DOD - FX33 Buzz Box  [schematic]

All about modern commercial stompbox circuits from Electro Harmonix over MXR, Boss and Ibanez into the nineties.
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kupfer_m
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Post by kupfer_m »

RnFR wrote:can someone tell me what's going on with Q5, Q7, and Q8?
These are "gyrator-circuits' (I too was confused about these..).
They emulate an inductor.
Do a google search for gyrator, you get a far more explanation than I can give you :scratch:

K_m

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mictester
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Post by mictester »

RnFR wrote:can someone tell me what's going on with Q5, Q7, and Q8?
They look strange, don't they? They are "gyrators" - they are a method of emulating an inductor. The inductor values you need to be useful at audio frequencies make for quite big, heavy, expensive components (take a look at the size of a 500 mH coil used in a Wah, and you'll see what I mean). Those little transistor circuits are actually the equivalent of a coil in series with a capacitor, so they are resonant at carefully chosen frequencies.

Some IC-based graphic equalisers use gyrator circuits these days - it's easily possible to design very effective filters without real inductors. It's also possible to build wah pedals without the usual inductor using gyrators (other approaches use "twin-T" filters and "state-variable" filters)

The gyrator is a building-block we should all be aware of - it's useful to read up on op-amp based versions (they have higher "Q", more accuracy and less distortion).
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Post by blkmagik98 »

I know this is an old topic, but I saw Greg Anderson of Goatsnake using one of these last night. He was punching it in during leads and he got some really cool sounds from it.

Michael


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Crumbchildz
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Post by Crumbchildz »

Arrrgh! Where was Goatsnake playing? I was gonna go to MDF just to see them and Neurosis, but Goatsnake dropped off the bill. :evil:
Loud's a tone, right?

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blkmagik98
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Post by blkmagik98 »

I saw them at the Doornroosje in Nijmegen. The show was good but not as good as their appearance at Roadburn last year...I remembered and took my earplugs this time! Six Sunn Model T's at full blast will take your head off.

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knutolai
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Post by knutolai »

Wow this pedal is batshit insane! Has anyone seen a layout anywhere?

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Post by FausterCraster »

UP !

I breadboard this circuit according to PDF on page1.

I have this issue on HEAVY Pot (P4) the one that mix the "dry/distort" with the "octave" ;

when it is full close to "octave" the signal the output is really low volume
This is what happen using this POT :
Form 0% full "dry/distort" signal is OK
Form 1% to 80% mix "dry/distort" with "octave" is OK
From 81% to 100% there is very low signal output

What could be ?

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Gila_Crisis
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Post by Gila_Crisis »

I was searching on the web and found this forum:
http://guitar-fx-layouts.42897.x6.nabbl ... 30721.html

Did anyboday every tried to build the pedal according this layout? I was trying to check it using the schematic, but have feelings not everything is 100% right.
I tried one this weekend and I liked it a lot, but he priginal units run for crazy prices on the web...
Attachments
FX33snipped.png
DODFX33.png
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thesmokingman
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Post by thesmokingman »

which parts of the schematic are you questioning the validity of?

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Gila_Crisis
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Post by Gila_Crisis »

thesmokingman wrote:which parts of the schematic are you questioning the validity of?
the input buffer for example, to me the layout is not the same as what the schematic tells
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Wulf_Nippel
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Post by Wulf_Nippel »

Hi everyone,
I am pretty new to the whole electronics world, but I am extremely captivated and compelled to learn as much as possible so that I can understand how these things work and be able to not only diagnose and repair them myself, but hopefully one day to create my own. Anyways, this post is NOT about me and my hopes, so I apologize for the rambling and enough about that!

My question is this- I was given one of these Buzz Box pedals from a friend who was about to throw it in the garbage- said it was broken and he didn't want it. so I grabbed it and took it home, and the first thing I noticed is that when I put a battery in and plugged a cable in, the check LED came on and stays on, pushing the footswitch does nothing. Next, I plugged it into an amp and all I got was some really loud noise, turning the knobs had no effect except the volume knob would kill the noise when turned to zero. I know it is going to take a lot more information than that for anybody to be able to help troubleshoot the potential problem, but I was hoping someone could maybe give me an idea as to why it stays on all the time and the footswitch isn't working. I feel like that is a good place to start. I really appreciate the help, its just got me stumped and I have no idea where to even start...

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