i found this nice community and i would kindly ask for help/advice. In case i'm here at wrong place with my qustion then sory and feel free to delete my post or
move it to proper section.

I have for years (probably 15 years) 8 6582A chips. I bought them with intention to build Wilba 6582A midibox SID synth -  but it never happened.

I decided to sell tem - mainly because it's a pity they are unused, and they may serve well to somebody. I almost dit, but weirdo who wanted to buy was not able for 3 weeks to get them at the post so i asked for returning them (which is not important for my question but just want to draw complere story)

Now, after all that, i decided i give a shot to them an try them. So i quickly finished my single chip test-board with midibox SID and tried all chips in it. At first round everything looked OK, they all were playing, all
parameters pf synth engine (oscillator types, modulations, everything just fine)

But then i notices strange thing - the resonnance on filter was almost none. Even with maximum setting, resonance is very subtle, almost not noticeable.

This surprised me a lot, because i readed that 6582A chips (9V ones) should aound exactly like 8580R5, and from demos on YT i heard noticeable resonance on filter in many demos.

So now i'm not sure - may it be that my chips are fakes ? Almost everything (at least to my ears) sounds OK, just that almost no-resonnance (on otherwise fully functional filter) is boggling me.

Is there anything i can do to sure that those chips are no fakes ? Because i don't want to sell
something which is not 100% ok :-((

Here i recorded some random
loop with some tweaking - in some parts i was tweaking resonance of filter to max but as you can hear it's almost no noticeable... … A.wav?dl=0

and here are photos of my chips from both sides … NxVGa?dl=0

Thanks for any advice !


To be the bearer of bad news, they are indeed almost certainly fake or at least remarked. As documented by Kevtris back in 2008, that specific date code was known to be sold by the same seller that sold him fakes. It's otherwise a good read on the topic. If you wipe the chip with acetone, the top layer will likely come off and reveal a 6581 chip. The "fakes" are not actually fake, but rebranded SID chips that are real but defective. Typically it's the filter that goes while the oscillators are still working.

I'm kind of torn on the issue morally speaking. Imo, it would be a waste of rare SID chips to throw away something that's almost working. Individually testing them and selling them with an honest description of any defects might be an option, but on the other hand that wouldn't stop the next person from passing them on as 100% working and making a big profit. Using them in a personal project might be an option instead, or maybe contacting Look Mum No Computer and suggest the idea of a mega SID machine consisting of only fake SIDs.


hm rebranded 6581 - that would make sense because as i know resonance on 6581 filter is almost none... except of resonance i really didn't found any other issue, and as you can hear in example i attached, they are basically sounding not bad.. basic filters (cutoff) works very nice, it's just that damn resonance what doesn't work

will try acetone ;-)

but in case they are actually 6581 - how it is possible
they're working powered by just 9 Volts ? 6581 needs 12 Volts, only 8580/6582A have lower voltage... I have 9V stabiliser in my test midibox board, and they're working just fine

Or it is that even 6581 can work at 9V, just they are less stable or something like that ?

Anyway if they are really just rebranded 6581´s, that's ok - some people even like more 6581 because of more raw oldschool sound :-) Will think what to do next, for sure this is good information for potential buyer...

Thanks for all advices !

Last edited by dendy (Oct 10, 2020 8:01 pm)


Like I said though, they are almost always defective in some way, mostly the filter. So keep that in mind.


hm at least printing looks like it is original, definitely not rebranded, tried acetone and nothing ...

i will probably simply rexord various sound examples, so potential buyer can decide if it is interesting for him... with additional info about source and not working resonance.. i think that would be fair

Last edited by dendy (Oct 11, 2020 6:10 am)


ok, now it all ended with totally umexpected result :-))

I ordered ARMSID chip - just to be 100% sure that my test midibox sid, which i used for testing those chips, is 100% ok.

Now, it turned out that with ARMSID sound is almost exactly same (just a bit less noise but that is normal) than all my 6582A chips !!!! Looks like they are all actually 100% ok and original, all features which i tested are workimg exactly same on them like they are working on ARMSID chip (including almost no resonance on filter)

I think this is very important, looks like this serie of chips (at least mine 8 pieces), even through they originates from seller with history of some fake chips, they are genuime and totally OK !!

I'm really glad that it is just some bug in my test board, not it those chips...

Last edited by dendy (Oct 15, 2020 10:47 am)

Bratislava, Slovakia

i have Commodore 64G, which have SID chip 8580R5, it works fine, maybe in the future i will add second via sidfx, but i really don't know which one, 8580R5 have pretty good resonance (when i change on-the-fly resonance in defMON from 0-F it is hearable change, but when is filter totally opened, i like to have no resonance), but 6581 have more raw sound, i also think that drums are more harsh.


SIDs 6582 and 6582A are 8580s that were used as replacement parts, most indeed were manufactured in 1992. They sound like 8580, and so does yours. Keep in mind that the sound of SID chips (even 8580 to some extent) may vary, especially in the filter departament.

Fake "China" SID chips do not produce any sound at all. They are just random chips that share the same physical measurements and amount of pins, therefore they are likely to damage your machine.

Last edited by F7sus4 (Oct 16, 2020 2:33 pm)