1W Punch / Chime Amp

[dwietzel]

I have been using the Chime amp PCB to build cigar box amps (see attached pictures) and everything has been going great.
I have one last issue that I am not sure how or if it can be resolved.
I have wired the power jack for guitar pedal 9V negative tip since a lot of players already have probably one of those.
With a input wire connected (for phone input or guitar) everything is clean and works beautifully.
In fact I connected two of these off of a stereo split cable and it sounded very good.
Now for the issue, when a cable is not connected I get a noticeable hum (I believe ground hum) but only using the guitar pedal power supply. On battery everything is quiet as well.
I have tried wall wart and my Voodoo Lab pedal board power supply and same issue.
Any one have some suggestions what may be the issue?

[GibsonGM]

If I'm understanding your problem correctly, you could use a grounding jack at the input, so that the input is grounded when nothing is plugged into it - this will kill any noise at the input...if you are trying to eliminate the hum, you might need to add additional power supply filtering.

If the wall wart(s) MADE for guitar effect use are humming, it might indicate something with your wall outlet (?) perhaps...so I'd check this with a different outlet just to satisfy myself that the outlet is wired correctly.   It depends on how MUCH hum we are talking about here...

[dwietzel]

At half volume it is barely noticeable. At 3/4 and full volume it is quite loud.
Also in trying different power supplies, the higher the amps provided the louder it gets (Voodoo labs, One Spot vs. Wall Wart).
All I have to do is touch the input jack with my finger and things go dead silent though.
Could you provide a link to a grounding jack?
Thanks!
Dave

[GibsonGM]

Hi Dave,

You get a '1/4" mono switched jack'.   There are 2 "prongs" inside it, that are touching each other when nothing is plugged in.   They are both connected to ground because the sleeve of the jack is, and this therefor grounds the input of the amp when nothing's plugged in.

When you plug in a cord, you see that the bigger 'prong' connects to the tip of your plug, which is where the signal enters from, and it springs away from a small tab or 'leaf', opening the ground connection to the tip.    You figure out (by diagram or continuity test w/meter) which terminal on the jack is this 'hot' one, and that goes to your amp input.   The one to the sleeve goes to ground....the one to the SWITCH tab will be grounded via this with no plug inserted (often the middle terminal).  That tab has nothing soldered to it.

You can test if this is working before you install it by sliding a guitar pick between the switch leaf and the tip 'prong'...no continuity to ground...remove pick, = continuity.

If you get a plastic, enclosed one, they will typically give you a diagram for which tab does what, or use your meter. As long as you don't get sleeve (ground) backwards with the switch leaf, you will be ok   

I'm about 99.99% sure Smallbear will have a mono switching jack!

[highwater]

If you want an open jack: http://www.smallbear-electronics.mybigcommerce.com/1-4-in-nc-tip-switchcraft-12a/

If you want a closed plastic jack: http://www.smallbear-electronics.mybigcommerce.com/1-4-in-mono-enclosed-nc-switchcraft-112ax/

[Domin]

Hi! Can somebody help me with one thing? I want to make this amp, but woth aux in so I can play along songs from phone and I want it to be in stereo, so I made something like "stereo" layout. What are your opinion? Im quite new into this...There are 2 inputs for aux which go straight into amp and 2 inputs which go thru buffers and i'll connect them together...

[iainpunk]

do you have a schematic instead of this layout? that's easier to read.
here's a simple simulator program that runs in the browser.
http://falstad.com/circuit/circuitjs.html

[mwelch55]

I built one of these about a year ago.  It's so quiet that I forget to turn it off.  Pretty good low powered amp.

This is not exactly the same, but close.

http://effectslayouts.blogspot.com/search?q=1+watt

[Domin]

Theres a schematic http://guitar-fx-layouts.42897.x6.nabble.com/file/n8493/Chime_Amp_Schm.png
Its not the same, with different Jfet cause I dont have J201...