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A Stretch

SparkyCal

Mar 11, 2020
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ok...so this next project is a stretch for me, as it is probably beyond my capabilities- but only enough to force me out of my comfort zone.

It is a schematic on how to build an overdrive guitar pedal- which i am very interested in

The guy who built this was kind enough to forward this schematic for me.

But I need help.

I want to try to put this together, but I need to determine a parts list for it. Some of the stuff, i can identify, but some I can't. Can someone help by listing what parts I would need? And is there anything about this schematic that i should be careful with? In other words, anytbhing that may trip me up?

Thanks!!!! Here is the video, if you care to see it:
 

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Nanren888

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We'd be guessing about what might give you trouble or what you should watch for.
The chip has two amps in it. On the board he shows, he's connected pin 6 to pin 7 to keep the unused amplifier from doing something noisey.
 

Harald Kapp

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The chip has two amps in it. On the board he shows, he's connected pin 6 to pin 7 to keep the unused amplifier from doing something noisey.
See the datasheet.
With pins 6 and 7 connected, the circuit will use amplifier A.
pin 1 = output of amplifier A
pin 2 = '-' input
pin 3 = '+' input
pin 4 = ground
pin 5 = unused )open)
pin 6 = unused (connect to pin 7)
pin 7 = unused (connect to pin 6)
pin 8 = Vcc (positive supply)
 

bertus

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Hello,

If the dual opamp confuses you, you can also use a single opamp version, the TL081.
They exist in single, dual and quad:

TL08X.png

Bertus
 

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Audioguru

Sep 24, 2016
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In addition to him using a dual TL082 opamp instead of a single TL081 opamp, the opamp is not powered in the schematic and the polarity of C3 is backwards.

The distortion sounds AWFUL!
 

SparkyCal

Mar 11, 2020
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Tha ks for all the help. I did reach out to the gentleman who made the unit. He sent me the li k to the video I posted, and said that this is the best he had, cause he ordinarily does his schematics on a scrap piece of paper and discards them. For clarity, he says he uses a dual op ampbe cause it enables him to swap chips on the breadboard easily, for comparison purposes. he says in the video, that if he did not use the dual, he could not do that easily. Not sure why, but I assume there is a reason.

I was initially confused by the inout of the far left of the schematic., but now I realize he is just trying to depict the guitar cord going in. Is that a correct read?

I am okay with the capacitor and resistor symbols and values, but I am confused as to what i am seeing in the middle of the schematic. I circled the part I am confused about.

I think I am seeing the following (please see the hand drawn labels in the diagram that i drew):

A). is the op amp (named OA1 TL082)

B) is a capacitor? is the value C31 100pF?

C) is this a diode? does the label 1N4148 pertain to it?

D) is the a diode pointing the opposite way as the one above? and does the label 1N4148 pertain to it?

E) I assume this is a 500K resistor


I ordered the op amp, and it should get here tomorrow. I plan to breadboard this and I think i will need your expertise, but I will try to be as clear as i can be along the way, and provide pictures etc. If you can help me with the above, it would be greatly appreciated!
.
 

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Harald Kapp

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A - D: right
E: no, this is a 500 k potentiometer as you can see from the tap indicated in the middle.
 

Nanren888

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D) is the a diode pointing the opposite way as the one above? and does the label 1N4148 pertain to it?

Yes, one diode each way, makes for a symmetrical transfer function.
1N4148 is one of the most common small signal diode types.
1N = diode (technically two-terminal device)
4148 - type of diode
1N4148 - should find in any catalogue of semiconductors
similar types 1N4148, 1N914 are small signal diodes vary a little from manufacturer to manufacturer but are common.
 

SparkyCal

Mar 11, 2020
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Thank-you Nanren888. I have a bunch of diodes that I purchased. These are them:
https://www.amazon.ca/gp/product/B07FMM5MSF/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.amazon.ca/gp/product/B07F7ZN695/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I have two issues:

1. Do you think any of the diodes that I have will be suitable for the project we are discussing?

2. I did not realize that i bought SMD diodes in one of the orders above. I have no experience with SMDs but i looked at a. few videos. I know you need special circuit boards to work with SMDs. but is there a way to use them on a regular through hole circuit board, if in a pinch?
 

Nanren888

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This second one lists

8 Types of Diodes(100Pcs): 1N4148, 25pcs; 1N4007, 25pcs; 1N5819, 10pcs; 1N5399, 10pcs;FR107, 10pcs; FR207, 10pcs; 1N5408, 5pcs; 1N5822, 5pcs;

that's 25 1n4148 diodes, if I read it correctly. The id will usually have it written on the side.

SMD parts usually bridge a gap between two circuit board pads, created at exactly the right spacing, and being held down by the solder at each end. They are often glued down, or held down by a combination of solder-paste, then the solder melted to complete the process and electrical connection. On boards, depending on the size of the component, these can often be aligned to bridge the gap between two tracks or pads on a board. They can be a bit fiddly to solder as they are small and will move as the solder melts. Hand soldering some small ones, they can be inclined to "tombstone", that is when you solder one end, the molten solder pulls then into an upright position standing vertically on the pad you are soldering, instead of bridging one pad to another.
Summary, can often be done, despite being small an fiddly. Other, more expert guys here, may be able to give you better pointers.
 

Alec_t

Jul 7, 2015
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They can not be used on a breadboard or veroboard.
Possible on veroboard, but fiddly, by bridging tracks (as per post #13). Another mounting option is to bend a tinned copper connecting wire into a hairpin shape, grip the component in the bend for soldering, then solder the legs of the hairpin to the pcb and cut the bend off.
 

SparkyCal

Mar 11, 2020
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Question: I am starting to build this. If you look at the far left, there is a 10K resistor (R3), followed by 470nF Capacitor (C3). Typo- meant to say (C23) I have a 470nf capacitor but it is polarized. Does the + terminal of the capacitor join to the 10K resistor (R3), or is it the - side?

Thank-you
 
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Alec_t

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Does the + terminal of the capacitor join to the 10K resistor (R3)
That's what the schematic shows. I'm surprised a 470nF is polarised, however. Using 470nF instead of the 1uF shown will reduce the bass response a bit.
 

SparkyCal

Mar 11, 2020
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I'm sorry..i have a typo. I meant to say C23. So, I am asking If you look at the far left, there is a 10K resistor (R3), followed by 470nF Capacitor (C23). I have a 470nf capacitor but it is polarized. Does the + terminal of the capacitor join to the 10K resistor (R3), or is it the - side?
 

Alec_t

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Connect the +ve side of the cap to the opamp input.
 
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