Eimac 100TL Output Transformers and Bias Point ?

HP8903B · 04:51 PM

I am thinking about building a SET amp using Eimac 100TL as output tube.

Could someone take a look at the datasheet and make suggestion on the impedance of the output transformers ?

Please also make suggestion on bias point.

euro21 · 10:43 AM

Looking for circuit of SE amp. for Eimac 100TH

http://www6.plala.or.jp/Michi/renewa...0SE%20Amp.html

hpeter · 17th February 2013, 10:55 AM

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(?)

IslandPink · 17th February 2013, 02:03 PM

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 .

HP8903B · 17th February 2013, 05:55 PM

The B+ will be 1000V - 1200V.

I will not need more than 20W, likely less.

IslandPink · 20th February 2013, 06:05 PM

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.

17th February 2013, 10:30 AM	#2
euro21 diyAudio Member Join Date: Sep 2004 Location: Budapest	Looking for circuit of SE amp. for Eimac 100TH http://www6.plala.or.jp/Michi/renewa...0SE%20Amp.html Last edited by euro21; 17th February 2013 at 10:43 AM.

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17th February 2013, 10:55 AM	#3
hpeter diyAudio Member Join Date: Feb 2013	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(?)

17th February 2013, 02:03 PM	#4
IslandPink diyAudio Member Join Date: Oct 2005	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 .

17th February 2013, 05:55 PM	#5
HP8903B diyAudio Member Join Date: Jun 2010 Location: Texas	The B+ will be 1000V - 1200V. I will not need more than 20W, likely less.

20th February 2013, 06:05 PM	#6
IslandPink diyAudio Member Join Date: Oct 2005	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.