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Sid Sammich filter sounds no good...


meech415
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my build partner has built many synths and wants to trouble shoot it from a schematic but there doesnt seem to be one for this box. we just built it and i recorded with it all weekend. i thought the filter in the chips must be dead. he doesnt think so. he is now looking for the pin out docs on the 6582. any ideas ?

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Like I said in your other thread, the schems are on ucapps.de. Since that apparently doesn't do here's some direct links :rolleyes:

http://ucapps.de/mbhp/mbhp_core_v3.pdf

http://ucapps.de/mbhp/mbhp_sid_v3.pdf

The only thing relevant to the filters (assuming everything else works) are the two filter caps per SID. If a) everything else is working correctly, and b) the correct filter caps are placed correctly, the only possible issue left is your SIDs.

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he is now looking for the pin out docs on the 6582. any ideas ?

There has been built many hundred MBSIDs, both the modular ones, MB6582s and SammichSIDs - and they all work :) i can say for sure that the pinout of the SID has been tested thoroughly through many years, so i honestly think you should look for the error someplace else.

Also the schems you ask for - these have been proven to work over and over again

On a sidenote; it would be very peculiar if the two SIDs suffered from the exact same filter problem :unsure:

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a few questions/suggestions

* did you test the all modes lowpass/bandpass/highpass and the combined modes?

* is "ext in" off (if the sammich sid has that option)?

* if you have a working C64-II (every good household should carry at least one :-)), you can test the 6582 in there, there should be some filter demos available.

if nothing works:

* can you post an audio example?

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  • 1 month later...

Looks like its a month since this has been posted, so i hope a solution has been found..

But i have the exact same problem with my sammichSID.. Everything works great but the filters are not really responding .. they make a bit of noise and little things happen.. but its totally not like the audio examples in the manual or like any other filter on any of my synths .. so something is definitely wrong..

Every voltage test checked out and the OS installed fine and well its all fine and rainbows except the filter part :/ ..

Im using two 6581 SIDs. And one is from an old HardSID card i had so im very sure at least one of them is working perfectly. So i dont think its a problem with the SID chips.

Could it be something with the C1L, C1R, C2L, C2R thingys? i used the 470pF (6581), but does it matter what holes i put them in?..

well hope someone can help :)

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After looking around a bit on how you others assembled the sammichSID i could see that it was the way i put the C1L, C1R, C2L, C2R thingys in :D .. i dont know if it was that i put them in the holes furtherest apart or that i did not face them the same way that was the problem..

but when i put them both in the holes cloest to the middle and faced them the same way it worked ! .. now the filter is working perfectly :)..

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  • 4 months later...

Hi!

Sorry to rez an old thread, but I have the exact same problem.

I get a loud hum when the filter cutoff is set to 000

I get a softer hum when the filter is assigned to all channels ( 123 ) and with some combinations (I'd need to analyze it further...)

Reading the last post, I tried to switch the filter caps around and, to my surprise, if I put them all facing right, the noise is even worse. If I put them facing left, the noise is not as bad but still present; maybe it's normal?

The filters seem to be working fine otherwise, and I do get this problem on both channels/chips

Thanks

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the hum could be caused by a too weak PSU. Check the SID supply voltage, it should be 12V on a 6581, resp. 9V on a 6582/8580

check it especially while the SIDs are plucked into their sockets and filters are turned on!

best regards, thorsten.

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yeah that's gotta be that because I remember the voltage was 8.7 or something like that :s

The PSU rates at 15 volts though (obviously unregulated lol)

I think it's 1A...

should that be enough or should I look for another PSU?

Thanks TK! I waited yeeeeears before I build my midibox but damn, it's everything I wanted it to be!

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nice ro read! :)

your psu has the right specs, could it be that you are using a 6581 SID and mounted a 7809 instead of 7812 volatge regulator?

(disclaimer if somebody else reads this posting without the previous ones: don't use a 7812 VR for 8580 or 6582 SIDs, they need a 7809 VR)

best regards, thorsten.

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Sorry, I thought I had replied but something didn't work!

I'm using two CSG branded 8580s...

Following the instructions on Wilba's "sammichSID building guide", I used a 7809 closest to the rear panel and the 7805 in the other spot... so I don't think that would be it

the only thing is, I missed the part where it said to wait 20 secs in between soldering leads...

I did work quickly, but I might have overheated the parts? Do you think that could be it?

I'm noticing, with more playing around, that the midibox's mode (Ld, Dr, Mul etc) has an influence on how bad the filters sound... when dealing with, for instance, Dr, the Filter is unusable...

Thanks for the help

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ok, i assumed that you are using 6581s since you forgot to mention this, and since 8.7V is in the good range for 8580s. There is probably no problem with the VR, it could just be a measuring error if you are using a low-cost meter (or measured from the wrong ground)

Back to your original posting: could you please attach a sample where we can hear different filter modes, just to get an impression about the hum that you mean?

Please also turn on/off the Ext. filter input - if enabled, you should hear a loud hum as long as no cable is connected to Audio In - nice comparison!

Best Regards, Thorsten.

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ok let's try to embed some audio

This is the idle noise on patch A041 - Math Game, followed by the idle noise on A040 - Ramp Up

A041-MathGame -> A040-RampUp

Here are some default patches that I figure are not sounding right:

A063-Slow Intro

A060-6 Octave Plug

This last one is the Drum Kit 2 default patch, I assigned a LP to 123 and I'm gradually cutting from maxto min, and again, over the loop

A034-Drum Kit 2 Cutoff Tweak

EDIT(s):

Ah, here is the EXT ON noise:

EXT Filter on idle noise + Filter tweaks

...ok now my LCD is starting to flicker o_O like there is not enough power...

Edited by XC3N
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