Ruby Doobie Bench Amp.... ROG Ruby with some COJONES

[pinkjimiphoton]

i gave my venerable ruby away recently... well, traded it, believe it or not, for a 100 watt kustom head. the guy didn't want it, and i wanted to
give him something for it. he really seemed to diggit.

so i was toiling in the dungeon earlier, dicking around and decided i'd build another.
sounded just like the first, but i was like... man... this thing just ain't loud enough, and needs some balls.

so i decided to try a cheezy little overdriver i'd worked up as a front end. wouldn't ya know it, it actually sounded pretty good!!
much louder, definitely marshally in a fuzzy kinda way... cleans up nice from the guitar. i like it pegged best, of course.
tested it with a bunch of transistors, it's sweetest with a lower gain, hfe somewhere around 175 (2n4401). i tried a bunch of transistors,
including of course some NPN ge's, but to my ear it sounded best with an mpsa6515 with a hfe around 415. you can go higher or lower of course, but that's what sockets are for.

also experimented with various diode clipping including led's, 914's 1n34/60's and finally settled on back to back 1n4001's. gave it more volume, and just the right amount of breakup. ge's sounded REALLY sweet, but ya lost a lot of balls. led's were louder, but ya kinda lose some of the distortion. combos were good, asym/sym etc etc. ge's and led's sounded really nice too.

there's a couple parts that could probably be lost from this, i'm presenting it as it was built... two separate boards, but this is the circuit that's between them.

if ya take a line from the node at volume 1 and the 47n blocking cap after the jfet, you can use it as a line out to drive another ruby

i tested it with an old 2x12 checkmate cab i had, 4 ohms. loud enough to piss off the girlfriend easily.

i used a 386N for the ic, i am probably wrong but if memory serves you can get almost a watt out of this particular 386.

i'd say socket and experiment with Q1 and d3-d6

i'd imagine a 500r gain pot may be better, but haven't played with it yet.

i'd reccomend making the 10r off the output a half watt resistor, maybe 1 watt. but that's probably just me.
should probably tie balls 1&2 together, but it seemed to sound better when pin 1 is left unconnected.

anyways, enough of my blather. this is presently built on two boards frankensteined together with my breadboard.
it's an easy build, not a lot of parts, and if ya always thought rubys were great little amps, but needed more balls, check it out.

first the obligatory horrible hand drawn schematic:



and a really rough pcb/perf kinda layout which could use some reworking and should definitely be smaller!!!



stupid pedal trick to come sometime soon... there's a backlog of them. be afraid....

anyways, check it out, if a brave soul ventures here have fun and let me know whatcha think!

[pinkjimiphoton]

http://www.futurlec.com/Linear/LM386N-1.shtml

[pinkjimiphoton]

and of course, the obligatory shitty vero layout

i'm'a'gonna build this up tomorrow morning as a gift for my bassist, it's his birthday. definitely something he can use in his studio.
so until then, it is not verified, but it should be tomorrow... i will report back. it matches what i had drawn up and what's on the two boards and my breadboard.

if you want a tone control, i'd reccomend adding a simple filter of your choice right around the node of the 47n cap and pin one of the volume.
that's kinda experimental. i didn't add it to this cuz i didn't think it was really worth it. this thing wants to grind and scream, so putting a muzzle on it seemed kinda counterintuitive

anywhos... here's the stripboard version. i ditched the first electro, the 47u cuz it seemed unnecessary.
also added a bright cap across the volume control, now labeled c6. this thing needed a little sparkle when turned down.
i tried various tone controls, but it lost that nice tubey edge...real responsive to the volume knob twiddles.
fairly hard to get a really "clean" sound. really easy to get a filthy one.
not surprisingly (seeing as how its me) it kinda reminds me of a fuzzface into a fender amp, fwiw

anyways.. babble babble it's 2:52 am and i gotta go to bed

[rutabaga bob]

For a person that just wants grit and grind, the MarshaRuby works pretty well...a Ruby amp with a slightly different front end, uses an NTE458.

