i have almost finished my new step C sid 1.7 project but i have a big problem
i have a strong background noise when i connect the control surface…
what can be the cause??
i have mounted the leds/buttons/encoder on the panel (no PCB) and i have connected all the grounds (for buttons / encoders/ led cathodes) with a single wire, without making a close loop, and with just one connection point to the DIN / DOUT module
what can you suggest to overcome this problem???
thanks!
Could you please record the noise with and without connected CS in a short .wav file, and attach it to this thread?
Best Regards, Thorsten.
the noise seems the sound of the current patch with a lower volume (i will record it…)
actually, i discovered soon after posting the last message that there are also other problems… and i was thinking about them this night! 
i think the main matter is the power supply
when i connect the LED (DOUT Modules), i observe a sudden decrease in the SID volume, coupled with an increase of th background noise. the DIN moudules does not have this behaviour.
moreover, the current regulators become very very hot.
i have a 16V, 1 A power supply and 3 voltage regulators: 12, 9, 5V connected in series (the 12 connected to the 9, the 9 to 5)
now i will use only SID 8581, so maybe i can take off the 12V regulator, but i will also have to change the power supply (16V are a lot for a 9 V regulator, i think)…
how much current draws a complete contorl surface with 100 leds (not all are lit…), 8 74H595 and 9 74H195 IC? is my power supply adquate or should i change the current regulators (i have the version with the attached metal heatsink, and i added an additional bigger cooler) with a more “powerful” one?!?
i will ask for a stabilized “big” power supply from a friend to make some test, but this will take a while… meanwhile, can you suggest me something??
i found that the 78S05 could be better for power supply, will ask to my local electronic shop. and i will search also for the 9V version…
thanks!
PS: erverthing else is working correctly… at least!
i have a 16V, 1 A power supply and 3 voltage regulators: 12, 9, 5V connected in series (the 12 connected to the 9, the 9 to 5)
I don’t know if this is the cause of your problems but for audio applications not a good design practice. Each VR that you add in series adds noise. You might want to get a second transformer for the 5V.
I don’t know if this is the cause of your problems but for audio applications not a good design practice. Each VR that you add in series adds noise. You might want to get a second transformer for the 5V.
I don’t think that this chaining can be the reason for the noise. I’m using this solution on my Der Brat, too, without problems. I don’t know if maybe 1 or 2 dB of s/n ratio is lost, but it definitely doesn’t add enough noise that anyone would complain about it.
S
also because everything works fine until i connect the DOUT moudule…
Getting a more powerful regulator won’t help because the ones you have now are max 1.5A and the PSU is only 1A… I think you’re going to need a new PSU 
That is assuming that there’s not a short somewhere of course…
How good are the connections to your filter capacitors?
Also, are the bypass caps mounted?
the noise seems the sound of the current patch with a lower volume (i will record it…)
This line seems to suggest a bad SID chip.
No idea why this only happens when the control surface is attached…
the 12v reg isn’t a 78L12, is it? that would explain the problem… fine for running a sid chip, not so fine for running a sid chip, a core and full control surface.
thanks for your help
the SID (chip and synth itself) worked well before the upgrade to step C contrl surface, so i can exclude chip malfunctions…
the fact that all the buttons/leds are working tells me that there should not be any shorts and that the connections are right…
from the fact that the SID decrease the volume when i connect the contron surface, i feel that the problem is really in the PSU or in the voltage regulator… i will wait for the test with the big stabilized power supply unit and we’ll see…
the SID (chip and synth itself) worked well before the upgrade to step C contrl surface, so i can exclude chip malfunctions…
That was then, this is now. It’s quite possible it got zapped while you worked on the box.
the fact that all the buttons/leds are working tells me that there should not be any shorts and that the connections are right…
I thought the same, but a multimeter will tell us with more certainty.
Good luck with the test PSU!
I DID IT!!! ;D
i mounted 2xSID 8580 so i could power the unit with a 12 V PSU 1A. (the old 6581 were OK, anyway!)
this save me to use the 7812 regulator.
now i have only a 7809 and a 7805 and everything works well. i think the 7805 was one i found in a cannibalized C64. don’t remember the history of the 7809 but the specs says it support 1.5A
(if i were using the old 16V power supply, the 7809 would become very hot!)
the weak part in the chain was the 12V regulator. now everything is fine!
the weak part in the chain was the 12V regulator. now everything is fine!
How can you be sure? It seems you changed three things at once (broke a ‘golden rule of troubleshooting’, see my signature ‘fix bugs’ link), you changed sid chips, and regulator, and PSU…
well, combining these three things worked!
the 8580 did not worked with the old PSU (16V, 1A) and the 7812, i had the same problems as i described. so it is not the SID type!
so it remains either the voltage regulator or the PSU… but since i could not change the 7812 with another one or use the 12V PSU with the 7812… it’s difficult to state which of the two was the cause…
but since the current supplied by the PSU is the same (1A) either with the new or with the old PSU, i thing the problem was indeed a current supply to the whole machine, and the 7812 was the main “current supplier” since all the other regulators were connected in series to it
according to me, the 7812 is, at this point, the only suspect for the murder… ;D
but now the SID is working!!
i have now 2x8580 SID 1.7303
the only matters that remains is that the filters for the two 8580 sounds very very different! (i don’t remember, but they are different releases). instead, the caps i used are the same for both chips.
i think i have to try different kinds of caps… or find another 8580!! ;D
