Fuzz Pedal Oscillation issues

[Dormammu]

Honestly, I do not understand the point to messing up with anything like FF, having a good IC opamp. It is quite tedious to adjust. While IC gives good predictable results.
And yes, the guitar should be tuned, when recording demo.   

Hey guys, can anybody tell me, how the D1 diode is supposed to protect the circuit against wrong polarity ?

[johngreene]

....

Hey guys, can anybody tell me, how the D1 diode is supposed to protect the circuit against wrong polarity ?

Most 9V guitar wall worts only supply 100mA max. So that diode will clamp the power supply to ground (well .7V) which is usually enough to protect everything long enough to figure out you screwed up. Many use an additional Schottky diode in series for additional protection but you have to be willing to put up with the added 0.2V or more drop. It can also introduce a step in the supply voltage with the indicator LED is switched if you connect it to the output side of this diode. Which is unnecessary since the LED, being a diode itself, is 'self' protecting against reverse polarity.

[RandyBeast]

Honestly, I do not understand the point to messing up with anything like FF, having a good IC opamp. It is quite tedious to adjust. While IC gives good predictable results.
And yes, the guitar should be tuned, when recording demo.   

Hey guys, can anybody tell me, how the D1 diode is supposed to protect the circuit against wrong polarity ?

There are 3 main types of distortion. Soft clipping, hard clipping, and Transistor base. each one has a unique sound. the Fuzz has a more squashy fuzzy sound. I've successfully designed the 3 types plus a few others. I'm now learning code and programming microcontrollers for tap tempo delays and memory banks. but anyhow. this video was to show you guys I got it working and have no Oscillation like I was before. it really came down to the PCB layout. PCB design is a whole other ball game that I am still learning.

as for the Diode question, current travels the easiest route to ground. so if the polarity is reversed, instead of going back through the wall mount, it will turn and go thru the Diode to ground. I hope that makes sense.

Thanks

[Dormammu]

as for the Diode question, current travels the easiest route to ground. so if the polarity is reversed, instead of going back through the wall mount, it will turn and go thru the Diode to ground. I hope that makes sense.

Won't it burn, almost immediately?
I think R5 should be placed before D1.

[johngreene]

as for the Diode question, current travels the easiest route to ground. so if the polarity is reversed, instead of going back through the wall mount, it will turn and go thru the Diode to ground. I hope that makes sense.

Won't it burn, almost immediately?
I think R5 should be placed before D1.

It's a 1A diode and power supplies are typically 100mA. It would be next to impossible to connect a battery in reverse. But if you somehow managed to, then yes, it would probably smoke. If he was to put it behind the resistor, the resistor would be doubling as a fuse. At 100 ohms it would need to be a 1Watt resistor or it would burn up instead! 

[RandyBeast]

as for the Diode question, current travels the easiest route to ground. so if the polarity is reversed, instead of going back through the wall mount, it will turn and go thru the Diode to ground. I hope that makes sense.

Won't it burn, almost immediately?
I think R5 should be placed before D1.

I don't see this circuit ever pulling 1A and if I connect a battery in wrong for some weird reason, then all the negative voltage would go to the ground before hitting the resistor. the resistor capacitor combo is doing two things. it's a low pass filter that filters out almost all high frequencies that could sneak into my audio path but also smoothes the voltage out to keep it nice and consistent through the transistors. I want the Diode before so the reverse voltage goes to the ground before hitting my circuit and burning out my transistor or IC.

[Dormammu]

It's a 1A diode and power supplies are typically 100mA. It would be next to impossible to connect a battery in reverse. But if you somehow managed to, then yes, it would probably smoke. If he was to put it behind the resistor, the resistor would be doubling as a fuse. At 100 ohms it would need to be a 1Watt resistor or it would burn up instead!

The R5 power dissipation and resistance should be calculated by box consumption.
In my practice, too often there were situations when used "nontypical" power supply.   

[johngreene]

It's a 1A diode and power supplies are typically 100mA. It would be next to impossible to connect a battery in reverse. But if you somehow managed to, then yes, it would probably smoke. If he was to put it behind the resistor, the resistor would be doubling as a fuse. At 100 ohms it would need to be a 1Watt resistor or it would burn up instead!

The R5 power dissipation and resistance should be calculated by box consumption.
In my practice, too often there were situations when used "nontypical" power supply.   

If you are going to use it for reverse polarity protection like you suggested then you could drop 9V across it causing it to dissipate over 800mW. I wasn't taking about normal use.

[Dormammu]

If you are going to use it for reverse polarity protection like you suggested then you could drop 9V across it causing it to dissipate over 800mW. I wasn't taking about normal use.

This is why it should be increased to 500-800 ohm. Then the power of the short will fall to acceptable values.

[johngreene]

If you are going to use it for reverse polarity protection like you suggested then you could drop 9V across it causing it to dissipate over 800mW. I wasn't taking about normal use.

This is why it should be increased to 500-800 ohm. Then the power of the short will fall to acceptable values.

Try it!

[Dormammu]

Try it!

I don't try it, I always do it. 

[antonis]

800R series resistor before D1 should be OK for circuit current draw of less than 1mA..!!
(considering Ohm's Law still valid..)

[Dormammu]

800R series resistor before D1 should be OK for circuit current draw of less than 1mA..!!
(considering Ohm's Law still valid..)

You really bad at math.  10ma at least.   

[antonis]

You really bad at math.  10ma at least.

In my country, 10mA through 800 Ohm result into 8V drop across the resistor, leaving ONLY 1V for circuit supply..

[Dormammu]

You really bad at math.  10ma at least.

In my country, 10mA through 800 Ohm result into 8V drop across the resistor, leaving ONLY 1V for circuit supply..

Ok. Take 500 Ohm.
Also consider actual current near 6ma, +capacitor like energy storage.

[antonis]

Ok. Take 500 Ohm. Also consider actual current near 6ma

That calls for 3V drop..!!
Only 6V left..

+capacitor like energy storage.

Is there any particular reason for worsen the ripple..??

[Dormammu]

antonis
Actually, if we take the original FF — well, you know.   

[antonis]

"Original" FF had more than reverse polarity serious reasons to worry about..

[FSFX]

"Original" FF had more than reverse polarity serious reasons to worry about..

The original FF only ran off of a 9v battery, had no LED indicator (wasn't commercially available at the time) and only took about one milliamp or so current. Also a lot of guitarists probably run it with flat batteries as they liked the sag sound.

Anyway, I am not sure what all of this obsession about polarity protection is about. Most simple one or two transistor circuits can withstand reverse polarity as the resistor values used in the circuits limit any current to the transistors to way below anything damaging and it is only the electrolytic capacitors that may suffer some damage. But the original never had an electrolytic on the power supply line, so no problem there. And the two electrolytic capacitors are behind resistors of sufficient value to limit any damage.

Of course, this is not the case with op amp circuits. Often, the polarity protection people use is far more damaging to other system components.

OK - I await the contradictory comments from the experts here   

[Phend]

Like the ski hills, maybe we need an Experts Only section on the Forum.
One run I won't be taking, my skis are dull.