Ruby Amp Static Noise

[joy0311]

Hello Everyone,

This is my second try at building a stompbox. The first one I built was a Trotsky Overdrive and damn it sounds great. 

Coming to recent events. I was trying my hand at making the ruby amp into a small and portable practice amp.
Now, here's the fun part. When I connect the Ruby's out to my guitar Amplifier I already own. It sounds Good. Some noise but i can live with that.
BUT, when i connect it to a speaker it gives out this horrible static buzz/fart/whatever you call it. Then again if i replace my guitar input with my MP3 player through a adapter. The songs come out pretty fine. I have tried all the basic fixes (like taking a 220uF cap from the positive to the negative) but to no avail.

Any advice/help will be appreciated. I'm also posting two phone recorded sound clips. One of the Ruby playing through my amp. and the second is of the horrible noise I'm talking about when connected to my speaker. Also, the speaker is 4 ohm, 10 watt.

Played Through Speaker: https://drive.google.com/file/d/0B1huE9NlE6zbNWlacGtUaXg0Yms/edit?usp=sharing
Played Through Amp: https://drive.google.com/file/d/0B1huE9NlE6zbTlRqRUpSZFFRM0E/edit?usp=sharing

[GibsonGM]

Wow, that sounds like crap.

Your amp sound seems kind of octave-like - interesting.

IDK why it would do that - can you get hold of an EIGHT ohm speaker and try that?  How about headphones? 

What are you using to power the Ruby?  It's almost like the power supply isn't stiff enough, so it could be sending the Ruby into oscillation (?)

A 2nd thought would be see what happens if you put a buffer in front of your guitar (thinking about what might be different from guitar to mp3 player).   Just ideas.

[joy0311]

It is doing the same thing on on my set of headphones (Albeit on one channel). And I don't have an eight ohm speaker. 

I'm using a 9 volt battery to power it up. Maybe the battery is dying, will have to check that.

Also, I don't have a buffer pedal.

Now, here's an interesting observation I made while tinkering around yesterday. If i connect the guitar line directly to the input (port 2) of the LM386. The weird frequency oscillation/fart/static noise vanishes, and I can hear my guitar. Of course, It sounds horrible like the 8bit soundtrack of a 90s video game. Maybe my 2N5457 is faulty. Will have to buy a new one to confirm.

[GibsonGM]

Ok, Duh - it's buffered by the FET, so that's not an issue.  (I didn't go review the schematic, should have).   Yes, you'll want a newish battery!  It would run even better on 12V, so try with a new 9.    I'd suspect the chip is junk before the FET would be.

When you test this with a spkr, are you keeping the Gain turned WAY down at first?   You really should be able to get at least a low-level cleanish sound, which will THEN go into fart-land as you turn up the gain and/or volume. Sometimes that's just cuz the speaker is junk and can't take much input (too much bass for it).    The fact it works with your amp tells me it's not oscillating at low settings (I'm sure you have it low when used with your amp, right?), but starts up when you turn it up, so it's feeding back somewhere.    Plug it into your amp, turn amp way down, and try to make it feedback with gain control to prove this.

Check the pinout of your FET, make SURE it's in there the right way!!    Lift the wiper of the 10k volume pot, and 'tap off' there to hear your signal.  It should sound Ok, and if so, you COULD have a wiring error around the 386.  Make sure all signal wires are routed well away from power wires and not crossing each other, too.

If all else fails, AFTER you have reviewed your wiring 100 times and you try the Ruby with a different speaker (which might be the problem, really),  add a .1u cap between pins 7 and 4  (+ and -)    add a .001u cap at the 386 input (between pin 2 to ground).  Final possible fix, replace the 100n cap on pin 7 with a higher value, like 1 or 10u in parallel with the one that's there....386s can be fickle and unstable - you can even try a DIFFERENT chip, and that may fix it!

I think you'll have better results if you try a different speaker, though, since it's working with your amp - but I mentioned an "octave sound", remember?  That could be oscillation that's just not front and center creating an overtone.