MI Audio - Crunch Box  [traced]

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Bernardduur
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Post by Bernardduur »

Isn't a Crunch box + tone stack more a Marshall Guv'Nor?
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Post by Mr. G. »

I just made a new slightly smaller layout, so could someone please take a look at it to see if everything seems ok?

Here's the new layout: Krunk w/ Marshall Tone Stack and v2 mods

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Post by Mr. G. »

Could someone please take a look at the schematic and 2nd layout I posted to see if I did things right? I think I've got the presence pot wired wrong. Should it's lug 1 go to K15 rather than K20 on the layout?

On the schematic, the numbering on ICB 5 & 6 are backwards, and I couldn't remove 4 & 8 from ICA so I just put an X through them.

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Post by drushton2002 »

hey,
great pedal i am breadboarding it now. i am assuming the led's are for clipping purposes, has anyone tried changing the configuration to symetric diodes or asymetric diodes? would it even work?

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Post by soulsonic »

It looks like the Volume control is an Audio Taper pot:
Image

Here's another board pic:
Image

More BIG pics can be seen here:
members/soulsonic/Gallery/MI_Crunchbox/
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Post by JHS »

IMHO those 2/3-band tone stacks in OD/distortion boxes are very disappointing. To much interaction between the bands and way to much fiddling to set up a convincing sound. If the FX doesn't match the amp or the guitar a 3-band tone stack will not cure the problem. If the FX sounds good on it's own and match the guitar and the amp a simple non sucking tone control is all I need to do some minor adjustment to the sound.

JHS

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Post by danielzink »

Hey All,

I'm really itching to build one of these - what's our best verified layout (as per original - 3 pots) ?

Thanks, Dan
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Post by Ripdivot »

Ripdivot wrote:Hi everybody, this is my first post. I have had a Crunch Box V2 for a while now and really like it. As you can see it is wired slightly different than anything I have seen on this site so far.

R7, R8, R9 no longer exist
R6 is now 470 ohms
C8 is now 0.022uf
VR4 (presence trimmer) is 20K

here is the schematic, changes are in red:

Image
I built this version which I reversed from my Crunch Box V2. I updated Matsumin's schematic with the changes from the V2. It sounds virtually Identical to the original.

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madbean
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Post by madbean »

Here's a new PCB layout based on v.2 of this box. It's verified by me!

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Mr. G.
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Post by Mr. G. »

Very nice layout! How did you do the pot connections in the layout? I've been messing around with Eagle, and that's where usually run into problems. Maybe I'm just using the wrong component in the schematic. Any tips will be greatly appreciated!

Any suggestions for a good substitute for the LM833?

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Post by mattpas »

madbean wrote:Here's a new PCB layout based on v.2 of this box. It's verified by me!
Did you use Matsumin's V2 schematic?

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Post by madbean »

Mr. G. wrote:Very nice layout! How did you do the pot connections in the layout? I've been messing around with Eagle, and that's where usually run into problems. Maybe I'm just using the wrong component in the schematic. Any tips will be greatly appreciated!

Any suggestions for a good substitute for the LM833?
I use Gaussmarkov's libraries for Eagle stuff Link
He has a library for pot and switch connections in it.

You could use any of the standard opamps as a sub, although the LM833 tends to have a little extra high end grit to it. I suggest NE5532 if you have it, or maybe LF353.
Did you use Matsumin's V2 schematic?
That's the one. Should be a direct copy, although for my particular build I subbed a 680R for R6 (that's what I had) and altered C8 to 15n to keep close to the same frequency response. Also, I used a 10kB for the tone pot as I don't have any "C" tapers on hand.

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Mr. G.
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Post by Mr. G. »

Thanks! I already had the Gaussmarkov library, I was just using the wrong pot. I was using the standard 16mm pot instead of just the "pot" pot. I do have a NE5532 that I can use.

Thanks again!

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Post by junkemail86 »

nooneknows wrote:
nooneknows wrote: IT WORKS!!! it suddendly became one of the best overdrive I've ever heard and built!
referring to the Matsumin schematics:
- 1uF film in place of the 2.2 uF electro C7
- 1K8 R in place of the 100R R7
- a B25K (tone) pot in place of VR2 and R8 (one external lug to R7, the other external directly to the volume lug), the central lug of the pot goes now to a 10nF cap, then to ground
- got rid of R9 and C9
Marcello
I also liked my Crunch Box v1 build, but was hoping for a little more high end. I just did part of the above mod (clipped off R9 & C9) and definitely like it better than stock. The tone knob is more functional for me now. I might try the other suggestions once I get some more time...

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Mr. G.
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Post by Mr. G. »

I just made a layout using Madbean's as a base, but I changed out the tone control for a BMP type of TC. I also added a switch which changes the mids from scooped to flat. No idea how it will sound yet, but I thought I'd give it a shot. What do ya'll think?

Here's the artwork: >Schematic< >Perf Layout<

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Post by soulsonic »

Anyone else not care for the Crunch Box's Gain control? I think it sounds crummy at low gain settings. I've been messing around with something derivative of this circuit, and I ended up with having the gain fixed on the two stages and used a standard volume control style gain control at the front of the circuit after a buffer....
"Analog electronics in music is dead. Analog effects pedal design is a dead art." - Fran

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Mr. G.
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Post by Mr. G. »

I agree about the gain control. On my original CBv2, once the gain knob is down below 9 o'clock, it starts sounding pretty crappy. I normally leave the gain at around 10-11 o'clock. It also doesn't clean up very well with the guitar's volume knob. Lastly, I think it has just a touch too much bass. I didn't get it for a low gain pedal, and I don't normally need to lower the guitar's volume while using it either. So, the CB works pretty well for my needs. It also sounds killer with an overdrive in front of it.

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Mr. G.
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Post by Mr. G. »

I finally got around to building the layout I did with the BMP tone control, and I'm very pleased with it. The only problem I have is, all of the pots are reversed. Should be a simple fix by switching the 1 & 3 connections on the pots.

I have a TL072 in there at the moment, but I plan on trying a few others to see what sounds best. The only thing I plan to add is a low pass filter (possibly like the presence control in the CBv2) on the output. It can get a little too bright as it is.

With the mid switch set to flat, it sounds very close to my real CBv2. The main difference is a tighter more focused low end. With the mid switch set to scooped, it can get some very nice metal tones. I think with the addition of a low pass filter this will easily bump my real CB off the pedalboard.


edit: After comparing my schematic to Madbean's, I realized that I made the drive pot backwards. If it is wired backwards, would that also make the tone and level work backwards?

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Mr. G.
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Post by Mr. G. »

I just updated the schematic and perf layout to show the correct drive wiring, and also added a presence control.

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Mr. G.
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YATS (many)
BOR
DLS
COT (Briggs mods)
Crunchbox
SHO (several)
Fuzz Factory
Several LM386 based distortions
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Post by Mr. G. »

Just curious... What effects do C5 and C8 have on the circuit, and how would different values affect the sound? I'm referring to C5 and C8 on >this schematic<. Also, would there be much tonal difference between using ceramic or silver mica?

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