F4 Beast Builders

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#144
and here with the FQP3N30 and FQP3P20.

It seems that the right k2/k3 mix is easier to obtain with the FQP, but I have to hear them still.
 

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#145
So yesterday I visited my friend Peter. He is a real HIFI maniac and it is a pleasure to see his trips.....

Newly arrived in his house, Klipschorns 70th Anniversary and an Italian Mastersound valve Pre Spettro.
He also owns an Mastersound Amp with two 845 in parallel, giving around 60W/8 Ohm.

But he prefers at the moment his Jims Audio Aleph 3 kit amp! 🙂

So we heard first the Horns with a digital pot, a friend brought him and later the Mastersound Pre Spettro.

Concerning the sound the Mastersound won the race easily, concerning the price difference.....🙂)

But it would have been a shame to use not the best Pre with these astonishing Klipschorns.

Now the part concerning this thread.

We heard my F4 beast clone against the Aleph3 kit.
O.k. my clone had a bit more bite, but the room, the body, the distribution of the details in the room was much, much much better with the Aleph3 Kit.

What now?😱😱😱

I am fairly sure it is what lhquam already said, you must go for negative k2 phase!

I looked yesterday for P and N combination that have a least a similar minimum-typical gm range value.
So that I can hope buying some 😱😱 I will succeed to find two pairs where the N Polarity shows lower transconductance than the P type.

A difference of 10% is enough?

so you see the show goes on.....

😀😀😀
 
#148
generg said:
I am fairly sure it is what lhquam already said, you must go for negative k2 phase!

I looked yesterday for P and N combination that have a least a similar minimum-typical gm range value.
So that I can hope buying some 😱😱 I will succeed to find two pairs where the N Polarity shows lower transconductance than the P type.

A difference of 10% is enough?

so you see the show goes on.....

😀😀😀
Click to expand...

It's mostly due to the fact that the bloody amp has no distortion, even adding negative K2, isn't going to make any difference at around 0.002%.

You can certainly add more neg K2 and I've already suggested 2 ways you can do it, but that would be moving away from the design specs of the amp.
In the end who cares about that anyway really, just build it the way it sounds best to you.
The XA25 is probably going to sound most impressive on speakers that are difficult to drive eg 2.5 ways and anything with impedances of 4 Ohms or less in the bass region.
For high efficiency speakers (like Klipschhorn) an SIT1 or 2 is probably going to sound better.
Just crank up the distortion till you like it.
 
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#153
generg said:
I looked yesterday for P and N combination that have a least a similar minimum-typical gm range value.
So that I can hope buying some 😱😱 I will succeed to find two pairs where the N Polarity shows lower transconductance than the P type.
Click to expand...

This is the case with IXTN40P50P suggested by pico and lhquam and the IXFN40N90P I suggested. Problem is, at least here in the states, I can't find the N channel part in a hockey puck. I can find both parts in TO-264, so might try that first.
 
#154
Look at more of the IXYS N-channel SOT-227 datasheets. You will find one that is even a better match to the IXTN40P50P than the IXFN40N90P. Also listen carefully to Nelson's BAF-2016 talk about important characteristics of these monster fets. I good choice is available from DigiKey.
 
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