Nice job, as usual, Jimi!  Of course, we're all waiting for the SPT...   

[pinkjimiphoton]

dude...

larry, the whole thing with mine is LOUD. it's the nigel tufnel of single 386 amps
SPT soon

[pinkjimiphoton]

but wait, the man said, there's more.....!!!!

yeah. BURRRRRRRRRP.

here's a slight return. no idea if it will fly but i imagine it should, as it's basically what is on my bench right now. i re-added the 47u cap for the overdrive part, and decoupled it with a small resistance... and re-arranged the way it connected so that the amp part gets more filtering and the preamp less... but it's after the amps filtering, so it should work. also moved a couple parts around some to accomodate the circuit changes.
gonna try and build this beotch up now.

check it out if ya feel brave only. i gotta build it up as drawn first.



no idea who the dead young lady is or was. just did a google search for PD b&w's tagged ruby and she came up.  so i figured hey mannnnn
it's like, karmaaaa or somethin dewwwwwwwwd



stay tuned.. off to my dungeon

[pinkjimiphoton]

made the usual couple mistakes.
very weird.
it works on my breadboard with the two circuits plugged into each other, but once i put it on one board... bizzarro land.

don't mess with this yet. stay tuned....

[pinkjimiphoton]

so far, at this point, i have it working from the bottom pin of the jfet to the output of the chip.
but from the input to the fet, everything is dead.
tried a couple different FETS, same deal. q's as well. voltages on the q seemed reasonable, jfet and chip too.

so i started working around with seeing what may have made it break down. i removed the 47u cap and 10r coupling resistor and hard wired the b+ to one rail for everything. voltages went up slightly. also removed the diode clippers by lifting the signal side of them. same thing. nothing.

lifting the output side of the overdrive part's output cap i get no signal either. i've desoldered the resistors on the original that i had guessed at (the glaucoma makes it kinda hard to read the codes on 1/4watt resistors) and they were on point.
i had thought maybe i mistook the 3.3k c resistor of the first stage for a 33k... hey, it happens... but nope, it's the right value and is passing voltage.

i'm thinking at this point i may have an open pot somewhere,  the "gain" and "volume" pots on the chip work correctly. but the bias pot for q1 isn't doing anything... making me suspect the pot, or one of the wires i used is open. that happens too sometimes.

i'm using a bastard son version of an audio probe, as this is an amp not a pedal... i've got roach clips connected to ground and tip on a guitar cord, and the wire from the tip i have a piece of cut off lead clamped by the other side's roach clip. strum the guitar, touch to different nodes working from the amp backwards (opposite of how ya use a normal audio probe) and that's where i figured out the signal was dieing.

also wondering if it's cuz i used a shit grade vero from tayda. seems like the plastic substrate melts kinda easy and may be contaminating the connections.

also thinking the problem may be with the power supply being on the same board. when it's TWO boards, they are effectively decoupled by the caps completely.. they only share the line connection between the boards, and each individual power supply is decoupled by it's own electro.

i'm thinking this may be the problem as well... something is shorting something where it doesn't seem it should, and coupling thru the common ground. with the breadboard, tho they share the same power supply and ground rails, they are decoupled by the output cap of the od stage and the two individual power supplies.

i'd thought that they should be able to share the same power supply and i think i'm wrong about that. it may be layout too. i dunno. but getting closer. i really wanna make this suckah work, cuz i think some of you guys may have fun with it.
it's LOUD. running it into my venerable tucknroll checkmate cab with 2x12s (@ "10 ohms") it literally screams, and is almost loud enough to keep up with a dynamic enough drummer.

there's gotta be a way to pull this off. suggestions gratefully considered and welcome.

back to my dungeon. gonna make this sumbitch work!!!!

[duck_arse]

people generally say the LM386 will behave best if: it gets the full supply voltage available, so it's supply pin connects BEFORE the 100R supply filter; and the supply decouple cap for the amp chip itself mounts RIGHT AT THE SUPPLY PIN, right at, not close to; and the amp chip supply cap is as big as you like to use. and then, the supply filter R//C for the rest of the circuit will isolate them some frum the silly stuff the 386 might get up to.

those general people say that the chip might oscillate and not do any audio, even if you can't hear it oscillating, unless you take the decouple precautions.

