[sdiy] TTSH - part/substitution questions

[John Ames]

On Wed, 1 Jul 2026 20:59:31 -0500
Pete Hartman <pete.hartman at gmail.com> wrote:

> I'm not sure if it's a generic shorthand, but I don't think the
> ferrites for these are intended to be anything fussy.

Thanks, I kinda figured but this is more than a little beyond me.

> BTW I looked at my images of rev1, rev2 and rev3 TTSH boards and I
> could only find the beads on the rev1.... is that what you're
> building?

V.4, per the SynthCube product listing. BOM is at
https://product-downloads.freshclick.co.uk/uploads/187269622300ec56c723fa76ec709111.pdf
if you're curious.

> I built it with the Transistors as spec'd but then again, I bought a
> rare parts kit from Thonk in the UK, so I didn't have to fuss about
> with that.  I don't think they're still selling those :(

TBH I hadn't checked if they were, since Stupid Circumstances have made
international shipping stupid expensive :/

> I would expect they need to be *matched* to each other, but aside from
> that, I can't see any reason why the can makes it special

That's kinda what I'd guessed, but good to have some backup on this.
Curious what you'd be matching for - resistance? Switching time?

(On which note, obvious newbie question, but: since the ideal JFET is
open at 0V, is it a reasonable first-order approximation of "matching"
to compare resistance across a totally disconnected transistor, or is
it important to note variance in resistance across a range of gate
voltages...?)

> Based on this I guess you're building a rev2 (or maybe later?).  On my
> rev1 bom I have BD236 and BD237 which were power transistors for the
> amplifiers that drove the speakers.

Good to know, I'll have another look. If it's the speakers I'm omitting
those as well, but it'd be nice to minimize complications for the time
being.