Fulltone Plimsoul clone too...hairy?

[alphadog808]

Hey guys,
  So I built a vero plimsoul clone from tagboardeffects.  Even though I think it sounds pretty good, the low E and A strings have a noticeable extra amount of..."hair" when plucking the note.  It's almost as if the bottom isn't tight enough?  I A/B'd it against a TS9 and the bottom end is definitely looser/hairier.  

It almost seems like there is too much of those frequencies coming out and it distorts it...in a bad way.  Farty is a good description!!

I read around and I tried changing both poly 20n caps to lower values; I tried 15n and 10n.  I think it got a bit better, but it lost some warmth as well.  That kinda makes sense as I believe that fix was to make the pedal less dark.  I eventually put the parts back to stock.

Anyone have any suggestions on a component/s I can try changing?  I thought most pedals have a bass filter, maybe if I filter out more bass coming into the circuit the problem will go away?  Or maybe it's supposed to sound like this?    

[Pojo]

Schematics are king!



Looks like we have a double (2 pole?) high pass filter in the neg. feedback loop of the clipping stage. I'd socket C16 and C12 and experiment with some lower value caps until you get a sound you like.

[Jopn]

Also, not all LEDs are created equal.  Try swapping around different colors as well, or any other diodes you have on hand.

[alphadog808]

Thanks guys! 

@pojo -  Where did you find that schem?  I've never seen it, just the vero.  I'll mess with those components.  Sounds like lower values the better...

@jopn - This issue happens with the stage2(LEDs) off or on, so I figure the LEDs don't come into play for this.  But I have tried other LEDs, no big change.  I did hear a difference when I put in regular diodes(I can't remember which model it was), but it made it sound more harsh. 

Thanks for the ideas, guys, hopefully that will fix the problem!

Jon

[PRR]

The 47 ohm doesn't make sense.

10K maybe? Or 47K as a likely typo?

[alphadog808]

The 47 ohm doesn't make sense.

10K maybe? Or 47K as a likely typo?

PRR, I'm not electronics guru, so what makes you think that that component is wrong?  Assuming I have a 47K at home, I can throw that in to see.  Would having a value too low there cause the fartiness I'm experiencing?

[alphadog808]

An update...so I tried replacing the 47R resistor with a 47K...no difference.

However, I started messing with C12 and C16 and made some progress.  Right now C16 has a 2.2u and C12 has a 470nf cap.  The bottom end is definitely less wooly/farty.  It seems that those 2 caps work in conjunction with each other.  It's possible there might be better values, but I had to work with what I had on hand. 

The bottom end is tighter, but I'm unsure if I sacrificed anything else in making this change, but it doesn't seem that way.

Any other components that might beneficial with a change?

Thanks!

[Pojo]

Glad you found some improvement!

It seems that those 2 caps work in conjunction with each other.

They do...actually those 2 caps and R9 and R25 all work together to form a pair of high pass filters, R9 and C12 form one of the filters and R25 and C16 form the other. If you do the math you can calculate the frequencies where the low end roll off begins. Or you can use this calculator here (but most here would prefer the less lazy way and actually plug the numbers into the formula):

http://www.muzique.com/schem/filter.htm

If you enter the stock component values you'll see that R9 and C12 are doing most of the work in filtering out low end with a corner frequency of 482.5. The other filter starts to roll off only at 16.9hz which is below the range of human hearing! Seems to me like it's just a waste of components and board space to even include them. Maybe those components and the 47R Paul pointed out are just relics from revisions made between prototype and production, and they wanted to not have to make a new pcb layout? Anyway, you should be able to get where you want to be just by tweaking C12's value.

*OR*

Take the approach of the PaulC Timmy and put in a low cut pot to adjust it on the fly...extremely useful!

Any other components that might beneficial with a change?

I'm sure there is, depends on what you want to do!

[Kipper4]

Are those not low pass filters rather than High pass?

[alphadog808]

I dunno guys, I ended up selling the pedal...I wasn't feeling it.