FOUR HORSEMEN OVERDRIVE

well, i came up with another dirt pedal the other day.  lately, i've been experimenting with mixing different types of transistors together to achieve new tones, and this one kind of  takes that idea to the extreme.  it's designed under the premise that the stages increase in breakup as it goes along in the circuit, but instead of using stages that increase in gain, different types of transistors are used that exceedingly distort as the the circuit progresses.  for instance, the first gain stage is a silicon BJT.  this is used to get a decent push going and a very slight amount of drive.  next, is a MOSFET transistor, which like to distort a little easier, and in a bit more pleasing and richer way than the previous Si transistor.  finally, there is a germanium stage, which of course loves to distort in a very full and heavy overdrive, especially when driven by the previous gain stages.  the result is a very clear, yet complex crunch, that has a very nice character to it.  to round things out, in the beginning of the circuit is a JFET buffer, which helps to increase the current, and gives a nice high input impedance for the guitar pickup to see.  so in the end there is a total of 4 different types of transistors, each of which i tried to use to their optimum potential.  hence the name, the Four Horsemen Overdrive.

the tone control is a variation on the SWTC, but it has an added pole for a steeper rolloff.  the frequency point where the curve begins is rather high, so it is really more like a presence control- just taming the highest of frequencies, keeping the basic tone intact.

this circuit was spawned from a simpler design called the Nice Little Overdrive.  you can see the evolution in the thread over at FSB.

http://freestompboxes.org/viewtopic.php?f=28&t=11745

here is the schematic as it is in the latest version.

here is a pic of a vero layout that i built up.

and here is a quick video i made on my iphone.  the video is of the previous version without the high end rolloff presence control, and the bypass cap on the last stage, which adds a bit more gain.  the voice of the circuit is basically the same, but there is a little bit more flexibility.   of course the quality isn't the best, but you can get the idea!  ignore the man behind the camera.

MONA LISA OVERDRIVE LAYOUT

i was asked to post a layout for the MLOD, so here it is.  enjoy!  i tried this circuit out with 2n5457, j201, and j309 fets.  they all work fine..  the Q2 position is where most of the magic is.  try different transistors for different tones.  i enjoyed a 2n5210 with an Hfe of 250-300 there, myself.  it had nice midrange content without sounding muddy.  the images are at 600 dpi, a current limiting resistor for the LED has been added, and the gain pot can go up to 10k  that's all you have.  this circuit is a great sounding boost/light OD/ line driver/buffer. i hope you dig it!

take it easy!

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LAYOUT IS VERIFIED.

MONA LISA OVERDRIVE

alright, here is my latest offering to the faceless electronic gods of the global interweb.  it's called the Mona Lisa Overdrive after everyone's favorite cyberpunk masterpiece, and dystopian premonition written by William Gibson.  if you haven't heard of  it, check it out!  anyway, on to the the goods- 

i thought i would build something that would turn on the guys that were into the lighter side of things- something different than my usual wall of fuzz tones.  with the MLOD, you can get a heavy boost, or a light overdrive reminiscent of vintage microphone preamps.  the fancy thing about this circuit is the lack of coupling caps in the audio path- something usually reserved for mic pres and hifi circuits.  this lends itself to the "transparent",  uncolored sound happening here.  if you encounter any oscillation at the highest gain settings, simply raise the value of the 100 ohm resistor near the gain control to lower the amount of maximum gain. 

as always, if anyone happens to put this on the breadboard, or if it sounds like something you might want to build, let me know, and i'll whip up a layout for it.

take it easy!

COOL STUFF FROM EE TIMES

here'a some interesting things i found on the ee times site.  an interesting article on audio myths, two audio amplifier design articles from john linsley hood's book, and another with a great vintage video of rca tubes being made.  very cool stuff!


http://www.eetimes.com/electronics-blogs/audio-designline-blog/4033511/Audio-Myths-Workshop-video

http://www.eetimes.com/design/audio-design/4015905/Discrete-audio-amplifier-basics--Part-1-Bipolar-junction-transistor-circuits

http://www.eetimes.com/design/audio-design/4015906/Discrete-audio-amplifier-basics--Part-2-JFETs-MOSFETs-and-other-circuit-configurations

http://www.eetimes.com/electronics-blogs/audio-designline-blog/4033497/Vacuum-tubes-A-valve-video-a-tube-amp-modeler-and-a-joke

ALL ABOUT CIRCUITS WORKSHEETS

this page from the ALL ABOUT CIRCUITS website has a multitude of worksheets for the electronic diyer to learn from and test themselves with.

http://www.allaboutcircuits.com/worksheets/index.html


there is everything from AC, to DC, to FETs, opamps, filters, and BJTs.  even such simple stuff as ohm's law and caps and resistors.  seriously, everything from atoms to active circuits!

for example, here is one of their "design projects".   the objective is to help you in designing tone control circuits.

http://www.allaboutcircuits.com/worksheets/proj_tone.html

with these worksheets, there should be no excuse not to have some serious kung fu!! hiiiiiieeeyahhh!!!!

