[sdiy] TTSH - part/substitution questions

[Pete Hartman]

On Wed, Jul 1, 2026 at 6:11 PM John via Synth-diy
<synth-diy at synth-diy.org> wrote:
> First, both the TTSH and the gate-boost BOM list ferrite beads with a
> part # of FB_226 - but I cannot for the life of me find any such thing
> online. Even a quoted-literal search returns nothing but results point-
> ing right back to these BOMs. Is this some understood shorthand for the
> specs on a generic ferrite bead? How does one read that?

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.  I have a drawer
full of this type of ferrite bead:
https://www.mouser.com/ProductDetail/Fair-Rite/2743002112?qs=X2DWwR3nihDJfxeTNAhF3w%3D%3D
and I just pulled from my own stock on hand.

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?


> Second, I'm sure I'm not remotely the first person to note that some of
> the transistors required are, erm, unicorn poop, either completely un-
> available outside of eBay or just wildly expensive :/ I'm curious, has
> anyone worked out alternatives for these?

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 :(


> The 2N3954 is a dual JFET used in the sine shaper; can two JFETs of
> equivalent specs be used in its place, or is it important that they be
> inna-can for tempco/symmetry purposes?

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


> The BOM lists MJE182 and MJE172, which appear from what I can find to
> be power transistors, but I don't see them in the power-supply section
> and can't spot them anywhere else on the board diagrams I've found. If
> I'm using a separate PSU, can I omit them?

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.
That's where I'd recommend to look, though I haven't dug into this
stuff in a long time now.