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#1 2009-08-08 22:25:00

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

I'm new, thi9s is my C64

Hi, I'm actually a Cynthcart user but this is the best forum I've found for C64 modding. I just wanted to share a few pictures of my modded breadbin.

http://secretagent036.googlepages.com/strap-scaled.jpg

At preset mods include:
2 pots (I don't think Cynthcart can use 4)
Grounded Audio Input
Reset button
Strap for keytar action
1/4" out
1/8" out
Paintjob /w racing stripe

At this point I don't think it's done and it still has a few issues but it's working pretty well. I've had this C64 since I was a kid and I love that I've found new life for it.

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#2 2009-08-08 23:02:31

deathstarchris
Nebulus
Registered: 2009-05-17
Posts: 64

Re: I'm new, thi9s is my C64

Very Cool.

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#3 2009-08-09 06:41:05

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

Tonight I installed a feed back knob. It seems to be wired correctly but it doesn't seem to do much.
What I did was wire a 500k pot between the audoIn and the audioOut. Mostly it just seems to control the amount of audio-IN noise I get. Not very feed backy. Now it's an older 1983 board, and I heard that these boards might not work the same with the feed back mod. Anyone know anything about this?

Last edited by agent036 (2009-08-09 06:52:41)

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#4 2009-08-10 17:28:05

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

This was excellent! It actually looks like a C64 keytar.. smile

I would also build an arm with some sound tweakable knobs and buttons on that one smile



About the loop back. I think the only way to reduce noise from the incoming port of the SID chip is to loop back the ground to the input.

You could do that by soldering a trs female to the output. In that way the output will be closed, that is, the ground is looped back, when no trs male is plugged to it. I do it this way, and it works superb.

/Daniel

Edit: Maybe I misunderstood what you were supposed to do...?

Last edited by D Vibe (2009-08-10 17:28:36)

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#5 2009-08-10 18:49:59

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

I had the input grounded to reduce noise, and that worked great. However I ungrounded it so I could hook it up the the output through a pot, which is how the feedback circuit is supposed to work I think (could be wrong). However I don't seem to get any feed back, just a knob that controls my input noise. Granted, it does that well, but that's not exactly what it was supposed to do.

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#6 2009-08-10 20:54:30

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

agent036 wrote:

I had the input grounded to reduce noise, and that worked great. However I ungrounded it so I could hook it up the the output through a pot, which is how the feedback circuit is supposed to work I think (could be wrong). However I don't seem to get any feed back, just a knob that controls my input noise. Granted, it does that well, but that's not exactly what it was supposed to do.

I found a page that might help you out..!

http://www.bigmech.com/misc/c64mods/feedbackloop.html

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#7 2009-08-10 20:59:12

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

I listened to the example sounds there.. Really cool. I have to make such feedback knob aswell! smile

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#8 2009-08-10 21:06:06

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Hmm! If I understand it right, it splits up the output signal in two, then feed one of them back to the input so it makes a feed back?

The knob is a simple attenuator that controls how much signal that should be fed to the input?

Seems simple to do such thing externally...

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#9 2009-08-10 21:26:12

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Btw, probably you've done all right, you just need to activate Mix In to get any noticable results..

I tried doing a feedback via my little behringer mixer, using aux send and aux return.. Works pretty alright, but since I hear both wet and dry signals in the mixer, I guess it isn't 100% effective..?

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#10 2009-08-10 22:13:33

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

I'm having a little trouble reading that diagram. My system is a simple Mono In/Out so I can ignore the bottom part, but the top looks like the In is routed straight to the Out AND the In is routed to the Out through a pot. This does not compute.

What I have is the In routed to the Out through a 500k pot. I think I did it right but I'm not getting much result. Can anyone double check me on this?

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#11 2009-08-11 11:34:08

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Uhm.. seems like at least the 8580 have some sort of feedback breaker since it stops the output if there's too much feedback.. anyone else experienced this?

