MBFM with crackling-noise issues

[Flemming]

Hi guys..

I finally built the MBFM, but my sound has a weird crackling feel to it.

Here is some examples -

First the initial patch 5 "Rhodes" which _almost_ sound correct.

patch 5.mp3

And here is patch 1 "Acoustic grand" which sounds pretty horrible (problem very audible here).

patch 1.mp3

(Patches uploaded using jsynthlib v0.20b, latest version)

I have the same result on all 4 outputs, and looking at the wavefile they seem to only go downwards.. very little soundmaterial is on the positive part of the axis.

I use a C64 PSU to deliver 5.18VDC (connected straight to IC3 - no vreg) to Core8 -> OPL3 - LED lights up fine. I use two 9V batteries to deliver -/+9VDC for the opamps. I measured 9.5VDC and -9.5VDC at pin 4 and 11 respectively on all 3 op-sockets, and no change in LED-brightness when batteries are connected.

I use a PIC18F4685 which is loaded with MIOS for PIC18F452 + the MBFMv1.1d app.

Despite my soundproblem I have full nice testtone on all 4 outputs, and i have checked all pins with the interconnection-test (i do have about 0.08V on pin A0 when it should be off, but i read in Wilba's "shorter-wire"-thread that this was not a problem to be concerned about??). Also my two interconnection-wires are pretty short (about 6-7cm.)

I have not connected any bankstick, LCD, DIN, DOUT or anything like that - it solely consists of OPL3-module and Core-module (which i strongly suspect to work just fine as it has been used to run 2 SIDs in a quad-SID box for a while). MIDI seems to work fine - i can upload apps at will, and i can upload a single patch to play around with until the thing is powercycled, returning to the standard patch. Sending note on/off also works flawless.

I resoldered the interconnection-wires and the 3 SMD chips to make sure they were ok, and it looked much nicer 2nd time, but it had no impact on the soundproblem. Also, i soldered a bit of a resistor lead to fix the "broken trace"-error on the OPL3 board.

I really hope someone inhere can help me out finding my error(s)??

[sparx]

I'd try a different supply. In particular one that supplies +/-12V, I was using a +/-5 and had something similair, switching to a different supply fixed it right away. It was as though the op-amps needed more "oomph" (technical term) to work properly.

[taximan]

Flemming,

I put the pix here for you of where I am at right now.

Regarding your mbfm...have you tried swearing a lot and kicking the dog? It might not get it working but you will feel a lot better...lol.

just keep at it Flemming you will get it working I'm sure.

cheers

Paul

PS I just realised the pix are shite....oh well

Edited March 8, 2010 by taximan