Ruby v1.2 noise elimination, performance Information
Hello diyAudio, I just joined yesterday, and having had a problem with the Runoffgroove.com Ruby amp had to sign up so that I might share some information that might help others experiencing the same problem. By the way, I love the Ruby amp, it really is a wonderful 1/2 watt practice amp when it works like it should. I can build a ruby (parts at hand) in under 5 minutes on a bread board, and, they always work great, full volume & gain with good clear sound. They are best when used with an actual guitar speaker, check out a Jensen MOD 8"-20 watt, 4 or 8 ohm (MOD-8-20) guitar speaker from Antique Electronic Supply, also known as Tubes and More. Well, I digressed, on the bread board worked great, when I would carefully transfer to perfboard, using a magnifying glass, checking each connection and checking for solder bridges and all pot and jack hookups being correct, the amp would squeal, and make all kinds of noise, if at all. I used the same parts that were on the brdbrd, how could this be. I took voltage readings of all the jfet pins, lm386, etc. on a brdbrd version that work good and those are: V+=8.94, D,1,=8.93/4, S,2,=1.64, G,3,0.0v, pins 1 & 8 (gain) on LM386 should be the same 1.33v, with pots turned down all the way, volume down also. pins 2, 3, & 4=0.0v, Pin 5=4.44v, Pin 6=8.93v(+v), Pin 7=4.46v and the speaker wire Positive(+)= 3.93+,-,variable, usually going down in volts. Readings on the Perfboard showed high volts 7-8+ on Gate pin, mostly the same as bread board on LM386 Pins 1-8. I started checking with Plus Probe, with ground clipped to circuit negative rail. I decided to check the actual circuit board it's self, on the Phenolic board material, and, near the edges there was no voltage reading, around the J-FET (MPF-102), there was voltage present, 8+v, where it should not have been. I cleaned the area with a tooth brush and HEET, ethyl alcohol, and scored fairly deep, not too, around all the pins, x & Y, and then tested the amp which now worked perfectly, pots worked when they did not, and was virtually silent as far as scratch, pops, etc.. full gain, full volume. Its most likely not your parts, my pots cost .50 cents. You can also use a 2N5457/8 or J201 J-FET in place of MPF-102. Check out Electrosmash's Ruby amp review, most informative. I'd like to thank All American Five Radio, most excellent electronics tutorials, and, John Audio Tech, both on YouTube, for the help they have been, still fairly new to electronics. Chip amp enthusiasts will learn a lot form John Audio Tech on proper grounding paths and other chip amp related information. Sorry if long winded, lots to tell. I'm happy to be a new member of diy Audio, and, I hope this information is of some help. Triple check your work, take your time, and dont be afraid to try and fail, I guarantee you will learn something from it. Be good. Cass, Oregon, USA.
