midibox_sid_v1_4_18f_stepBC

[TK.]

I must say that I haven't expected this quality from a 8580. At many websites you can read that the filter of the 8580 are worse compared to the 6581, so I didn't try to improve the sound until last week - the result is amazing.

No, the 6581 filter cannot be improved. They have a very warm, but sometimes also slushy (german: "matschig") and distorting sound. The cutoff frequency goes over the whole 11 bit range.

The 8580 filters have a limited range of only 9 bit (sometimes you will hear "clicks" when sweeping the values very slowly), but it sounds precise and strong. Also the signal/noise ratio is much better (less than -90 dB)

However, due to the different characteristics it makes sense to use both chips in a 4*SID box (like me :)) For example, the distorting lead sound from the mbsid_demo8.mp3 cannot be realized with a 8580..

Best Regards, Thorsten.

[TK.]

I just have uploaded a MP3 which compares the two filters on a very extreme situation: an evelope sweeps the frequency over the whole cutoff range. Btw: the sample is the absolute MP3 killer, a bitrate below 320 results into a lot of digital noise:

http://www.ucapps.de/midibox_sid/mbsid_v1_5_filter.mp3

1) 6581 with low-pass

2) 8580 with low-pass

3) 6581 with high-pass

4) 8580 with high-pass

Best Regards, Thorsten.

[d2k]

wow! both sound killa T :) they both have they're own sound for def - equally useful tho i think...;)

Nice...

Dan

[pay_c]

So I just will built the 4x6581 SID. Sounds dammit cool.

And then, in some time, I´ll just built an 4x8580 one!!!  ;D *HARHARHAR* DOUBLE SID POWER!!! (and much more less money then...  ;D)

[Stigmata]

Can´t wait to start build again!

To make things clear to me:Can I have two 6581 and two  8580 in the same box and use the C64 PSU??

Should I make the slave CORE with the PIC16F or the 18F or does it matters? (for the future).....

Thanks

Christoffer

[TK.]

Hi Christoffer,

yes, you can use the PSU either of the new or of the old C64 for the 6581 and the 8580 - both units deliver 5VDC and 9VAC (note that the additional 7809 shifts the voltage level to +5VDC+9VDC = 14VDC).

My own MIDIbox SID is stuffed with two 6581 and 8580 - in my oppinion the best combination :)

Currently it doesn't matter if you are using the PIC16F or PIC18F for the slave cores, but I'm not sure how long I can ensure the availability of the same features for both firmwares (yes, the next V1.5 release will be 1:1 compatible, although my effort for the implementation of the PIC16F adaption was about 4 times higher than for the original PIC18F solution!).

So, if you don't already own some old PIC16F, use PIC18F. The PIC18F provides also a much larger MIDI buffer which prevents stucking notes!

Best Regards, Thorsten.