CIRCUIT SPLINTERS NO.2 - SZIKLAI PAIR BUFFER AMP

ok, here it is, as promised, AA's Circuit Splinter No.2!  but first, a little warning- i am not an electrical engineer, nor do i claim to resemble anything close to one, here or on television.  please take everything i post as just what it is- the off kilter ramblings of a misinformed diy enthusiast- nothing more, nothing less.  i'm trying to learn just like you.  

now-

we are continuing our limited look into DC coupled buffers and amplifiers.  in this case, a JFET/BJT Feedback Amplifier.  this amplifier configuration is known as what is called a Sziklai Pair, otherwise known as a compound transistor, which is similar to a darlington pair, and sometimes called a compound darlington.  this wikipedia article goes into the sziklai pair a bit more, such as how they are often used in discrete solid state output stages. 

http://en.wikipedia.org/wiki/Sziklai_pair

here is a great article as well from answers.com-

http://www.answers.com/topic/sziklai-pair

in this article is a description of the feedback involved-

http://www.angelfire.com/planet/funwithtransistors/Book_CHAP-5.html

and finally, a jensen transformers app-note for a piezo buffer amp-

http://www.jensentransformers.com/as/as098.pdf

basically, what we have done that is different here from the last edition of Circuit Splinters(in my limited understanding), is to reduce the amount of feedback from one stage to the next.  previously we had an infinite amount of feedback, which gave us a voltage gain of 0.  by inserting R5 into the picture, we raise the resistance, and therefore lower the amount of feedback.  in doing this, the gain of the stage rises.  as you can see below, the gain of this stage is equal to the ratio of R3 to R5.  so, lower R3, or raise R5, and the gain goes up.  the circuit below has R3-470, R5-4700, so 4700/470 = a gain of 10.  the great thing about this kind of stage is that you have a high input impedance from the FET, a buffered output, and you get voltage gain instead of just current gain as in a classic buffer.  remember that R2 may have to be adjusted to 1/2 your supply voltage on the drain of Q1 for the proper amount of headroom.

i think that this circuit tends to sound best when used in a "clean" gain type of stage, with just a slight amount of breakup.  never the less, many different adjustments can be made.  instead of R3, put a large bypass cap, and move R3 to the emitter of Q2 for more gain.  try different bypass caps for different frequency responses.  bypass Q2's emitter.  if you adjust your bias circuit, you can use a bjt for Q1.  try a Ge pnp for Q2.  see what happens when you put a small cap from the source of Q1 to the collector of Q2.  

here is an example of an RIAA circuit that uses this configuration.  you can see what has been done to tailor the frequency response of the stage for the RIAA curve using RC filters in the feedback section.

(click to enlarge)

here's a version from John Linsley Hood that uses a bootstrapped input-

(click to enlarge)

here's another one that uses a bjt for Q1, and has an interesting baxandall-style tone control based on feedback as well.  note the bias configuration for the BJT input transistor.

(click to enlarge)

as always, if anyone out there has any real knowledge they can share, feel free!  the sky's the limit.  go nuts.  have fun.  take it easy!  

ELECTRONICS CALCULATORS

here's number of handy electronics oriented calculators from around the web.  enjoy!


