freestompboxes.org

This is a circuit that has been around quite awhile.
This could fall into the "Classic" DIY category.
Many have built this simple OD and Many Love it!

https://i17.photobucket.com/albums/b72/ ... LAYOUT.png

https://i17.photobucket.com/albums/b72/ ... ANSFER.gif

Does it sound good? How would you describe it?

grolschie wrote:How would you describe it?

COT-like.

MoreCowbell wrote:

grolschie wrote:How would you describe it?

COT-like.

Yeah!
I would agree with that.

Somebody has the vero board layout for this project?

Thanks

guisquil wrote:Somebody has the vero board layout for this project?

Thanks

This is an awfully simple circuit....why not do your own vero layout?

Does it sound similar to Tim E.'s Harmonic Jerkulator? Just curious.

http://www.harmony-central.com/Guitar/F ... ldFuzz.txt

In the link you'll find a similar distortion circuit which doesn't feature the NPN PNP pair, but just an NPN, that's the schemo Arsenio seemingly started from in below build report.

• From: Arsenio Novo
  Date: 04 Jul 95 23:04:50
  Newsgroups: rec.music.makers.guitar
  Subject: New Overdrive Circuit[/b]
  
  Hi,
  
  I've noted that talk on this echo always comes back to the subject of
  overdrive distortion. Whether generated by a vacuum tube amplifier or
  a transistor amplifier there seems to be undeniable differences to me
  as well.
  
  Lately, I was tinkering with an unusual transistor circuit
  configuration I had come upon a few years ago and made a few
  modifications to the circuit that turned it into one beautiful
  screaming "tube-like" overdrive but without the wall of noise these
  things usually make. When pushed it even makes that distintive
  "zoo-zoo" sound...!!!
  
  The original circuit was simply a complementary matched pair of
  transistors connected so that all the terminals overlapped. i.e. both
  bases tied together, emitter of the PNP connected to the collector of
  the NPN, and the collector of the PNP connected to the emitter of the
  NPN. Thus:
  
  
  
  This transistor pair is then biased by 2 equal value resistors in each
  of the compound legs, one to the positive supply and the other to
  ground common. The signal is coupled to the base pair leg and the
  output is picked off either of the other 2 legs.
  
  The result is that the above circuit exhibits the behaviour of a
  multiplier over a range of signal values. It basically performs a
  sin function: in other words a frequency doubler.
  
  This doesn't have a very good distortion sound though because it is
  rather "burpy and buzzy". However, lately I was toying with the
  circuit when I offhandedly decided to try doing something to it just
  to see what would result.
  
  After adding a large cap from the NPN's emitter to ground the thing
  went wild on me... WANGO ZE TANGO! SUPREMO DISTORTION! I then
  proceeded to refine the circuit a little more and got a better
  understanding of what it was doing.
  
  The final schematic follows but first a couple of notes on the
  circuit. The "bias balance" trimmer should be adjusted for a
  symetrical clipping threshold of the output signal as viewed on a
  scope. Short of this it can be easily set by "ear" for the most
  sensitivity somewhere around mid-turn.
  
  The input should be driven by a lo-z stage if your electric guitar
  doesn't have a built-in pre-amp. You can alter the emitter capacitor
  value in a range from 0.1uF to 1uF in order to obtain various basement
  characteristics but I found the indicated value is a good compromise.
  The input capacitor should not vary much either though because if it
  is made too large the circuit goes balistic and cuts out on the tutti.
  
  
  "Tube-sound" Distortion Overdrive Circuit:
  
  
  
  
  The operation of the circuit more closely resembles a vacuum tube than
  a diode clipper does because of the strong square law characteristic.
  This is due to the negative feedback around both base-emitter pairs.
  This feedback accentuates the junction non-linear behaviour manyfold.
  
  Thus each transitor drives the other even harder so that the transfer
  curve ends up more logarithmic than is typical of a single transistor.
  In other words: the clipping is gradual and not abrupt like it is in
  the case of a silicon diode. Typically a lot more 2nd harmonic is
  produced as well. As a bonus the waveform folds over on itself when
  the circuit is overdriven!
  
  Now in the interest of the common good I donate this design to the
  public domain for personal use but retain copyright and reserve all
  rights for any commercial purpose. In other words build one for you
  and your friend but if you have it massed produced for profit I only
  ask a fair share.
  
  Please, do try the circuit and leave any comments in private at my
  e-mail address: arsenioDOTnovoATmbaDOTorg

[/quote]

Looks a whole lot like this. http://www.geocities.com/j4_student/electra.gif

RLBJR65 wrote:Looks a whole lot like this.

Yes you are right, but note the difference between Electra and the first circuit - electra lack gain and bias controls. Note also the difference on the collector resistors. Don't know the transistor for the electra, low gain 2n3904?

Anyway it's just a one transistor gain stage, so many difference are not likely to occur except in the setup of bias and gain.

But who is Arsenio Novo?

I should have said it started out like the Electra.

DEon't know who Arsenio Novo is but if you Google him all kinds of interesting stuff pops up

Would this schematic work to build the Tubesound OD? I know it's a crude drawing.



OK, I just breadboarded this circuit and it's totally cool. Not what I expected at all. All I can say is man that's a '70's sound if I ever heard it. I thought the overdrive was fuzzy yet smooth. Once the trim was set it really sounded nice. So now I have to decide between the Harmonic Jerk or this. So, you guessed it I'll have to build both. I was thinking of using them both in the same box. The HP as a rhythm and the Tubesound for the lead sound. Just thinking out loud.

Yesterday i tried this little circuit on my breadboard. After some tweaking i got very nice overdrive sound. Cleans up very well and works great with guitar volume pot. Here's the schem i used:
schematic
and here's a sound sample:
sound sample - 650kB. PRS SE->OD->Pandora PX4D as speaker sim->Compact4->PC. Mixed in Reaper. Bass guitar is the same guitar but shifted down one octave with pandoras octaver. Musically poor, but i think that it shows the overdrive structure.
I think adding another one OD stage will make a screamin monster from this circuit. I'll defeinitely try it and post the results.

That sounds great!

I've never heard of this one before.

DougH wrote:That sounds great!

I've never heard of this one before.

Freakin' good!

thanks
here's another sound sample. This time only one guitar. I tried to play some different techniques to show how does this circuit respond to picking and what is the gain range. Again - PX4d used as speaker sim. with a touch of reverb.
sound sample 2 1.8MB

I tried cascading two of such circuits, but the sound was to muddy, to much gain and compression, even when i put the voltage divider between the stages to take the signal a little bit down. With only one stage this od sounds great, probably would be good as booster too.

any layouts of this circuit?

polarbearfx wrote:any layouts of this circuit?

um, markm's layout, the one in the very first post

yeah but I don't etch.

a) start etching
b) ask somebody to etch it for you
c) use the layout on perfboard

yeah, it really is that simple