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Mb6582 plus 4 SSM2044 VCFs - use of a passive 4 channel stereo mixer?


Hermes
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Hi everyone. I am in the process of building a MB6582 to which I plan to incorporate 4 SSM2044 VCFs (seppoman s pcb x 2). The thing is that I want to have one case for everything - and since I am going to have 4 " unfiltered" SIDs and four "SSM2044 filetered" ones I was thinking that the use of a passive mixer would ease things up. So the question is , would something like this passive stereo mixer do the job? The idea is that instead of having four stereo outputs one foe each pair of SIDs, these outputs go to the mixer inputs, so as to have one combined stereo output of all 4 pairs... Of course a custom panel will be used which will provide thespace for the mounting of the 4 mixer pots. Please tell me what you think, if this is doable, and most important, if it is worth it

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Hi,

imho this is not worth 50 bucks for just four 100k pots and a few sockets...

you could just use the same passive mixer design as in the MB6582 - use 10k resistors on every channel and chain them together, it is good for 8 channels and should also good for two times 4 channels (just try it out)

best regards,

Peter

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Addendum - had a little intermezzo with some opamps a few weeks ago ´cause I needed to repair a mackie mixer channel strip with a dead one... it is not difficult to understand how it works even for an electronics noob like me... for line-level sources (no mic-preamps, no eq stage) a simple active mixer is quite easy to create.

Best regards,

Peter

Edited by Hawkeye
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Perhaps =sidr8tr#audiobus]this might help. It's my idea of combining an op-amp (Cmoy-inspired) design for line-level mixed out while also offering discrete outputs (which basically used the same design as the MB-6582). Dunno if it might be useful to you, but thought I would offer it.

I myself want to do SSM filters and my solution was to use a 3U case to stuff everything in plus a custom control-surface. I haven't found a project case that could fit all that and I'm a rackmount fanboi anyway. You can find info about my work on the same link as above.

I haven't worked on it in a while as I am finishing up another project at the moment. I'm hoping *crosses fingers* to have the synth up and running, perhaps minus the SSM stuff, by the end of this year.

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This should help. You can control them using the EXT Filter option on the MidiBox SID. The settings can be saved with your patches just like any other filter settings. They connect to headers on the CORE, though I'm not totally sure how you use multiple filter modules (though I'm fairly certain you can). Of course you need to route the audio through the filter to hear it - on the MB-6582 you can just use the headers above each SID. That does mean you can't easily use the 1/8" jacks on the back of the MB-6582 if you want to hear the filtered sound which is why I'm putting all that in a custom case.

The MB-6582 has the expansion port you could use if you wanted an external filter solution. You could route all the wires to it and then over to your filters, which could be in a nice external case or something like that.

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the routing is done in the menu. eg you need 1/2 Aout_NG for a dual SSM board. the second core would then be connected to the remaining Aout inputs. at least that's how i expect it to work. i'll try to use SSM2044 VCFs and SSM2164 VCAs with the MB6582.

that's of course all dreams of the future right now, haven't even completed the synth itself and only 2 working NG's and just one of each SSM boards finished.

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This should help. You can control them using the EXT Filter option on the MidiBox SID. The settings can be saved with your patches just like any other filter settings. They connect to headers on the CORE, though I'm not totally sure how you use multiple filter modules (though I'm fairly certain you can). Of course you need to route the audio through the filter to hear it - on the MB-6582 you can just use the headers above each SID. That does mean you can't easily use the 1/8" jacks on the back of the MB-6582 if you want to hear the filtered sound which is why I'm putting all that in a custom case.

The MB-6582 has the expansion port you could use if you wanted an external filter solution. You could route all the wires to it and then over to your filters, which could be in a nice external case or something like that.

Okay. Thank's. I just recieved an old SSM2044 chip from ebay as a backup for my KORG Mono/poly, and I have a finished midibox. So I was wondering if it was worth a try. :tongue: But then I would need two SSM2044's to get that gritty stereo SID sound. :thumbsup:

Would you then control the SSM2044 from the MB6582's control panel? Does the SID generate the envelope for the filters?

