Hot Rod Ruby....almost there....oscillation problem...

[R.G.]

so even if the answer is amz, it sometimes still comes from geo. thanks rg.

No, not at all.

I have just been bitten by underdamped decoupling inductors a couple of times.   

[GibsonGM]

I've been bitten by oscillating 386's a couple of times      

Tell me, have you tried powering the amp and the booster off 2 different batteries yet?  Just using jumpers? That's one good way to 'diagnose' what is going on here.  Seems to me that they are coupled pretty closely and you're having tons of feedback.

[momo]

I am just about finished with shortening the pot wires to a minimum, will fire it up and will see...
I know this is so close to gold, I fire it up this afternoon and all was good, I was so happy, then I changed the battery as the one I was using was about 7 volts, then it started howling again...
My parents always say I must be patient.....
Its quite the workout right now, so close but then again, hanging at the edge of the cliff.
As soon as I finish the wireing I will try and power indipendently.
I don't get what you say about using jumpers..

[GibsonGM]

Jumpers....just that you can use wires with alligator clips on them to temporarily attach 2 different batteries, so it is an easy thing to do...

[momo]

Grrrrrrrr

I fired it up and got nothing, no noise at all, silence.
I went thru a continuity test and so now I see I have a short on the ruby, the other circuits are fine.
I do continuity on voltage and pin 3 and 4 connects to voltage, ground and input...
ggrrrrrrr

I am now taking a break, time for a few beers!

Its probably an angel hair, one freaking brand in a braided wire that decided it went for a walk.
lets see when I get the courage to get back on this..
Its great to know that all of you reading this have been there!
yep
drives me crazy, but i will make it work...soon......

[Seljer]

Yesterday I had a LM386 on the breadboard that was going crazy whenever I hooked up the speaker because I had skipped the zobel network. Mostly visible on the oscilloscope, but it was audible as well, as the superimposed high freq oscillation prematurely drove the output into clipping. Cleaned right up as soon as I added 100nF+10ohms onto the output.

[momo]

Got it!
Thanks GibsonGM...
The two battery trick did it.
I have to admit, even with the pot wires as short as they can be and at 90 degrees from everything else, its right on the edge or motor boating. I had some of that until I fiddled with placing the wires.
I just hope everything stays stable if I have to carry it around.
Only thing not working right now is the speed doubler switch on the tremolo, will get to that soon.
Other than that I'm very happy with the results.
I use 12v for the tremolo and Ruby and 9 volts for the booster.
The booster works with 12v but its not practical for me to have 2 12v supplies.
I will post sound clips soon enough..
It sounds surprisingly nice and fat, even with the 7inch(18cm) speaker, the cabinet is heavy and tight so it helps with the bass.
I like it best with my big muff , that really sounds fat, nice Santana sustain and whoosh!!..

[Lurco]

Yesterday I had a LM386 on the breadboard that was going crazy whenever I hooked up the speaker because I had skipped the zobel network. Mostly visible on the oscilloscope, but it was audible as well, as the superimposed high freq oscillation prematurely drove the output into clipping. Cleaned right up as soon as I added 100nF+10ohms onto the output.

http://www.diystompboxes.com/smfforum/index.php?topic=75530.msg615394#msg615394

[GibsonGM]

Very cool, momo!       Now, you could get a nice piece of Luan plywood (1/8" thick, etc).  Mount your boards on THAT, then attach the luan to the amp, and it will all be stable!   

The 2 power supplies are telling you something...maybe the answer is in the link Lurco posted above, maybe not.   Personally, I would try to make it all work off the 12V supply.   You can use what are called "Pi filters" between sections to decouple the PS from each board.       Your problem was likely junk circulating thru the power supply and acting just about like another input, causing oscillation.

The way I'd go about it would be slow (maybe someone already has the correct info for this?), because you'd need to experiment a bit.   
The power supply inputs to the most "current-heavy" board, where you have a capacitive input filter that feeds it.   From that point, you tap off, to the next board, where you feed a pi filter (C in parallel, R in series, C in parallel), and you could bring it to 9V that way.     

Just about every tube amp has this scheme going to isolate the preamp from the power amp.  You probably need to do the same!    It's the values I'm not sure of....10u to 100u caps/100R resistors??  At least for one stage, that would work, but you're dividing down the voltage....you'd need to set up how much voltage/current each thing needs.   At any rate, it's the 'power amp' that's causing the trouble, and I bet decoupling it properly from the other boards would go a long way.

Not sure if you mentioned - what are the specs of your 12V supply?  Is it a regulated wall wart, etc?    Some might say just use the 2 supplies, and that's cool too - just very curious about how you could actually FIX the issue, and use one supply. 

[momo]

Not sure if you mentioned - what are the specs of your 12V supply?  Is it a regulated wall wart, etc?    Some might say just use the 2 supplies, and that's cool too - just very curious about how you could actually FIX the issue, and use one supply. 

Hi, thanks for the tips, I will get more in detail on this one in the futur, but for now I am moving on to other stuff on the bench that is in progress. I am using 3 volt batteries that I had from my job, PL123A. They have good current and last longer than a 9v.
I use 4 for 12v and 3 for 9v obviously. I have no holder for them, I just tape them together and add a rubberband to put pressure.
Its way to funky in a pro setup, but for now its good to go with this amp!

[GibsonGM]

Ok, I was just wondering. Batteries are, of course, 'real DC' without ripple.  If you were using a transformer + rectifier or unregulated wall wart, that could've been adding to your troubles.    If you power this later with a power supply, make sure it's regulated, and isolate the different boards (esp the amp) from the other circuits!