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Direct-Coupled Audio Amplifier with Cathode Follower
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=4576
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Author:  Gab [ 13 Jun 2019, 22:09 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

Thanks for the links ! How do you get the load resistance in the first link ? I’m not shure how to
Calculate this...

Author:  ILoveHiFi [ 14 Jun 2019, 02:41 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

https://encrypted-tbn0.gstatic.com/imag ... XMx1QH4Ur- (normally use this one to calc ripple)

If you want to use previous one. If you know the total current in system.
Then you can do V=IR
EG : 55mA load and 350V
350 = 55mA.R
350/55 = R
R = 6.36k Ohms

6.36k*55mA = 350V

Author:  Gab [ 14 Jun 2019, 06:48 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

ILoveHiFi wrote:
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSJwntTlt2uiMKGQLVnw_BwhKMrUX4h8ga0roIchXXMx1QH4Ur- (normally use this one to calc ripple)

If you want to use previous one. If you know the total current in system.
Then you can do V=IR
EG : 55mA load and 350V
350 = 55mA.R
350/55 = R
R = 6.36k Ohms

6.36k*55mA = 350V


Oh ! I didn’t know that it was as simple as applying ohm’s law to the whole circuit. I feel kinda dumb now lol ! Sometimes your search way too far when the answer is in your face.

But as you said before, I think i’ll build a simple psu with RC filters since I don’t have any spare choke on hand. I don’t mind using multiple stages and making it too slow at the same time since it’s only for testing purposes.

And again, thanks for sharing your knowledge, I really appreciate it !

Author:  ILoveHiFi [ 14 Jun 2019, 17:49 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

You don't need low noise supply for testing.
Can be high noise, all this means is that you have some noise when there is no input if you actually listen to it

Author:  ChrisABC [ 19 Jun 2019, 00:38 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

from the article," T1 have a resistance of approximately 250 ohms, as the resistance of this winding determines the grid bias for the 6V6. A check of the various types of transformers on the dealers...."

approximately 250 ohms, your transformers are 230 ohms (may measure more.... or less). Go for it.

Author:  ILoveHiFi [ 19 Jun 2019, 00:44 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

R3 and R5 has most effect on setting the DC operating point, can increase resistance of R5 to compensate for varrying transformer dc resistance

Author:  ChrisABC [ 12 Jul 2019, 23:59 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

another amp to check out: the Magnavox 8600 (Dave Gillespie) DG SE-1, it uses the p-t31 ot
page 6 has the schematic

https://audiokarma.org/forums/index.php ... re.665735/

Author:  Gab [ 13 Jul 2019, 08:54 ]
Post subject:  Re: Direct-Coupled Audio Amplifier with Cathode Follower

I will soon start the build of the dc coupled amp. I’m waiting for my Digi-Key order to arrive, but appart from that, i’ve got all the parts needed for it. I started to drill the chassis this week. I think I will have to start my own thread now !

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