Haunting Mids project

What’s Haunting Mids?

Haunting Mids is a Big Muff variant. In a nutshell it’s the input buffer, and first two clipping stages from the regular Big Muff circuit. It drops the tone control and the output buffer of the original circuit. There are a few other changes in part values but the the circuit is otherwise the same.

Haunting Mids Fuzz is not to be confused with JHS pedals Haunting Mids which is a completely different circuit that came later.

I created this PCB layout from version 3 of the original Haunting Mids. I made small change by moving the sustain/gain control to the outside of the box. The original circuit used an internal trim pot with only the volume accessible from the outside.

this video compares 5 Big Muff Variants, Haunting Mids in is in the Middle


Another demo of the Haunting Mids



PCBs

The PCB was designed in Eagle PCB. You can order boards from OSH Park for fairly cheap but you must order three. You can order boards here:

https://oshpark.com/shared_projects/Wu8UpzQE

Build

this should be a pretty easy build. Without the tone control and output buffer there are fewer parts than the original Big Muff. Pots and LED are mounted to the board. And most of the off board connections are lined up along the bottom of the board for easy wiring.

The parts are standard and easy to find. You should be able to order all of the parts at Tayda.

Capacitors
C1220n
C2470p
C3150n
C4150n
C5470p
C6470n
C7150n
C8470p
C9470n
C10220n
C1147µ
Pots
VOLUME A100k
SUSTAINA100k
Diodes
D11n4001
D2 LED Red 3MM
D3 LED Red 3MM
D41n4742
D51n4742
D6 LED
Transistors
Q1BC337
Q2BC337
Q3BC337
Resistors
R133k
R282k
R3120r
R4470k
R518k
R61k
R78k2
R856k
R9100r
R10470k
R1110k
R128k2
R1382k
R14120r
R15470k
R1618k
R17RLED


Haunting Mids Fuzz schematic


The circuit shows BC337 transistors but these don’t seem to be so special. You should be able to replace these with just about any NPN device. The usual suspects 2N3904 and 2N5088, or maybe 2N5089 if you want more gain.

The diodes are the same. You can probably experiment with anything for diodes in this circuit. The choices here are interesting definitely try them. But if don’t have these parts or can’t get them use what you have!

Wiring

New work in progress

A nice opamp big muff PCB 
Mad bean Shark Fin. Based on the maestro filter sample and hold. I’m obsessed with this circuit, I’ve built several versions of it and own some boutique iterations.
Ooh look an ugly face, this is another effect that had become a minor obsession. I’ve built more than a few of these. 
Mad bean zero point mini.  

Okay so, here we take a look behind the scenes at the pile of unfinished work. This picture was taken inches the left of the previous images. 

Zeke Bass Distortion – OSH Park

This Zeke Bass Distortion is a clone of the D*A*M Ezekiel 25:17 Bass distortion. The PCB came from OSH Park. This worked out well. The board is pretty big so soldering parts is easy. The rotary switch and pots are all mounted on the board, which makes assembly easy, this is a good PCB.

There was no documentation on OSH Park for this, so I reverse engineered the board to match the parts in the schematic. Here is the schematic I used with part numbers that match the PCB.

zeke

Overall the board turned out pretty good. I used a socket for the dual op-amp. I threw a random 1458 in that was sitting in a pile of parts on my bench, and it fired up first test. This is supposed to use a JRC 4558. I think I have a couple of these squirrelled away, I’ll dig them out before I box things up. I might try some other op-amps also.

There are three sets of diodes. D2-4 are Ge, D5-6 are Si, and D7-8 are LED. I used some 1N34 for the Ge, and 1n914 for the Si, and random 3mm LEDs from the parts bin.

With 3P4T switch the circuit is only using one pole. I only soldered the pins used by that pole. This way if I made a mistake, it’s been known to happen, I had fewer pins to de-solder. With these switches there is a small ring with a tab under the nut. Be sure to set this for four positions.

To mount the pots, I would suggest making a box first, mounting everything in the box. This will position the pots at the correct height above the board compared to the switch. Then solder from the top of the board. I made some holes in a piece of cardboard, and mounted everything in that before soldering, since I didn’t have a box drilled yet.

I put everything on the test rig, and it fired up first! Good for me, and thanks to bmossma at OSH Park. It’s always inspiring when things work on the first attempt. The sound was pretty good, it didn’t sound like much with guitar, with bass, the effect started to make sense. I tested with my baritone guitar and it seemed to sound pretty good with that also. Definitely more of an overdrive, distortion, than a fuzz to my ears.


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Fuzz Factory – OSH Park

Just soldered the first of three Fuzz Factory PCBs from OSH Park. Fired up on the first try. The board didn’t come with documentation, I had reverse engineer the board against the schematic to verify part numbers. Here is the schematic I used:

fuzz-factory

I used some AC128 transistors for Q2 and 3. The random choices from the lot sounded alright. I built this first board with sockets for the transistors for testing. I can test transistors on this board, if they sound good I can solder them into the other boards.

I like this board, the layout has pads for 16mm or 9mm pots. The width fits the narrow dimension of a 1590B box, which gives you the option to arrange the box in landscape like the original, or in portrait, like most standard stomp boxes. The Stab and Volume pots are mounted off board. While this adds some wiring, it saves cost by making the board smaller, OSH Park charges by the square inch, it also provides flexibility in how the box can be arranged. Hats off to the designer. Hats off to mr vex also.
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Osh Park PCBs

IMG_1158.JPGI just received this order from OSH Park. I order four boards. You are required to buy three copies of each board you order. The cost is $5 per square inch for 2 layer boards (with 3 copies of your board included in that price). Which is not bad, if the boards are small it’s a deal. For example, the SHO was $3.20 for three boards! The Fuzz Factory boards, were $7.75 for three, still a good deal. The Haunting Mids boards were just under $5 each, and the Zeke Bass Distortion was about $8.50 each.

Of course getting boards for designs that people upload with little info can be chancey. There should be more options on the site to comment, and mark boards as verified. Looks like not all projects are shared. User decide to share a project. Hopefully people make an order and test it before sharing.

The quality of the boards is great. A couple things I noticed. There is no solder mask. The pads are gold plated, which is nice. I find the solder mask easier to solder with. Look at the first image. You can see the backside of each of the four boards. Notice the board in the upper right. The pads are fairly small. I think, this is the default pad size in Eagle PCB. It’s not easy to solder, It’s not super difficult either. The two on the left have a more generous pad size. This size makes for a better soldering experience.

I’ll post again when build these boards…

For reference here are some links to the boards I ordered here:

https://oshpark.com/shared_projects/JtR27cHU

https://oshpark.com/shared_projects/xaBILSTV

https://oshpark.com/shared_projects/KE0blXBg

https://oshpark.com/shared_projects/nsJTeQK0

 

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