@bigo
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I am revisiting this topic due to recent discovery. While I was trying out different transistors in a modded bazz fuss I built, I discovered why the 2N3391A transistor didn’t work in the circuit. It is because it has a non-standard pinout for a 2N**** TO-92 package transistor. I didn’t look carefully when testing the transistor with my Atlas DCA 55 checking the HFE at the time of my original build. All transistors worked in the bazz fuss except the 2N3391A, so I retested it with my Atlas DCA 55 and being suspicious, checked the pinout. It did not have the typical EBC of a 2N TO-92, but instead it had an ECB pinout, confirmed by checking with available datasheets on the internet
I had checked out a 3391 pinout previously on Small Bear’s site where they had a “house” version of the transistor and it had the standard EBC pinout typical of a 2N TO-92, and that is why I got fooled. I could have modified my vero layout had I known this ahead of time, but I can’t find an easy way to make it work now. The 2N4401 at Q1 works fine and has a similar gain bucket as an old 3391 anyway. Learned another lesson – always double check the pinouts of transistors previous to designing a vero or other circuit layout.
Thanks Cybercrow, your comments are greatly appreciated, which I look upon as POSITIVE criticism. I enjoy discussing the old circuits and that is pretty what I like building from scratch, but with some modifications. I wish others would jump into these discussions as I quite enjoy them and they are a learning experience for me as I am not by any means an expert in these type of circuits. I only have some limited knowlege of circuits from my college and post grad physics courses, but I enjoy using what little knowledge I have in trying to figure out what is going on in the circuit and attempting some simple mods.
Now on to finishing the modified bazz fuss that I have bread boarded and getting it onto a GBOF board (along with some additional vero and/or perfboard circuitry) and then boxing it up.
When I get some time I will attempt to make an audio recording of the pedal, but that may be awhile off.
Cybercrow, you are right, I made a mistake in my haste to redraw the corrected vero board layout. I know what I did on the board as I had it in my mind what had to be done to correct the circuit, but for some reason I didn’t translate it into the drawing properly. Below is the corrected layout. I believe this follows the schematic correctly.
With regard to a “Sziklai pair” I screwed up my sentence in my reply to Wilkie. I forgot to put in “like” a Sziklai pair “but not quite.” That is what happens when your wife is talking to you when you are trying to type, and I lost my train of thought. A Sziklai pair is similar to a Darlington pair, but instead of two NPN’s, it utilizes an NPN paired with a PNP. A Sziklai pair can be used to make a negative ground Rangemaster with a low gain NPN and PNP pair. If this was a true Sziklai pair situation, the transistor portion of the schematic would have to appear as below.
I agree on both of your comments. And I know you know what both Sziklai and Darlington pairs are. I put my comments in for those who may not know what these are (although this may be basic knowledge for most reading this forum).
Sorry I haven’t responded back right away. I have had a bad upper respiratory illness that finally has started to improve with antibiotics, and maybe this was the lite version of the flu as I had a flu shot, but this year it has only been about 50% effective (attenuated the illness without eliminating it altogether). And then we had new floors installed with 5 days of moving furniture, etc. out of the rooms, 3.5 days for installation and then 6 days putting everything back and rearranging things somewhat. So this is the first chance I had to respond.
Wilkie wondered about the two 10K resistors instead of two 1K resistors attached to the tone pot (and yes it appeared to me that this was a Sziklai pair circuit).
From my research on this circuit, others who have tried it had problems with the output signal getting lowered a little when the effect is switched on, and that the signal was below unity. The proposed solution was to raise the two 1K’s to 10K, and a poster did that which brought it up to a usable volume, keeping the tone the same.
Wilkie stated: “Also you have a 10K attached to the collector of Q2 instead of a fixed 10K resistor.”
Another suggestion to increase output was change R8 (10K Ohm) lower, such as 3K or even lower, although this will start to change the intrinsic asymmetry, apparently. Someone noticed that as the resistance was lowered, there was a slow increase in volume along with some extra highs. The last few percent down to 0 (Zero) KOhm gave a sharper treble & volume increase. Some of the blattyness disappeared at 0 KOhm. So it basically gets nastier as the resistance is lowered but the overall tone doesn’t change too much at all. The thought was to highly consider a 10K pot there, especially since there is no volume control. Hence my “Output” control. The controls some of the volume and fuzz characteristics.
To address Cybercrow who was curious as to why I believed moving the 8K2 resistor had any bearing. To me it appears different schematically, as below (mistake on the left and correction on the right). Maybe I am wrong, and as Cybercrow suggested that electronically, its the same schematic-wise. It’s still connects at the junction of the collector of the 2nd transistor and lug #2 of the “LOUDNESS’ pot. It would be informative to me why there should be no difference between the resistor placement.
Correct Vero layout. I also should note that this is a somewhat noisy pedal, the same as others have observed. I would have liked to put some sort of filtering in the circuit to try and abate some of the noise, but that is way beyond my expertise.
