Sweet Thing booster not much effect from Tone pot

[matopotato]

I have built a Sweet Thing Booster by Doug Hammond based on Aron Nelson's Booster 2.5. (Earlier thread on other issues and questions)

The modified schematics:



where C10 ended up 12nF, C9 68nF and R19 became a B10k external pot.

I feel that the Tone pot (R18, B50k  ) does not change tone very much. The R19 does have effect as discussed in the other thread, but with the tone pot itself I feel hard pressed to detect any changes.
I am aware that a resistor in circuit does not always measure as marked, but still
the Tone pot swings between 0 and 6.75k.
Is that a bit too low vs expectations?
I try to wrap my head around the schematics and foresee what the resistance might be between lug 2 of R18 and R17, R15, R20 (and as a consequence either side of R16).
I get readings that vary with the turn of the pot, but they are all small.

What would be a rough expected value between lug 2 and other points in the circuit nearby?
R17 measures 6.64k "in the box"
R16 6.62k
R15 20.5k
R20 90.8k
R18-Lug2 to Source on J5/R15/R16 jnct swings from 6.6k to peak at 7.6k then back to 6.6k.

Maybe the circuit has a very weak Tone control, but I have a very distant memory of getting more out of the swing range during breadboarding.

Any other checks I could make?

[antonis]

I try to wrap my head around the schematics and foresee what the resistance might be between lug 2 of R18 and R17, R15, R20 (and as a consequence either side of R16).

[aron]

It's the Booster 2.5 with the Hot Cake tone control (from what I remember). I remember it being fairly effective.

[antonis]

It's the Booster 2.5 with the Hot Cake tone control (from what I remember). I remember it being fairly effective.

True & Correct, aron..

But OP halved caps values and raised R19's one so he might make R18 100k..

[matopotato]

It's the Booster 2.5 with the Hot Cake tone control (from what I remember). I remember it being fairly effective.

True & Correct, aron..

But OP halved caps values and raised R19's one so he might make R18 100k..

Thanks!
Ok, the cap values I got from Rob Strand and tested on breadboard, which were fine to me. Didn't expect it would have dampening effect on the tone control itself.
R19 is from 0 to 10k, so in a way it is not necessarily raised. Not arguing against any suggestions, just wanted to be clear that 2k2 original is still available within the swapped R19 10k rotation.
So would tone pot R18 to 100k make the tone sweep more useful?

Because in the condensed R section from the picture, I interpret it as that I should get a sweep 0 to 14k3 (ish) with current schema.
So my 6,7k reading instead is an indicator of something being wrong?

And would a fix resulting in 14k3 have made the tone much better, or is R18 100k pot needed anyway to get some useful swing in for the tone pot?

[amptramp]

I would be inclined to move the tone control to the input of the source follower so that the behaviour is consistent regardless of what is connected to the output.  In an ideal world, a stompbox has an input buffer and an output buffer with everything else between them so that external connections have no effect on performance.

[matopotato]

I try to wrap my head around the schematics and foresee what the resistance might be between lug 2 of R18 and R17, R15, R20 (and as a consequence either side of R16).

I did some "reversed calculations" to see what value of the Tone pot would yield the measured values at R20-R16 junction and R16-R17 junction. In both calculations I come up with that the Tone pot has to be 10k...
So the most logical conclusion has to be that I have mixed up R19 with R18...
So I will have to take it apart again. That is the messiest part since I managed to fit it into a nice golden 1590B.

[matopotato]

Yes, that was it. I had swapped R19 and R18.



Fixed it now. Tested it and it sounded better although I feel that the Tone range is not huge. The Corner Frq sweep does some, but nothing huge  either.
After tightening all the nuts and finish the boxing, that feeling remains. Perhaps even a little bit increased.
I might have done some other blunder in the process, but all pots do something in their allotted area and it serves more as an Overdrive/Distortion than a Booster imho, so I think I will let it be for now.

Thanks for help, support and ideas!