bazz fuss + sziklai + Ge = moefass + dysleksica (w/ notes)

[duck_arse]

everyone else has had a go at the bazzfuss, now it's my turn. I have a pair of v. leaky npn Ge's I want to shift. they wouldn't work as a straight darlington, so I tried the Sziklai (which always looks to me like "szyslak") config, with a crummy pnp, and it worked. as per all bassfuzz and variants, all values are variable, and affect the overall one way or other. here's wot I came up wit:



my npn's are ac127 and measured leak/gain in a modded keen-o-meter of 353uA/116 and 496uA/142. the pnp's are 2sb156 w/ 44~55uA/30~32. the smallbear page on darlingtons shows how to bias low-leak, low-gain pairs for a rangemaster, which is a different thing altogether. I breadboarded both these circuits, the npn version only to show it worked. I fiddled about with the pnp and found as follows:

R5 is the magik pop-prevent, its value (1M) is a secret. I tested orange and red (HE) leds, probably green and yellow would produce similar results, w/ about 1V6 max output level. a 1N914 reduced the output level too far to be much use, IMHO. R1 sets the gain/operating point and 10k works ok. C3 can be anywhere between 150nF and 1uF, the 50kA seems about right, so that's 5 values you don't need to worry about.

start with some nice softish fuzz and not much sustain and add the following:

R2 lifts Vc to a usable level, and works to reduce the gain ( .... you can short it to ground). these are both good things, as it happens. C2 increases the gain, and tailors the frequency response, which starts out as not much good. a value of 4u7 here provides a decent low end response, go as high as 10uF if you like more woof, or as low as 1uF for a trebley sound.

C1 interacts with C2 and can go as low as 47nF for a bright boost, as high as 330nf for more lows. I tried an easyface blend, but couldn't hear it, so I would find a value I liked, or just switch between the two extremes.

R3 and R4 improve the high frequency response, and do some biasing, I think to account for bum leakages, like Q2. they both affect the overall gain, and shift Vc about a little, and can be opened for different fuzz/sustain characteristics. I used pots and tuned for max gain: Q1 has low leak, so anything 1M or more is good, the 680k was best for Q2. I'd be leaving R3 as is, and adding a switch to open R4.

with C1=330nF, C2=1uF and R4 open, you get less crackle and more sustain and a "wahh", about the only way I can describe. with C2=4u7 you get more "dark, doom". with C1=47nF, C2=470nF, you get a wild jaw-harp/feedback/oscillation twanggg, not guaranteed controllable.

with C1=47nF and C2=4u7 and R4 open, you get a much cleaner boost than fuzz, w/ C2=1uF the sound "hollows" somewhat.

the voltages marked on the pnp version are what I measured: they are not necessarily target values. watch your polarised component orientation and the wiring of the two transistors. I miss-drew them a couple of times before I realised they weren't straight darlington connected.




I dunno if any of this will be repeatable or usable, but it seems to be another way to shift some of those less-than-prime-spec Ge's that you've got laying about, and only took two afternoons to get this far. seeing as I can't play guitar, I really can't do the things that get out the good stuff, so if anyone would lash it up and give it a go, or has questions, answers, suggestions, I'd like to hear from. it might end-up worthwhile after all.

[rugeb]

Cool!
You've tried other transistors and other diodes?
The Vulcan Overdrive it's with inline diodes providing compression/limiting because they absorb some of the peak input, can be a good mod for moefass...
Vulcan Overdrive schematic: http://diystompboxes.com/analogalchemy/sch/vulcan.gif

[duck_arse]

no, not other transistors, I just was trying to darlington a pair of npn's, but it didn't work good. when I tried a second time w/ sizlak pair, it was all good. I tried w/ 1N914, but output was too low.

I was going to try a switch between silicon transistor and germanium, but that fell over early.

[smallbearelec]

I suspect that it would be possible to use a "composite" transistor with 80-ish gain in an FF circuit, but I am always too busy with other stuff to try it out. If it works, there is plenty of suitable raw stock out there.

SD

[duck_arse]

now that I have your attention, smallbear, thanks for the darlington page, even if only for the sizlak connection.

[rugeb]

no, not other transistors, I just was trying to darlington a pair of npn's, but it didn't work good. when I tried a second time w/ sizlak pair, it was all good. I tried w/ 1N914, but output was too low.

OK! Thanks.
If you try with other transistors or diodes, please: post it!

[thehallofshields]

Looks like the image is gone. Do you still have the schematic?

[EBK]

"Hello. Moe's Tavern. Moe speaking."

"Is Leaky NPN there?"

"I'll check. Hey, is anyone here leaky 'n peein'?"
"Why you little...."

[duck_arse]

I will need to havva search, can't remember what the local file name is .....

also, 6666 posts.

[edit :] I think this is a redraw I did from notes, for kipper.

[Steben]

https://electronics.stackexchange.com/questions/77520/resistors-within-a-darlington-transistor

Leakage? Old germaniums have possibly lots of leakage or less but always more than Si. Leakage ... which is multiplied within a darlington config!

[thehallofshields]

I breadboarded something very similar to this and I got a very Trumpety, Saw Wavey type sound like the Boss-tone. I guess I shouldn't be surprised...

[mac]

Ten years after,



Q2 can be any Ge PNP.
If both are Ge then Q1 leakage will be multiplied by Q2.

mac

[thehallofshields]

^ Mac, what happened to your +1M resistor to Bias the base that you were such an advocate of?

[mac]

^ Mac, what happened to your +1M resistor to Bias the base that you were such an advocate of?

I use a >1M resistor from Vcc to B for single transistors, ie, 2n5088, bc550C, 2n3904, etc.
The idea is to make the resistor feed the base while the diode just clips.
In other words, the diode's leakage is so small that you need to use a big resistor at the collector >100k.

With darlingtons gain is astronomical, so leakage is enough to feed the base with a 10k at the collector.

I wrote that a Bazz Fuss, and its cousin Arsenio Novo distortion, has a sweet spot when Vcollector = Vbase

mac