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Old 16th April 2011, 03:04 AM   #1
Bigun is offline Bigun  Canada
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Default Integrating tube into F4 ?

Hi,

I read about the F4 and love the suggestion of using it as a trans-impedance amplifier for a tube-based voltage amplifier.

So, my question is about making the combination simpler by integrating a tube into the F4 itself. I'm looking for your input on the idea, cautions, suggestions etc.

I'll try to explain using a couple of diagrams. I've taken some liberties with the F4 schematic to keep it simple so it might not make much sense without checking out the original schematic [http://www.firstwatt.com/f4.html]

Option A: This shows a tube voltage amplifier capacitively coupled to the F4 much as would happen if the tube amp and the F4 were separated.

Option B: integrates the tube into the F4 itself. There is still a coupling cap but now it has to be at the input of the tube - I'm not claiming any advantage for this.

In both cases I'm looking at using a single rail supply for the F4 - my trafo's have no centre taps

I know this isn't the tube forum but I'm looking for some F4 experts to give me some input on whether the changes implied in option B would have some unintended consequences on the performance of the solid state part ?
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File Type: jpg OptionA.JPG (38.5 KB, 350 views)
File Type: jpg OptionB.JPG (41.1 KB, 347 views)
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Old 16th April 2011, 08:08 AM   #2
Itsmee is offline Itsmee  England
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Have a look at the Moskido thread
http://www.diyaudio.com/forums/tubes...amplifier.html
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Old 16th April 2011, 01:49 PM   #3
Bigun is offline Bigun  Canada
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Thanks for the tip Itsmee - seems though that it is not based on a single triode which is what I'm looking for here. I can see some discussion (after post 930'ish) about using an F4 with the JFETs chopped off, but without the JFET buffer to shield the tubes from the capacitance of the output FETs I don't think it's going to be a good idea to use a simple single tube to driver it.
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Old 17th April 2011, 04:03 PM   #4
Bigun is offline Bigun  Canada
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no more input - my design is that awful ?

I was wondering of I could further edit the F4 so that the JFET buffer were replaced with a B1 buffer so that I only need same-sex JFETs ?
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File Type: jpg OptionD.JPG (46.6 KB, 256 views)
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Old 17th April 2011, 09:36 PM   #5
Itsmee is offline Itsmee  England
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Quote:
Originally Posted by Bigun View Post
I was wondering of I could further edit the F4 so that the JFET buffer were replaced with a B1 buffer so that I only need same-sex JFETs ?
Don't see why it could not be done, although it will sound different to the standard F4, build both, see which you prefer and don't forget to post your results.
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Old 7th May 2011, 03:47 PM   #6
Gyuri is offline Gyuri  Hungary
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I'm wondering, there's a chance to replace jfets with tubes, in F4 amplifier. May be this is a stupid question, I know, there is doesn't exist P type tube part, but after all...
Wacky Gyuri

PS.:
It is also appropriate for me if anyone knows a good tube front-end for F4, as is.
Seems to me, the Borbély Balanced Tube Lineamp not really a good solution:
Suggest me a preamp for my F4!
Although I have not tried this.
But anyone can say anything, I'll try this out.
They are the experts to find some solution to this.
I am not an expert, as we all know this.

YouTube - Laurie Anderson / Only An Expert / Maybe if I Fall
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Old 7th May 2011, 04:30 PM   #7
Itsmee is offline Itsmee  England
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Quote:
Originally Posted by Gyuri View Post
....anyone knows a good tube front-end for F4
Have a look at the Aikido
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Old 7th May 2011, 04:43 PM   #8
Gyuri is offline Gyuri  Hungary
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Hm, you're thinking about this thing?

Aikido 4 -- Aikido

But I thank you, I am taking your advice!
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Old 7th May 2011, 04:48 PM   #9
Gyuri is offline Gyuri  Hungary
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This is certainly good, but I forgot, for me should be balanced amplifier. Because this is a jing-jang thing.
If I build four of this, they could do the job?
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Last edited by Gyuri; 7th May 2011 at 04:51 PM.
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Old 8th May 2011, 08:37 AM   #10
Itsmee is offline Itsmee  England
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There is a balanced version.

Balanced Aikido
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