Substitution components question

[dfp123]

Hi,

I have a question about substitutions for the Sabbra Cadabra build. I have read through all of the comments there, but I figured since the build has been out for a while, there might some solid substitutions specifically for this build. I am new to diy pedals (this is my second build).

What would be the best sub for the 1N5817 diode:
1N5818, 1N4001, or 1N34A

What would be the best sub for the MPF4393 transistor:
2N5457, J201 or MPF102

Any information would be greatly appreciated. Thank you.

[Chris60601]

The 4001 will be Ok to use. Pretty certain I used 201's - its been a long time since I built this

[induction]

The diode is not in the original circuit. It is inline polarity protection, and was almost certainly chosen for it's fairly low voltage drop (it's a Schottky, so Vf should be something near 0.3 V). Of the diodes listed, 1N5818 would be closest (they're very close relatives, and are listed on the same datasheet), but nearly any of the usual suspects will work. I'd choose the 1N5818 over the 1N4001, which has a typical Vf around 0.7 V. I don't know if the reduction in supply voltage will be audible, but I expect it will not be significant. If you want to be certain, you should breadboard it and see for yourself.

[Chris60601]

Either or really. The fact is, there are several versions of the schem (3 that I have seen) out there and each reflects something different.

One uses the 5817, another uses a 4007 and the one I prefer to use as a guide (located here: http://pedalparts.co.uk/docs/WarPig.pdf) uses the 4001. Since this was traced at FSB, I would probably use the one from there that uses the 5818. But I really don't think the diffs are going to be noticeable by the average user.

Especially us guitar players simply because we're pretty much deaf by our own means, LOL.

[induction]

As I understand it, the protection diode is not present in the original pedal, it was added by IvIark. So despite the various schematics, the most accurate clone would not include it at all.

But it's a good idea to include it, and lower Vf is preferable to higher. (I keep a stock of 5817's for exactly this purpose.) I agree, though, if you can't hear the difference, there's no reason to be too worried about the diode type.

[Chris60601]

Agreed - You may recall, it wasnt too long ago I was asking about the whole polarity thing and what not. Why resisters were used (or not) etc. Obviously I knew nothing about it although I was copying it anyways.

Now, I have at least a very basic understanding and why we ought to use it. To the Op building this, dont forget to check the datasheets. When in doubt, I find this link (for trannies and although the example is the J201)
http://alltransistors.com/mosfet/transistor.php?transistor=19202 
you can find a suitable sub for the item in question. But, you probably knew that anyways.

[dfp123]

Thank you everyone for all the information. I am very new to all of this and greatly appreciate the help.

I have not looked into datasheets yet, but will now delve in. Thank you for the link.

[dfp123]

Chris60601 wrote

The 4001 will be Ok to use. Pretty certain I used 201's - its been a long time since I built this

Do you recall how the 201's sounded? Did you consider it a successful build?

[dfp123]

I have looked up the data sheets for the MPF4393, J201 and 2N5457

MPF4393
Vds, Vdg, Vgs: 30, 30, 30
Ig: 50
Pd: 350

J201
Vdg, Vgs: 40, -40 (no Vds listed)
Ig: 50
Pd: 360

2N5457
Vds, Vdg, Vgs: 25, 25, -25
Ig: 10
Pd: 310

The values for the J201 are higher than the MPF4393.
The values for the 2N5457 are a little lower than the MPF4393.
Is the better to go a little higher or a little lower? But both have negative values for the Gate Source Voltage. Does that matter?
The 2N5457 has a much smaller Forward Gate Current (10 instead of 50).

Which values are most important when finding substitutions? Which way would be better to go with?
Thank you again for the help!