Ruby Question - unwanted fizz/distortion

[captntasty]

I recently built a Ruby and I love this little thing... but.........  I hear this annoying distortion (apart from the natural overdrive which is great!) at the attack and then slowly rides the decay and dies out.  The best way I can describe it is as an additional distortion that is "next to" the main signal.  Also, sounds like a bad speaker, but I've checked it through numerous speakers and it's always there.  I've heard this type of very slight but annoying crackle/fizz/distortion on many effects and amps and it drives me insane, but I've never found any kind of answer.  I don't even know how to start debugging it...  I think I did read somewhere about an AC voltage leaking into the audio signal and creating some sort of unwanted noise. 

Any ideas?

[captntasty]

bump

Anybody?

[Boprikov]

Maybe your Ruby is oscillating? My Ruby starts to make strange sounds when battery (9V) gets weak. Does that un-normal distortion go away at lower volume levels?

[aron]

>I hear this annoying distortion (apart from the natural overdrive which is great!) at the attack and then slowly rides the decay and dies out.

My guess is it's either a mis-bias or oscillation like Boprikov says. It drives me crazy too when I get this.

[Quackzed]

i had this happen too (i think) sounds like 'hash/noise' thats noticable as the note starts to fade out... i used a 4 ohm speaker and i think that it was making the chip distort i changed it to an 8 ohm and it lessened, and then i used a different 8 ohm speaker and it was gone...
strange... tho i feel its probably what the little 386 chip is happy pushing... and it may be different for different chips.. you could try some different speakers and a fresh battery and see if it helps...
btw, i made a ' grace overdrive ' from rog and its doing the same ' hash / noise ' thing its a jfet-->lm386 circuit.
so i wonder if i can change something at the end of that circuit to make the 386 amp chip happier...

[narov]

Has anyone found a solution for this?
I am experiencing the same thing with one of my Ruby's.  It was working great, clean sound, no fizzy decay, and then inadvertently had power polarity get reversed.  Had to change the Fet, changed the LM386 chip as well.  Now the fizzy distortion is riding the normal signal.  It is powered from a bench power supply (with the proper polarity) at 9v or 12v with no difference.  Turning the volume lower just lets the fizz come through more.
I am using a Jenson Mod 6" at 4ohms, higher speaker impedances up to 16 ohm's don't seem to solve it, although it does lessen a little, but so does the overall volume.  Because of my screw up with the power supply polarity it appears I damaged some component, but can't figure out which one (short of replacing them all, which I'm about ready to do at this point).  Will the 5uf cap across the speaker out put fix this?

I also built a second Ruby and it doesn't have the fizz at all so I know the circuit can sound good.

Suggestions? Any help would be appreciated.

thanks,
CV

[casey]

i wanted to resurrect this old thread.  i have noticed the same thing when constructing any lm386 based overdrives, etc....

any solutions out there?

[chilecocula]

I have the same problem with a ruby based amp i built, but is only noticeable when it starts to overdrive.

[jefe]

I seem to remember having this same problem myself... and I also seem to remember another thread on this issue... maybe...

[grolschie]

Any solutions to this? I notice this too, esp when using the Ruby as a pedal. Thanks in advance. 

[grolschie]

Maybe if I swap from a LM386N-1 to a LM386N-3 or LM386N-4, this might help? If I use other FETs in the buffer, do I need to change anything? Thanks in advance.

[earthtonesaudio]

It was working great, clean sound, no fizzy decay, and then inadvertently had power polarity get reversed.  Had to change the Fet, changed the LM386 chip as well.  Now the fizzy distortion is riding the normal signal.  It is powered from a bench power supply (with the proper polarity) at 9v or 12v with no difference.  Turning the volume lower just lets the fizz come through more.

This points to a problem with electrolytic cap(s).


If that's not the problem, my other thought is that the ground is noisy.  Keep power/ground traces short and wide, keep leads short, keep signal away from power, etc, etc.  All the usual "lead dress" stuff.  Most of these designs have the (+) input connected to ground, so if it's not really ground, that could be the problem.

[grolschie]

I don't think I ever reversed the polarity of my Ruby circuits (one as an amp, the other tweaked and used as a pedal), but both have said crackle/fizz on the decay.

[grolschie]

Maybe if I swap from a LM386N-1 to a LM386N-3 or LM386N-4, this might help? If I use other FETs in the buffer, do I need to change anything? Thanks in advance.

No different with a LM386N-3. Sounds actually like what captntasty mentions in the first post. I am using the Ruby with a tone and volume control on the output as a pedal.

[snap]

the usual Boucherot or Zobel issue with no RC member attached to the output?

[grolschie]

It's got a 10ohm+47n Zobel before the output cap as shown in the latest Ruby schematic.  I see that somewhere that some people instead attach a Zobel to the gain section between pins 1 and 8 of the LM386 in some circuits.

Using the LM386 as a pedal instead of an amp is not going to have the load of a speaker - so I wonder if this is a factor?

This is interesting, especially the bottom diagram:
   http://www.wentztech.com/radio/Technical/Misc/lm386.html


Thanks.
grol