Original Four Banger – Schematic & Layout

18 02 2011

I haven’t posted in awhile. I’ve been unbelievably busy with all sorts of stuff. To make up for it, here is the schematic and a layout for the original version of the Four Banger.  The connections for the controls aren’t labeled on the board, but if you use the schematic as a guide, it should be easy enough to figure all the connections out.

Even though the schematic shows an AC128 for the germanium transistor in the Rangemaster section, this circuit can accommodate a wide variety of PNP germanium transistors easily with the (proper) Emitter trimmer to set the bias however you see fit.

Please don’t flood me with how-to questions. I honestly don’t have time to answer them all, and there is more than enough help available to you on the various DIY forums.


New Site Soon

17 09 2010

Greetings Everyone,
I haven’t posted in awhile… I’ve been exceedingly busy and distracted these last few months. Three moves in less than a year is enough to really jumble your senses! Most importantly, after much thought, I’ve decided to finally commit myself to building effects and custom electronics full-time and treat it as a real business.

Sometime during the next few weeks, I will be updating my commercial site, www.soulsonicfx.com. After much thought, I’ve decided to do the entire site using WordPress. I’ve been very pleased with the results I’ve gotten using this WordPress blog, so I’d like to stick with something that I’ve grown very comfortable with. I also enjoy the challenge of seeing what I can do with it.

If you’ve tried to access the site in the past 24 hours, you’ve probably noticed it’s down. My host says they’re performing file maintenance, so it should be back up soon. This has affected the email accounts as well, so if you’ve had trouble getting in touch with me, please use my secondary email address: solgrind (at) lavabit.com

I have some exciting new things in the works like, a cool new tube overdrive, an Echorec-inspired delay, and an innovative fully-modular mixing system!


Four Banger mk2 – FINALLY!!!

3 12 2009

First, I must apologize for not posting for such a long time. I’ve been exceedingly busy with a number of things, so I’ve neglected this site. But, I have certainly not neglected building wonderful new effects!

I first built the Four Banger during July 2008. Since then, it has gotten alot of attention. I am very pleased that people have found it to be a useful and good-sounding tool; but the original design was quickly thrown together as a one-off build, and despite the fact that it sounded great, I found it to be deficient in several ways from a technical point of view. So, I decided to stop taking orders for it and went back to the drawing board to re-design the entire thing from scratch and try to improve it in every way possible.

Here is a photo of the first build:
Four Banger mk2

The hardest decision was deciding what kind of enclosure to put it in. After much consideration, I decided upon the standard “125B” enclosure style. The reasons are because it is a fairly compact size – but can still easily fit a battery (unlike the previous Four Banger Mini), it is readily available, and it is reasonably priced. I also put much thought into how I would paint it. Enamel paint or powdercoat are the usual choices, but I decided to go with a hand-painted acrylic finish over a matte enamel primer with a lacquer top coat. I like acrylic because of the wide color pallet available, the brightness of the colors, and the fast drying time. The lacquer top coat protects the finish very well from everyday wear and gives a nice gloss.

Here, we can see inside:
Four Banger mk2 guts

I’ve taken several new approaches in this design. First thing you may notice is that the jacks are mounted directly to the circuit board. This greatly reduces the amount of material and time required to wire the circuit. I have chosen this style of jack because they have proven to be very reliable when used this way and they are of very good quality. The next thing that catches your eye is the bypass switch. I have chosen to move away from the standard “Taiwan Blue” 3PDT footswitch as I, and many other builders, have used. Instead, the Four Banger mk2 uses a miniature 4PDT pushbutton switch with an external actuator to activate it and protect it from damage. I have chosen this switch because it is higher quality, is more suited for guitar-level signals, and has a much lighter feel without the loud “KA-CHUNK!” sound and no need to stomp on it to turn the effect on and off. Despite the lighter feel, it can easily withstand heavy stomping without any danger of accidental damage; the amount of force required to damage it would easily do equal damage to a standard large footswitch. And because it is mounted on its own board, it can easily be replaced if necessary. The Boost Select switches are now small pushbutton switches instead of toggles. I chose them because they make installation easier and there is less chance of damage if they are accidentally stepped upon.