Anyway.. all I get is squeeky sound since the resonance is self oscillating, not any crunchiness like the sound examples posted on the bigmech site...

Maybe I've misunderstood the whole thing?

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#12 2009-08-11 12:26:12

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Okay, I did misunderstand. You should have Mix In disabled when you're only out for crunchiness (and also some self oscillating when 100% is fed back), and Mix In enabled when you want a lot of self oscillating effects.. smile

I've done this with my mixer, and it works. The problem is that the mixer is also amplifying the signal, and not only attenuating it... therefore a simple passive potentiometer should work better...

/Daniel

Last edited by D Vibe (2009-08-11 12:26:33)

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#13 2009-08-11 12:28:36

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Are you sure you've soldered the pot right btw?

The first pin should have the output + to it, the second (middle) to the input, and the third to the ground...

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#14 2009-08-11 14:14:03

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

I'll double check my wiring, but I know I have is soldered with 1 leg to one and two to the other and none to ground. If ground needs to be involved then I screwed it up.

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#15 2009-08-11 17:21:02

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

AFAIK you need to have ground involved..

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#16 2009-08-11 21:43:27

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Okay, so I soldered an external feedback mod.. Works fine. Tomorrow I'm going to drill some holes in a box and install the trs's and the pot.. Maybe there will be some photo and some sound example smile

/Daniel

Last edited by D Vibe (2009-08-12 10:32:34)

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#17 2009-08-12 05:34:24

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

So I redid the connections and it seems to work better now. The effect is subtle but it's there. I was hoping for a much harder cruncher effect.

Also tonight I built a Amp/Mixer so I can mix my various crap together. I do all my music with portable devices (except the C64) and I wanted a little portable mixer/amp. So I built the Biscuit Box:

http://photos-h.ak.fbcdn.net/hphotos-ak-snc1/hs194.snc1/6560_1220629998842_1321702534_30619759_1629767_n.jpg

3 channels in, 2 channels out. All mono, though the "stereo" output will give you two channels (of the same thing). Has a volume put per channel plus a master volume, and the speaker can be cut in or out.

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#18 2009-08-12 10:32:01

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

Hah! That was one of the nicest mixers I've ever seen! Good work! big_smile

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#19 2009-08-12 11:19:34

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

agent036 wrote:

So I redid the connections and it seems to work better now. The effect is subtle but it's there. I was hoping for a much harder cruncher effect.

Yes.. With Mix In enabled you will get self oscillation, which means that the resonance will be louder.. With Mix In disabled however, you will get a crunchier effect..


/Daniel

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#20 2009-08-12 12:17:04

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

So I want an on/off switch along the line from the output to the feedback pot?

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#21 2009-08-12 15:05:49

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

No, I'm talking about switch off the mix in in software. I'm not sure if it's possible to do that in Cyntcart, but in P64/MSSIAH there's a switch in the synths where you can turn on and off mix in.. The SID chip seems to be affected even though you have turned mix in off in software.

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#22 2009-08-12 18:29:09

agent036
GI-Joe
Registered: 2009-08-08
Posts: 13

Re: I'm new, thi9s is my C64

Ahh. No, Cynthcart doesn't do that. It's pretty bare bones software but it fills my need. I want to try Prophet64 but my project budget is all spent right now.

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#23 2009-08-12 18:36:20

D Vibe
The Last Ninja
From: Sweden
Registered: 2007-02-03
Posts: 254
Website

Re: I'm new, thi9s is my C64

agent036 wrote:

Ahh. No, Cynthcart doesn't do that. It's pretty bare bones software but it fills my need. I want to try Prophet64 but my project budget is all spent right now.

Ah.. so probably Cynthcart is programmed that way that it always listens to the input port.. maybe you can hack your software? wink

I'm finished with my external feedback mod now. If I get time I can post some photos and sound examples tomorrow..  Right now I'm busy with my 6 months old son. Writing with one hand and holding him with my other one.. wink

Last edited by D Vibe (2009-08-12 18:36:44)

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