TFA-204 designs

MagneQuest/Peerless Forum

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Hi fellas,
I started to brainstorm once again about a low powered SET series fed amplifier. Here is what I am thinking:
1) Input stage using a WE396a and EXO-99 plate choke. Fully Cathode bypassed. I am wondering what bias I should look into so that direct coupling is possible. I'm not sure it would work though, since the WE396a has a maximum plate dissipation of 1.5 watts!
2) Direct coupling between the input stage and 300B.
3) Output stage: Running the 300B very conservatively at 40-50mA maximum into a TFA-204. I am open to options on how to run this tube. Either fixed or cathode bias, but I need some help with this since I want to direct couple the driver and output stages..
4) BCP-16 Grid choke between the WE396a and 300B.
5) Maximum power output like 2.5-5 watts.
Should be nice for a pair of medium to high sensitivity speakers like the Adire HE10 (93-95dB sensitivity) in a reasonably small room about 10 by 12 feet.
Let me know if you guys think the WE396a can swing it as a driver, and if this design can be direct coupled. The operating points for the 300B I have been eyeing at are:
plate volts 250
grid bias -52
plate current 40 madc
load resistance 3000
power out 4 watts
And:
plate volts 200
grid bias -37
plate current 50 madc
load resistance 2500 ohms
power out 2.5 watts
THD (2ncd then 3rd) 30 and 45 db down
Power output is lower, but that is ok.
My goals are to use the TFA-204, 300B and WE396a together. I need a lesson on direct coupling so if any of you can help, I would appreciate it.
Anand.

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Topic - TFA-204 designs - AnandR 06:45:10 03/24/05 (6)

Thanks guys... - AnandR 09:48:58 03/25/05 (0)

Re: TFA-204 designs - Paul Joppa 23:18:35 03/24/05 (0)

Re: TFA-204 designs, I run them with direct coupled 2A3's - j rodney 10:57:08 03/24/05 (0)

Re: TFA-204 designs - Thorsten 10:55:40 03/24/05 (1)

Re: TFA-204 designs - JIMMY 14:35:43 04/02/05 (0)

Re: TFA-204 designs - mqracing 10:25:07 03/24/05 (0)

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