Freestompboxes Temporarily Down

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

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.

-MC

True Bypass For Boss (without ruining the box!)

Greetings,
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

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

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

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.

-MC

Octavia Experiments/Improvements

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.
http://analogguru.100free.com/193/schematics/Tycobrahe_Octavia.gif
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!

-MC

Four Banger Discontinued

As of February 28, I am no longer taking orders for the Four Banger.
All outstanding orders will be completed, don’t worry if you’ve been waiting, it will get done and you will be contacted when it’s ready.
The response for this as been overwhelming and I quickly realized this is too big of a thing for me to tackle building at home in any kind of quantity quickly and be able to maintain the quality I desire, so I am discontinuing it in order to focus on building other things instead.

But don’t worry… the Four Banger will most likely return in a new (better) form this upcoming Summer! It will be back.

-MC