Adding more treble to Fulltone OCD circuit?

[elenore19]

Hi all-
I Love the OCD circuit. I've built quite a few with Madbean layouts. I run two on my board right now. One of them I have is so much darker than the other in terms of tone and I'm wondering why. Looking for insight as to what parts to start messing around with in the circuit- maybe a capacitor got put in at too high of a value adding more low end? Or would it be something to do with what clipping diodes I used in each?

I dime the presence knob on my darker sounding one and it has about the same treble effect as the other one does with the presence knob at about 2 O'clock.

[idy]

So many little things could be wrong, a solder bridge....
These caps are the ones that stand out as treble reducers:
C2 and C5, the feedback loops on the opamps;
C4, but only when mosfets are selected with the clip switch;
C8 at the tone knob.

Any one of these too big and goodbye highs.

[GGBB]

^ Also check R1 and R3 - too small and they will lower input impedance which will drop highs at the input. Wrong op-amp can also cause this (TL082 has very high input R). This circuit already does that a little. (OCD v2 raises input impedance.)

[eh la bas ma]

I tried to have more treble from an OCD, quite recently. I am really pleased with the result :

https://www.diystompboxes.com/smfforum/index.php?topic=128285.msg1234331;topicseen#msg1234331

see reply #4.

[niektb]

For me it was an impedance problem! 500k output pot is ráther high. And R10/R11 don't help. stack a buffer/digital pedal after and see if it's fixed, then you know if it was impedance or not

[tubelectron]

For me it was an impedance problem! 500k output pot is ráther high. And R10/R11 don't help. stack a buffer/digital pedal after and see if it's fixed, then you know if it was impedance or not

I have 2 OCD V1.4 at home for the moment :



One borrowed to a friend, which made me sell my V2.0 that I found inferior to my taste and needs - S/N° : 23507



The other bought recently to replace my V2.0 - S/N° : 53673



Looking closely to the two pictures showing the PCB, you notice that one has a A500K volume pot (my friend's) while the other has a A100K volume pot (mine).

The tone of those two V1.4 is different and I prefer the tone of my friend's older one with A500K pot : the high end is subdued, undelining the presence slightly, giving more expressivity to the sound.

So I am thinking about changind the A100K for a A500K, but : is it the only difference between these two versions, by your knowledge  ?

Here's what I note :

- all the R are the same value and same place.
- all the non-blue caps are the same value and same place.
- same chips from Texas Insrument TL082CP too.
- the pots are same value and taper, with the exception of the volume pot.

Of course, I will dissassemble both in order to read the marked values on those tiny blue caps - if I can read themwith a magnifier ! - and see if there is a difference here...

A+!

[idy]

one take on differences:

[tubelectron]

one take on differences:

Thanks @idy ! 

A+!

[duck_arse]

C8 - what value is it?

[antonis]

C8 - what value is it?

22nF..
15Hz cut-off frequency, neglecting R8..

(do I win anything..??) 

[duck_arse]

no sir, nothing for you. I was looking at the boards, and one has what looks like an mlcc at C8, the other has a green electro looking cap there. it only struck me on a second look that the micc-aloike might be a tantalum instead, in which case both caps might well be the same microfarads-range value.

22nF?

[antonis]

Not my business, for sure, but it never happend to meet a 22nF tantalum cap..

[anotherjim]

I second that tant. And think Ducks meant to type a mu instead of an en.

[antonis]

A HPF of 15mHz cut-off frequency shouldn't work even for dogs..

[PRR]

> even for dogs..

Elephants.

Or Great Pyr dogs. My girl can hear a large deadly Diesel a mile away.

[duck_arse]

I second that tant. And think Ducks meant to type a mu instead of an en.

well sir, no sir. when I said:

22nF?

.... I was quoting :

22nF..
....

... but neglected to use:

" "

and I would never say moo in an antonis thread, cause I cop it from him everytime for poor keyboard technique.

.... in which case both caps might well be the same microfarads-range value.