Author Topic: Non-inverting Bazz Fuss - help please  (Read 6370 times)

leigh

Non-inverting Bazz Fuss - help please
« on: February 05, 2014, 03:53:25 PM »
I built a Deluxe Bazz Fuss years ago, and it has worked very nicely. However, I just rearranged my pedal board, and it includes a parallel effects chain now, and I discovered that the output of the Bazz Fuss inverts the phase (polarity) of the input signal.

Without adding another active stage (e.g. an output buffer), is there a graceful way to modify the Bazz Fuss to be a non-inverting pedal?

Thank you!

(The circuit I built is exactly as you see below, with the addition of a SPDT toggle to switch the "pickup simulator" transformer coil in and out.)

references: http://home-wrecker.com/bazz.html


slacker

Re:
« Reply #1 on: February 05, 2014, 05:08:07 PM »
Unfortunately not, the only way to make it non inverting is to add another stage after it to invert the signal again.
A better idea if you're mixing things in parallel is probably to build a standalone box that will allow you to flip the phase of things.

mth5044

Re: Non-inverting Bazz Fuss - help please
« Reply #2 on: February 05, 2014, 05:13:21 PM »
+1 for Slacker's external box thing. Check this out: http://www.runoffgroove.com/splitter-blend.html

PRR

Re: Non-inverting Bazz Fuss - help please
« Reply #3 on: February 05, 2014, 06:37:51 PM »
If you have another 42TM018, just do this:

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leigh

Re: Non-inverting Bazz Fuss - help please
« Reply #4 on: February 05, 2014, 07:44:01 PM »
If you have another 42TM018, just do this:

That's a smart approach, PRR, although I'm pretty much out of room to add more (big) parts inside:



Regarding the other suggestions here to build a standalone phase-flipper box, that would work great if the Bazz Fuss was always by itself in this chain, but there are other boxes too and sometimes the Fuzz is on and sometimes it's off - so if I flipped the phase of this effects chain, it would still be going in and out of phase with the rest of this pedalboard setup.

So, looks like it's either:

1) Pull this Bazz Fuss out of service here, or

2) Find a compact way to add another (unity gain) transistor stage, to flip the phase back around. Can this be done with a transistor and just a couple other small parts?

dwmorrin

Re: Non-inverting Bazz Fuss - help please
« Reply #5 on: February 05, 2014, 08:50:24 PM »
2) Find a compact way to add another (unity gain) transistor stage, to flip the phase back around. Can this be done with a transistor and just a couple other small parts?

You can make a unity gain, inverting, single transistor stage by making collector and emitter resistors equal, and taking the output from the collector.  Added such a stage to your schematic.  Just have to figure out Rb1, and Rb2 to bias the base.  Copying the Univox Super Fuzz schematic (where this setup is used as a splitter), the values 220k and 150k should make it work.  However, since you're only taking collector out, you could rebias this to get more swing out of the collector, if desired.



PRR

Re: Non-inverting Bazz Fuss - help please
« Reply #6 on: February 05, 2014, 10:40:07 PM »
> a unity gain, inverting, single transistor stage....  Just have to figure out Rb1, and Rb2

Actually... the inverter's emitter should be near 1/4 of supply for max clean output. Say 2V. OTOH the signal is already *severely* beat-up by Q1 D1, and we don't need "max" output. And Q1 Collector is always low but non-zero. Between 1V and 2V. We can feed a Q2 Base direct from Q1 Collector, use a suitable Emitter resistor and same/similar Collector resistor, and get the inversion for just one Q and 2 R.

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dwmorrin

Re: Non-inverting Bazz Fuss - help please
« Reply #7 on: February 05, 2014, 10:51:29 PM »
We can feed a Q2 Base direct from Q1 Collector
I glad you posted that.  I initially wanted to suggest the direct connection, but I wasn't sure if it would work well.  Another enlightening post, as always.

chptunes

Re: Non-inverting Bazz Fuss - help please
« Reply #8 on: February 06, 2014, 05:47:34 AM »
..so, (in Paul's illistration) does Q2 need to be another Darlington (MPSA13) or an unassuming 2N5088/2N3904?

bool

Re: Non-inverting Bazz Fuss - help please
« Reply #9 on: February 06, 2014, 06:08:46 AM »
an "ordinary" NPN

... or perhaps a mosfet.

leigh

Re: Non-inverting Bazz Fuss - help please
« Reply #10 on: February 06, 2014, 01:40:58 PM »
Brilliant, thanks guys! One more transistor and a couple more resistors sounds doable. I too was wondering if a direct (DC coupled) connection between Q1 and Q2 would work, so I'm glad to hear from PRR that it would.

I'll be trying this mod, and will report back!


PRR

Re: Non-inverting Bazz Fuss - help please
« Reply #11 on: February 06, 2014, 04:43:38 PM »
> another Darlington (MPSA13)

ARGH!! That IS a Darlington!!

(ponder ponder) No matter. Q1 Collector sits ~~0.5V higher, which is actually a wee bit better for biasing Q2.

Q2 can be junk. hFE greater than 20, or up to infinity. Vce(max) at least 8V. Ft over 0.4MHz. You can't hardly buy a transistor that won't work.
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leigh

Re: Non-inverting Bazz Fuss - help please
« Reply #12 on: February 06, 2014, 11:44:40 PM »
Success!

Using a stock 2N3904 I added Q2 just as shown in PRR's mod (10k's off both collector and emitter), and it's working great.

Thanks for salvaging this pedal for me!

I'll post a photo once I open it back up to physically reinforce the innards. It's getting crowded in there, and there are parts just kinda hanging in mid-air right now...

leigh

Re: Non-inverting Bazz Fuss - help please
« Reply #13 on: February 07, 2014, 12:44:34 AM »
Here's an updated post about the non-inverting mod, and here's the ugly guts!