Modified Big Muff Pie (Pi) NYC

[TRyan5289]

So I was perusing at the local music shop when I found a Big Muff NYC. The price was right, so it came home with me. Right off the bat, I was digging the sound, but (always a but), I hated the scooped mids. So, I decided to change that.

With some searching and careful thought, I decided which mods I wanted to give to the BMP;
Mid control, increased gain, and a noise gate.

After completing the modifications, I enjoy this pedal more. The mid control is slightly less than I expected, but is useful. The extra gain is awesome. MOAR FUZZ!!

What really sets this pedal apart from the original is the noise gate mod. I can't speak highly enough of it. It's so useful, I'm moving the internal trim pot to the outside of the enclosure. It's range is huge. It can be dialed in from a volume drop, to clean fuzz with no static, to roaring!
Click image for larger view.

The pot on the top of the enclosure is the mid control, the noise gate will fit next to it on the left.



Please excuse the delays between posts, I am editing the thread as I go.

 

[moosapotamus]

Very cool! I'd be interested in knowing some more about your noise gate mod, schematic and how you hooked it up.

~ Charlie

 

[TRyan5289]

Noise gate mod: Copy and paste: Add a 100k trimpot (wired as a variable resistor) parallel to the 100k to ground of the second gain stage (R14). father of fires points out the second gain stage is R20.

Using this schematic. (Please note: the board schematic has changed many times, even within Version 9)


I think the noise gate mod has more function because I increased the gain. Thus, making it more useful.

 

[TRyan5289]

Please excuse the messy hot glue, it was added for stability.
AGAIN, Click for Larger Image.
If you look closely (which you can't see), you would see that only two leads from the trimpot are connected to the board. The leads were bent to fit directly to the solder joints, and wham bam thank you m'am, she's ready to go. This was the easiest part of the mod.


For the increased gain, I jumped R12 and R16. However, I did this differently than what most people would do. I ran a wire from one solder point to the other, with out taking out the resistor. Please refer to the picture in post #3 or #12.

 

[TRyan5289]

For reference, these sites were used.

Basic outline of mods available - [Invalid or Expired Link Removed]

Schematic - http://www.bigmuffpage.com/Big_Muff_Pi_versions_schematics_part3.html

Starve - http://www.beavisaudio.com/projects/DBS/

Thanks for looking!

 

[TRyan5289]

Also, I noticed on my board, that when looking at one side of the board, and flipping to the other, R24 and R20 are mixed up when flipping back and forth.

 

[father of fires]

Noise gate mod: Add a 100k trimpot or full size (wired as a variable resistor) parallel to the 100k to ground of the second gain stage (R14).

Do you mean R20?

 

[TRyan5289]

EDIT:R14 was modified with the noise gate.

I used R14, it works...

 

[father of fires]

I used R14, it works...

Ok but R14 is for the first gain stage. Just want to know which gain stage was modded.

 

[moosapotamus]

Nice. I gotta add this to my list of stuff to try.

Have you tried bypassing the tone stack? That's another good BMP mod. Opens up the sound and also gives you more gain.

~ Charlie

 

[TRyan5289]

I have not tried bypassing the tone stack. Though, I have heard it could be a useful tool. I might possibly do this in the future with a toggle switch.

I decided to to leave the pedal intact to preserve the origins of the pedal. Personally, I thought that if I was changing too much of the pedal, I was redesigning the pedal that I stared with.

Who buys a car, and immediately redesigns this car, top to bottom?


There are many options to do, but have not decided to go all out on switches, potentiometers, and etc. YET

 

[TRyan5289]

Obligatory enclosure and gut shot picture.
More pictures for the gallery. Click to enlarge.
The metal shaft controls the mid-range sweep, and the plastic shaft controls the noise gate

With a little time on my hands this weekend, I decided to remove the internal trimpot, and add a full sized pot to the outside of the enclosure.

The pot that was purchased has a plastic shaft, so was easily manipulated to the length of shaft desired. I simply cut down the long shaft to a size that would be accessible, but not sticking out like a sore thumb. I don't want the shaft to get bumped and have a terrible effect.
I switched from a trimpot because I really liked the functionality of the noise gate modification, felt it was a useful tool, and should be utilized without having to open the enclosure. Also jumping a few resistors, there is increased gain, but the noise floor increases as well.

To further follow up;
After tinkering around, a desirable sound can be achieved, IMO. Switching to a quality pot, the sweep was clean and smooth compared to the trimpot.
I believe the Sustain and Volume knobs interact together to achieve different sounds. With a setting of near full output and full input, a sound can be generated which is pleasing to me. Because of the near full gain and volume, by my preference, a volume jump and a "static/noise" results of this combination. I can dial back the noise with the new pot, and get a less noisy, but still full square wave at the same time.
If I set the noise gate to a higher resistance, I can bring the pedal to boost territory, I think... I will have to do more tinkering between weekend activities.
If the there less resistance, the pedal becomes more and more of a noisy monster than shrieks, squeals, hisses.
However, the sound I'm chasing is a sound I cannot describe with words, and would be best left unsaid, or described at a later date. All I know is it's a gainy mess, and I'm getting close.

**Note: I run all of my gain structures through a clean blend circuit.**

For those who wish to inquire about sound clips, I wish to give you a sample. However, I need to invest in some better equipment, which includes a audio interface. I intend to provide as much information as possible, given the opportunity of time.

Please correct me if anything is wrong.

Stay tuned!

 

[TRyan5289]

I decided to add the starve pot to the enclosure. So, I've been doing my homework, getting ready for this weekend, when I can do the mod.

Using this schematic:
I will be able to add in the starve pot. Seems simple enough right?

Can't wait to try this puppy out!
I'll let you all know what I think once I get the mod performed.



Soon, I had to work out a few kinks, but will be doing the mod this weekend.

 

[TRyan5289]

So, after being busy for the past few months, I decided to get back into this pedal, perform a last mod, and call it quits. This time I added a tone bypass switch.

http://www.muzique.com/lab/tbypass.htm

Above is the link for reference.



My thoughts:

The starve pot, IMHO isn't a good mod. It did not behave the way I expected it to, so I am less than thrilled.

With the tone bypass, it really opens the pedal up, and sounds less filtered, also adding some low-mids. If I toggle between the two throw positions on the SPDT switch, I can make the tone stack sound similar to the tone bypass with some tweaking between the mid control, tone, and noise gate.

Being a fun project, I really enjoyed learning about electronics, and consider myself an informed individual now. Through my research I have learned how to read BASIC (did I say basic?) schematics. I would recommend that anyone wanting to try something along these lines, GO FOR IT! However, if you plan to keep tweaking, opening, closing, or moving things around. Get a breadboard. I ended up putting myself through more work than I should have. If I had been a little more patient and did this all at once, I could have saved myself some aggravation. One of the problems I ran into was the ribbon cable connecting to the PCB. I didn't disconnect the foot switch every time I opened it up, hoping to save myself some labor, but it cost me. All the bending back and forth caused the wires on the ribbon to break, and I had to reconnect them. What a PITA!

Have any questions? Don't wait, PM me! I'll try to get back to you ASAP.