Help me mod the horrible Boss PW-2

[dirk]

Hello,
I want to mod the Boss PW-2.
It is now quite harsh sounding, so I need some highend cutoff and probably some asymmetrical clipping.
I do like the tone controls and amount of drive.
Here's the schematic:

It seems to have simple opamp clipping and no highend cutoff, witch could be the reason it sounds harsh.
So what can be done to tame the highend and create asymmetrical clipping?
Any other tips to improve the sound would be great to.
Greetings Dirk.

[DiamondDog]

Hello,
I want to mod the Boss PW-2.
..
Here's the schematic:

It seems to have simple opamp clipping and no highend cutoff, witch could be the reason it sounds harsh...

Well, there's your problem... (I don't see a schematic. Maybe it's me, tho.)

[dirk]

I can't see it either. It was there when I made the thread.

Edit: You have to be logged in to see it.

Here's a link: http://www.freeinfosociety.com/electronics/schemview.php?id=165

I have put asymmetrical clipping in it by putting 3 schottky diodes between the 10uF cap and the 4.7k (witch is actually a 47k resistor) resistor and the normal input of the opamp. It has improved the sound, but the output level is quite low now. Changing the 15k feedback resistor should help with that. It still has to much highend though.
Any more options?

[dirk]

Can someone explain the circuitry between the second buffer and drive pot?
Its the two 2SK184 fets and a 2SA1048 transistor.

[PerroGrande]

Dirk,

The 2SK184's and the 2SA1048 form a discrete op-amp. 

In this case, the schematic is missing a "dot" to show a connected point. The collector of the 1048 has to be connected to the output (near point "A" on the schematic).

Essentially, the input runs to the non-inverting input of an op-amp.  The output is fed back to the inverting input through a variable resistor/voltage divider to determine the gain ("drive"). 

[dirk]

Thanks PerroGrande, that helped a lot.
I'm gonna try a TS diode configuration to see how that sounds.