@bigo
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I was talking about the threaded base above which the switch shaft protrudes. The shaft appears to be around 6mm, which will fit a 1/4 inch hole. However, the threaded base of the switch is about 8.5mm (0.335 inch) by my estimates (I was too lazy to dig out my calipers which are buried deep in a closet). After resetting up my drilling rig and changing up the step bits, It fits perfectly through a 11/32 (0.344 inch) hole. I do not have a metric step bit, unfortunately, which would be helpful, but the standard US bit gets me close enough.
So the answer is 11/32 inch for the Rototone threaded base for those who don’t have metric drill bits and would like to know the hole size. Just something to add to the general knowledge base.
Now on to assembling the pedal, which will take awhile due to it’s complexity (for me). Hopefully I will have it done in a couple of weeks, but I have my first post-pandemic trip coming up and that may delay the completion by another month or so.
Love the idea of a testing platform Barry.
I have 3 Fuzz Faces. Two are from BYOC and another is a Hartman pedal with variable input impedance (I believe) to match pickup strength – that is low output to high output pickups. The two I built are slightly different.
The first is a stock NPN circuit with NOS AC128 Germanium transistors and an external bias control, which is very handy. When I first built the pedal, it didn’t work at all. I was about to give up on pedal building as this was my first attempt and I spent many hours trying to debug my build job. Finally after socketing supplied low HFE S9013 transistors, the pedal roared to life. I found out that one of the transistors guaranteed to be in working order, did not. The other was fine and worked well paired with one of the S9013’s. I contacted BYOC and they sent me a new matched pair and the pedal worked fine. Pedal building almost became a dead end hobby for me, but sorting out the problems and finding I could perform diagnostics and “fix” a problem got me hooked.
The second FF is a hybrid Ge-Si NPN using the leftover Ge transistor from the bad set and a low gain S9013. I just ordered a PCB from BYOC and built it with components I had on hand. I honestly can’t tell the difference between the Ge-Ge pedal and the Ge-Si pedal. They sound exactly the same.
I hate to revisit this, but I tested the approximately 20 Ge diodes I have on hand and found two with a forward voltage of 0.35V (0.350-0.353V). According to Bill Finnegan, the builder of the original klons, he hand selected two Ge diodes labeled 1n34a that had a measured forward voltage of 0.35V and that is the “magic” he put in his original pedals.
I took out the 1n34’s in the diode sockets and replaced them with the selected diode pair. Voila! There it is, the magical holy grail tone that the owners of $3000-5000 original centaurs talk about. I am now willing to part with my MKC for the bargain price of $2500! Act now if you don’t want to lose out!
Hopefully, the readers of this got the sarcasm. No, there is no real discernible difference to my musically trained ear (years of playing guitar, saxophone, bassoon and baritone as well as over 40 years of critically listening to music). Maybe matching the forward voltage of the diodes as closely as possible might get you a little more consistency in clipping, but really is this audible? IMO, I think not.
I have discovered that it is probably a good idea to use a external pot for the clean gain. As opposed to what is stated in the instructions about the clean gain being a subtle effect, I have found to my ears that this is really not so subtle. The main reason is that with a more distorted dirty gain setting, a louder clean signal blended in the dirt mix helps make things less muddy, primarily with the fat switch engaged. That is the real magic of this pedal.
This is why I avoid buying chips and transistors off sites like E-bay. I will buy only from well know sources that I know should be reliable such as Barry, Small Bear, Mouser, etc.
Thanks for your response, Wilkie. I guess the unknown is how the 100k pot will react with the trimmer in parallel. Looks like I will eventually remove the trimmer and add an outboard gain pot. I have done this before on other pedals I have built, although I removed bias trimpots and replaced them with an external bias control. This made those pedals more useful (most with Ge transistors).
Two of those are in my avatar image in the back row. The red on white pedal (Tonebender MkII pedal) and the light blue on white (fuzz face – first pedal I ever built).
I did some research on the diode subject. Apparently the original Klons used 1n34a’s chosen to have a measured forward voltage of 3.5V. If you have some Ge diodes that have close to the 3.5V measurement, they should be good in the MKC circuit. Mine measure around 3.2 to 3.4, so I am satisfied. I have D9* Ge diodes as well, but these have forward voltages slightly over 4, so I guess I could substitute to see if there is any appreciable difference as I socketed the diodes, but that is a project for a later date.
Maybe a simple RC filter? If so, you could design the filter with regard to how much frequency you want to roll off. A simple R-C filter rolls off the frequency response at 6 dB per octave above the cutoff frequency. There a online calculators for figuring out the corner/cutoff frequency.
