From firstpr@ozemail.com.au Sun Nov 10 22:00:12 1996 11 Nov 96 01:00:05 +0500 11 Nov 96 00:59:43 +0500 Comments: Authenticated sender is 10 Nov 96 21:28:11 +0500 Comments: Authenticated sender is From: "Robin Whittle" Date: Mon, 11 Nov 1996 12:52:50 +0000 Subject: TR-808 Kick decay and tuning Here are two simple mods to the TR-808 kick circuit: 1 - Increased decay time - to the point of self oscillation ----------------------------------------------------------- Solder a 390k resistor in parallel with R164 (47k). This boosts the gain of the Twin-T feedback path. In the machines I have worked on, this provides enough extra gain for the circuit to self oscillate when the decay pot is nearly at its clockwise limit. If this does not get you oscillating, then try a 330k or less. The decay depends on how close to a gain of 1.0 the circuit is. Since there are a number of +/- 5% resistors in the circuit, some TR-808s have markedly longer or shorter decays than average. This mod is very simple once you find the resistor location - just solder it on the back of the PCB. There is no need to take the PCB off the front panel. 2 - Kick tuning --------------- This involves lifting the PCB from the front panel and removing or cutting a track to R165 (also a 47k). Replace it with a 100 k pot. I use a 100k log pot, and this gives fine control over the higher pitches at the anti-clockwise end of the range. - Robin . Robin Whittle . . http://www.ozemail.com.au/~firstpr firstpr@ozemail.com.au . . 11 Miller St. Heidelberg Heights 3081 Melbourne Australia . . Ph +61-3-9459-2889 Fax +61-3-9458-1736 . . Consumer advocacy in telecommunications, especially privacy . . . . First Principles - Research and expression - music, . . music industry, telecommunications . . human factors in technology adoption. . . . Real World Interfaces - Hardware and software, especially . . for music .