I've built a 12v Ruby amp and have been playing around with it over the last several weeks.  I've noticed at medium to high volume and gain settings that I'm getting some unwanted background noise and was hoping the wise folks here could help me identify the source.

When I strike a chord, it will first ring out clear and then as the chord decays I get this nasty crackling sound in the background along with dying chord.  I'm not sure if I'm just overloading the 386 chip and getting some crackly distortion (seems a little odd at only medium gain and volume settings) or if its possibly coming from a bad speaker connection?  I'm running the Ruby into a custom 2x8 speaker cab I built.  Maybe I need a better speaker cable to connect them with?

Any thoughts would be greatly appreciated.  Thanks.

I found the source of my hiss.  Turns out it was coming from my pedal chain.  One of my high gain pedals was the culprit.  I had my pedal chain hooked up to the Ruby in my initial tests.  The other night I plugged directly from the guitar to the Ruby and presto, silent as could be even at high gain!  I re-routed my power wires closer to the chassis and fiddled with my pedal chain and got things under control. 

The Ruby is sweet!  Love this thing.

Thanks all.

Thanks for the excellent suggestions.  I am running this at 12v with a regulated power supply.  I suppose all circuits will have some degree of hiss, but I'll give your suggestions a try and see what happens.  Thanks again.   :tu:

I just finished my ROG Ruby project and I am very impressed.  I've been running it thru different settings of the vol and gain pots, guitar pickup configurations, pedals in front of it, etc. trying to get a feel for the various sounds produced by the circuit.  So far so good.  I did notice that on high gain settings that I can hear a constant hiss thru my speaker cab.  Using the headphone output the hiss is noticeable even at low gain settings.  My headphone output has a Zoebel network per the GGG layout using a 47uf cap and 10R resistor (I read somewhere that this can help reduce hiss).  My 20 watt commercial SS amp also has constant hiss at high gain/volume settings and it drives me nuts!!!  I'm not sure if this is specific to SS or if the same is true with tube amps as well at high gain settings (I don't own a tube amp)?

Is it possible to completely eliminate hiss from an amplifier or am I doomed to live with hiss whenever I use high gain/volume settings?  Maybe you have to go hi-fi before hiss is noticeably reduced?  Any thoughts?

Thx

Happy holidays all.  First post here.  Great forum.  :tu:

I'm in the planning stages of my first 386 based amp.  I'm considering a bridged design like the ROG little gem mkII.  If I wanted to wire the output to a line out jack so I can use it with various speaker cabs, do I simply wire the positive output to the jack tip and the negative output to the ground sleeve?  The ROG schem shows the outputs directly wired to the speaker rather than to an output jack and I'm a little confused.

Would the same wiring go for a headphone jack?  I would imagine that I may need some way to attenuate the volume as described in the ROG FAQ (for non-bridged amps) so I don't go deaf from using headphones.  Any suggestions on how to do this with a bridged output?

Another question just came to mind.  If I wanted to build 2 different buffer/booster "preamp" sections with a switch to select between them, could I have them all running to a single 386 power amp section or would I have to have the switching system totally remove the unused buffer/boost section from the circuit.  For example, if I want to use the stock gem II buffer and one of the AMZ boosters as my two "preamps."  Can i set up a spdt switch at the input to select one of the two the preamps, but have them booth connected to the same point on the power amp (right after the .22 cap on the schematic found at the bottom of the page here http://runoffgroove.com/littlegem.html)?  Or would I have to use a dpdt switch to remove the unused buffer completely from the power amp?  Not sure if there would be problems with the signal flowing back up into the unused preamp section or not.  I'm still pretty green when it comes to this stuff.

Any advice from someone more experienced than myself would be greatly appreciated, thx.

I'm planning a 386 based amp and also was wondering how much louder the bridged 386 was compared to a single chip.  Which design would you guys recommend for maximum clean volume (ruby, gem, gem mkII, cricket, etc.).  I wouldn't mind a little overdrive at higher settings, but would like some good clean tones so I can test different effects, pickups, etc.  Also, any input on which design has the least amount of noise?  My current SS amp hisses and hums like no other.

Thx.