F4 power amplifier

[2 picoDumbs]

Both will do fine.
Harris will give lower distortion though.
It might be a matter of taste which one you prefer.
From a technical standpoint Harris is better.

 

[cal3713]

All gone.

Due to a miscommunication, I have 6 matched Harris 9240s left (two matched trios). Anyone want them?

 

[2 picoDumbs]

Packaging looks genuine.

 

[2 picoDumbs]

First one out of the tube.

I will measure it up.

I specifically wanted to try 9140, so that's why I have these and not 9240.

 

[cal3713]

Curious to hear the report

 

[Zen Mod]

bloody bztrd

 

[2 picoDumbs]

Thank you

 

[Zen Mod]

 

[soldersmoker]

I built my F4 a few months ago and I had to come back and declare that I couldn't be happier with how this amp makes music. So beautiful. I had asked earlier if there would be enough gain in my medium-sized room with most music. Yep, no problem.

I use a LTA MZ2 preamp and Omega high output alnico magnet monitors (97dB/w/m). Qobuz through a Border Patrol DAC or Audiolab transport for CDs. I also play "rekkids" via a WTL Simplex and Ortofon 2M Black. Love it!

Thanks, Nelson, you are the best!

 

[2 picoDumbs]

Nice one.
Awesome.

 

[william2001]

What you do is build all of these amp circuits, and then pile them up in your workshop, except for the F4. That one you will use and enjoy every day. Then you just roll preamps / speaks / sources until the end of your days...

 

[2 picoDumbs]

Yeah.
Makes a lot of sense

 

[soldersmoker]

Yeah, I've never truly felt I had an amp that made me feel as if I had "arrived" until hearing the F4. And I owned a commercial First Watt F6 and heard a friend's DIY F5 (through Altec 605s), among others, including owning SET amps (which of course are very nice in their own right). I've waited a few months to get over the "DIY bias," but, yeah, it's my favorite-sounding amp ever. That's probably why I gushed over it yesterday, as I've never felt this way about an amp before.

 

[dBel84]

It is next on my "to build" list and thanks to @cal3713 I have a set of matched Harris 9240 mosfets..dB

 

[william2001]

6moons says "relaxed ultra resolution.." yep. An unrestrained proper linestage in front of this thing is killer. I don't throw away much signal to ground the way I used to, before I knew any better. With the proper gain structure a lot of detail gets through, finally...

 

[cal3713]

Now that I have two extra channels of f4 amplification, I'm going to use them and Nelson's 6-24 crossover to power a distributed bass array. Unfortunately for system matching I need to start out with more gain. I was thinking about placing some form of a transformer on the input of the boards to accomplish that.

Can anyone recommend some options?

Obviously I could also just pad down the input of the rest of the system too (using the crossover circuit), but it seems weird to pass the most critical part of the signal through more circuitry just to reduce gain.

Thanks.

 

[6L6]

I’d put the gain after the crossover. Remember that the gain stage needs to swing all the voltage of the F4.

 

[marconi118]

Anyone ever listened to a F4 with only a pair (1 n and 1 p) of output devices?

 

[Zen Mod]

boys listening M2 are (sorta) doing that

 

[marconi118]

M2 VS F4 is the damping factor the only difference? The F4 uses 3 pairs only for higher damping factor? Any other subtile sound difference?