Tone Bender vs fuzz face, what's the point?

Started by m_charles, June 10, 2015, 01:39:18 PM

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R.G.

Quote from: mac on June 20, 2015, 06:59:22 PM
QuoteI have never built a NPN MKII. I have no idea where I'd get suitable transistors.

You could search for 2N1117 or 2N388 from TI, but these are trebly.
On the other hand, Sanyo 2SD72K have a very low transition frequency Ft. And Matsushitas 2SD352 Ft is even lower.

For silicons, 2N2369, 2SC1730, 2SC1215, hfe below 100, but Ft is very high.
You could try BD237 or BD175 that have low hfe, and Ft is close to an ACxxx.
Even TIPxx or 3055 might work.
I'm sorry to be difficult, but I do not understand what you wrote. Transistors can't be "trebly". They respond all the way down to DC. In general, ft is a non-issue for pedals in simple circuits, as it's almost never low enough to be a problem with the half-audio range of guitar pedals.

CIRCUITS may be trebly, and may have hfe dependencies.

Or did I completely misunderstand?
R.G.

In response to the questions in the forum - PCB Layout for Musical Effects is available from The Book Patch. Search "PCB Layout" and it ought to appear.

mac

QuoteI'm sorry to be difficult, but I do not understand what you wrote.

I mean, put a 2N1117 in a simple circuit like a Rangemaster and listen to it, then a 2SD352 of similar hfe and leakage. You'll notice that the 352 cuts more highs than the 1117.
Since 352s do this in every circuit I try, I blame, or bless, the output capacitance, or frequency transition.
As a matter of fact, if you use 352s in a MKII, you can omit the 103 cap at the input, or the 220p in the 3-knob.

From your article,
"The frequency response of the transistors matters, too. The AC128 originals were not particularly stellar; this also turns out to be a happy combination, as we now know that clipping with razor edges sounds -- well, like listening to razor blades. Most guitarists (there's that personal preference thing again) seem to want the rough edges smoothed off. At highest gain, any amplifier exhibits frequency response limited by the device characteristics. The AC128 has parasitic capacitances typical for then-current germanium devices, meaning that it was working hard to do the full audio range. This almost certainly has something to do with the softened edges of the sound. In simulation, I could play with the parasitic capacitances of the simulated devices, and found that adding high junction capacitances from collector to base made for softer distortion. The lesson here is that you can soften the sound of a FF even further by connecting a 10-100pF capacitor from the collector to base of the transistors. This dodge was used in later silicon versions of the FF."

Sorry if my english can be confusing sometimes.
Let me say that I speak one language, spanish... and very bad :)

mac
mac@mac-pc:~$ sudo apt install ECC83 EL84