Fuzzhugger - Algal Bloom [gut shot]  [traced]

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digitalzombie
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Post by digitalzombie »

EBRAddict wrote:Are you getting 9.45 at both sides of the starve pot?
I assume you're talking about lugs 2 & 3 of the Starve pot since lug 1 isn't connected to anything. Taking new measurements, reading 9.5v+, and 9.31 on both lugs.

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Post by EBRAddict »

Here's the readings from my notes, with starve fully CW:

Vs 9.49V

Q1
C 1.322
B 0.759
E 0.172

Q2
C 0.773
B 0.571
E 0

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Post by digitalzombie »

9.58v

Q1
C 1.359
B 0.742
E 0.174

Q2
C 0.755
B 0.555
E 0.0

:hmmm:

Looks consistent, and both trannies read close to 400 Hfe on my DMM, so why does it sound like poo?

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Post by EBRAddict »

I'd put a scope or an audio probe to it, your voltages look OK so maybe you're getting signal bleeding off or an intermittent connection somewhere. Double check your resistors with the DMM.

Miro did a vero of this over at tagboardeffects and it was verified so the schematic is OK.

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Post by digitalzombie »

EBRAddict wrote:I'd put a scope or an audio probe to it, your voltages look OK so maybe you're getting signal bleeding off or an intermittent connection somewhere. Double check your resistors with the DMM.

Miro did a vero of this over at tagboardeffects and it was verified so the schematic is OK.
You mean double check the resistor values? I'll do that. Since it's on the breadboard it's easy to move the output around to hear how it's sounding. The end of the Electra portion sounds loud and flubby, which if I recall is how it should sound until you introduce clipping diodes, but I think the Bazz section just isn't Fussing correctly. I put one of those on the breadboard recently and it was monstrous, not clean at all like this. I posted the breadboard layout I'm using, that all look right?

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Post by digitalzombie »

So, super stupid mistake. I had my bloom 3 on the same row as bloom 2 :slap:

So it's working, and loud & fuzzy. What exactly is the Starve pot supposed to do to the sound that the gain pot can't do? I have a 50k hooked up to this as per the verified vero layout, turning it CCW just makes it less gain-y, not like the weird fizziness I'd expect from a "starve" pot on a fuzz.

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Post by HighDeaf1080p »

Can anyone help me understand the orientation of C4 (2u2) in this schematic? It seems from my understanding of polarized capacitors, that C4 should be oriented with the positive side towards Q2, and not the negative side, as it clearly appears to be oriented, from the board photos, and traced schematic. Shouldn't C3 (100n) block the voltage coming from Q1, leaving the higher voltage side to be toward Q2? (I'm referring to the parts identifiers in EBRAddict's Schematic and photos)

I would really love to know what effect turning that capacitor around the way it is shown has on the sound, and understand better the logic behind the way it is oriented. Any insight is greatly appreciated.

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Post by EBRAddict »

I agree, it looks backwards. It looks like the board silkscreen was for a film or other non polarized cap.

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Post by HighDeaf1080p »

Well, it appears from the photo that the actual pedal has it installed backwards...and I am assuming the people who have built working clones from this thread or the vero layout installed it backwards, so...I guess the question is, what does it do to the sound if you turn it around the right way? Would the pedal become quieter (lose extraneous noise caused by voltage hitting the pot between C3 and C4)? I'm working on a similar layout to this (though admittedly different transistors, etc.) but I used this schematic as one basis for my layout. Some guys on another forum caught the discrepancy. I will experiment with it on the breadboard and see if turning it backwards/forwards makes an audible change, and report back when I get to that point.

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Post by digitalzombie »

The breadboard template I posted works, so you can use that as a jumping off point if you like. My understanding of electronics though tells me C4 is oriented just fine. It's filtering DC isn't it?

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Post by HighDeaf1080p »

Not sure my layout is close enough to this schematic to make use of the breadboard layout, but I'll take a look. I have some additional pots and a slew of clipping diodes and capacitor, etc between the two transistors, and things that are gonna take up a lot of space...

To my knowledge, polarized capacitors are supposed to have their positive leg oriented towards the higher voltage source...which would be toward Q2, thanks to C3 that is already filtering out voltage from the other direction. As I understand it, if its in backwards it functions as a low resistance source instead, and allows the voltage to go on through and hit the "bloom" pot causing it to be noisy.

