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Old 18th February 2007, 04:44 PM   #1
Gluca is offline Gluca  Italy
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Default Fixing this 100TH


I am running a 100TH at 20mA/915V/-9V loaded by a 180H choke and 0.1uF coupled to a 2:1 interstage tranny (parafeed). Weird thing is that I get -12db@20Hz and -15db@20kHz. Heck?! I used those irons before with no problems. First time here with a 100TH.

Any hint?

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Old 21st February 2007, 01:05 AM   #2
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hey gianluca,

i figured this would be worth a bump.

Do you have any rough guesses at what the Rp of the 100TH is at your operating point? I'm guessing it is upwards of 40K which could start to explain your problems.

From the simple model of a choke loaded stage, increasing source impedance (Rp) shrinks bandwidth on both ends due to the finite inductance and fixed parasitic capacitances. Something that gives you 2hz-200khz bandwidth with a 1K source will only net you 20hz to 20Khz with a 10K source.

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