Would Y'all Mind Taking A Look At My Modified Bazz Fuss Schematic?

[LzeroKI]

I have breadboarded the basic Bazz Fuss a couple times in the past and had fun with it, but now I would like to actually build one (with some modifications to the circuit).  So, would y'all mind taking a look at the schematic below and let me know if y'all see any obvious problems?




Also, I had a couple (some what beginner) questions about this schematic....

-I am unsure of the value to use for the "Bias" pot.  The collector resistor in the MPSA13 version of the bazz fuss is 10k, should I just use a 10k pot?  I was thinking 20k (though 25k seems to be what I would have to order, 20k is not availible) in order to give me more adjustability to find the "sweet spot"; I also want to be able to use this pot to mis-bias the transistor and get that splattery/synthy/extra gated tone.

-Do I need to worry about polarity of the caps in this circuit? The only cap that is clearly marked for polarity is the 4.7uF input cap.  Do I need to worry about the polarity of the rest of the caps?

-Orientaion of the pot lugs....are all the pots in the schematic oriented the same way? That is to say, with lug 3 at the top and lug 1 at the bottom?


Thanks for any help y'all can give me!

[nocentelli]

I am unsure of the value to use for the "Bias" pot.  The collector resistor in the MPSA13 version of the bazz fuss is 10k, should I just use a 10k pot?  I was thinking 20k (though 25k seems to be what I would have to order, 20k is not availible) in order to give me more adjustability to find the "sweet spot"; I also want to be able to use this pot to mis-bias the transistor and get that splattery/synthy/extra gated tone.

-Do I need to worry about polarity of the caps in this circuit? The only cap that is clearly marked for polarity is the 4.7uF input cap.  Do I need to worry about the polarity of the rest of the caps?

-Orientaion of the pot lugs....are all the pots in the schematic oriented the same way? That is to say, with lug 3 at the top and lug 1 at the bottom?


Thanks for any help y'all can give me!

Have you tried the above circuit out on the breadboard? That should give you an idea of what bias pot to use. I'm not sure there really is a "sweetspot" with the Bazz fuss, full on low parts count filth is the main attraction of this circuit. I would assume the fun comes from increasing the collector resistance above 10k, so at least 25k, maybe 50k or even 100k would give a wider range of special effects. Reducing it below 10k is likely to lower the gain and not yield many interesting sounds. If you're worried about being able to easily dial in the stock Bazz fuzz sound, you could use a 10k fixed resistor in series with the bias pot. If you use lug 1 and 2, minimum setting on the pot would be stock Bazzfuss 10k, turning it up from there would increase the mayhem.

I personally found the 1k gain control was not very useful, it just reduces the gain and since it sounds best with the pot at max, i.e. grounded emitter. The lower gain sounds didn't do much for me.

If you assume the "top lug" on all the pots is lug3, the thickness pot is drawn so it will actually reduce the thickness as you turn the control up (clockwise). Use lug 2 and 3 for the thickness connections if you want it to increase thickness. The tone, volume and gain pots are all wired as one would expect. For bias, see above.

[LzeroKI]

Have you tried the above circuit out on the breadboard? That should give you an idea of what bias pot to use. I'm not sure there really is a "sweetspot" with the Bazz fuss, full on low parts count filth is the main attraction of this circuit. I would assume the fun comes from increasing the collector resistance above 10k, so at least 25k, maybe 50k or even 100k would give a wider range of special effects. Reducing it below 10k is likely to lower the gain and not yield many interesting sounds. If you're worried about being able to easily dial in the stock Bazz fuzz sound, you could use a 10k fixed resistor in series with the bias pot. If you use lug 1 and 2, minimum setting on the pot would be stock Bazzfuss 10k, turning it up from there would increase the mayhem.

I personally found the 1k gain control was not very useful, it just reduces the gain and since it sounds best with the pot at max, i.e. grounded emitter. The lower gain sounds didn't do much for me.

If you assume the "top lug" on all the pots is lug3, the thickness pot is drawn so it will actually reduce the thickness as you turn the control up (clockwise). Use lug 2 and 3 for the thickness connections if you want it to increase thickness. The tone, volume and gain pots are all wired as one would expect. For bias, see above.

Thanks for your reply and advice!  I haven't put this modified BF on a breadboard yet because I don't have the components, I need to order them from Small Bear/PPP.  I think I will go with your idea of the fixed 10k collector resistor in series with a "Bias" pot; I have a question about it though, with it wired as you suggested (9v+ to 10k resistor to bias pot lug 2 and bias pot lug 1 to the MSPA13 collector, do I need to send lug 3 of the bias pot to ground?

Thanks again for your help!

[nocentelli]

Short 3 to 2, or just don't connect it. The pot needs to be a wired as a variable resistor, not a voltage divider.

[mth5044]

For your cap question - the only polarized cap is the 4u7. The 0u1 and the 1n aren't polarized.

[PRR]

> value to use for the "Bias" pot

If you turn Bias to zero, and Fuzz to zero, the transistor blows-up.

The collector resistor value can just be 10K. Variations around this don't make much difference (until something smokes).

If you must prove it to yourself, at least put 1K ohms fixed resistor in series with the Bias pot so you won't go to zero total resistance.

> worry about polarity

When you buy caps of those values, you will *probably* find that the "other" caps do not have polarity markings.

Caps 0.5uFd and down are made with plastic film. It does not care which way voltage is.

Caps 2ufd and up made with film want to be big/expensive. So we often use "electrolytic", which works fine _IF_ they do not see reverse DC voltage.

Caps in between are awkward. Both film and electrolytics are available in this range. But you have not called for any.

[Derringer]

for ideas, take a look at the Whisker Biscuit
http://www.home-wrecker.com/whisker.html

it's a take on a bass fuzz / big muff pi hybrid


and as has been stated, I would not worry too much about making the bias adjustable of the darlington transistor
there's not majorly discernible "sweetspot" for them in bassfuzz configuration and they are easy to fry if you're not careful