#1
I currently have a cheap modtone distortion speedbox...i repainted it, signed on it, and now it looks like something of worth..

And besides, i actually really like the tone...its smoother than most others i've tried and gives quite a thick creamy distortion..for the price ,its nice

except one problem, its volume level is disgustingly low. And after redoing the looks of the pedal, i'm looking at trying to save this pedal instead...

Crap, i talk to much

My question is :
The circuit consists of just Symmetrical diode clipping, one diode upwards, the other in the other direction and beside it...

But will stacking another diode right on top of either one in the same direction give me 1) More volume and 2) a tubier tone.

Is it even correct to just solder an additional diode ontop of another, into the same points in the circuit?

EDIT: Gosh its good to be back after a year or so...
Last edited by NoobOnZone at Sep 13, 2010,
#2
as in 2 diodes in each direction? Yes, that will give you more volume, but probably less distortion. You could also put some schottky diodes in for the second instead of another silicon, so you have 1 Silicon and one Schottky in each "direction".


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RBY CYOA
#3
The diode clipping can be "soft" or "hard". Soft clipping has the diodes in a loop while hard has one end of the diode leading to the ground. The symmetry isn't going to effect the volume that much if at all. Adding diodes, will not increase maximum gain but will increase the usable range of distortion.

To increase the volume of the pedal you could. Remove the diodes (loose distortion gain volume), use a softer clipping circuit, replace diodes with diodes the require less forward voltage (germanium) or switch the diodes with LEDs (rat distortion does this). This is a poor way to get volume out of a pedal though. You need to adjust the balance points at the transistors or op amps to increase the signal amplification.
#4
you cant paralell the diodes. they have to be in series. you'll have to pull one lead of each and solder another diodebetween the old hole and the other lead.

it will essentially double the output level but the clipping wont be as hard (which can be a good thing).

using diodes with a lower forward voltage will only decrease output level and give harder clipping.

if by 'balance point" you mean bias, adjusting that will just screw up the bias, making the effect sound terrible and gated.
#5
sorry but please bare with me..

how do i tell which part of the circuit is ground? What does it mean to have diodes in a loop for a softer clipping? i connect a diode onto holes already used by the perpendicular pre existing diodes?

And i've just read, diode in series means they are in opposite directions...

and what does it mean to ''pull one lead of each''? I can't just solder on another diode in the opposite direction onto the old holes?


The circuit only has 4 holes...
Last edited by NoobOnZone at Sep 13, 2010,
#6
in this case you dont need to know which side of the diodes is ground. just put the new diodes on the same side and going the same direction as the one each is connected to.

putting diodes in anti-paralell (what the clipping configuration is called) in a feedback loop creates softer clipping because not much goes on in a feedback loop. a feedback loop is part of a circuit. it controls the gain of a stage.

pick a side of the diodes to unsolder and lift off the board (thats what i meant by pull one lead of each...). note where the black band is facing. solder a new diode with the band facing the same way to the lead you unsoldered and into the now empty hole.

it will look like this. The X's are just marking the leads where you add the other diodes. The O's are the holes in the board. Note that both sets face the same direction.
     __________              __________
    |       || |            |       || |
O---+       || +-----X------+       || +---O
    |_______||_|            |_______||_|
     __________              __________
    | ||       |            | ||       |
O---+ ||       +-----X------+ ||       +---O
    |_||_______|            |_||_______|
#7
Quote by Invader Jim
in this case you dont need to know which side of the diodes is ground. just put the new diodes on the same side and going the same direction as the one each is connected to.

putting diodes in anti-paralell (what the clipping configuration is called) in a feedback loop creates softer clipping because not much goes on in a feedback loop. a feedback loop is part of a circuit. it controls the gain of a stage.

pick a side of the diodes to unsolder and lift off the board (thats what i meant by pull one lead of each...). note where the black band is facing. solder a new diode with the band facing the same way to the lead you unsoldered and into the now empty hole.

it will look like this. The X's are just marking the leads where you add the other diodes. The O's are the holes in the board. Note that both sets face the same direction.
     __________              __________
| || | | || |
O---+ || +-----X------+ || +---O
|_______||_| |_______||_|
__________ __________
| || | | || |
O---+ || +-----X------+ || +---O
|_||_______| |_||_______|



Awesome! You're an awesome help! Greatly appreciate your diagram and explanation!

Well, so now the question is, germanium diodes, silicon ? Which ones offer smoother distortion?

And will the above mod you've shown cause me to lose distortion?
#8
The clipping is based around the forward drop voltage of the diodes. Silicon have a fwd drop of about .6V while Germanium is normally about .3V, half of the silicon.

If you know what a sine wave is, it has both a positive and negative cycle, and the guitar signal is a variation of that sine wave.

When the diodes are attached like they are, will cut off your voltage at that forward drop, So no voltages above .6V can pass by. Then when your guitar signal goes negative, they have it doing the same thing in the opposite direction.

When the signal is clipped, imagine the top of the sine wave being cut off. That introduces different harmonics which can distort it.

When you have two diodes, like Jim was talking about, you would add the forward drops together, so 2 silicon would add up to be a 1.2V drop, 2 Ge would be .6V and a Si and a Ge would be .9V. You can also vary the diodes on each side, so that the positive or negative is clipped more than the other side, known as asymmetrical clipping/distortion, where as using the same diodes on each side is symmetrical.

The more your signal is clipped, the more it distorts, but the less signal you have, as you are literally taking part of the signal (anything above that forward drop) out. The higher the forward drop, the more signal you will have left, but the less distortion.

And as for Si Vs. Ge, there is supposed to be a difference, I'm not really sure, as I have not had a first hand experience with them. Supposedly, Ge are supposed to sound more "tubey" and "natural." I'd imagine that the difference in material would matter more for a device like a transistor, while this is just using it's forward V drop property, but again, there is the mojo.


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RBY CYOA
#9
gj monkeylink.

as for Si vs Ge... Ge can get fizzy and buzzy. It sounds worse compared to Si imho. general concensus is that the best clipping diodes out there are the internal protection diodes of MOSFET transistors. You can wire a MOSFET to be a diode. according to reliable sources, they sound the most tube-like and natural.

Si is the standard in diode-clipping dirtboxes. I like 1N914 types (1N4148 are more common and electrically/mechanically identical).

Most people who like Ge seem to prefer 1N34A diodes.

You can also use LEDs. different colors have different tones. I read once that for a "Marshall-y" tone use amber and blue ultra-bright LEDs. LEDs can sound compressed though. You can put resistors in series with them to counter this.
#10
erm, so adding more diodes as shown would cause less clipping? So less distortion but more volume?

How do i tell if the current diodes are silicon or germanium?

So in increasing mA values, its germanium, silicon and then LEDS? And to increase the volume i just need greater mA?

Maybe i should find out what diodes are currently in the circuit board so i can revamp the thing...so how can i identify the diodes?
#11
yes.

you cant unless you know the type # and have a datasheet. 99.9% chance they are silicon.

sometimes (less often than not) the type # is printed on the diode. usually it isnt.

where did you get mA? we are not talking about current. we are talking about voltage.
#12
yeah the two are silicon diodes...

But won't adding just one germanium diode in series with either silicon diodes be enough already? And wont this already give me a asymmetrical setup?

Whats the purpose of adding two more diodes? Sorry for the noob question!
#13
the purpose of adding diodes is to increase output level, which is what you want.

you can add ge instead of si to increase the output a bit and still keep alot of the distortion.