The diyAudio Firstwatt F6

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#983
Stopher said:
Here's a picture of the board I made..

Does anyone happen to understand why R11, 12 are 110ohm in the build guide while the original schematic uses 47ohm (I think he used a 9.1V zener instead of the 5.1V in schematic, as well?)

I've read through quite a bit of this thread and I can't seem to find an explanation so if there already is one I apologize, just please point me in the right direction. I am actually placing the components right now so I need to make a decision before I proceed.
Click to expand...

Beautiful boards 🙂 Are you willing to share your Eagle files?
 
#985
Sure here you go..

It should be noted, however, that this is a somewhat modified F6. Everything should be identical with the exception of increased bypassing on the board itself. Of course, you don't need to use them, and I'm not even sure if I will but I didn't want to rule it out..

As far as thermals I just don't feel that they really help me, but you can turn them on if you want 🙂

Also, I had to modify some of the component packages so I don't know if that will be a problem.
 

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#986
I've been examining the PCB along with the schematic at the beginning of this thread and I noticed that 'pins 1,3 and 2,4 (on the Jensen transformer) are tied together on the board but on the schematic 1,2 and 3,4 are tied together. Is this a mistake on the original PCB or am I reading the schematic wrong.

It's pretty important that this is resolved as my design assumes that its 1,2 and 3,4 that are tied together. If not I'll need to remake the board😱
 
#988
Can someone please explain what the pros/cons of using a 9.1V zener diode instead of the 5.1V ones shown the schematic around the pots? I am only asking because it seems that the build guide utilizes a 9.1V zener and I was curious why this was done.

The info regarding the gate stopper resistor was very useful. Thanks for the help..
 
#991
Finally my turn comes to ask a stupid question, sorry. Maybe 6L6 could respond as he may have the experience in matching the Linear Systems JFETS sold in the store. How close are the LSJ74C Grade to the LSK170B Grades? Is it worth the wait for the store to get stock in or order some C rated fets to match to the LSK170B pieces and live with it? Or, if stock is not forthcoming for quite some time it may be better to have some C's in hand? If they are by your experience to far apart I will wait. I'm not in a hurry. Thanks, Holzarbeiter
 
#993
Does anyone know if the biasing process is similar to that of the F5Turbo? If so, would nodes TP1-2 and TP3-4 be between R7/R9 and R8/R10 for P1/2, respectively? Sorry for such a convoluted question but the F6 build guide doesn't seem to be complete yet. Get to work! 🙂
 
#995
Holzar - Wait for matched sets. It won't be too long. Trying to mix a N-channel B with a P-channel C will not work very well at all.

Stopher - Place leads across the 0.47R source resistor and measure DC volts. Adjust the bias pot until you get about .5v . Then zero the DC offset, and re-adjust bias as necessary.
 
#996
Stopher said:
I've been examining the PCB along with the schematic at the beginning of this thread and I noticed that 'pins 1,3 and 2,4 (on the Jensen transformer) are tied together on the board but on the schematic 1,2 and 3,4 are tied together. Is this a mistake on the original PCB or am I reading the schematic wrong.
Click to expand...

Yes, that was an error in the original layout... Sorry. 🙄
 
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