Buffer impedance question

[armdnrdy]

This is my second build on this thing. The first one I routed my own board, making it much smaller. I included the input buffer section of the gate board on the input but left out the JFET switching for obvious reasons.
I didn't have the excluded pull down info that I outlined earlier, so I included those as shown in the schematic.

I could never get that first build sounding right so I verified the PCB layout that's in the gallery and tried from scratch.

Same result! it still didn't sound quite right! So I think I'll try adding the gate board and see how that works. I might also try adding a JFET buffer with a higher impedance to see if that makes a difference.

Thanks for all of the help! and for breadboarding the buffer!

[gritz]

Thanks for all of the help! and for breadboarding the buffer!

You're welcome - I'm really impressed by the amount of dedication you have towards reverse engineering this classic piece of goodness. Keep us posted.

[Thecomedian]

Ther's some guy who looks like he's hopped up on drugs on youtube explaining how to calculate all the numbers for resistance in a circuit out.

basically, you use the parallel formula of two resistors to keep reducing all resistors in parallel down to a single number. In more complex circuits.

For example.

http://www.geofex.com/article_folders/fuzzface/fftech1.gif

afaik, we have 33k in parallel with 330 (or 470).
we have 100k in parallel with 1k.

This is for the DC.

so 100+1K paralleled out we call that R(a).
330+ 33K  = R(b).

Now we only have "series" resistors to add together R(b) + 8.2k + R(a).

the formula for adding resistors in parallel is turning the numbers into reciprocals and then adding those numbers together and then making the reciprocal of the new sum.

the 100k and 1K added together make something like 99.98k, for example.

That's impedance for the DC within the circuit. For AC i have no idea how the path travels. The signal doesn't seem to go onto the node between the DC and the 33k/330 voltage divider, so I would guess that:

for AC input, 100k and 1K are series.

8.2k and 500k are series.

turn that into 101k and 508.2k In parellel, do the formula, and total value of resistance in the AC's path.

This is just my understanding and theory of how it works. Im not an electrician or engineer, and I need to go find and watch those videos again. You should see if you can find them. A guy on youtube with a whiteboard who looks like a little crazy and has some intense teaching style.

- I forgot to add the variable impedance of the condensers (capacitors)..

[PRR]

YES, you can reduce any circuit by taking things two at a time.

But...

Work on something simpler. The FuzzFace is trickier than it looks.

The 33K and 330 are not quite parallel-- there is another 8K and the very variable/uncertain path through Q2 C-B.