The F5X Preamp

[gl]

Hi Patrick,

I really like your circuit. It definitely does have a UGS look to it.

I don't see why you included R51 and R52. If it was an X type circuit then I would understand.

Graeme

[wuffwaff]

Hi Patrick,

that sounds good. If you need a beta tester..........

Wiliam

[EUVL]

R51, 52 are optional.

William, we'll get in touch when the time comes.


Patrick

[gl]

Is there a reason why I would want to include them as an option?

Graeme

[EUVL]

No.

But there is also no reason why anyone would need a Porsche.
And many have one.




Patrick

[gl]

Thank you for the advice on cars. However, I don't think my wife would let me buy a Porsche.

By the way, in your post you forgot to give the technical reason why R51 and R52 would be 'optionally' included in your circuit?

Thank you.

Graeme

[apassgear]

Might be wrong, but looks like a JC topology?

[gl]

Hi Patrick,

After re-reading your last post I see that you did answer my question regarding R51 and R52. Thank you.

Graeme

[EUVL]

> Might be wrong, but looks like a JC topology?

If you read the article carefully, I immediately acknowledged the similarity to the JC-80 and gave the credit to John.
We did worked out the circuit ourselves before John published the JC80 schematics.
So like Nelson has to refer the F5X topology to ProFET, we do the same to the JC-80.

But the devils are in the details. And they will follow.

To answer your question directly, I personally like to include a ground return path of the outputs.
Especially when the input is a floated X or a H, like in the schematics in the article.
You can argue it is not necessary. Straightly speaking it is not.
But this is what I like. Hence it is optional.




Patrick

[Blues]

I would venture to guess it's from PMA's interpretation of JC's Blowtorch (official circuit not published yet) embellished with jfet cascodes and F5 feedback to set the voltage gain.

9/23/2009:
John Curl's Blowtorch preamplifier part II