Noisy shift registers

[zgba]

So I managed to run my Midibox without any major glitches. BUT... There's always something that makes me crazy. This time it's noise. Before I start to make some, I have to get rid of high frequency digital noise. I already found, that this noise are shift registers. Not the PSU (it hums nice and quiet, besides I tried couple of different ones). It always starts when I power up the Core module. I plugged out 8580-noise. 74HC595-no noise. What am I doing wrong? Maybe there's another 'solder on the bottom side' part I forgot to put in?

[cimo]

What am I doing wrong? Maybe there's another 'solder on the bottom side' part I forgot to put in?

have you placed the bypass caps on the bottom side? you can also try to solder a 100uF polarized cap at Vin in the DOUT module, but i can t guarantee it will stop the noise.

Simone

[zgba]

No, bypass caps are on the parts side. Does it really should make a huge difference? With a 100uF cap I can hear a little less high frequencies, but still too loud.

Edit: Even a 2200uF polarised cap doesn't do the job. It kills some high freqs, but not enough. How can I add an mp3 file?

[nILS]

When you write a post, there's an "Additional Options..." below the input field.

Adding random caps won't really help. You've got to add the right caps in the right place. Let's hear what your noise sounds like and we'll take it from there. Btw, attach a short .wav rather than a long mp3.

[zgba]

Here it goes:

SID CC Send.wav - Noise, than some more noise caused by CC sending.

SID (not really) Nice Lead.wav - 'Nice Lead' patch and of course some noise.

Noize.rar

Noize.rar

[nILS]

Dude. Something is seriously wrong with your setup. Remove all the hardware you don't absolutely need (DIN/DOUT...), noise still there? If so - do you have another sid to try?

[zgba]

I haven't made DIN/DOUT yet. My current setup is Core + SID and sometimes LCD. I have 2 cores (1 faulty, but caused comparable noise level) and 2 SIDs (8580 each). Tried both ones with similar results. With/without 8580 there's audible noise of shift registers. Testtone app - no noise. No shift registers - no noise (and anything ;) ). Is it possible, that my 74HC595s are hmm... not suitable?

[nILS]

I personally have never heard of such a case, but possible, well sure. Measure the voltages again, make sure everything is nice and neat. A photo of the whole thing + wiring could be helpful, too.

[zgba]

You don't want to see my wiring. It's a big mess. You know, I'm such a guy that won't go to the store when he needs a wire or a plug, 'cause it takes too long. I rather use anything I have spare. But, okay. I'll shoot a foto after I eat something. And then some shame.

Ok... Please, don't laugh too much:)

Edit:

My camera is dead, so I have to wait till the batteries get charged. More detailed photos tomorrow. Cheers.

[nILS]

That is *exactly* why I wanted to see the wiring. Try getting the audio cable out of the data/power lines. That might help a lot.

[zgba]

Guys... especially nILS... Please do laugh at me. Maybe I'll be smarter next time... 1. My audio connector salvaged from an old PC - i soldered a wire instead of using this old cable. 2. I had the recording volume cranked up with additional +20 dB boost turned on... That what we heard was distortion and boosted shift registers' noise... I'm so ashamed... But I had to confess. So now everything seems to be OK! Step 2: *BUY* some proper connectors and stuff core module with 2 SIDs:) Thanx for help:)

[lief138]

Hey Dude,

I think you did a great job, for whats worth. You ended up fixing the issue with help from the usual suspects.  I have had problems with just about every project I am up to but people around here help out alot. Specially if you listen to what they say.

I want to tell you to keep up the spirit of salvaging stuff. Give the old junk a new life. Your efforts will keep that stuff from poisoning the planet for a bit longer plus save you some loot.

Alot of people around here make such nice looking boxes, I hope that doesnt discourage the dude that makes ugly box out of someone elses trash that rocks just as hard...

I am still trying to take my own advice... Ill shut up now.

[zgba]

I feel godlike after a short jam session:D Now I can say it: if I had to spent like 10 more hours fixing it, I'd do it. And than again. There's no greater motivation to continue your work than audible results. About salvaging stuff: it's a great idea, but sometimes it's better to use brand new parts than search for bugs everywhere. Thanks Midibox SID project, hundreds of C64s were revived to live in synthesizers rather than to lie next to old pants in the closet. Making Midiboxes is probably the most pleasant way to save our planet. Love, peace, unison!

[arumblack]

I agrre with Lief, I try to salvage as much as i can. All the buttons, case, and many connectors used in my seq are salvage. Soon I will put up some pics.

Your work looks good, just needed to tidy up that wiring A bit. I know it is sometimes a pain during tetsing when you need to take stuff apart all the time. At least you have learned the lesson to keep audio away from noisy signal lines, and perhaps a good lesson in gain staging.

Anyway keep up the good work!

[zgba]

Thanks for all advices. Of course I'll put some pics when I modify something. First I have to make a proper chassis to keep the boards in place and wire them properly. My target config is a stereo SID and full CS. I think it will be the hardest part, as I plan to make the frontpanel on my own, and modify the C64 case (paint, fiberglass etc). So keep the fingers crossed:)