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5678 sub mini projects?
Posted: 21 Dec 2011, 00:30
by RnFR
so i recently picked up 20 of these little guys up on ebay recently for cheap, but have been having a hard time finding projects for them. anybody know anything off hand, or what i should do to adapt other submini schematics?
Re: 5678 sub mini projects?
Posted: 21 Dec 2011, 01:00
by frequencycentral
Almost identical to 5672 which I've used a lot. I think the pinout is changed for a couple of pins. Probably microphonic due to the (spring) nature of the filament.
Easy way to power the filament is a LM317, without any resistors it will naturally give 1.25v. Or use a 220R 1 watt resistor instead.
I know some people have used 5672 to make Pentaboosts.
https://www.diystompboxes.com/smfforum/ ... #msg569387
https://www.diystompboxes.com/smfforum/ ... ic=70533.0
As for an amp, you could certainly cascade a few together for a preamp section, and also maybe run a few in parallel for an output section.
They're ugly lookin MF's though ain't they?
Re: 5678 sub mini projects?
Posted: 21 Dec 2011, 02:18
by RnFR

yeah, kinda ugly. i don't really care about that though. actually, i kind of like the looks of them. very "industrial".

i got 20 of them for something like 15$. many raytheons. i'll try and check out some of those 5672 projects. i was thinking something with some decent voltage, most likely a preamp. i could always use a different tube for output if i went for an amp. so, you think i'm going to have some problems with microphonics? thanks for the tips!
Re: 5678 sub mini projects?
Posted: 21 Dec 2011, 11:40
by RnFR
Rick- have you ever tried using that max1044 50v supply with an overdrive like the pentadriver/pentadriver turbo? is there a clip for the turbo mode? i havent been able to find one. or how about using these little pentodes as triodes?
Re: 5678 sub mini projects?
Posted: 21 Dec 2011, 14:16
by frequencycentral
An early version of what ended up as Murder One was 3 x 5672 cascaded @80v, so yeah, it's good.
I never did a clip for the turbo mod, higher voltage is the way to go really, the turbo mod was a bit fakey.
To make em into triodes connect grid 2 to the anode.
This is on the breadboard at the moment:
These are two DM160 indicator tubes
http://www.r-type.org/pdfs/dm160.pdf They're the smallest tubes I've ever seen! I'm cascading them into each other for overdrive. I'm running them from a 120v SMPS

. They flash in time with my strumming.

I was thinking of entering it into the competition's Dirt Catagory.

But they're microphonic as hell.
