Pass mosfet citation 12 clone

[Tekko]

I improved the biasing by replacing a transistor and mounting it to the top of one of the mosfets.

Video:
YouTube - HK Citation 12 modified to use power mosfets

 

[NVD33]

Hi,

You are very fast in building amp! How do you like the sound? Will you try also the complementary version? I didn't start mine yet because I am busy with an another amp.

Regarding the bias of my quasi complementary version, I set it 150 ma when amp is cold and I have around 100 ma when amp is warm. (I used IRFP240).

 

[Tekko]

It sounds pretty good.

I just did a power output test, into a 1.95ohm load, it pushes 15-16V at clipping which is around 115-130W.

I used two IRFP450's but will change to laterals when they arrive.
I don't really like P channel fets.

 

[Tekko]

The laterals have arrived!!

 

[Tekko]

ok laterals did not work in this design, with a dummyload it kinda worked but i was only able to get 57W into a 3.9 ohm load, with a speaker it dident work at all, oscillation, huge dc offset and loud humming.

Need to find some other design to be able to use the laterals.

 

[Tekko]

Turns out they do work if the gate resistors are increased to 2.2k, tho i also added some 680pF caps to the gates and source resistors and lowered the bias even further than it was before.

Theres still a hint of a very high frequency left though but its down in the millivolts range.

 

[Tekko]

Im thinking of trying out complementary mosfets in my citation 12 clone.

Is the 2SK1058 and 2SJ162 any good ? I found a deal with two of each on ebay for 14 bucks + 2 bucks shipping.

 

[osscar]

Hi Tekko,
Today I tested comp. version (240 & 9240 Irfp) in SPICE, THD was low- looks good. How is reality with turn-on thump>? Mr.Pass spoke about it in his article.

 

[Tekko]

Mine with quasicomplementary is dead silent on turn on.

 

[balaboo]

I have a design similar to the Pass Citation 12, but more like the IR application note - take ilimzn's advice and use IRF240/IRF9140 as complementary pair.
They sound pretty good !!! Even the wife noticed the difference.

 

[Tekko]

Im thinking of trying this too:

 

[Tekko]

Now i have this hooked up and working:

At the onset of clipping it gives 83W into 3.9 ohms.

 

[Tekko]

And the second current source in place:

 

[Tekko]

Due to the lack of interest in this thread i've been thinking that maybe it doesent belong in the pass section anymore since its no longer a harman kardon/pass design after my changes.

Perhaps this thread would fit better in the solid state section ?
What do you think ?

Anyways i upgraded the amp by adding a second pair of output fets, output power only increased by approx 10 watts though.

 

[balaboo]

What is happening is that your modifications are making this circuit the same as all the rest.
In other words, it is has been beaten to death and beyond.