This is a circuit I have had in my hard drive for years but never tried or simulated.
It's based on a LT700 small output transformer. This site (https://www.petervis.com/electronics/lt700-transformer/lt700-transformer.html) says specs are 550mH 63 ohm Primary, 2.25mH 0.63 ohm Secondary.
TB1 at the right is the original circuit. Basic guitar circuit added.
Simulation shows a "bell-like" response (TS808 ?) when the pot is at zero and a bass boost when maximized :o
So I modified it a bit to make it more like a Rangemaster.
TB2 mods adds C2 and C4, and TB4 C2, C4 and the secondary.
Note that both mods can be transformed to the original with a double switch --> in TB2 SW1 bypasses C2 and SW2 breaks C4 path to ground.
At around 5k the curves "look like" a Rangemaster with a 8.2nF input cap, just a bit more Q-ish.
(https://i.postimg.cc/Vkgt8R46/PE-treble-booster-jpg.jpg) (https://postimg.cc/WdDzm0BL)
The PDF is available at the other forum (https://www.freestompboxes.org/viewtopic.php?t=31544),
or do a google search: practical electronics treble booster russell
mac
https://worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1972-04.pdf
12MB PDF file
I find the article on magazine page 320, PDF file page 58
Thanks Paul. I got caught at the next article, the silicon controlled switch fuzz :icon_mrgreen:
mac