My MOSFET amplifier designed for music

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#921
question to some parts

hi Karl,
due to some missing parts here with specified value a few question,


- alternative to the 150pf LP capacitor 100pf or 220pf possible, which is preferred?

- is C3 as 25V version necessary, or is a bipolar 470µF/16V sufficient
- regarding D1 Zener 1,3W version ,or 600mW sufficient
values for the big electrolytics between the MOSFETs are missing, also the values for the 2 small electrolytics at the power supply inputs.
referenced are all comments to the dual MOSFET version from member prasi.


Best regards
Günni
 
#922
I'd probably go with 100pF given the those choices.

C3 only sees around -5 volts across it and so a 16 volt component is fine in practice. I'd definitely go with a normal polarised cap here (and remember to watch the polarity as it is a negative voltage at that point)

The Zener dissipates very little and so can be a 600mw part. If you are using lower rails than the original -/+45V then reduce the 10k to suit. Its not critical, you just need a couple of milliamps Zener current.

I'm not sure which caps you mean as the original version should have them all on the diagram and so I assume these are just rail decoupling added to the dual FET version. As such they are not at all critical and anything in the 100uF to 220uF range is fine. They are just local decoupling, not big reservoir caps.

Hope that helps 🙂
 
#925
Thanks a lot Mooly for the requested informations🙂.


My knowledge as former hardware engineer still works😀.
Ok, i will go for a higher limit frequency for the input low pass filter(C2=100pF). Also D1 will be equipped as 600mW type. For C3 i will use a Frolyt EKSU bipolar cap 470µ16V.
With the missing values of the electrolytic caps, i refer to the schematic on post #904 from prasi. They are located on the right side of the schematic and are working as decoupling caps for the supply voltages (i will use 1000µF/50V and 47µF/50V). The 47µF/50V is located at the supply voltage Faston connectors and as i see on the pictures from Bandol83, they were unequipped on his pcb



Best regards
Günni
 
#926
Mooly said:
If you post a link or links (or the post numbers) to the relevant sections of the thread showing the dual FET circuit and the final PCB layout etc then I can add them to the first post 🙂
Click to expand...

the following post contains everything, schematic, stuffing guide, gerbers, 3-D layout, etc.

My MOSFET amplifier designed for music.

To schillg11 ,
the caps between the mosfets need to be high temperature type as they are near heat source.
If one doent have high temperature type, then one can populate the caps between the fastons.
And as Mr. Mooly said, they are not that critical.

regards
Prasi
 
#928
Dear Mooly
Regarding the single pair output version Re post #719 by Prasi:
The PCB is in advanced stage of assembly.

There is a doubt in the order of output Res (R26/31), Zobel (cap+res) and Inductor //Res. Is the order shown in post #719 PCB correct ? This is different from post 1.

Rough idea for 6uH inductor, no of turns of 18 SWG on AA Battery or AAA battery ?

--gannaji.
 
#929
Post #267 here will give you an idea of the physical size of the coils I originally used. They are probably oversized to what I would do now if I were making it again.

Output Relays

The board layout looks OK as it has the Zobel network connecting directly to the main amplifier output and the 0.22 ohm and coil feeding the speaker are series connected from there, the order of the coil and resistor doesn't matter. A 10 ohm damping resistor goes across the coil.
 
#935
Hello Mooly and Prasi,


according to post #904, are the the published layout and schematics correct. on all Latfets i see the drains connected to a 0.22Ohm resistor and all sources are connected directly to the power supply voltages. is this correct?
 
#939

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