mosfet opinion?

[tadiam]

Diy opinion of this mosfet amplifier......

http://www.pcpaudio.com/pcpfiles/proyectos_amplificadores/ssub-mosfet/Schematic.pdf

 

[tomahauk]

looking quite good ;]

 

[Tube_Dude]

Diy opinion of this mosfet amplifier......

Hi tadiam

If you connect R 17 (22K) to ground instead the negative rail , you get much more PSRR...

 

[tadiam]

ok

thanks tube dude

 

[tadiam]

when up all volume have an motor boating in tha bass and one fet are more hot (no modification original circuit)

 

[CBS240]

Do you think Q9 is saturating and causing the bias of Q5 to change? Maybe a base resistor on Q9 would help this.

 

[davidallancole]

Is R17 even required?

 

[Tube_Dude]

Is R17 even required?

No!

Without R17 the distortion will be lower.

But some people think that lower open loop gain is better...

Another tip , use two 1N4148 diodes as voltage reference for the CCS of the LTP, a Zenner is a very noisy reference...

 

[jaycee]

I'd say R17 is a silly idea...

Why bother with the diode in the VBE multiplier... the BD139 on the heatsink alone will be plenty. Also, don't wire the bias pot like that - an open circuit wiper will spell disaster.

I agree about the zener in the CCS, although I would use an LED (better temperature stability). 1K in the base of Q9 will also help prevent saturation in that transistor killing the CCS.

 

[Ipanema]

For better thermal tracking and stability, you can replace BD139 with a Hexfet.

 

[Leolabs]

Replace the HEXFETs with LATFETs,then subsitute the bias network with a variable resistor.

 

[ilimzn]

Replace the HEXFETs with LATFETs,then subsitute the bias network with a variable resistor.

And the obvious question: why?

 

[kASD]

And the obvious question: why?

I think you already know the answer...dont you..For some people Hexfet isn't that easy to stabilize if we compare it with lateral types...

 

[tadiam]

ok

good debate now see this link
more complex class a amp good or not
more debate now......
http://www.pcpaudio.com/pcpfiles/proyectos_amplificadores/Vag/etapa.pdf