Bigfoot FX Magnavibe  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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KindaFuzzy
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Post by KindaFuzzy »

With the money I got from the Vibrostomp I went ahead and got one of these guys because the soundclips were great. Good news the pedal lives up to the clips, it sounds exactly the same as the vibrato on my 214, and has more depth without getting muddy like the Vibrostomp. Great pedal for the price too, solidly built.

Was a little tricky to get all the goop off, it was latex stretchy stuff in two layers. It's an upside-down pcb, which is odd, but functional, and a super simple circuit with only two transistors. I haven't breadboarded it yet to test, but should be right. I put a full photo gallery together of the de-gooping in my flickr, but here's a taste of the final product a soundclip comparison and the schematic:

http://soundclick.com/share.cfm?id=10394655
http://www.flickr.com/photos/35422385@N ... 139715275/
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Magnavibe vibrato.jpg
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Magnavibe flasher.jpg
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Magnavibe board.jpg
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Magnavibe 3pdt.jpg
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jwpartain1
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Post by jwpartain1 »

No! I JUST got the parts to build the Vibrostomp! :slap: Now you say this is less muddy?!

:)

Thanks for all your work man, you're really on the vibra-hunt.

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RnFR
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Post by RnFR »

nice degoop! looks really clean. can't wait to try this out. I'll volunteer for the redraw again if you need a hand.
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Post by sinner »

:thumbsup I love you for it. I was looking around for vibe simple enough to tagboard it :)

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KindaFuzzy
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Post by KindaFuzzy »

RnFR wrote:nice degoop! looks really clean. can't wait to try this out. I'll volunteer for the redraw again if you need a hand.
That would be great.

It's a cool little circuit, and both the vibrostomp and this one have a different thing going on so just build both.

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Bernardduur
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Post by Bernardduur »

CooL!

Could you turn it in a tremolo pedal by putting the LDR to ground?
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KindaFuzzy
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Post by KindaFuzzy »

Bernardduur wrote:CooL!

Could you turn it in a tremolo pedal by putting the LDR to ground?
I was thinking the same thing, that's the first thing I'm going to try once it's on the breadboard.

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danielzink
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Post by danielzink »

A double sided PCB in it's simplest form 'eh ?

:D

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KindaFuzzy
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Post by KindaFuzzy »

This is a schematic of what this pedal is based on, I thought it looked familiar, so I dug through my pile of schematics and bingo, Wobbletron with an LDR.
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vibrato wobbletron.gif
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Nocentelli
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Post by Nocentelli »

Excellent work chaps, many thanks!
Now, I'm working on.a layout to jam this tiny beauty into a 1590A
Any advice about avoiding ticking? I've only done layouts for fuzz/OD/distortion, but I get the impression that it's a distinct possibility with DIY modulation. Would separate electros to ground for both audioi and flasher circuits help?
Steven_M wrote: 21 Jan 2011, 17:52
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greenskull
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Post by greenskull »

Yes, maybe have the grounds separated and star ground connected to output jack.
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Nocentelli
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Post by Nocentelli »

Here's a quick go at a small vero layout, unverified. Still waiting for ldr, so i've not even breadboarded this. I'm thinking of trying to mount extra filtering board on the dc jack: Is it likely to help?
Magnavibe v1_render.gif
Steven_M wrote: 21 Jan 2011, 17:52
biffa wrote:Sorry,but u r not the only member here
I'm not? Well fuck this site then. I only want meaningful conversations with myself.

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Post by madbean »

I built up a version of this. Sounds really good. I went with the stock values and decided to give the vibe/trem switch a try. As a tremolo, it sounds great but there is a significant volume drop. So, I'm thinking of using a DPDT for that and dropping another resistor in parallel with the 7k5 off the emitter of Q1 for tremolo switching.

I used a super bright orange 3mm, but I think I will switch that out for red diffused as the LED right now is brighter than it needs to be. Also the Rate could use a little adjustment. I will probably drop the 2k2 down to 1k5k and the 27k down to 10k for a little more range.

Anyway, it sounds super cool!

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kinski
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Post by kinski »

Okay, so I built this thing, but can't get it to work. I get no sound and the LED (with the photocell) does not light up either. Any ideas?

1 quick questions, the layout shows the LED facing one direction but the + / - signs are on the wrong sides. Which way should the LED face? I tried both and still did not get any sound.

Oh yeah...please don't laugh at my soldering skill: :lol:
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flatcrabs
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Post by flatcrabs »

I can't quite tell from the dark photo, but it looks like there may be some solder bridges between rows 2 & 3 and rows 3 & 4.

Did you use the continuity checker on your DMM?

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kinski
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Post by kinski »

i dont have a multimeter to check....

I triple checked for bridges and ran a box cutter between all rows. Still no sound....

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Post by Nocentelli »

Yeah, it's probably the LED direction - I just fired my version of this vero and it's definitely verified - Please note the flat side is reversed compared to the layout posted above - Also please note I am not confident which is correct OR which way I used, cos mine fired up first time :hmmm:
Magnavibe v2_verif.gif
Magnavibe v2_verif.gif (17.63 KiB) Viewed 5627 times
I didn't bother with any filtering, polarity protection etc, but I've attached the .DIY file if you want to have a tinker with it:

[The extension diy has been deactivated and can no longer be displayed.]

All values are as per photo-schematic, the speed range is definitely a bit limited but useable (check out Madbean's tweaking recomendations to extend the control range). I also found the depth lacking with a red LED and a 1 Mohm LDR, so I swapped in a blue ultra-bright and now it's just a leetle too much with depth up full, i.e. just right.

I'd quite like to work in a LFO-drive status LED if anyone's got any simple suggestions (I can't even get the standard on/off one to fucking work yet, so there's no rush).
Steven_M wrote: 21 Jan 2011, 17:52
biffa wrote:Sorry,but u r not the only member here
I'm not? Well fuck this site then. I only want meaningful conversations with myself.

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kinski
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Post by kinski »

Hey, thanks for this info! The layout you just posted has the transistors facing the other direction. I'll swap them around and see what happens. I'm out of town all week for some gigs, so it will have to wait till the weekend!

Ill keep ya'll posted! Would love to get this working!

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Post by Nocentelli »

Yep, my fuck up again. In my defence, I do have two contradictory datasheet pinouts for the MPSA18, m'lud.
Steven_M wrote: 21 Jan 2011, 17:52
biffa wrote:Sorry,but u r not the only member here
I'm not? Well fuck this site then. I only want meaningful conversations with myself.

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kinski
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Post by kinski »

No worries! So the most recent layout you psoted, does that have the correct transistor direction, or the first one?

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