From Wikipedia: Standard electrolytic capacitors are polarized components due to their asymmetrical construction, and may only be operated with a higher voltage on the anode than on the cathode at all times. Voltages with reverse polarity, or voltage or ripple current higher than specified, can destroy the dielectric and thus the capacitor. The destruction of electrolytic capacitors can have catastrophic consequences (explosion, fire).

There is just no voltage source between C4 and its neighbor C3 for the anode to be pointed at...

This is all theory that was explained to me by more knowledgeable people in this arena, and not being spoken to from my own experience or deep knowledge...however, when my layout is on the breadboard, I will swap it around a few times and see if I notice any more hiss or grit, and difference in biasing on the second transistor, or anything out of the ordinary. Hopefully it wont explode and blow my hand off. :lol:

I agree with EBRAddict, now looking at the picture, the part intended in that location does appear from the silkscreen to have been a film cap...not sure why a polarized cap got stuck there. :scratch:

Curiouser and curiouser.

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Post by digitalzombie »

Correct me if I'm wrong (and I very well might be - maybe an expert can chime in), but I thought one of the purposes of a polarized cap is that it passes voltage only from positive to negative - see the 100uf's use in the VCC section. So in that respect it makes sense to me the way it is, because AC voltage is coming from Q1/C3, but it travels through the A100k pot. Having a polarized cap after that would ensure no voltage coming from Q2 is getting grounded by that pot.

I'm just theorizing on basic knowledge though. I'd love this suggested application to be verified or corrected (in a way I can understand).

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Post by HighDeaf1080p »

digitalzombie wrote:Correct me if I'm wrong (and I very well might be - maybe an expert can chime in), but I thought one of the purposes of a polarized cap is that it passes voltage only from positive to negative - see the 100uf's use in the VCC section. So in that respect it makes sense to me the way it is, because AC voltage is coming from Q1/C3, but it travels through the A100k pot. Having a polarized cap after that would ensure no voltage coming from Q2 is getting grounded by that pot.

I'm just theorizing on basic knowledge though. I'd love this suggested application to be verified or corrected (in a way I can understand).
Haha, exactly why I asked the question. I only have enough knowledge here to be completely confused.

The part where this gets hard for me is that 9V+ is coming into Q2's collector. I presumed the capacitors on each side of the bloom pot would be to keep DC voltage out of it from both sides...and in many schematics similar to this, they are both non-polarized, so I don't think any is getting past C3 anyway.

NOTE: I see that mirosol's schematic in this thread shows the capacitor with the positive (anode) towards Q2, and not the way the picture of the pedal's guts or the schematic from EBRAddict orients it.

The rule seems pretty clear. Put the anode towards the higher voltage side, or you destroy the capacitor. If measuring with a multimeter, the higher voltage should be towards Q2.

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Post by digitalzombie »

HighDeaf1080p wrote: The rule seems pretty clear. Put the anode towards the higher voltage side, or you destroy the capacitor.
See, that's where I'm at a loss. I get where you're coming from because that's pretty much verbatim from Forrest Mims. Just browsing through my pdf of Getting Started in Electronics, I'm going to quickly surmise that the base of Q2 wouldn't normally have current flowing out of it, so in normal circumstances there's no concern of DC and no "higher potential voltage" to figure out, but the diode bridging the collector and base is acting as a half-wave rectifier, converting AC to DC, and thereby requiring the polarizing cap to keep the current flow from going the other direction?

Image

Image

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Post by EBRAddict »

By definition the base of the Q2 will be at least ~0.7V higher than the emitter, so 0.7V. The only DC path on the other side of the cap is to ground via parallel resistors so 0V. Therefore the cap should be the other way around. Musically a reversed electro cap adds nothing to the circuit.

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Post by HighDeaf1080p »

Thank you. To verify this with my multimeter in future layouts, I would set it to DC volts, place the black lead on the ground bus near the input side of the circuit, then place the red lead to each side of the capacitor in question and record the values? Then just turn the capacitor until it faces the higher voltage number?

Or would I place the test leads on either side of the capacitor in circuit, and see if it gives me a positive or negative number to determine which direction is "more positive" at that point in the circuit?

Appreciate the help!

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