30% off all Honey Amp kits, check it out at https://store.ssguitar.com !
Started by joecool85, March 31, 2006, 01:20:51 PM
Quote from: RDV on April 01, 2006, 09:45:57 PM*Here's one I did design with some improvements*.
Quote from: teemuk on April 04, 2006, 04:42:18 PMQuote from: RDV on April 01, 2006, 09:45:57 PM*Here's one I did design with some improvements*. I do not wish to sound like i'm nagging, but isn't the gain of 22 quite high for the first stage regarding the fact that it has no gain control? Allthough guitar signal is usually around 20mV - 200mV, a humbucker pickup might give an output of even 2 volts. 2 x 22 = 44! Sounds like serious distortion to me. I know the circuit's benefit lays in it's simplicity but consider this option: Lower the resistance of either 4.7k or 100k resistor and connect it in series with a suitable potentiometer or trimmer to have a gain control. With it you should be able to get rid of any unintentional preamp distortion.I didn't too any calculations but the 100n capacitor in the gain set of the first stage seems rather small. There might be some issues in producing the full bandwidth. Then again, maybe not. As i said, i didn't do any calculations. As more practical additions, i'd leave PCB a place for a high frequency NFB capacitor in the second stage (in order to avoid any disappointments considering oscillation), add an RF filter in front of the first stage and protect the opamp inputs from static charges with diodes. These little additions only should lift the circuit into a way more "professional" and reliable level.The stages might also benefit from a mild diode clipping. In my opinion it's always a better option than driving the opamps to clip. (Unless you find an opamp with fast recovery or nice clipping characters of course). Connect diodes, leds or zeners in series to the feedback loop so that their voltage drop will go just below the opamp's voltage swing per rail. (Which unfortunately depends on the opamp model. 13V is a quite safe bet, 14V might be a good value too). The diodes could be made switchable for an "extra clean" output. An effect loop or reverb would be a nice addition also.