Schrabikus Posted January 15, 2012 Report Posted January 15, 2012 (edited) Hello, friends! Can you please listen to attached mp3 and tell, is it normal, or something wrong? Noise remains when i disconnect LCD and CS from the core. So far i can not exclude PSU (it's one from dvd player +12v/-12v/+5v) but noise lasts about half a second after switching PSU off. Cable from core to OPL3 board is about 12cm, soldered directly to core. Thanks in advance. And the OPL3 +5v led lights with only J2 connected.MBFM_noise.mp3 Edited March 3, 2012 by Schrabikus Quote
Shuriken Posted January 15, 2012 Report Posted January 15, 2012 (edited) Although not easy, i would try a different PSU. The PSU is probably a switcher, which can cause noise if the switching frequency is low. Edited January 15, 2012 by Shuriken Quote
TK. Posted January 15, 2012 Report Posted January 15, 2012 It sounds like the noise is coming from the LED switching matrix, this could be the result of a certain coupling between the 5V and +/-12V voltage domain. Try the following: - ensure that the ground of the audio jacks + the OPL3 board is directly connected to the ground of the PSU (and not to the core module) - add 100 uF caps between ground an the -12V and +12V supply input of the MBHP_OPL3 module (take care for the polarity!) - if this still doesn't help, add 10 Ohm resistors in serial between the +12V and -12V output of your PSU and the appr. MBHP_OPL3 inputs, this helps to decouple the noise as well! Best Regards, Thorsten. Quote
Schrabikus Posted January 15, 2012 Author Report Posted January 15, 2012 (edited) Have no words to thank you, Thorsten!!! With 100 uf caps at OPL3 board the noise decreased by half (MBFM_noise_capacitors.mp3) Than i've changed 47 uf PSU caps with 200 uf and added 2x10 ohm resistor Aaaand the noise disappeared completely!!!!! (MBFM_noise_capacitors_resistors.mp3) :sorcerer: conclusion: switching PSU from dvd player can be used in audio apps!MBFM_noise_capacitors.mp3MBFM_noise_capacitors_resistors.mp3 Edited January 15, 2012 by Schrabikus Quote
Schrabikus Posted January 15, 2012 Author Report Posted January 15, 2012 I've removed additional caps from OPL3 board and voila!!! No noise at all! So increasing capacity of PSU output caps + adding 10 ohm resistors totally eliminates the noise. Quote
TK. Posted January 15, 2012 Report Posted January 15, 2012 Very cool! Great to know that this simple method works! :) Best Regards, Thorsten. Quote
mrspring Posted March 20, 2013 Report Posted March 20, 2013 (edited) I just had this problem, an idle noise in the background, using a TRACO TXL 035-1212D - a quite high end PSU for this application in fairness. Cured it totally by moving the sleeve of the audio outs to the - on the PSU rather then the one on the Core as i was doing previously.. No need for caps or whatnot, this is a total solution! Edited March 20, 2013 by mrspring Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.