common emitter voltage divider calc
http://www.diystompboxes.com/biascalc/vdbias.html
big muff bias calc
http://www.diystompboxes.com/biascalc/bmbias.html
fuzz face bias calc
http://www.diystompboxes.com/biascalc/ffbias.html
electronic math helper page
http://www.diystompboxes.com/analogalchemy/emh/emh.html
opamp gain calc
http://www.csgnetwork.com/opampcalc.html
LED resistor calc
http://www.csgnetwork.com/ledsingresistancecalc.html
capacitor calculators
http://www.csgnetwork.com/capacitorinfoconverters.html
ohm's law calc
http://www.csgnetwork.com/ohmslaw.html
parallel resistance calc
http://www.csgnetwork.com/parallelresistcalc.html
transistor sim and calc
http://www.csgnetwork.com/transistorcalc.html
sound studio and audio calculations
http://www.sengpielaudio.com/Calculations03.htm
capacitive reactance calculator- what's the resistance at this frequency of that cap?
http://www.electronics2000.co.uk/calc/reactance-calculator.php
electronics2000 calculators- a bunch of em!
http://www.electronics2000.co.uk/calc/
-many calculators for amplifiers are available at Amp Books.  including these--
cathode bypass cap calc
http://www.ampbooks.com/home/amplifier-calculators/cathode-capacitor/
coupling capacitor value
http://www.ampbooks.com/home/amplifier-calculators/coupling-capacitor/
bright boost cap calc
http://www.ampbooks.com/home/amplifier-calculators/bright-boost/
grid stopper resistor calc
http://www.ampbooks.com/home/amplifier-calculators/grid-stopper/

GREEN BOMB FUZZ

here's something i was working on the other night.  it's a revved up mosrite fuzzrite based off of gus's gusrite circuit.  i basically juiced up the gain even more, did some stabilization and frequency response adjustments and added a nfb based tone control to add even more weird phase shaping possibilities than what was had in the original.  it's basically like a fuzzrite on steroids.  i'd suggest a mid gain transistor for Q1 and a high gain for Q2.  different transistors do different things, so it's worth trying out some different ones.  oh, and it can totally do that spirit in the sky thing perfect!  when you turn the gain all the way up you get that ratty almost misbiased thing that greenbaum had going on in his onboard fuzz.  back the gain off and rattyness goes away.  this thing is my new go to for crazy psych madness.  if you want more of a honky sound, lower the transistor gain a bit.  i'll probably try and do some more tweaks in the future, and i'll post them when i get a chance.

also-  i've got a tagboard layout that i'll post when i get it verified. ;]

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here are the schematics from Gus's rite fuzz and the mosrite Fuzzrite for reference.  if the owners have a problem with my posting them here, i will gladly take them down.

also, i was asked on FSB to describe the added tone control.  i tried to explain it to the best of my ability.  if anyone has anything to add, please, feel free.

the fuzz control on the fuzzrite works by adding the output of the first stage, an out of phase signal, with the output of the second stage, in phase signal.  this is what produces some of the thin, hollowed out, phase cancelled sounds that the fuzzrite is known for.  the shape control takes the non-inverted output of the first stage, with the output of the second stage, which also gets mixed in with the output of the first stage with the fuzz control.  the shape control has a low pass filter due to the .01 cap to ground, so when when it's negative feedback takes place, it only cancels out the lower frequencies and leaves the highs.  with this control you are still able to get the brite, zippy sounds of the original fuzzrite, but are now also able to get the thicker sounds of gus's ritefuzz- all through the same negative feedback techniques similar to what was used in the original fuzzrite!  

TRIODE FUZZ NO.2/ AMZ SIXTIES STYLE FUZZ TAGBOARD LAYOUT

a while back, i posted this little article on a couple of fuzz circuits i found on the triode electronics site. the first is very similar to a fuzz face style circuit, where as the second is a little bit different. it has what appears to be an emitter follower into a kind of dc coupled complementary gain stage pair. very much similar to the jordan bosstone. here is a link to the original article.


http://apocalypseaudio.blogspot.com/2009/05/triode-fuzz-1-2.html 

while surfing around the voluminous pages of Jack Orman's AMZ effects website, i saw something that looked a little familiar.

http://www.muzique.com/schem/sixties.gif

it seems that the triode fuzz and the amz sixties style fuzz are one in the same!  most likely, this is an old circuit taken from one of the many electronics "cookbooks" from back in the day.  regardless, i've heard from a good source that it's supposed to be a great sounding circuit, so i decided to draw up a layout- this time for tagboard construction.  tagboard, eyelet board, or turret board can be a fun way to do your circuit board construction for a change.  there is no etching or drilling to be done, and you get to use those nice sounding axial foil caps that would've never fit on your pcb circuit.  i really like using this particular tagboard that can be found at weber as well as apex jr. for very reasonable prices.

https://taweber.powweb.com/store/fb-v.jpg

it has 3 different solder points per tag that makes it very easy to find holes for your passives, actives, and wire without running out of space.  the layout i made for the triode/sixties fuzz circuit was made specifically for this type of board, but you could easily adapt it to other types of tagboard out there.  i haven't built it yet, but i do plan to in the near future.  as always, let me know if you decide to build it yourself.

