jackan Posted February 28, 2007 Report Share Posted February 28, 2007 Hi, guys. I have quite recently completed my 4x Midibox SID, but now I have started to notice all the noise it generates. It is only noticeable when not playing and it sound really "pointy" like a sawtooth wave. The noise can be reduced almost completly by setting the filter, and on some patches, for example "NT Bass" there is almost no noise at all. What I'm wondering is if the noise comes, internally, from the 6581:s or if something else might contribute to the problem? I have tried with different PSUs, without any luck. My filter capacitors are all 470p and all my chips sounds pretty much the same.I hope I have described the problem well enough and I really appreciate all the help I can get!Best Regards, Jack from Sweden. Quote Link to comment Share on other sites More sharing options...
pay_c Posted March 1, 2007 Report Share Posted March 1, 2007 Hi!First stuff first: CONGRATS to your working QuadSID! :DThe noise you describe indeed comes directly out of the SID and is pretty normal. The 6581s are a little bit noisier than the 8501s, but the noise is a little "bug" (if you want to call it so) of all SIDs. It´s very typical for C64 vintage synthi sounds and come in pretty handy even. If you *really* do not want this you could use e.g. a noise limiter.Greetz Quote Link to comment Share on other sites More sharing options...
Rio Posted March 1, 2007 Report Share Posted March 1, 2007 yes, only 6581 have this afterburner feature included ;D Quote Link to comment Share on other sites More sharing options...
jackan Posted March 6, 2007 Author Report Share Posted March 6, 2007 Okay, thank you for answering.So the 8580s are less noisy? I tried these newer chips when I started my designing, but as I rembermber they did not work very well. I changed the filter capacitors, voltage regulators and loaded the 8580-program. But (still as I remember) I could not get sound from some patches. Is there anything else I have to change when switching chips?By the way, someone said something about grounding audio in order to reduce noise? Ground in what way? Like shorting the pins?Regards, Jack of Sweden! Quote Link to comment Share on other sites More sharing options...
Wilba Posted March 6, 2007 Report Share Posted March 6, 2007 So the 8580s are less noisy?Yes.I tried these newer chips when I started my designing, but as I rembermber they did not work very well. I changed the filter capacitors, voltage regulators and loaded the 8580-program. But (still as I remember) I could not get sound from some patches. Is there anything else I have to change when switching chips?The different program just changes the way the filter is controlled. If you're not getting sound from some patches, this is probably a dead filter (i.e. one 8580 I had would stop making sound as soon as you start using the filter, even after you switch to a patch that doesn't use the filter) or could be just a dead oscillator.By the way, someone said something about grounding audio in order to reduce noise? Ground in what way? Like shorting the pins?That someone is me, I tend to say it a lot! Short the pins of J4 on the SID module. This is because the audio input is always routed to the output, through the filter or bypassing the filter, so if it's floating, it's amplifying noise! Quote Link to comment Share on other sites More sharing options...
jackan Posted April 17, 2007 Author Report Share Posted April 17, 2007 Hi again, folks. Now I have another problem with my SID!Sometimes when I switch it on the SID "stalls" and all the LEDs go bright, with no other signs of life..If I open it up and "play around" with the internal cables, the SID usually reboots and starts working. But it seems impossible to locate exactly where I have to touch in order to get it working. And sometimes I can just manually reboot the machine and everething will work fine (without touching anything else). This leads be to believe that its accutally not a bad cable or anything like that..Does anyone have a clue what might be the problem?I would really appreciate the help! Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 19, 2007 Report Share Posted April 19, 2007 Have you shorted the audio in's? That will reduce the noise significantly. Just make sure this is done with everything off Quote Link to comment Share on other sites More sharing options...
jackan Posted April 20, 2007 Author Report Share Posted April 20, 2007 Thank you for answering.I have shorted all J4. Unfortunately that did not reduce any noise. But I have learned to live with the noise :) My problem now is the stall thing... Quote Link to comment Share on other sites More sharing options...
Jaicen Posted April 20, 2007 Report Share Posted April 20, 2007 Have you shorted all the pins on J4? I'm not sure that's right, you only need to short the audio in pin of the SID to ground. Actually, you shouldn't short it, you should wire in a large cap (>1uF) to ground, because there's a DC offset on the Audio in pin, which can mess up the VCA if it's shorted to ground. Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 20, 2007 Report Share Posted April 20, 2007 I have tried with different PSUs,What are you using now? Quote Link to comment Share on other sites More sharing options...
