
I'd hazard that increasing L means increasing turns. That also means increasing secondary turns, which brings up secondary DCR, not what you'd want. I'd also guess that increasing L will also increase the winding capacitance.
That's not the issue.
Zen Mod said Lp CAN be lower due to the lower internal resistance of transistors versus tubes. However because of that, the parafeed cap needs to be large.
All I was saying is that if there's nothing wrong with the high Lp transformer, then I don't see any particular benefit in using a lower Lp transformer simply because you CAN.
se
If you are worried about the inductance of of the choke in a parafeed LC circuit being too low and hence having to make the capacitance high, why are you concerned with the resistance of the secondary winding of the output transformer? The output transformer doesn't have to be gapped and only has to be able to handle the AC power. It could have as high an Lp as 500H and still have a reasonably low Rs.
Bumpie, anyone have a transformer update, by chance ?
Ho ho ho, speaking of card-boardwalk update...
Ho ho ho, speaking of card-boardwalk update...
Part Duke of Earl (found a nice cape in the dumpster, it's getting cold)
Attachments
Forgot to tell you. I received several letters commenting on articles in Linear Audio. I put them on-line, together with the author's reply, so you don't have to wait for the next volume to read those comments.
It's all here: Linear Audio | Letters .
Also, Nelson Pass article The Arch Nemesis published in Vol 0 has been put on line for free download: Linear Audio | Online Resources .
Have fun!
jan didden
It's all here: Linear Audio | Letters .
Also, Nelson Pass article The Arch Nemesis published in Vol 0 has been put on line for free download: Linear Audio | Online Resources .
Have fun!
jan didden
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