F4 power amplifier

[DaveM]

Nice build.

 

[spencer]

Did you just reduce the value of the source resistor until the voltage was a certain percentage different on all the MOSFETs? What's a good guideline on how different the voltage drop across resistors can be and still have good performance?

I think if the voltage or current is within 5% is very good, 10% should not have any issue. The total power will be shared among the 3 mosfets. For performance I have no idea. I think a distortion meter or FFT analyzer is needed to see if any differences in harmonics content.

 

[jackinnj]

That is really a nice example of "purposing" materials to fit the application. Congrats.

 

[bakpaosiomay]

can anyone tell me what is the different between F4 and F5.

and which one is better?.

thanks

 

[Nelson Pass]

Worlds apart. Read the articles.

 

[chrismercurio]

the 6moons F5 review has a little contrast if I am remembering correctly. It's pretty cheap (relatively) to build a single power supply and F4/F5 channels and have both.

Chris

 

[bakpaosiomay]

are we need a speaker protector if i build F4?.

thanks.

 

[bakpaosiomay]

sry i forgot to ask.

actualy what size of transformer we need to build F4?.

is 300va enough for 2 chnl?

 

[Zen Mod]

are we need a speaker protector if i build F4?.

thanks.

generally - anticlick ( delay circ ) and spk protection is welcome addition to any amp which is not containing output xformer or output cap .
but - it's not necessary

sry i forgot to ask.

actualy what size of transformer we need to build F4?.

is 300va enough for 2 chnl?

say that 300VA is lowest value you can use , and still sleep well .....

 

[bakpaosiomay]

will my speakear blow if i dont use any speaker protector?

 

[bakpaosiomay]

for the FET can i use 2sk246/2sj103 insteed 2sk370/2sj108?

because in my place very hard to find those type FET.

thanks

 

[Zen Mod]

will my speakear blow if i dont use any speaker protector?

nope - if you make amp properly

for the FET can i use 2sk246/2sj103 insteed 2sk370/2sj108?

because in my place very hard to find those type FET.

thanks

well ..... think of paralleling at least 3 of each , to replace original ones ;

is it possible for you to buy anything outside your country ?

that amp deserves that trouble , believe me .

any Papa's amp worths at least quadruple money , looking at price of his commercial products vs. other competitors .

 

[Nelson Pass]

If you have a source which can drive 5 Kohm and a couple hundred pF,
you can dispense with the JFETs altogether and simply drive the Gates
of the Mosfets.

A little more work, and you can use a single pair of Mosfets and raise
the impedances of the bias circuit, and then it would be about 22K and 70 pF.

 

[bakpaosiomay]

nope - if you make amp properly






well ..... think of paralleling at least 3 of each , to replace original ones ;

is it possible for you to buy anything outside your country ?

that amp deserves that trouble , believe me .

any Papa's amp worths at least quadruple money , looking at price of his commercial products vs. other competitors .

If you have a source which can drive 5 Kohm and a couple hundred pF,
you can dispense with the JFETs altogether and simply drive the Gates
of the Mosfets.

A little more work, and you can use a single pair of Mosfets and raise
the impedances of the bias circuit, and then it would be about 22K and 70 pF.

how about 2sk170 and 2sj74?

thanks.

 

[bakpaosiomay]

If you have a source which can drive 5 Kohm and a couple hundred pF,
you can dispense with the JFETs altogether and simply drive the Gates
of the Mosfets.

A little more work, and you can use a single pair of Mosfets and raise
the impedances of the bias circuit, and then it would be about 22K and 70 pF.

it is okay to dispense the jfet?.

it will not affect the sound?

if the quality of sound is decrease i will consider to buy those jfet in another country.

thanks

 

[Zen Mod]

how about 2sk170 and 2sj74?

thanks.

they are same jfets as in original

 

[bakpaosiomay]

they are same jfets as in original

okay i think i will purchase those j-fet overseas.

what do you think about f5 and f4.

what is the main difference?.

i realy confuse.

what is the strength and weakness?

thanks.

 

[cviller]

okay i think i will purchase those j-fet overseas.

what do you think about f5 and f4.

what is the main difference?.

i realy confuse.

what is the strength and weakness?

thanks.

Main differences:
F4 has no gain
F5 has less power fets

Both are push pull, which is a good thing if this matches your speakers and you like the sound (I do).

 

[jackinnj]

what is the strength and weakness?

thanks.

F4 makes more heat!

I am going back to F4 from F5 -- now that I have an Impasse preamp!

 

[wirewiggler]

What surprised me about the F4 is how much difference the preamp made. Just put my Pumpkin on them and they are a new animal. They probably are more neutral then most amps and more revealing of the other components. In any case have half the parts for an Impasse gathered it should be interesting the one I will prefer.

Bill