I am revisiting this post and agree about Mammoth not quite getting things right. After testing my new Fuzz circuit and then starting a vero build (first one ever as in another one of my posts on this forum) I was testing each component as I added them to the veroboard in order to make sure everything was the correct values according to the schematic. I got to the last capacitor in the build and discovered the cap in the Mammoth supplied plastic bag labled as 0.022uF measured 0.22uF. Sure enough, when I got out the magnifying glass the part code was 224J. It should have been 223J. Fortunately I had a spare 0.022uF cap in my parts bin (fishing tackle box).
I put everything back on the breadboard to test it out and the tone control, the part of the circuit where the cap was located, actually worked way better than it had previously. It certainly helps to test each component to verify it is correct before soldering! This is not the first time the part was labeled incorrectly from Mammoth. I also had a supposed MPSA18 transistor that turned out to be a voltage regulator. These mistakes were made on my last two orders with Mammoth.
Hopefully I will have the new fuzz boxed up and working in a couple of weeks.
And I have also used Small Bear several times in the past and my experience with them has been excellent!
I know the switching I drew out isn’t exactly accurate, but I just copied the old drawing I had to show the general scheme of what I was trying to accomplish. Now I hope to get this thing built sometime this winter, but have a lot on the plate right now and don’t know when I am going to get around to it.
Basically an electra distortion with diode clipping variations mated with a paramix in order to mix in a clean with dirty signal. Sort of what EVH does with his stage setup according to what I have read. He supposedly blends a dirty amp with a clean amp to keep some articulation along with the distortion.
I found my original concept schematic for the clipping. It is different from what I originally posted. I don’t know if this would work, but it puts a 3rd diode in parallel to ground along with the original two clipping diodes. See below.
At the time I thought this would give similar clipping to #1 and #2 on a single Rototone as below (borrowed image). I don’t know if this would accomplish assymetric clipping or not, because it looks like to me when the 2nd single diode Rototone is switched into the circuit it would place 3 diodes to ground similar to what I assume is position #2 below.
I didn’t know about all the problems you had with them Barry. Maybe you can work with the new owners if they continue to sell pedal parts, and maybe they could offer your boards alone, but it is just easier for me ordering them from Guitar PCB. I like supporting independent small businessmen and I feel a bit of kinship since you live close to where I went to college (used to drive through your town on the way to go skiing).
I can say I only had a couple of small problems over the years with mammoth, but their enclosures were always fine. I just discovered that an MPSA13 transistor I ordered from them a couple of years ago was not a transistor, but instead a voltage regulator. I don’t know how that happened, but they didn’t even sell that type of part.
Fortunately I have a bunch of spare parts such as transistors, caps, resistors and hardware other than enclosures. Looks like I will have to learn how to use Mouser’s site. I have used others such as Small Bear, PPP, etc. so hopefully obtaining reasonably priced parts won’t be a problem.
Thanks for your input. I already thought of that one. I wanted something a little more versatile. I can’t think of any other way to do it, unfortunately. I don’t know if the symmetrical/asymmetrical switching does much anyway, since to my ears most dirt is dirt. I must have at least 20-30 dirt pedals and listening and comparing one to another (which I have done in the past) there doesn’t seem to be a lot of difference, except maybe for some of the more crazier fuzz sounds. But when it come to OD and Distortion pedals, there doesn’t seem to be a whole lot of difference to me when it comes to the basic dirt of the pedal, although the different circuits tend to color the sound in different ways.
Wilkie, you are absolutely correct. Duh, on my part! The switched single diodes preceding the diode pairs would act as a half rectifier. I suspect there is really no way using the Rototone to add or subtract a diode to the diode pairs to effect a switched asymmetrical/symmetrical clipping situation. I believe even running the the single diode and diode pair Rototones in parallel rather than in series wouldn’t work either.
Repost of the pedal picture as I changed image hosting sites.
Finished exterior.
Also, my Guitar PCB version of the pedal with 2N2222 transistors instead of the 5088’s, which I recently changed out. Pedal is a little more knarly than previous.
Here is a repost of the images. I changed image hosting sites due to multiple issues.
Below is a photo of the top of the pedal.
Below is a gutshot.
Below is the basic circuit, although I used slightly different input cap values and a 1M pot for the boost control as it was what I had laying around (would have used a 500K instead). Also I later changed out the transistor from an approximately 180 HFE 2N3904 to a similar gain S9013 because the 3904’s I tried I found radio interference in the background when I cranked things up. The S9013 and other transistors I tried didn’t have the radio interference for some reason. The PNP transistor in the original positive grounded circuit was 2N4081 that had gains around 90-330 HFE, so anything in that range should work.
I totally agree with Wilkie. If I had only 4 input cap values instead of 7, I would have gone the Rototone way. I supposed I could have run two of them in parallel for even more input cap values, but that would have been even crazier than what I already was doing in the circuit. I do have a few Rototones for future projects such as an Electra style distortion with one Rototone for 4 clipping diode pairs and another switched Rototone with 4 single diodes to make an asymmetrical clipping option. I plan to pair this with a paramix to blend in the straight guitar signal. Crazy!
That is why this is a great hobby, although I think I may using some out of the box thinking on this, but just like everything else, somebody probably has already done this.
