Revised Adjustable Tone Pot

[frets]

Hi Guys😺😺😺 Happy Monday!

Some time ago I posted an adjustable tone pot.  Well I have revised it.  Although for the extreme guitar tone junkie, it allows me to set the tone to the customers liking.

The change I made was changing out the dip switch to a rotary hexidecimal switch, that in combination with the four smd capacitors, allows for 15 tone cap values of:
0033
.0056
.009
.011
.013
.016
.019
.022
.025
.028
.031
.033
.035
.037
.041

The resistor will actually push the depth deeper than this once you get up in the 100k to 200k zone.

As an RLC Network, the guy can then fine tune the selected tone by rotating the 200k adjustable resistor.  The audio signal transformer measures around 1.8H.

Anyway, completely over the top but does have a niche.   I actually sell quite a few of these.  I thought you all would like to see the revised pot with more tonal options.

[asmith]

This looks cool as ice, but I don't fully understand it yet.

So, you open up the guitar, adjust the DIP switch to set the capacitance value you want semi-permanently, and then close up the guitar? And you use the 200k pot (log? lin?) as a regular tone control but with your chosen capacitance value?

Where does the inductor come into it? And what's the blue and white component that looks like it says '204' on it?

Thanks for your patience with my confusion, and thanks for sharing this.

[frets]

Hi ASmith,
Thanks for asking😺😺😻,
Let me try to answer everything you asked.  First off, “yes”, the rotary hexidecimal switch is rotated with a little flathead screwdriver to select the “cap weight” one desires.  Then, using the blue and white thing (adjustable resistor or trim), you further monkey with the tone.  As it is, you hit upon a negative given you have to have the guitar open, set the board, play, adjust, etc.  But, what I have is a guitar with two tone controls wired outside of the guitar.  I work with the client to help them decide which tone they want.  The other control I have wired is just a cap version of this concept.

So, the guy can decide what tone he desires and whether he just wants cap tone or the RLC tone board..
The pot is an A250k or A500k.
If a guy likes a couple of the tones generated by the tone board, I will offer him a push pull with 3 tone settings that he can choose.




Oh, I forgot.  The transformer is positioned in series at the end of the circuit before it goes to ground.  

It’s just another thing I offer when guys are tone junkies and want to experiment with something different and possibly put it in their harness.

[unreg]

Oct 3, 2022 17:43:49 GMT -5 frets said:

Judging by ancient screenshots you’ve taken, that I’ve seen, you have an iPhone too.

Next time you’re about to take a pic, first press on the screen on the part you want in focus. We all know what a pot shaft looks like, so I’m under the impression that you’d rather have the actual meat and potatoes of this pic in focus.


Or maybe it is in focus for others?

This tone change smorgasbord is really cool frets!

[Deleted]

In ye old days .. some electronics would have a hole in the case so you could change the Value via the use of a "Twiddle Stick"

Might be a way to be able to still adject the Trim Pot or Hexadecimal Switch (there is a 5bit switch if you want to go SUPER CRAZY) but I would suggest some thing strong behind it.
Used to have things like this in Radios with Variable Inductors and Trim Pots

[asmith]

Oct 3, 2022 17:43:49 GMT -5 frets said:

[explanation]

OK, so, like this?



Where SW is the dip switch, 1, 2, 3, ... are the capacitors the circuit offers, X is the blue-and-white variable resistor, Y is the regular 'tone pot' potentiometer, and Z is the inductor?

Since all components are in series it could be differently ordered, but, am I getting the gist of it?

(Drawn on a phone on the go — I never knew I drew in italics)

[Yogi B]

Oct 15, 2022 3:30:08 GMT -5 asmith said:

Since all components are in series it could be differently ordered

I think the trimmer resistor is in parallel with the cap selection. That's what the traces look like on the PCB, and would correlate with frets' description of "the resistor will actually push the depth deeper than this once you get up in the 100k to 200k zone."

Where 1, 2, 3, ... are the capacitors the circuit offers

There are only a total of 4 capacitors (3n3, 5n6, 11n, 22n), the switch just selects them in varying parallel combinations to give 16 different values (15, plus all off), like four binary digits.

No.	22n	11n	5n6	3n3	Total
0					0
1				on	3n3
2			on		5n6
3			on	on	8n9
4		on			11n
5		on		on	14n3
6		on	on		17n6
7		on	on	on	20n9
8	on				22n
9	on			on	25n3
A	on		on		27n6
B	on		on	on	30n9
C	on	on			33n
D	on	on		on	36n3
E	on	on	on		38n6
F	on	on	on	on	41n9

[frets]

Yogi is correct pertaining to the hexidecimal cap values and resulting nF selectivity. And correct pertaining to the trimmer resistor position.

[unreg]

Oct 15, 2022 13:37:44 GMT -5 Yogi B said:

the switch just selects them in varying parallel combinations to give 16 different values (15, plus all off), like four binary digits.

Excellent analysis sir! You’ve got the chart in correct binary representation of the hexadecimal values!


fyi: The short term for 4 binary digits is “a nibble”. Just like 8 is a byte.

And this is a weak pointless post in nutz eyes… sorry. 😔 Just noticed Yogi B’s proper binary.

[asmith]

Oct 15, 2022 13:37:44 GMT -5 Yogi B said:

I think the trimmer resistor is in parallel with the cap selection. That's what the traces look like on the PCB, and would correlate with frets' description of "the resistor will actually push the depth deeper than this once you get up in the 100k to 200k zone."

Ah! Understood! Cheers.

Where are you seeing the traces on the PCB? I can't see a clear circuit outline at all. 🤔

There are only a total of 4 capacitors (3n3, 5n6, 11n, 22n), the switch just selects them in varying parallel combinations to give 16 different values (15, plus all off), like four binary digits.

So, while on the go, I abstracted down "various capacitor combinations" to "chosen capacitance values" for the purposes of the switch element in the diagram, but in the cold light of tomorrow I see that I wasn't clear on that at all, and now I even look a little silly trying to explain myself. 🤷