• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

yagoolar's tube amp projects

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#21
tinitus said:
what does two secondaries mean ?
Click to expand...

See attached picture. One can connect primaries and secondaries in series or parallel.
 

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    OPT-connection.png
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#22
ehh, shouldnt the cap be coupled to other side of cathode resistor, directly to ground ?

are you sure your "opt" is not an interstage, and not an opt ?
 

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  • 20101112 C3g 6C4C noled PF cap cath-trafo 1u-100u.png
    20101112 C3g 6C4C noled PF cap cath-trafo 1u-100u.png
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#23
OPT

The xformer is definitely an OPT - 10W does not imply an IT, does it? I have used it before with 6C4C SE - it is air gapped one.

I changed cap connection as you suggested - the same response.

So it is time to make it real.
 
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#27
I think I reached the optimal schematic. So I start building a prototype.

First approach of a look below
 

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  • 20101123 C3g 6C4C led PF.png
    20101123 C3g 6C4C led PF.png
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#32
disco said:
Is that high value for R3 necessary? Did the C3G suffer from oscillation?

Is there no noise issue on the 6C4C cathode with all those LEDs?
Click to expand...

Soldering is ahead of me. That is also my first experience with C3g - so your question is to be answered.
As for LED - I replaced RC cathode bias with LEDs and there was a huge improvement. I did not measure noise though.
 
#36
just one tad bigger pictures, please
much too small to see anything

hey, btw, thanks to you(partly) I just now realized why voltage drop over the plate resistor should be calculated and added to supply voltage :clown: nice to know 😀
 
#37
#39
I am rebuilding the existing amp with LED bias, yet improving / experimenting with some elements i.e. filament power supply and driver stage. I decided to leave output stage bias as is. If I went to fixed bias I would have to change at least mains transformer, add another regulator. And then I would end up with another enclosure, and that would be new amp. I have 2 more projects on the table: SET w/300b and PP w/6C4C. So perhaps then.
 
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