If you like to do the math yourself, the formula is Frequency = 1/2(Pi)(R)(C) where R is Resistance in Ohms and C is Capacitance in Farads. For example, a TS has a 4K7/0.047uf combination that yields a bass rolloff frequency of 721Hz. Say you want to use 3K3 and 0.33uf, this will drop the value substantially to about 146Hz, letting a lot more bass through. You can figure what you think might suffice using the calculator. Then using SIL sockets do the socket and see method for the R and C values. I found this information on the Learning about Electronics website under calculators years ago. I made a switchable RC filter in a modified OD1 pedal and it works quite well.
Maybe this is what you were describing? Component A in Blue, Component A in Red and Component C in Magenta based upon the way the center position of the switch is oriented.
Regarding the 2 different internal patterns for the center “ON” position from different manufacturers, I always test out the pattern of the middle position with a continuity tester and use a sharpie to label it on the outside of the switch. That way less mistakes are made as I have learned from experience during my first use of an On-On-On switch.
Looks like I will be investing in some of these boards in the future. Maybe it would be good to add some of this discussion in the documentation of the DPDT board. It might help out some of us less ingenious people figure out some different configurations and uses of the board switch combination.
Not quite sure I follow you on this. I do not what the topology of the GPCB DPDT wiring board is. That is, what is connected to what and how each pad is labeled. Once I know this then I could figure out the switching arrangements. The switch lug # convention you show above is different from what I learned where #1 is side by side #4. Below is how I thought the connections (yellow) are made on the board, but I am probably wrong about this. I assume one would connect component C to one of the pads on each side of the board depending how the switch was oriented.
Finally finished this puppy. Many thanks to Barry who sent me replacement 1N34’s, confirmed to be genuine working Ge diodes this time by both of my diode testers. I suspect that maybe the original set may have had thermal damage as they were traveling by mail during the time period of the coldest, frigid spell of the winter this year. I also reversed the direction of the fat switch as I originally placed it in the enclosure in the wrong direction for the pedal graphics. This was accomplished easily as I purposely left enough slack in the switch wiring to turn the switch 180 degrees and then re-tighten it. I don’t know why I installed it in the wrong direction at first because I used different color wires to try and keep the orientation correct, but I failed. You can tell by my original gutshot as the left sided white switch wire from the board is going to the right sided lug on the switch.
I think the only thing I would change is actually taking out the trimpot for the clean gain and replacing it with a pot mounted on the outside of the enclosure. I was on the fence about this and wish I had done this at the time of the original pedal build.
New gutshot with fat switch reversed and 1n34’s installed in the diode sockets.
Thanks Wilkie. I just don’t know why I couldn’t figure that out. Simple loop switcher for 2 separate loops, which I have actually made before. I think I must have had a brain fart, plus trying to accomplish the circuit with using cheaper SPDT switches instead of DPDT switches. Finished diagram below.
If you want to go cheap, the Blackstar Debut amps have a speaker-emulated output and a tape-based delay effect for $80-100. I bought one of these for my wife who was using my 1976 Marlboro 10W practice amp, but it was starting to have some issues (fading in and out on low volume settings). It is more than an adequate replacement due to the delay, speaker emulated output (which can be used with headphones or out to a PA system), and MP3 input if you want to play along with backing tracks.
Re: What makes you suspicious of the diodes?
Diodes have around 0.7V forward voltage or slightly greater and do not appear to demonstrate thermal variations in measured forward voltage. I know there are fake 1n34’s out there, so I am not convinced. Pedal does sound fine with the current diodes provided in the kit, though.
I recently added up all of the pedal kits I built as well as all of the commercial pedals I purchased over the last 20 years or so. Before researching current prices of pedals and kits as well as the price of discontinued pedals and kits when I obtained them, I figured the total would be around $1000. I was a little off. The total was around $4000. That is about $200/year or $4 per week.
A Few of Mine:
American Fuzz
4 Track Fuzz
Hot Chilicon (Now – Sriracha Fuzz)
American Fuzz Version 2 (Kitty Bread Version)
This thread demonstrates the challenges of more complex builds. Even very experienced builders have problems at times. I can say in the last couple of years building a few pedals using all or one or two GuitarPCB boards I have really upped my game in problem diagnosis and solving skills. I have two pedal building sayings from my own experiences.
First – Build. Build. Build, for experience.
Second – If something can go wrong, it will go wrong every now and then. Just expect it.
