Tonebenders for Dummies

[11 Gauge]

how accurate is my BYOC MKII? (non-ESV version)

From a cursory glance, it all looks to be there.

Like a Fuzz Face, the circuit so so simple that it's easy to account for everything.

And since folks tend to build these things w/o using metal film resistors, it's easy to reference them, as well.

Your's also has the .1uF cap that is missing in that schematic - it's coming off Q1's collector!

 

[11 Gauge]

why does a fuzzface clean up better than a tonebender? is it the trannies?

It's not the trannies. You can sub stuff around and it doesn't matter.

It's the .01uF cap to ground at the input, IMO. While it's great for cutting out harsh trebles that you'd get because of the addition of the 3rd transistor, it's also always in the signal path.

Also, the Fuzz Face has no base to ground resistor @ Q1 like the MkII does. The MkIII also has this resistor.

Speaking of the MkIII (since it was brought up), there's also a relatively massive 220pF cap from base to collector @ Q1. That will really round things off. Dropping it to 100pF, or maybe even just down to 150pF will make things a bit brighter. Again though - it might get harsh sounding.

Despite the Tonebenders using germanium, the 3 transistor setup means enough more gain than a Fuzz Face that it precludes the need to remove some treble, hence things like a .01uF cap to ground, or a small value cap across the base and collector.

...Silicon-based Fuzz Faces tend to get small value caps across one of three points in their circuits:

- base to collector of Q1

- base to collector of Q2

- parallel to 100K negative feedback loop resistor

Guys like Marc @ Skreddy like to put the cap across the NFB loop resistor because it equally effects Q1 & Q2. And in something like the Eric Johnson sig FF, there's just a small cap across the B&C of Q2.

...As the gain of the transistors comes down, so can the value of those caps that roll off treble.

So - if it is indeed different transistors that account for differences in cleanup, it could have to do with their gains.

It's also a matter of bandwidth for any given transistor, and that isn't to be confused with something like "headroom" or gain. Germaniums typically have very low bandwidth figures, so they "naturally roll off more treble."

...THIS is why just matching the gain of a silicon transistor with a germanium one won't yield the same results - the si transistor will typically have much better bandwidth performance. So you NEED TO "sack it" to match the germanium device.

Lots of folks chalk all this stuff up to "the magic of germanium," when IMO it is all pretty easily explained. Or - at least if you spend enough time playing with designs like the Fuzz Central Axis Face, you can actually witness it. There's also the "smooth" control, which changes the series input resistance, and a blend control like in the Easy Face will also allow you to dink around with the input signal AND the bandwidth of input frequencies. All of these little mechanisms allow you to "sack" or "hinder" the performance of a silicon transistor to basically give it the same handicap as a germanium.

...But all of these things can be done with any transistor despite its composition. Guys like Bjorn @ BJFE/M.P. are getting really cool fuzz sounds mixing jFETs with bipolar silicons, for example. And the Skreddy Screwdriver has a mosFET for Q1...

 

[surfoverb]

From a cursory glance, it all looks to be there.



Your's also has the .1uF cap that is missing in that schematic - it's coming off Q1's collector!

sweet...thanks!

.1uF for the tonez!

 

[11 Gauge]

.1uF for the tonez!

Well, .1uF for proper DC decoupling off of Q1's collector...

I feel for all the DIY'ers who start with a schematic/layout/info that is incorrect, only to have something nonfunctioning, and they swear they matched what they used...which they DID!

SO - here's a corrected schematic with the MkII/Mk1.5 switching (but still with a "separate" fat switch). This one both includes the missing .1uF cap AND has the simplified switching technique that simply re-routes all the MkII stuff thru a "separate" input cap.

...I also changed the cap values to reflect what is currently and readily available. No need to make this some sort of "unobtanium representation" beyond tracking down the same or similar transistors...

 

[surfoverb]

the oc81s are hard to get for some reason. oc75's are dime a dozen. wtf