Now, to discuss the re-designed circuit: Let’s begin with the Rangemaster (R). I have painstakingly designed a new modern silicon-based treble boost circuit that gets as closely as possible to the sound of the original germanium version of the Rangemaster. I built an original spec circuit with a vintage black glass OC44 to use as my reference, and I believe I have captured that sound. The main reason for dropping the germanium circuit in favor of a modern version is because of consistency. It is simply too difficult to find a large enough supply of great sounding germaniums and be able to offer the unit for a reasonable price. Additionally, I relished the challenge of a new design… as always ;). Moving on, the MOSFET (M) boost is my “No Crackle” re-interpretation of a certain popular boost. After coming up with the initial No-Crackle design, I haven’t seen much reason to change it, though I may tweak it a bit before final release, to try and reduce the noise a little bit. The Opamp (O) boost is another new design. Though the original Opamp boost was nice, I personally found it to be a tad boring and I wanted something with more versatility. Now, the Opamp’s gain can be dialed from a transparent buffer all the way up to a great hot overdrive. I’m very pleased with how that one turned out, and I’m going to be offering a deluxe standalone version that will compete against such heavy hitters as the Klon Centaur. Finally the JFET (J) boost has been re-worked as an SRPP style circuit instead of the previous Mu-Amp stye. The SRPP has lower noise, lower output impedance, and greater drive capability. It is a small change, but surely a worthwhile one.

I will be passing around a demo unit to some known pedal guys to get some first-hand feedback and reviews. I plan to begin officially shipping these at the beginning of January 2010. The projected price will be $200USD. This price will included worldwide shipping cost. I am also working on a deal to get these and other SoulSonicFX products distributed in Australia so it will be easier for my Australian customers to obtain them. Also, the soulsonicfx.com website will soon be updated with more information about this and other products I will be selling.

I have now officially opened a pre-order list for the Four Banger mk2. This will allow me to more accurately judge the demand and plan production accordingly. If you would like to be on the pre-order list, please send an inquiry to preorder@soulsonicfx.com.
If you have previously contacted me about the Four Banger, PLEASE send a note to the above pre-order address. This will allow me to organize all the requests and keep track of everyone. Thanks to all of you for your patience, I know some of you have been waiting to hear about the new Four Banger for quite some time.


Freestompboxes Temporarily Down

4 07 2009

My favorite forum, Freestompboxes.org, is currently down due to hosting and server migration issues. If you are a member, please be patient, and hopefully Johan will have everything squared away soon.

Here is the quote from his blog:

What happened, in short, is the following: we registered with a new hosting company 3ix.com, everything seemed to be fine and the people very helpful. Until this afternoon CET they just pulled the plug without any prior notice.

There was no explanation given and no illegal material pointed out by the provider, but as a matter of fact, the terms of service mention that in case of abuse they are allowed to take measures without any justification.

The Honey Bee Challenge – Folk Driver DIY Overdrive

19 04 2009

Hi everyone, as some of you may already know, Björn Juhl sent me a Honey Bee pedal to play with. The idea was to listen to the sound and see if it can inspire a nice DIY project. Well, after spending some time with it, I’ve come up with something that sounds good and will certainly remind people familiar with the sound of the Honey Bee.

My goal was to keep the design as simple as possible, but still try to fit in some tricks. This uses both positive and negative feedback to get its sound. R8 is something I learned from the big old red RCA book – it’s positive feedback to boost the gain of the first stage; it was suggested as an alternative to using cathode bypass capacitor in a tube stage, well, it works just as well with a transistor. The combination of R9+C4 is negative feedback to reduce the high frequency gain and give the signature smooth sound. It also promotes stability in the circuit. I settled on the clipping diode combination after trying several different kinds, and the 1N4001+1N4148 combo had the best sound for this thing and reminded me most of the HB.

