by fuzzy1 » Mon Dec 01, 2014 4:42 pm
Okay so ill try to keep it simple.
First of all the sustain problem is BIAS Issue! for this solution a 1n4148 diode and a 2n3904 transistor was used.
Step 1: That resistor connected to the collector, usually I see it on some schematics as a 100k or 10k resistor, replace it with a 10 trim pot!
Step 2: connect a 1Meg resistor directly from the 9V supply to the base of the transistor.
Step 3: Bias it.... this is tricky as fup! for my test from what I can remember when I done this the collector was about 200 mV above the base voltage.
A Volt meter isn't really necessary tho as you really will need to do this by ear.
Basically start at the highest resistance of the trim pot, play a chord and search for the sustain by varying the trim pot until you get a thick wall of dense sustain.
I went past this point loads of times trying to get it perfect, you will see what I mean if you try it, its a tiny point on the trimpots rotation.
A quick note, a 1n4148 wont really turn on till you hit 500mV so a 200mV potential difference between its two sides ( the collector and base ) means its not turned on fully.
Hope this helps im new to this fist post so dont know how to post a schematic will be happy to if any one wants one or such like.