jackan Posted April 20, 2007 Author Report Share Posted April 20, 2007 Jaicen: I have shorted the Audio-In on J4 to ground with a wire. I'll try using a cap, thanks for the tip!Altitude: Now I'm using and SMPS from an old scanner or something. I know it's not ideal, but since the noise dosen't really bother me anymore I'll stick to it. Unless you think that this can be related to the "stall problem"? Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 20, 2007 Report Share Posted April 20, 2007 My guess is that its power supply related. Are you sure that its a linear PSU and not a switcher? What is the max current and output rails for the PSU? A 4xsid will pull quite a bit off of the 5v rail and if there are not enough smoothing caps in the system, you could be getting ripple noise. How hot are your 5V regulators getting? They could be shutting down if they dont have heat sinks and you are running 12V directly to them and that would explain your freezing Quote Link to comment Share on other sites More sharing options...
jackan Posted April 20, 2007 Author Report Share Posted April 20, 2007 As I said, it IS a Switcher. I believe that it produces about 2A on the 5V, and something like 1A on the 12V. That should be enough, right?But as you say it might be voltage noise related... Too bad I don't have a scope.. I guess I could add a couple of caps on the 5V lines. 0,1uF? Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 20, 2007 Report Share Posted April 20, 2007 it IS a Switcher.There ya go then, there's the source of your noise :) Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 20, 2007 Report Share Posted April 20, 2007 As I said, it IS a Switcher. I believe that it produces about 2A on the 5V, and something like 1A on the 12V. That should be enough, right?But as you say it might be voltage noise related... Too bad I don't have a scope.. I guess I could add a couple of caps on the 5V lines. 0,1uF?Sorry, not familiar with the SMPS term, but yeah, thats the source for sure. I thought is was mentioned in the walk-through that you should use a linear supply, but i cant seem to find it anywhere. Unless you want to dive into the linear power supply happy fun design world I would look for a C64 psu Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 20, 2007 Report Share Posted April 20, 2007 the linear power supply happy fun design worldLMAO Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 21, 2007 Report Share Posted April 21, 2007 LMAOIt kinda become my quest to design an efficient one. I have a good step down design on the protoboard using a mosfet with a pair of caps that discharge in parallel but charge in series and it seems to be a very efficient system but it needs some tweaking since it is designed for 18V AC and I'll be using 12V AC for powering a 4 x 6581. Dissipating almost 10V before hitting a 5V regulator pulling over 500 mA and keeping everything from becoming a space heater is not trivial (at least for me) Quote Link to comment Share on other sites More sharing options...
stryd_one Posted April 21, 2007 Report Share Posted April 21, 2007 Dissipating almost 10V before hitting a 5V regulator pulling over 500 mA and keeping everything from becoming a space heater is not trivial (at least for me)Same here, I wouldn't know where to start! Don't get me wrong, I was laughing with you, not at you .... It's a deceptively complex subject for sure.... I just thought your choice of words was hilarious :D Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 21, 2007 Report Share Posted April 21, 2007 I was laughing with you, not at youI got it, ;DThis was a loooooong topic last year and hopefully I'll have something to contribute soon Quote Link to comment Share on other sites More sharing options...
napierzaza Posted April 23, 2007 Report Share Posted April 23, 2007 How easy is it to determine whether a PSU is switching or linear? Quote Link to comment Share on other sites More sharing options...
Jaicen Posted April 23, 2007 Report Share Posted April 23, 2007 Generally, if it's small and has transistors, it's switchine. Linear PSU's tend to be much larger with big-ass chunks of Iron. For example, virtually all cell-phone chargers will be switching PSU's. Quote Link to comment Share on other sites More sharing options...
jackan Posted April 23, 2007 Author Report Share Posted April 23, 2007 More trouble....I changed all the power wires (5V, 12V) in a desperate attempt to fix the freeze problem... And (of course) I accidentaly switched +5V and + 12V, now (after I switched back) all my SID does is lighting all the LEDs, and never start... :) Not a sound neither...Any ideas of what might have died when from running of 12V instead of 5?Regards, Jack. Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 23, 2007 Report Share Posted April 23, 2007 More trouble....I changed all the power wires (5V, 12V) in a desperate attempt to fix the freeze problem... And (of course) I accidentaly switched +5V and + 12V, now (after I switched back) all my SID does is lighting all the LEDs, and never start... :) Not a sound neither...Any ideas of what might have died when from running of 12V instead of 5?Regards, Jack.Thats a good question. The regulator should be OK to 35V (it will just get hot) so I suspect that the problem lies somewhere else. Check your supply voltages to the PIC while it is running Quote Link to comment Share on other sites More sharing options...
jackan Posted April 24, 2007 Author Report Share Posted April 24, 2007 I don't have any regulators :) I have wired directly from my PSU to all the COREs and the SIDs. Quote Link to comment Share on other sites More sharing options...
Altitude Posted April 24, 2007 Report Share Posted April 24, 2007 I don't have any regulators :) I have wired directly from my PSU to all the COREs and the SIDs.Um, that was a BAD idea. Chances are you can say bye bye to all your pics, they are not designed to take more than 5.5V. If your using a 6N138 Opto, then that could have been damaged also Quote Link to comment Share on other sites More sharing options...
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