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i got this thing on the breadboard, and had a rough time getting it to bias properly.  i'm going to try and figure it out, and i'll post anything i find.

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due to problems with this circuit biasing correctly, i have pulled the layout.  i'll post a new tagboard layout for a better design shortly.  looking at this one with a more informed set of eyes, there are many things that could be done differently to make this a better design.  i'll post another tagboard layout for a proper fuzz circuit once i get it checked and verified.

SOME COOL PARTS SOURCING SITES

here are a few kick ass sites to source parts on the cheap. the first is EVITA. they are a great source for any russian parts that you might want, and are even cheaper than what you can find them for on ebay. plus you don't have to buy a box of 100 of a single type, you can mix and match as you please. i have heard that they have reasonable shipping, and EVITA has all of the datasheets available for download on there sight, so you have some idea of what you are getting into.
as you can probably tell, i have a serious passion for these russkie germanium trannies, as many types are about as consistent as any silicon transistor out there, and unlike euro, american, or japanese trannies, many types have absolutely no leakage. the consistency of russian ge transistors is pretty much unparalleled around the world. i think this must be due to the fact that the soviets were producing germaniums well into the 80's where other sources had stopped long before. also they used them for many military uses as well, so their standards were set very high. you can tell the transistors and other parts meant for military use as they have a small diamond printed on the side.
along with transistors, there are many excellent russian teflon, paper in oil, and polystyrene capacitors offered at EVITA, so if you have an urge for cheap, quality soviet parts, now you don't have to be a slave to ebay.

if you have ever built an analog delay, you know how hard it is to source bucket brigade delay chips. you can end up paying a hefty price for what may end up being total counterfeit crap. you can go to a parts sourcer, but there may be a large minimum order that puts buying the parts well out of your price range. well, i recently was turned on to UTSOURCE, who source hard to find, out of production parts with very small minimum orders and good prices to boot. give em a shot if there are some rare chips you can't find.

lastly, is TEDDS.COM. they have lots of cool vintage capacitors and other parts with only a ten dollar minimum. also, they have pics of every cap in their inventory so you don't have to have every model number memorized. good stuff.

DIRTY BOOTS GERMANIUM OVERDRIVE

this little circuit is really what got me started in the whole DIY effects design process. i needed something that i could use to dirty up a loud, clean amp just enough to where it would have a touch of grit. it's a great little overdrive that can be used as a germanium booster as well as a fuzz if your pickups are hot enough.

it all started when i decided to breadboard the Trotsky Drive by Beavis Audio, which is basically a GE version of the Electra Distortion with a bias adjustment pot. using a russian GT313A transistor, i was fooling around with it, messing with values and such, when i remembered that the Bazz Fuss uses a diode in the C to B position instead of a resistor like the Trotsky/Electra. so i tried it out, and i got an excellently biased gain stage with just a bit of compression. then i realized that the circuit i was working on was PNP, where the BF is NPN. so the diode configuration is actually reversed. eventually i came to learn, with the help of many generous folks in the DIY community, that the GE diode that i was using was leaky, all of them are leaky, and it is this leakage that is actually acting as a large resistor and biasing the transistor. cool,huh? along with that, i'm sure that the diode is adding it's own little stamp on the situation with a bit of compression an break up.

after messing about with a ton of diodes this way and that, with filtering, in series, etc., i decided that i'm just not that big of a fan of diode clippers. i find them unnatural sounding, and their clipping just sound too "obvious" to me for some reason. so i ditched the clippers, added a small cap from C to B to roll off a bit of highs, and just put a whole nother stage in series with the first.

Lo! the Dirty Boots was born.

eventually i ended up trying a bias pot on the second stage and some different switching options for changing gain and tone, etc., but ended up with a normal emmitter controlled gain stage, a pregain control, and a volume pot. the latest mod was the series resistance between stages and ditching the cap from C to B on the second stage to open it up a bit.

it's really a great sounding little circuit using ge trannies which can be found on the bay for dirt cheap. the basic gain stage can be used for other things as well- it became the basis for The Toecutter.


give it a try sometime, or i'll send my band of mutated hobbit rat people to dig you out of your bomb shelter and eat you for second breakfast.

the thread at FSB about the Dirty Boots can be found HERE.

many thanks go out to Martin Chittum, Marcelo "Mac" Tripodi, and others that helped me understand along the way!



here is a layout using common sized parts. i have another for use with the extra mojo axial caps and such that i will post later.





daniel zink made this great version of the Dirty Boots in a Hammond 1590A box. a little killer!







here's another one from mr. zink- very stylish!