MB6582 build. Issue with 12V 6581 sids chips

[dreamer]

So i am bussy building a MB6582 and i am this far to start testing sound. I build a MB6582 with 12V - 9V and 5V options. So that i can use all types of sid chips if i want.

The problem is when i'm using 12V 6581 sid chips. When a "note off" is played you will still keep hearing the last played note but a little less louder. I don't have this issue when i'm using 9V 6582 / 8580 sid chips. So i guess there is a problem somewhere in the 12V power line. Any ideas where to look?

Grtz

[latigid on]

As far as I know this the (in)famous VCA issue inherent to SIDs

[dreamer]

ah i just googled the issue.. hmm.

Is it possible to do something about it.. Dont think so right?

Grtz

[Hawkeye]

Hmm... could you post a demo recording (without audio compressor/noisegate! :-)) of the MBSID default/init patch? Just one short note on/note off event and the tone, that emits afterwards...

Normally, it should be silent enough to properly use a noisegate... :-)

Does it occur in all engines, did you test multiple 6581s?

Many greets,

Peter

 

 

[jjonas]

A few years ago I made a stereo noise gate (an MXR guitar pedal clone) to solve the same problem as you have with 6581s (if it is the VCA issue). Here's a forum thread about it with a link to a demonstration video.

 

Since then I've drawn a more compact design and had it made at OSHpark.The minimum order of three boards was $18,85. If you want the Eagle file I can send it. I could also just share the OSHpark project, but you need the Eagle file to know which resistor goes where etc., so you might just as well use the Eagle file to make your own order (if you're interested).

Here's the compact PCB for a stereo noise gate:

Edited January 23, 2016 by jjonas

[dreamer]

bassline-6581-sids

Above a soundlcip from the bassline engine running on 6581 12V sid chips. In this example you almost can't hear the vca problem. It's indeed low volume.

I also noticed that the 6581s get very hot.. This happens without anything covering the sids.. Almost so hot that you can't touch the outside.. 

 

Edited January 23, 2016 by dreamer

[Hawkeye]

Sounds good. Everything is normal, this is the character of the 6581s :-)! Recommendation: add a noisegate per sid pair and glue on some IC heatsinks and increase air circulation! :-) Jjonas' work is great!

(The 6581s can take some heat, but putting 4 or more of them in a MB6582 case causes more heat than in the original C64 case. The heatsinks help, if there is any kind of (passive or active) air circulation.)

Many greets!

Peter

[Shuriken]

Sounds fine to me. The 6581 get very hot. The 6582/8580 run cooler.

[dreamer]

There won't be 8 6581 is my build. I only want 1 channel the have the 6581s. They sound way more dirtier then the other sids. And i like that. But in case 1 dies. i got some spares 

But still we won't want that ofcourse. They are rare enough nowadays.

And JJonas.. any kits available?

Grtz

[Shuriken]

I have two here but they have different sound level so not usable. Anyway i have enough 8580 and 6582.

[jjonas]

19 hours ago, dreamer said:

And JJonas.. any kits available?

No, unfortunately, I just made this for my own use. The required parts can be found on tagboardeffects, where I got the stripboard schematic for the first gate I made; the parts have to be picked up from the stripboard schematic by hand though, there's no list there. But all the components are common enough, they should be easily available in one order from Reichelt, Musikding.de etc. Perhaps with the exception of a 500k log dual potentiometer, which I had to buy from a UK seller on eBay.