[all this from the collected readings, I have very limited expeirence w/ the 386, but have not had any problems with.]

[pinkjimiphoton]

wow, thanks stephen,
this thing has been driving me nuts. i will try doing that too. on the breadboard, there is no ps filtering for the 386, so i bet ya that's what's going on. i think it's too current hungry.

i think i'm gonna try a layout where the two circuits are separated, but share a power and ground rail only between them and will try to take your advice to heart on this. i am pretty much certain at this point it has something to do with the power supply letting something happen that i didn't expect.

i'll get on it after i go shovel snow for a couple more hours

[duck_arse]

you can bring yer shovel round here, but there's not much snow at the mo, let me tell yah.

[pinkjimiphoton]

dude i hates sner!!
we godda foot and a half the other day, more today. more coming. hell done frozed over again. seems to happen every 4-8 years.

anyways, i didn't get back to my bench yet. too damn tarred.  but i did whip this up in my sleep or something. ambien state. walking betwixt realities and dimensions and trite shit like that.
here's the same thing as before, but laid out completely different. if need be i can separate the whole mess into two separate circuits.

top half is my overdriver. bottom half the ruby. betwixt them is a couple power rails and one common ground. we'll see if it flies this time.

i mean, it works on the damn breadboard..... so,,,,,,,





balls and volume 10k linear
gain 1k linear

[pinkjimiphoton]

well i @#$%ed up again
that said, i DID get it working...
kinda.
had to ditch the diode clipper. switched it to a single 1n914. done.
changed a couple cap sizes...input from 470n to 100n, output of overdrive from 680n to 470n.
ditched the treble bleed cap.
also ditched the buffer. it just plain would not work with it in it. so i ditched the 1.5m resistor to ground, and ultimately the jfet too.
no idea why the hell it worked with my breadboard, with the od and ruby connected by my breadboard with that massive ass diode clipper.

i still gotta @#$% with it some, but it's now working and sounds pretty good. lotta balls. it will self oscillate easily when everything is cranked full, but it's LOUD.

anyways... here's a vero (adapted from the one already posted ) with a schematic, a rework of the old one. hey, it's 2:27, i shoveled snow all day and hippay is tired.

but anyways.. it's not really a ruby per se anymore. but here it is, have at it if you dare....

[anotherjim]

I wonder if the "Balls" now "Bias" is drawn as you had it on BB? Being able to turn the emitter to 0v would seem odd - either the pot end don't go to 0v or order of pot & 3k9 resistor are swapped maybe?

[pinkjimiphoton]

I wonder if the "Balls" now "Bias" is drawn as you had it on BB? Being able to turn the emitter to 0v would seem odd - either the pot end don't go to 0v or order of pot & 3k9 resistor are swapped maybe?

the emitter has an e resistor i changed from the original 18r to 100r hoping for a little more stability. it could be bypassed with a cap for more gain.

the bias can be done as either a variable resistor or a pot. i'm still playing with that. the 3.9k is coming off the b+ rail, and the output of it goes to the pot. frankly, wiring that pot can go any number of ways. the basic idea was to keep the pot from being able to short the power supply, there's always a bit of resistance as the pot is turned off. yeah, it is as it was on the breadboard.

i found the diode clipper was killing everything. normally ya want the clipper before the output cap. the original circuit had nothing but that solitary 4739. i had a normal clipper made from them but it didn't sound as good as the single one so i ditched it long ago.

i tried re-arranging the clipper and cap to a more normal config, and it worked, but sounded absolutely horrible,

again, the biggest issue was i couldn't get the fet to function. on the ruby schematic, it's just a buffer really with a gain slightly less than unity.

with it left in place i got a barely audible output. i decided screw it and just ditched it. tried it without the 3.9k resistor to ground between the output cap of the clipper and the input cap of the chip. it definitely sounded better there and seemed to have a better tone than just using the single coupling cap.

