This one ( Lil' Green Watter! ) seems to have both decent cleans, and decent overdrive (though not entirely clear if the overdrive near the end of the video is from an external FX pedal, or not).
The design uses one 12AU7A followed by a solid-state chip amp, a tiddly LM386 in this case. But that only does clean power amplification, so any chip amp of your choice should do the trick, class-D modules being the obvious choice these days.
I don't have a membership on that forum and can't see posted files, but it looks like the creator of that design uploaded them so they are available for all members.
-Gnobuddy
The design uses one 12AU7A followed by a solid-state chip amp, a tiddly LM386 in this case. But that only does clean power amplification, so any chip amp of your choice should do the trick, class-D modules being the obvious choice these days.
I don't have a membership on that forum and can't see posted files, but it looks like the creator of that design uploaded them so they are available for all members.
-Gnobuddy
I built a couple little palm sized amp using the LM386 and a 4" car speaker. A buddy used it to busk with for years. The chip does have a following among the lo fi crowd, I thought about using one in a distortion circuit but since I started listening to what others have been doing with SS devices I'll pass on the LN386.
Just pulled up the schematic to the little green thing. A TL702 feeding two cascaded 12AU7's running on 12V into another TL072 into the LM386.
Just pulled up the schematic to the little green thing. A TL702 feeding two cascaded 12AU7's running on 12V into another TL072 into the LM386.
12AU7 seems to run nicely on 12V, by all reports (if you can't find a 12U7). I'm sketching up a 18V (laptop powersupply) combo with one channel 12AU7 and the other a Run Off Groove "Thunderbird" feeding a chip amp & 5" speaker for a local "young'un" who wants those sort of sounds. (e.g. Dead Kennedys - power chords one moment, jangle the next)
Still to determine if I need a cab/sim (or Gnobuddy's "nastiness remover" ) to meet the brief!
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Depends on what you are looking for. Just to say there is a tube in there then it is ok. I tried the Valvecaster thing (think that was the earliest 12AU7 pedal build) and I not that appealing. Mind you I did not try to equalize it any more than a treble roll off control. 18V should be better, I think I tried it up to 45V, the maximum of my variable PS.
valvecaster - Google Search
valvecaster - Google Search
I saw that at the beginning of the video, but I'm not sure if that was still the case at the end.
I'm fighting off a cold, maybe I'm just being stupid. I'm not the sharpest tool in the shed right now.
-Gnobuddy
Anyone know if the "Lil' Green Watter" is based on Merlin Blencowe's low-voltage white-paper ( http://www.valvewizard.co.uk/Triodes_at_low_voltages_Blencowe.pdf )?
Blencowe's designs are the only ones I've seen that use opamps to drive valves operating at low anode voltages.
-Gnobuddy
Blencowe's designs are the only ones I've seen that use opamps to drive valves operating at low anode voltages.
-Gnobuddy
Thank you very much! (I hate signing up for an entire forum just to download one single file I might be interested in.)
The first triode has a 220k anode resistor, feeding a 250k pot, and a 100k grid bias resistor in parallel. That seems like a pretty heavy load for a stage with a such a large anode resistor.
The second triode stage is even stranger, with a 270 anode load feeding a 10k (!) tone pot. Yeah, there's a 100nF cap in series, but that is down to 1.6 kilo ohms reactance by 1 kHz, so it's not helping the loading situation much.
I know virtually nothing about valve circuits running on such low anode voltages, and the posted sound clips of this one do sound good. That said, maybe there is some room for improvement in the design.
This is the kind of circuit where I think ordinary discrete BJTs and JFETs may be perfectly good options for buffering, without having to use an entire op-amp each time.
-Gnobuddy
The reason the amp values seem odd is the person 'designing' the amp did not seem to have a full grasp of electronics, at least from what I gathered from the posts. Basically mismashed a few online diagrams together.
I would not have bothered signing up, I did a search for the amp and it came up with the link.
I would not have bothered signing up, I did a search for the amp and it came up with the link.
Yeah, I kinda got that feeling too. Still, it does seem to sound good...
I tried a Google search too, but "lil green watter", "lil green", and a few similar variations each produced 50,000 hits, none of which was even loosely related to what I was looking for.
It probably didn't help that "Watter" isn't even in the actual PDF file name, and Google was very keen to turn "Watter" into "water" for me!
-Gnobuddy
I have been doing a lot of Googling (thousands of hours) on a medical condition, by now to me it is like a puzzle trying to find stuff with Google. Lot of chaff out there to find a nugget. 50,000 hits my ***, after the first 2-3 pages you might as well be playing darts blindfolded.
Google's entire success was built on the accuracy and effectiveness of their page ranking system. It used to be vastly better than every other search engine that came before it (remember Altavista, Ask Jeeves, WebCrawler, etc?)
Current Google management would be incredibly stupid to allow that much-vaunted accuracy to slide. If Google starts returning nonsense results, someone will step in and fill the gap with a better search engine. I hope.
-Gnobuddy
Current Google management would be incredibly stupid to allow that much-vaunted accuracy to slide. If Google starts returning nonsense results, someone will step in and fill the gap with a better search engine. I hope.
-Gnobuddy
