JHS Morning Glory - more gain?

[alange5]

apologies for another Morning Glory thread...

I built a Morning Glory for a friend.  At max on the drive knob, the signal is a bit hairy, but I'd like there to be a bit more dirt on tap.  I used this layout:

http://tagboardeffects.blogspot.com/2013/05/jhs-morning-glory.html

I dropped the 12K attached to the JFET source to 10k and that seemed to help a little bit.  What component changes could add a little more dirt?

LM833 voltages:

1 - 4.91v
2 - 4.94
3 - 2.5v
4 - 0v
5 - 9.25v
6 - 4.59v
7 - 4.81v
8 - 4.64v

I'm getting about 4.6v and 4.3v on each side of the diodes

2N5457:
D - 6.01v
S - 1.15v
G - 0v


Any help is much appreciated.

[GGBB]

The Morning Glory is a slightly modified Marshall BluesBreaker with an added JFET output stage for make-up gain. So the BluesBreaker gain mods work equally as well here. Basically - use a bigger drive pot or add series resistance before the drive pot.  Adjusting the gain on the output fet isn't really going to do much since the op-amp stages are where the distortion is created.

[alange5]

on the layout posted above, where would I add series resistance to increase the value of the drive pot?

[GGBB]

Between the board and drive pot lug 1.

[alange5]

Thanks for your help.  I put 10k in series and didn't notice a huge difference.  Probably could have increased the resistor value but I ended up bumping the 220k (feedback resistor?) up to a 270k per a suggestion in another thread.  That seemed to do the trick.  I still really like the 10k on the JFET source.  The pedal seems a lot more lively than with the 12k.  Thanks again.

[GGBB]

They all do different things and produce different results.  Changing the fet source resistor will boost the fet a hair and maybe make it distort a bit.  Increasing the feedback resistor raises the gain of the second stage which is the lower gain of the two. Changing the drive pot resistance (need more than 10k) increases the gain of the first stage which then in turns hits the second stage harder.

[Mark Hammer]

Just a little aside...mostly because this is a concept that many get wrong and it bugs the daylights out of me.

Gain does NOT equal distortion.  They are two inter-relatyed, but DIFFERENT things.  Gain CAN result in distortion in the appropriate circuit.  But consider that many of the very best, and cleanest, microphone preamplifiers in the world rely on gobs more gain than the typical distortion pedal applies.  Consider that a gain-stage before a clipping circuit will increase distortion, but the very same gain stage after a clipping circuit (total is identical) simply makes the pre-existing distortion level a louder version of itself, without otherwise altering it.

So....

If you folks want more clipping from a circuit, say so.  It just may be that the route to achieving that more severe clipping IS to increase gain in one or more stages, but the objective is not to add gain.

[alange5]

Thanks for clarifying

[Mark Hammer]

Sorry if I came off a little harsh.