a resistance into a cap is a lo pass filter, a cap into a resistance is a hi pass filter so i guess it's doing a little of both.
i don't understand all this stuff fully enough to ellucidate on why it works or doesn't.

just a monkey with a breadboard jim

i think i just figured out what you meant. yeah, the pot can go to a short between input and output. but the 3.9k resistance is always in series with it from the battery supply. if i put the resistor on the other end of the pot, the lowest it could go would be the same thing, but the pot could get smoked... i've done it. not smoking pot, per se...(yeah.... right) but putting a battery right into a pot can definitely kill it. the way i have it, you can turn the pot down all the way and just kill the whole thing, or you can turn it "up" to the max it's set at. it's almost like having a 15k pot instead of 10.
i think when i did it originally, it was just to set the range of the biasing more than anything else. i wanted it to work with the crap i had on hand.
monkey again, ya know?

originally, this overdrive was an input cap, an output cap, the e tied to ground and a 100k pot on the c. input to the b. it's evolved just slightly but i've been seeing how much mileage i can get from it. 

[anotherjim]

Yer right -  the pot can't go at the B+ end.
carry on...

[pinkjimiphoton]

still workin' on it. got two of them going on different boards.
can be kinda prone to oscillation if not careful, so trying to work out the best ways to prevent that.
will work up a new schem first once i get done, then work up a vero.
it's gotta lotta balls at this point. one has a line out so you can use it to overdrive another amp, or in parallel with another amp.
went back to a voltage divider on the bias. been back and forth on which way i want to be 10.
also added a resistor or two for stability.
gonna box one up and see how it goes.

stay tuned..... yeah, like THIS is exciting

[pinkjimiphoton]

ok, no stupid pedal trick yet. i hope to do a quick one before this goes off to foppelicious tonite.

i got it running. i added a couple small resistors here and there to limit the gain so no more spurious<<< i love that word

oscillations.

also added a cheezy line out that sounds half way decent plugged into anything reverb

changed a couple cap values. less motorboat. swapping out the 100u cap for a 220u may not be a bad idea.

it's pretty stable now.

also made the bias a 50k. you can go from quasi clean to starved and sputtery with it.

i'd start with the gain control off and the volume about half. bias somewhere around 30-40%.

want clarity of tone with your guitar cranked up?
FUHGEDDABOUDDIT. not gonna happen. this thing wants to grind.

but turn your guitar down and it cleans up just like an amp should. an amp with a GOOD fuzz in front of it.
kinda brassy clean tones that cut well. very responsive to volume and tone twiddles from the guitar.

different q's will give different tones. you can plug damn near anything npn in there. ge's sound very sweet as well and may end up on a switch in mine.
like brutal nasty tones? reverse beta the transistor. some will work, some won't, but you can get some ridiculous distortion happening that way.

i tend to like the bias where it sounds sweetest with a hint of breakup and the gain and volume pegged.
running the line out to my princeton reverb sounded pretty amazing. other than the reverb, i couldn't really tell which amp was which, which was an amazing phenomenon for me.

my bud dave tried it . on 11, of course. he seemed to diggit. he's a strat and a tube amp guy and he kept going. for hours it seemed like.
i put a vibe in front of it and it was even cooler.

ANYWAYZZZ

here's some pics and a quasi refitted layout. as shown it should work, tho it could most definitely be made considerably smaller for sure.

[pinkjimiphoton]

as promised. one stupid pedal trick. complete with modulation pedal failure. live. enforced recreation. live, off stage....

[pinkjimiphoton]

egads...
shucked a couple clams on the last layout dealio.

this one should be better
thanks rutabaga bob for noticing my @#$%ups

had a gig last nite, so just got a chance to fix this up
here ya go. haves at it.
where it says 100-220r resistor you can go anywhere ya want, it's just there to snub a little gain so it doesn't go into oscillation on ya.
keep your leads short. shielded cable to pots jacks is a good idea. i didn't bother. kept the leads short, and tend to solder 'em right to the node itself with other stuff with gain pots. just seems to work better for me than using long sections of track.