are this type tubes made even today, like 4-250 , 833 etc..?
µ 14 nice sweetspot, Ra 4k6
old rule of thumb -primary should be 2-3x of plate resistance(?)
µ 14 nice sweetspot, Ra 4k6
old rule of thumb -primary should be 2-3x of plate resistance(?)
I have no hands-on experience of 100TL or TH , but a friend of mine built one a year or two ago, so I'll pass on what I know .
Bear in mind the Ra drops if you are going into A2 . He used a 10K output transformer I believe , and reported very nice results, better overall than VT4C he reckoned. You will need an A2 driver for either 100TL or 100TH .
On that basis 100TH is actually no more difficult than 100TL , in fact the voltage swing for the driver is less , which helps. The 100TH are apparently cheaper than 100TL , I'm told .
I think the start point is deciding on available B+ . My friend used at least 1000, perhaps 1200 V . From that he got about 30wpc with the A2 driver. If you can decide B+ then you should be able to narrow down an operating point with some help .
The driver my friend used was the J.Ross McDonald ACM ( augmented cathode follower ) No.2 variant, using some hefty triode-wired pentodes for the driver (CF) part .
Bear in mind the Ra drops if you are going into A2 . He used a 10K output transformer I believe , and reported very nice results, better overall than VT4C he reckoned. You will need an A2 driver for either 100TL or 100TH .
On that basis 100TH is actually no more difficult than 100TL , in fact the voltage swing for the driver is less , which helps. The 100TH are apparently cheaper than 100TL , I'm told .
I think the start point is deciding on available B+ . My friend used at least 1000, perhaps 1200 V . From that he got about 30wpc with the A2 driver. If you can decide B+ then you should be able to narrow down an operating point with some help .
The driver my friend used was the J.Ross McDonald ACM ( augmented cathode follower ) No.2 variant, using some hefty triode-wired pentodes for the driver (CF) part .
Try contacting Dave Slagle on his 'Intact Audio' forum .
Either he or the Colorado boys ( C4 group ) know quite a bit about Eimac operating points.
Either he or the Colorado boys ( C4 group ) know quite a bit about Eimac operating points.
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