Blue Magic

[Peter B]

G'day all,

I've just finished the Blue Magic pedal... it works well, maybe too well hence this post.

In comparison to other distortion/overdrive pedals both commercial (BOSS SD1) and home made (TubeScreamer and Fuzzface) the Blue Magic seems to have heaps of gain.  By this I mean that with the others I can set the Gain/Drive/Level pots almost anywhere in their range without things sounding too "loud".  I know this is a subjective thing but bear with me.

With the Blue Magic on the other hand I find that with the Drive control at zero I get no output (no surpises there?) but once I move the Drive control I have to keep the Volume control way down without things getting "too loud".

I am wondering if this is typical? Anyone else had any experience with this circuit or type of effect.  For what it's worth I cannot get the voltage at the drain of the JFEt down to the 4.7V recommended in the circuit, the lowest I can get is 5.2V.

Thanks for any comment/help.

Peter.

[RDV]

:idea: Try a larger trim pot than 50k(like 100k), or add a fixed resistor in line with the trim to reduce the voltage to the JFET drain.  :idea: If you're using a 100k linear instead of audio taper at the output, that will cause the volume to sort of hit you all at once. I'm gonna build this one meself soon. Good luck & HTH.

Regards

RDV

[Ed G.]

I think I would first try an audio taper pot. You'll have a wider range of pot movement per volume change. The blue magic overdrives gain stages, which increases gain and volume, instead of smacking the signal up against passive diodes, which reduces it.
I haven't built the blue magic, but if it's one of Jake's designs, it's got to sound great! Others have said it sounds heaps better than a tube screamer.

[Paul Marossy]

I built a Blue Magic about six months ago, and I really like it. In fact, it has a home on my pedal board now. It has a bit more gain than a Tube Screamer, but if I don't want too much distortion, I just roll back the volume a little bit. Perhaps my transistors have a little lower gain than yours?

[Peter B]

Hey guys,

Thanks for the advice and comments. The more I play with this effect the more I like it, it has lovely smooth distortion. "Creamy" is the word I think?

I do have a 100k Log pot for the volume and am now getting used to the range of operation... was just a little different to my other experiences when I started off.  As for getting the voltage at the drain of the JFET down to 4.7V I don't think I'll bother too much.  It seems the lower the voltage the more gain the circuit develops.  I am currenly running at about 6.0V and find this gives me plenty of gain.

Now to fiddle with a few caps as suggested in the build notes... WOOHOOO

Peter.