From: https://groups.google.com/forum/message/raw?msg=rec.music.synth/hG3OoGjE9nA/Ps0AIKRuY8gJ -- Path: gmdzi!unido!mcsun!uunet!samsung!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!ucbvax!edison.cho.ge.com!mfs From: m...@edison.cho.ge.com (Martan) Newsgroups: rec.music.synth Subject: MT32 Noise Modification Message-ID: <9008071957.AA19269@edison.CHO.GE.COM> Date: 7 Aug 90 19:57:02 GMT Sender: dae...@ucbvax.BERKELEY.EDU Reply-To: Martan Lines: 61 Posted: Tue Aug 7 20:57:02 1990 Noise Mod for MT32 ------------------ This mod should help those with 'noisy' MT-32's. As the amount of grundge seems to vary greatly from MT to MT, this may or may not make much of a difference on your unit. This is taken from the Burr Brown manual on the PCM54 (which is used in the baby D's and the MT) and from the D110 schematics. Luckily, there is no cutting of traces or desoldering of pins as the MT design is well suited to adding this mod. Be sure to use a good trimpot (like a Bournes or equivalent) and keep your leads nice and short. The D/A is on the left hand side of the board (assuming the front of the module is facing you) and is a standard 28 pin chip. Appropriately enough, the words Burr Brown are printed on the top :) Here is the stock wiring: --------- ! !-- Pin 1 (no connection) ! ! ! ! ! ! Pin 27 ! PCM54 !----------+ ! ! ! ! ! --- .1uf cap ! ! --- ! ! Pin 22 ! ! !----------+ ! ! ! --------- ! GND Add this: --------- Pin 1 470K ohm 100K trim pot ! !-----------------------RR--------------RRRRR-------+ ! ! ! ! ! ! ! R 470K ohm ! ! Pin 27 1 Meg ohm ! ! ! PCM54 !----------+---------------------RR-------- ! to Pin 28 ! ! ! ! (-v) ! ! --- .01uf cap ! ! --- ! ! Pin 22 ! ! !----------- ! ! ! --------- ! GND Don't expect a lot - the MT only has so-so samples anyhow and this can't cure that. But this should help the MT's that are equipped with marginal D/A's. Martin Sant Blue Ridge Music 3571 Sandstone Rd Ch'ville, VA 22901 m...@edison.cho.ge.com