mosfet substitution in Blue Magic circuit ?

[pedro]

Hi all,

having built a couple of Shaka's and Tubescreamer clones I'm keen to build the Blue Magic circuit next ( whilst I build the Neovibe )

I have plenty of surplus parts at moment and wondered whether I could sub the BS170 MOSFET for another type - say IRF520 or IRF510 - as I have some left over from clipping circuits for Shaka 5 designs

what MOSFETS could I use ?

PS I have plenty of J201s for the JFET stage so thats not an issue.

Any thoughts ? Also has anyone built this design and how does it perform ?

Rgds
Pedro

[Paul Marossy]

I built it. It's a nice sounding little circuit. I found that the mid boost switch didn't seem to do much, but I remember a discussion here a little while ago about how to make it more effective. Unfortunately, I don't remember the details.

Other than that, I think it sounds great for what it is.

As far as those MOSFETs are concerned, they probably would work fine. Just verify the pinouts between them. You could also look at the respective data sheets and see how they compare in their stats.

[WGTP]

Different ones may require different bias resistors.  The 2N7000 has been subbed for the BS170 and has more gain, but I'm not sure abou the bias.

[Ge_Whiz]

I subbed a Zetex ZVN0350A (350V MOSFET) and it worked perfectly. Had to push the mid-boost capacitor up to about 1.5nF to hear its effect, though - tin ear, I guess. Great sound.

[ahermida]

where can I find the schematic?  

Thanks.

Alf

[Zero the hero]

On general guitar gsdgets you find the complete project.
I've built it a couple of months ago, I'll try the 1.5nf cap mod, cause it seems that mid boost swithc doesn't affect the genreal sound of this effect.

[pedro]

Finished the build last night ( exc enclosure ) and set JFET drain voltage at 4.7 and tested with my beloved McCarty....

Great pedal - much less crackly distrotion artefacts than the shaka 5 IMHO - but I still need to tune the shaka so maybe thats a daft comparison !

Circuit goes in the case tonight then its going straight onto my pedal board.   I'm a big tube nut, having built several tube amps point to point.
This circuit sounded great with my 18watt amp even at low volume for a glassy blues bite...
Also has heaps of compression distortion at full tilt...
I will try some other MOSFET subs to see what they do , and post info.

Very pleased indeed with it - no little niggles like I usualy find with the sound of finished pedal projects.

Rgds
Pedro