Sub-mini tube amps

[Scruffie]

Aha! Looks very cool, enclosures a bit big for my liking though

[thomasha]

Hey guys,
nice to see that this thread is still alive!

I'm working on a second subminiature combo, now I'm tolexing a 12x17x8cm box for it. The schematic is the same as the 3 tubes version.

Unfortunatelly my board for the jcm version was too noisy, hopefully this one works better.

Just in case, I would add a small metal chassis around the SMPS circuit part, like you see in the univibe, just big enough to cover that part (or the mosfet and the inductor), you could use it also as a heatsink for the mosfet, just remember to use some electrical isolation on the mosfet, so you can ground the small cage.

I think I forgot to post this, so here it comes>

Made a PDF available here, if someone is interested
https://dl.dropboxusercontent.com/u/10420127/RussianJTM.pdf

[joesatch]

a byo lunchbox amp ala tiny terror would be great, the smaller the better!

[jubal81]

Now that is a genius little head, Thomasha! Love it!


I've been doing some SMPS sub mini work lately and I've gone to an SMD shielded inductor. There's still a bit of EMI coming off, but it's greatly reduced. Bonus is that it's only 12mmX12mmX10MM.


http://www.mouser.com/Search/ProductDetail.aspx?R=SRR1210-101Mvirtualkey65210000virtualkey652-SRR1210-101M

[thomasha]

Nice Jubal81,

found a similar one from bourns on a local store, will give it a try.

It's the 47uH version with 3.1A and 0.085 ohms. With the 47uH it should give me more current availability if Rsense is also changed to 0.025 ohms.

[Scruffie]

The one thing i've yet to have issues with is any RFI noise injected from the SMPS, Nick does state that the efficiency drops with shielded inductors too, I think good layout is more important than specialist parts (others than those stated in the original) unless you do actually have a problem.

I'd think a lot of the noise issues you had with the mini JCM800 are from cramming 4 high gain stages in to a 1590B, although I don't know if going up to a 1590BB will have negated that too much as I did have to go with some long traces and miss out some proper tube layout techniques to do it all single sided and board mounted, but i'm holding out hope for good luck perhaps with just a bit of tweaking.

[thomasha]

I will give it a try and see how it turns out.

for now finished my small cab, this time with tolex.


A small orange amp would also be a nice donor amp for this builds, since it already has the tolex and grill cloath.
It's a shame that the small marshalls are made of plastic...

[HamSandwich]

That's amazing!

[thomasha]

Some updates...





still fighting some noise

[nzCdog]

Beautiful work

[ozzy666]

Awesome!!!

[thomasha]

[m-Kresol]

you're crazy, you know that? In a good way of course.

[Niquel]

Impressing Thomasha, as usual.
What kind of tubes did you use this time?
Cheers.

[Niquel]

I saw the answer in the other forum, tubes are 6111 and 6112. Very nice amp!
Cheers.