The Timbre control adjusts both the low-frequencies and the amount of drive. At the 12 o’clock position is the minimum drive amount. At one extreme it’s max gain with lows emphasized, and the other is max gain with the lows cut. It’s sort of like having the HB’s Gain and Nature controls on one knob.

Here is the schematic: Folk Driver
I have a PCB design done up with ExpressPCB so people could order some if they want, and the board is a single-sided design so it is easy to make yourself. I will post the file up after I verify it (probably tomorrow…).
Stay tuned for the full build project.


True Bypass For Boss (without ruining the box!)

15 04 2009

Many people are hot on the “True Bypass” thing. The electronic switching as used by Boss, Ibanez, and many other popular effects is considered passé, as now people want to have their bypassed signal completely un-tainted by superfluous buffers. And in some cases they have a valid point, if you have 6 Boss pedals all strung together, your signal is going through as many as 12 buffers, and in the case of the transistor emitter-follower type as is used in these pedals (which always has slightly less than unity gain), this can result in a substantial signal loss.

So, it has become popular to modify these effects to have mechanical switches that fully bypass the signal when the effect is turned off. There is one big problem; most people seem to think the best choice of switch is the large 3PDT footswitch sold by New Sensor (or Cliff, or Fulltone…) that is popular in many DIY and boutique builds. This is generally a good quality switch, but it is LARGE, and there isn’t adequate space in the Boss Compact series case design to accommodate it. In fact, the Boss case is designed to have a large actuation plate pressing on a very small switch, so there is no space at all for anything but a very small switch. In an attempt to make the large switches fit, there have been countless examples of the attractive and functional appearance of pedal ruined by drilling holes through the actuator plate to fit the switch. You’ve seen them… these ugly things with huge footswitches sticking out of them… terrible.

But there is an elegant solution to this problem, and it’s actually quite simple – just use a small mechanical DPDT pushbutton switch that fits correctly under the actuator. You can see one here:

True Bypass in an old Boss BF-2

True Bypass in an old Boss BF-2

The only trick is to get the height of the switch plunger adjusted so that the actuator presses on it correctly. Foam rubber makes this easy.
I etched a board to hold the switch and simplify connections. It is held in place by a bolt which is mounted through the stud that holds the actuator spring.
Bypass board for Boss Pedals

Bypass board for Boss Pedals

You can see a tutorial which describes using a small switch like this at Small Bear Electonics (and yes, they sell a similar switch). http://www.smallbearelec.com/HowTos/Shell/Shell.html
For switching the LED, I am using R.G. Keen’s brilliant Millenium Bypass circuit. You can read about that here: http://www.geofex.com/Article_Folders/Millenium/millen.htm
That’s it, very simple really – there is absolutely no reason to hack up a Boss pedal to put true bypass in it. And doing it this way retains much of the “soft” feeling that makes Boss’ Compact pedals such a great design.

And as for the rest of this old BF-2? I did a handful of simple mods to help to improve it. Firstly, I removed elements of the old switching circuit to accommodate the new mechanical bypass circuit. Then, I replaced the old worn-out electrolytic caps and upgraded them with better types. I also replaced the signal opamps with better low-noise types. The stock 4558s are fine for an old Tube Screamer, but they’re pretty lousy if you want a nice hi-fi sound. Some the two 1uF electrolytics in the signal path were replaced with Nichicon MUSE audiophile grade bipolar types, and a pair of 220nF caps that were previously electrolytic have been replaced with film types for a definite improvement in fidelity. That’s about all this on needed to get some good improvements and lower the noise a bit.
Here’s a pic:

Modded Boss BF-2

Modded Boss BF-2

I hope this little article gives you some ideas for your own mods to the Boss Compact Series. They’re really fun to work on, and little changes can sometimes go a long way.


