Not true. I like cascodes for VHF receiver inputs, and have been considering a form of cascode for a high performance HF receiver mixer. I have this peculiar notion: use the appropriate circuit for the job.TUBESMAN said:
No, low noise is irrelevant in a driver. You do not "make a circuit better than it needs to be" by choosing a topology which lacks features you need, introduces problems you don't want and has good points which you don't actually need.
That circuit was published in the 1950s, so the patent would be irrelevant even if it wasn't out of date.
I wish I would publish all my circuits in a single magazine back in 1950'th, then repeat in 1970'th, and so on, but unfortunately I was born in 1957 only. 😀
Do you care who went the road through the forest in some direction the first? I don't. But if somebody cares sue me! I know this forest better so while you are gong to sue I will find the better way! 😀
Do you care who went the road through the forest in some direction the first? I don't. But if somebody cares sue me! I know this forest better so while you are gong to sue I will find the better way! 😀
with Mile Prower's kind permission.....
An externally hosted image should be here but it was not working when we last tested it.
i was responding to Tubemans' post, he seems to want a cascode driver so i posted one such design......no need to reinvent the wheel....incidentally i have 6F12's and 6P15P's to try out your driver circuit.....that is slated for next year.....
6F12 was too much for a typical "power amp" sensitivity. If to add more feedback Edcor transformers started ringing wildly, or I had to add dominant pole compensation with longer time constant than I liked. 6F1P I believe will be right in ball-pack, I did not try yet.
I don't know, may be ECF180?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
i found a stash of old tubes numbering about 500pcs, some still in cartons from a shop that closed, got it for cheap, i am still sorting them out....
Been there; done that -- Le Renard.
When doing the design for this, I figured that a hollow state cascode just might do the job here. This I borrowed from SS design practice, where you see audio cascodes quite frequently. I couldn't find any examples "in the wild", so I just decided to go for it. It worked out just as well as the SS counterpart.
Thought about a 6SN7-oid, but not enough gain (you lose half of it in an LTP) and the RCA manual provided info on the 6BQ7 -- designed for cascode service up to 300MHz, no suggested audio specs, but a good audio loadline can be found, even if the plate characteristic is a bit squirrelly (undocumented variable-u characteristic?) Has a u-factor that falls nicely between that of a 6SN7 and a 6SL7.
As for designing cascodes, it's a two stage voltage amp, so draw up some loadlines.
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