From roberts@pharm.sunysb.edu Wed Feb 03 21:46:03 1999 Return-Path: by taz.hyperreal.org with SMTP; 3 Feb 1999 21:46:02 -0000 by pharm-1.pharm.sunysb.edu (Netscape Messaging Server 3.62) with ESMTP id 482 for ; Wed, 3 Feb 1999 16:45:49 -0500 Date: Wed, 03 Feb 1999 16:46:57 -0500 From: "roberts" MIME-Version: 1.0 Subject: [Fwd: |||||SH-101 owners Important info|||||] This is a multi-part message in MIME format. --------------4B91658F1BA974CF0A9D6DFC --------------4B91658F1BA974CF0A9D6DFC Content-Disposition: inline Return-Path: by pharm-1.pharm.sunysb.edu (Netscape Messaging Server 3.62) with ESMTP id 407 for ; Sun, 31 Jan 1999 11:29:23 -0500 by warhol.informatics.sunysb.edu (8.9.1/8.9.0) with ESMTP id LAA21711 for ; Sun, 31 Jan 1999 11:29:23 -0500 (EST) 31 Jan 99 11:29:22 -0500 for ; 31 Jan 99 11:29:18 -0500 31 Jan 99 11:29:15 -0500 by warhol.informatics.sunysb.edu (8.9.1/8.9.0) with ESMTP id LAA21704 for ; Sun, 31 Jan 1999 11:29:15 -0500 (EST) by hme0.smtp04.sprint.ca (8.8.8/8.8.8) with SMTP id LAA23897 for ; Sun, 31 Jan 1999 11:20:13 -0500 (EST) Date: Sun, 31 Jan 1999 12:27:07 +0000 From: Philip Organization: The Lab MIME-Version: 1.0 Subject: |||||SH-101 owners Important info||||| Hi all, I just spent 2hrs trying to figure out what was causing the 120Hz noise throughout the 101. I have noticed this for 6 years and knew it was a problem with 101's but never bothered to chase it down. I did notice that different wall warts from Roland seemed to be better or worse wrt causing more hum. In my investigation I tried different wall wart transformers as well as changing the various capacitors associated with the 101's internal DC rails. None of this killed the noise. When I started looking at the 101's dc switching power supply, I noticed the strong 120Hz on the +9V primary side. When I checked the wall wart's output it was flat with no 120Hz!! So I went on another wild goose chase trying to figure out if the circuit's switching frequency was some how causing the problem or if the 101's switching transformer was a great 60Hz receiver. It was not until I decided to use a high quality lab test-bench power supply by HP that I solved the problem!!! The noise immediately dissappeared. My findings are: - Wall wart transformers are all of varying quality. - Wall wart transformer's DC output quality varies when load and no load is applied. - SH-101's seem to bring out the worst in wall warts. - SH-101's are very suseptible to poor wall wart supplies. Solution: APPLY HEAVY CAPACITANCE TO THE DC SIDE OF A WALLWART FEEDING AN SH-101. 470uf.....mild improvement 1,000uf.....acceptable improvement 10,000uf.....equivalent to lab test bench supply You can mount the capacitor in the 101 or on the cable feeding the 101 from the wall wart transformer. Note the 101's center pin on it's DC jack is - while the sleeve is + Finally I experimented with the variable power supply and found the 101 to be quiet at 15Vdc in. 9V is much noisier. At 15V the 101 draws only 150mA. Hope this helps someone Philip -- Philip Pilgrim The Lab Audio Works 5 Evan's Drive - Analog/Digital Recording/Processing Hammonds Plains - Computer/Synth Interfacing Nova Scotia, Canada - Hardware/Software Development B4B 1M8 Phone +1.902.835.7844 Email mailto:thelab@sprint.ca Web Page: http://www.robotnik.com/the_lab --------------4B91658F1BA974CF0A9D6DFC--