[WORK IN PROGRESS] GnognoFasciani's Wuthering 8

[gnognofasciani]

Hi bass folks!
I'm trying to design something "new" for a bass player that i met some days ago (not so new because i used the blend circuit from the sprkleDrv)...
It originally had 7 pots, but i couldn't call it Seven  so i had to add another one (the comp one)


That's NOT VERIFIED,

I posted it because I need advice about values (I have no idea of the freq that are right for bass) and/or components that i missed, Can anyone help me?



Thaks to all and particularly to Pentotal (the diyitalia.it member that designed the tonestack)

[Processaurus]

Hi, I don't have an idea what the tonestack values should be, but I noticed the buffer around Q2 is redundant, no need for it because the output impedance is quite low from the previous opamp.

Also I'm wondering if the comp and gain knob do almost the same thing?  If you need an 8th knob to do something, have you seen Jack Orman's warp control on muzique.com?

Oh, as far as a good place to start on modifying the tone stack, if it was a design originally for guitar, it is reasonable to shift all the filters an octave down (may be as easy as doubling certain caps).

[gnognofasciani]

Hi, I don't have an idea what the tonestack values should be, but I noticed the buffer around Q2 is redundant, no need for it because the output impedance is quite low from the previous opamp.

Thank you for your advice!

Also I'm wondering if the comp and gain knob do almost the same thing?  If you need an 8th knob to do something, have you seen Jack Orman's warp control on muzique.com?

Isn't it the same thing? Maybe I just called the wrong way

The tone stack: it was designed for a bass amp, so I think it doesn't need tweaking (But we'll see during the testing)

Thank you again!

[gnognofasciani]

That should be better

[Processaurus]

Cool!  Nice work on your schematic, it is looking to be what may be a versatile and interesting sounding bass pedal. The warp control looks interesting, I wonder if the warp pot may need to be bigger, to isolate the two clipping sections from each other better?

Using variable gain is a great idea for the volume control on the output stage, to keep headroom as high as you need it on the clean signal.  Right now, though, there will be an issue, that's that the clean signal will only be able to get to ~.6x its original volume, with the volume control maxed.  I would breadboard the circuit to get your values right, but a 1M pot for volume might be a good place to start.  You could mess with the value of R13 to match the distortion volume with the clean, so that the effect more or less stays an even volume when you pan the blend pot from clean to dirty. 

If it is noisy with a 1M volume pot (hiss, generated from that point in the circuit)  you could lower the impedance of that and the stages feeding it (10K for the dual blend pot, R8 and R7= 10K, volume=100k).  Also, R12 isn't helping, with an inverting summing stage, you want the two summing resistors (R8 and R7 in your case) to meet right at the opamp's inverting input.

hope that helps, good luck with your project.

[gnognofasciani]

Thank you for your help Processaurus!
I've just updated the schem because another member of diyitalia.it told me that it should be better to put the tonestack in the clean part and to use a guitar-like distortion circuit (in particular the values used for the guitar one or just a little bigger) to distort just trebles and mids...

Here it is the updated schematic:



What do you think about it?

[jrc4558]

I wonder if your bass roll off is a little too drastic in IC1A setup. For bass its better to have less gain but in all spectrum, rather than lots (your's is over 450) of it in just trebles (your setup rolls off 6dB per octave starting from 329Hz downwards). You may want to increase the value of c4 to 22uF.
Otherwise - looks good! Nice take on Sparkle drive!

[gnognofasciani]

Do you think that 10uF for C4 and 4,7k for R2 is a better choice?

Thank you too Constantin!

[jrc4558]

Perhaps. This will reduce the gain though. Depending at what you're aiming for, this may or may not be a desireable effect. Just a thought.

[gnognofasciani]

Ok, I'll check it out during the sound test...

btw I've just finished a (double) pcb, can anyone take a look just to be sure that it is correct?



And this is the tone control with all knobs at 50%

http://picasaweb.google.it/pentotal82/Amp/photo#5055072985614131010

[gnognofasciani]

I corrected some bad connections of the previous layout

[gnognofasciani]

That pcb is wrong!

I'm testing the w8 with my guitar, waiting for bass player sound check (I need to find one this weekend)

It sounds preety loud and mean, but needs more tweaking to find the right balance...

The Warp control is freaking nice, thanks Jack!

[gnognofasciani]

After a sound test I decided to change the circuit:



The warp control doesn't work very well the way i used it, so I preferred to put a filter control and another pot (DFR) to have full control of the frequencies passing trough the dist circuit

The listed values are not definitive

[gnognofasciani]

My last improvement for this circuit..I promise I won't change it anymore



The bass player who tried it was satisfied by the sound of the previous version, but with these mods it should be more versatile and have a killer sound (not just a good one I hope)

Stay tuned