Octavia Experiments/Improvements

5 03 2009

I finally got around to trying the Octavia circuit. I’ve been fooling with it on breadboard in my spare time the past couple days, and I’ve figured out some interesting things.
Just to make sure we’re on the same page, I’m using the Tycobrahe Octavia schematic on Analogguru’s site.
There are a couple minor differences in my test circuit; firstly, I’ve oriented the MPSA18 the correct direction with the collector towards earth. I did try it the original backwards way, and it does work, but it sounds so bad it’s not worth messing with to try and be “vintage correct” with Tycobrahe original. For the other two transistors, I’m using 2N2907… not for any special reason, that’s just what suitable PNP silicon transistors I had handy. They do the job fine. The transformer is the Mouser 42TM022 that Small Bear sells for DIY Octavia. I’m using 1N34A for the diodes. Most of the resistor values are the same as the schematic with a couple little subs where I didn’t have the exact value, but nothing that would make a difference.

So, I build up the basic “stock” circuit. It works, but it sounds rather… ugh… not so great. It gets octave, but it’s only really happening when you play high up on the neck. I know that’s a well-known characteristic of it, but that doesn’t mean it has to be that way. It also gets incredibly splattery/mushy when you turn the fuzz up. I guess this is normal too. The problem is that the distortion of the fundamental totally hides the octave when the fuzz is up… you can hear it better with lower fuzz settings, but it’s still very dependent on dynamics and working the strings to get the note to come out. I suppose this is a testament to Hendrix’s mastery of the effect.

I listen to these things, and to me, they sound like problems that can be solved. So, I play and listen… and what do my ears tell me? They tell me there is too much low frequencies saturating the primary of the transformer and that the overall response is too slow to dynamics. I try a much smaller capacitor coupling from the third transistor to the transformer – C6 in AG’s schematic – this is normally 33uF… I try 330nF…..
Now there is octave all the way up and down the neck; on the low strings, too! Then, I replace C7 (220uF) with 47uF; dynamics are now much improved; less slow compression at high fuzz settings.

I don’t like the diodes going straight to the volume control and then the output; it looks like you would get inconsistent results with different amps/effects after it, and that might affect how well it does the octave thing. I put a buffer after the diodes with another PNP transistor. Works great. Put the volume control at the very end after the buffer. The signal coming from the diodes is low enough that the buffer stays clean even with the full output going to it.

Now, I want to be able to have both the “traditional” Octavia splat sound as well as my new improved octave, so I did a compromise and tried a 10uF coupling cap with a 100k pot to fade it in on top of my new lower value C6. Works very well at dialing in two very different responses; though you may want to experiment with tapers/values for the pot. I keep my new value of 47uF for C7 in any case because it sounds better than 220uF regardless.

One more thing I tried: put a resistor in series with the transformer’s primary connection to ground. The idea here is to reduce the loading of the primary on the stage that’s driving it. This is another attempt at reducing the amount of squishy-ness in the sound. I just tried a 1K resistor. It worked to a degree. As expected, the output volume dropped a bit because the driving signal is now being divided between the primary and the resistor, but there was still enough output to be usable. This gave a very dramatic change to the timbre of the octave effect… very hard to describe; it was still a fuzzy octave sound, but just sounded different than it did before. To me, it sounded like the octave wasn’t as pronounced in a subtle way, so I dropped the resistor, but it has given me reason to experiment with a transformer that has a higher-impedance primary in the future.

My conclusion is that the transformer and how it interacts with the drive circuit is absolutely the determining factor in the character of sound you get from this. The changes I made to try and improve it were all centered around changing how the circuit responds with the transformer, so I’m certainly going to get different transformers to play with.

I’m going to build one up based on what I have on the breadboard now – it sounds really neat and I was able to get some super-cool sounds with different pickup selections and different playing techniques. I totally got this cool “Robot Blues” thing happening.

I’ll draw up a schematic and share the final design as a full DIY project once I get it put together. But, before that, I have a bunch of Four Bangers that need built!