Audio of (fried?) SID

[Steev]

Hi all,

I built a core and sid module.  Everything passed all the voltage checks and the LCD says the default lead patch is active (no bankstick yet).  I am using Smash's kits and the latest version of the MIOS.  The sid I am using is a 6581.  I understood going into it that there was going to be some noise with this kind of sid.  However, the noise is pretty overwhelming. 

I couldn't build the optimised PSU as the C64 PSU that I have was flawed.  From my reading, the second best option was to provide separate PSUs to the core and the sid, so that is what I did.  The sid has 15V 1A and the core has a separate 9V, 600ma.

I was wondering if anyone had an opinion on whether this was just a burnt-out sid or whether there is some other problem that I should be looking into.  My guess was that the audio path is messed up, but that is as far as I could take it.  ???

Only the background noise is heard up until 0:04. Then I played a series of rising and falling notes in MidiOX.  This ends at 0:10 (if you listen carefully you can hear it).  In the remaining portion, you can hear that when I move the "pitch bend lever" in MidiOX, the noise floor rises and falls accordingly. 

Thanks for any suggestions.

midiboxsidsample.mp3

midiboxsidsample.mp3

[/tilted/]

My completely useless suggestion is: attach a high-gain opamp to it, put it in an old Speak'n'spell and call it "aleatoric".

Or, try disabling the filter (the SID has this option, try the menus, sorry...) as the older chips often get/have bad filters.

[stryd_one]

Wow that's cooked.

"Aleatoric" hahahahah

[Peake]

Congratulations on discovering the hidden MIDIbox Bagpipe OS!

Seriously, I'm sorry and hope that it works out easily and quickly.

[Steev]

Haha - aleatoric  ;D  Maybe I will write a book on Aleatoric Projects for SID Chips.

Chapter 1 - The Dentist's Drill Replicator

Chapter 2 - The Washing Machine Emulator

Chapter 3 - The Ultimate Dog Repeller

...

Thanks everyone.

[/tilted/]

so steev, did you try disabling the filter?

also, did you try checking, re-checking, and re-re-checking your soldering?

are the core/sid on Smash/Mike boards, or homemade boards, or veroboard?

did you try using the testtone app? or the interconnection app?

what were the results?

[Steev]

First, thank you so much for asking!  It turns I am not sure what I am doing so it could have been me.  I haven't really gotten the hang of reading the diagrams and when I put the project down for a few days and come back, it is like starting all over again.  It's not easy being "green" ;D

I tried the interconnection app and I have MIDI connectivity.  The chip did respond to MIDI input so that's good.  I checked all the voltages and they were fine before I put in the chip.  But I may have shorted it when I plugged in the guitar cable to the audio jack.  The whole audio jack part was pretty fuzzy to me. 

Here's what I gathered from a couple of rounds of reading.  From the wiring diagram at

http://www.ucapps.de/mbhp/mbhp_sid_c64_psu.pdf

it looks like you wire SID jumper J3, pin "O", to the jack.  I have the Smash SID R3A board but it is not labeled "O" and "Vs" like in the PDF file.  Rather, the left pin is + and the right pin is -.  So I had to start making some assumptions.

In the wiring diagram it looks like the signal comes out of the "left" pin, O, and then another line is connected to the ground to complete the circuit.  So I guess the + and - on the SID board are not what I thought they were (i.e., run the connection from + to - like in a battery).  Rather it looks like the + and - on the SID board are to link up the signal to one side or other of the stereo field. I.e., + is "O" and - is "Vs".   

Also I don't really understand the jack either.  There is a diagram at

http://www.midibox.org/forum/index.php/topic,11434.msg90833.html#msg90833

for this kind of jack.  There it says that the ground is the "bottom right" pin. 

So in summary it looks like I take the SID jumper J3, pin "O" (which is on the left as I look at the board right side up) and wire it to the + pin on the audio jack.  Then, the ground of the audio jack needs to be wired back over to the Core's ground, or the SID board's ground.

If you happen to know if I am on the right track, that would be great.  At least I can start ruling some things out...  Thanks again for asking - with all the helpful Midiboxers maybe I will actually get sound someday. :)

[/tilted/]

It's not easy being "green" ;D

That's OK, my personal incompetance is matched only by my willingness to help!

Here's what I gathered from a couple of rounds of reading.  From the wiring diagram at

http://www.ucapps.de/mbhp/mbhp_sid_c64_psu.pdf

it looks like you wire SID jumper J3, pin "O", to the jack.  I have the Smash SID R3A board but it is not labeled "O" and "Vs" like in the PDF file.  Rather, the left pin is + and the right pin is -.  So I had to start making some assumptions.

Easy now, you want to be careful about those assumptions... you are correct, though.

"O" = "+"    ; "O" is short for output, and "+" is a naming convention where "+" is also "hot" or "signal"

"Vs" = "-"    ; "Vss" is an old electrical engineering term, it basically means the same as "0 volts" or "Ground". "-" belongs to the same naming convention as the "+" above, and also means "cold" or "return".

There are two (very simplistic) ways of looking at this.

One is to say that the two pins form a current loop pair, so both connections are required to create the loop, and to have a current flow.

Another is to say that the two pins for a voltage and reference pair, so both connections are needed; one as a "here is your signal relative to ground", the other as "here is that ground I just mentioned"

Neither of the above examples is more correct than the other, but they both show the same point:

- if you miss one connection, you either have no current flow, or you have no voltage reference point. net result: no sound.

So I guess the + and - on the SID board are not what I thought they were (i.e., run the connection from + to - like in a battery).  Rather it looks like the + and - on the SID board are to link up the signal to one side or other of the stereo field. I.e., + is "O" and - is "Vs".

OK, not a battery connection (good news is that you probably haven't destroyed your sid if you've done this...)

No, stereo field has no bearing here, the SID 3a board from SmashTV is a mono device.

Yes, "+" = "O" and "-" = "Vs".

So in summary it looks like I take the SID jumper J3, pin "O" (which is on the left as I look at the board right side up) and wire it to the + pin on the audio jack.  Then, the ground of the audio jack needs to be wired back over to the Core's ground, or the SID board's ground.

This is correct. Assuming you are using a 1/4" jack  (see also guitar jack, 'phone/phono plug', audio jack, jack plug, etc..), then you should wire it so the tip of the plug when inserted connects to "+" or "O", and the sleeve connects to "-" or "Vs".

Good luck!

[Steev]

Wow - this was perfect!! Even I could understand it.  All I can say is *thank you* for your perfect help ;D ;D ;D ;D.

Anyway, based on that I guess my suspicions on how I had wired up the audio jack were well founded.  I originally did not have the jack wired to the ground but to the other peg on that jumper.  Apparently, that is what was causing the massive amount of noise (actually, I think the noise floor is still there but the signal was very very low, hence the result.)  I am EXTREMELY pleased to share the first notes of my Midibox SID!  It's a bit like Christmas in June over here so I thought I would play something appropriate through the MIOS Studio keyboard.  Anyways, I am psyched!  /Tilted/, you are the BEST!!!  Another happy Midibox ending  ;D ;D ;D ;D

A very siddy Christmas.MP3

A very siddy Christmas.MP3

[/tilted/]

Good good news!

Glad it's working now.

enjoy! ;D