My F4 Build

[Einric]

If I was to raise my bias to 400mV what would I gain, theoretical or otherwise?

 

[6L6]

Heat.

My experiments into bias have shown that past .300mV it takes lots of wasted bias for very small gains in distortion.

 

[Einric]

But what about power & dynamics and all that jive?

 

[Bigun]

You didn't fall for that one did you

 

[buzzforb]

http://www.firstwatt.com/pdf/art_leave_classa.pdf
I was thinking about 500-600mA in my upcoming multi-output bridged F4.

 

[Einric]

Now I'm just waiting for my dog to put her nose in the fan.
I've already chased her off 3 times, hopefully the newness wears off.

 

[6L6]

But what about power & dynamics and all that jive?

Listen to lower bias amounts - it changes the distortion characteristic.

 

[Einric]

I'm afraid I like it too much to wanna even mess with it.

 

[6L6]

That's fair.

 

[Einric]

Jimmy Buffett is singin' away in my living room.

I can't help it, I just feel the need to say to anybody on the fence, BUILD IT DAMNIT!!!
You won't regret it and if you do I'm sure there are many people willing to take it off your hands.

 

[Einric]

LOL, my cousin asked if I could fix it's inefficiency!!!!
NO, Then it would be AB and suck!

 

[Einric]

Now having listened to this amp for about 5 hours I can't help but think how many "Bad Speakers" there are out there falsely accused because of a crappy amp with a brand badge on it.
There are many people that don't like the Tweeters I'm using (Dayton DC28-F) but just contrasting between my LM4780 Parallel and the F4 I think it sheds a little light on those poor forgotten "Bad Speakers" in the junk heap.

 

[6L6]

Compared a Firstwatt amp you will find that most Chipamps are kinda, well, unlistenable.

 

[Einric]

I'm really going through the gamut tonight.

Jim Croce has never sounded so good.

Now I need a Pearl to go with this thing and get a source selector shoehorned into my Aikido.

 

[6L6]

Pearl 2 = The most amazing phonostage. I can't recommend it enough.

 

[WalterW]

Hi 6L6, I thought you ordered a few 2SJ74s at BandD, do they proof to be legit? or didn't you test them yet?

 

[6L6]

I haven't had time to test them yet, and honestly all I can do is measure Idss. I was going to send a couple to a friend with a curve tracer and see how they fair.

 

[henryve]

Don't worry about the fans yet, you have enough heatsink to keep things from burning up. (at normal bias)

Get the amp working and then finish the fans. But yes, you can take the fan power from wherever you like.

The alternative to paying lots in shipping costs is ordering multiples of things when you make big orders, to stock your shelf full of handy things... That's actually more expensive, but nobody will honestly tell you that...

Thats the only way I run down here in the bottom of darkest Africa. If I order transistors I order by 25 or 50 batch sizes, resistors and diodes by 50 or 100s.

Feels like I am building a small electronics store. My wife will kill me if she knows the worth of my stash.

 

[Einric]

I just picked up a pair of 6DJ8's to boost my preamp gain by 3db.
That should allow me to get the full 25W.

 

[Einric]

Well, my 6DJ8's are in my preamp.
Now I can swing 17V @ 1k tone soundcard as my source (measured by Fluke 87) into my 81db efficient speakers.
I know that Nelson says to stick with 87db and greater speakers but this thing is just a real peach.
I lost a smidge of low bass but I have gained Focus and Power.