F6 Illustrated Build Guide

[Bare]

Ok.. Zeners and resistors swapped, fairly easily.
Jfets Q2 & Q3 on the clearly Goofy BOM are as Q3 and Q4 on My version PCB and on the build guides' one as well.
I looked at the Schematic and sorted it .. Q3 = 2SK170 and Q4 = 2SJ74
Presumably correctly?
Would be nice if the BOM was accurate/trustworthy though

 

[Milkduds]

Are the IRFP240 mosfets at the diystore matched?

Jim

 

[Bare]

Who Knows..apparently there's neither need nor point in matching those Mouser sells 'em for ~2$ each

 

[jackinnj]

Is the IRFP240PBF sold by Mouser now the same as the obsoleted IRFP240 mostfet and ok to use in the F6? Specs look the same.

Jim

The PBF means "lead (Pb) free" --

 

[JimM]

I ordered 15 of the IRFP240 from mouser and did check the vgs, they were very close right out of the tube.

 

[Bare]

Sidestep question
Transformer ? to order.. 400va is adequate to needs? (18v part I understand)
I have 93db speakers, not too many watts needed for my usage.

 

[Dennis Hui]

Sidestep question
Transformer ? to order.. 400va is adequate to needs? (18v part I understand)
I have 93db speakers, not too many watts needed for my usage.

Yes that's fine. (The standard transformer in the First Watt amps
is a 300VA 2x18VAC Plitron.)

Cheers,
Dennis

 

[drpro]

F6 build

Another F6 build coming together. The various subsystems are completed, power system has been tested and solid at 26.5vdc. Taking a small break then let the final wiring begin!!
Followed by amazement and enjoyement!

 

[drpro]

Completed the basic wiring to check the boards and yes I had the dreaded LED on one channel install backwards. Those late night builds!
Bias at .5 with 0 offset and supply steady at 26.2vdc for both channels.
Gonna let it cook for a bit.

 

[ammel68]

So what's the consensus or is there a consensus?

9.1V zeners with 2.2k ohm resistors or 6.8V zeners with 3.3k ohm resistors?

Thanks...

 

[2 picoDumbs]

You can also do 5.6V or 6.2V zeners.
Make a choice.

 

[drpro]

I went with 6.8 zeners and 3.3k. Working well. Without any instruments other than dvm

What bias seems to work for most folks. I am at .5vdc at the moment

 

[Zen Mod]

palm rule , just crank them

 

[2 picoDumbs]

I went with 6.8 zeners and 3.3k. Working well. Without any instruments other than dvm

What bias seems to work for most folks. I am at .5vdc at the moment

I went with 0.64V across 0.47 Ohm resistor, but I also generally go with the "crank it till it's hot rule"

 

[drpro]

Thanks guys for the update. I will let it cook for awhile at .5 and then up the bias.

 

[drpro]

Wow, I am listening to the amp now biased at .5vdc, all west coast sound, amp by Nelson, speakers by JBL, music by Beach Boys.

Really nice sound. More in your face than the F4 I built. I like both, the F4 seems more fluid, though the F6 is equally great sounding just different.

Preamp for both is a BA-3.

All wonderful. Thank you Mr. Pass

 

[Bare]

OK so now I realize that I 'should' have ordered more (all ) PCB's from the DIY audio shoppe.
Not a full complement of Newbie help info in there.

Will the soft turn on prevent the dreaded 'Turn on Thump' which I dislike
Or just make life easier on my PS caps? which isn't a huge worry for me TBH.

What about speaker protection?
How likely/real is the possibility of the Amp failing and dumping DC?
No opinions, just asking as I forgot to order all the boards at one go

Although I do have perf board on hand as possible workaround..
Wondering if SGK's soft start is a good path to follow?

 

[drpro]

I guess I am just anal. I like the extra protection added from the two boards. Probably adds 50usd to the build. I also come from the old Heathkit era and enjoy building, so that is part of my motivation.

 

[ammel68]

More in your face than the F4 I built.

More in your face in the mids, highs or both?

 

[drpro]

To my ears both. Keep in mind I am listening on JBL L-220 speakers