It sounds pretty exciting.

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Hi,

imho this is not worth 50 bucks for just four 100k pots and a few sockets...

you could just use the same passive mixer design as in the MB6582 - use 10k resistors on every channel and chain them together, it is good for 8 channels and should also good for two times 4 channels (just try it out)

best regards,

Peter

Hello Hawkeye,

I like building stuff up and would like to build the device you mention for my mb6582 based sid (wilba's boards with 4x8580 and 4x6581 with shitty home made enclosure).......problem is I can't visualise circuits very well and need schems n pics.

Any chance of helping a silly old bugger out?

cheers

Paul

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Hi Paul,

no problem, if you do a little searching, you will find loads of descriptions how to build them... If you want to start with a passive mixer, look here, for example

http://www.nirvis.com/mixers.htm

The upper part only shows a mono mixer (left or right side only), you have to build two of them.

You can of course add potentiometers "behind" the fixed resistors (they used 2k, i think the MB6582 uses 10k, which I would also suggest) for manually reducing each channels signal level.

That should be exactly what the passive Rolls mixer does...

Best regards,

Peter

Edited by Hawkeye
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Would you then control the SSM2044 from the MB6582's control panel? Does the SID generate the envelope for the filters?

The SID doesn't control the VCFs, that's done by the 4 core modules. Env and VCF data is local to each core (no, it's not shared from a "master" CPU via CAN) so you'll need one AOUT_NG per core if you want the full custom shine. AFAIK the AOUT_NG is connected using I2C SPI to the core, I don't think that's set up as a multi master bus as is. Perhaps TK, Wilba or one of the guru's can tell us if that will change later down the road?

The connection is: Core -> SID, Core -> Aout, SID Audio -> VCF/VCA, AOUT CV -> VCF/VCA. Plus control bits as necessary using the available port headers at each core.

Best,

J

Edited by jojjelito
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The SID doesn't control the VCFs, that's done by the 4 core modules. Env and VCF data is local to each core (no, it's not shared from a "master" CPU via CAN) so you'll need one AOUT_NG per core if you want the full custom shine. AFAIK the AOUT_NG is connected using I2C SPI to the core, I don't think that's set up as a multi master bus as is. Perhaps TK, Wilba or one of the guru's can tell us if that will change later down the road?

The connection is: Core -> SID, Core -> Aout, SID Audio -> VCF/VCA, AOUT CV -> VCF/VCA. Plus control bits as necessary using the available port headers at each core.

Best,

J

Allright. Thank's! :thumbsup:

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Jojjelito,

so that means i can't share one Aout_NG for two cores.....

i just took a look at the Aout board. couldn't just connect pin 4 of J2 to a second core? without studying the schematics right now it seems as if it were planned that way (visually).

but if that's not possible it's still not that dramatic, as one can share each Aout-NG then for one dual VCF and half of a quad VCA (seppoman's of course).

dang i have to RTFM !!

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Hi Rosch,

Pin 4 of J2 would be Dout, e.g. for chaining multiple AOUTs to one core, I think you mean Pin 4 of J1? Anyways, the Wiki says that even chaining is not supported by any existing apps.

If I understand things correctly the TLV runs SPI. SPI is not a multi-master bus, so there's no collision handling if several cores would like to write data to it at the same time. Had this been doing I2C that would have been fixable, but the SID portion of the app also doesn't share envelope, LFOs or such data globally across themselves. Therefore each core only knows what it is doing, not the status of others unless MB-NET got extended. All this is AFAIK, TK or other gurus could say otherwise.

Also, this has been stated before in the forumshmm.png But, on a positive note: You could share the quad VCA board across since each VCA has its own CVs, just connect those where applicable. However, the full-on 4-pair stereo SSM filtering requires 4x dual SSM2044 PCBs, along with 8 SSM 2044ICs and all the rest.

It could end up being costly, but given the lengths people will go to pimping their SID synths, why not?

Cheers,

J

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hehe i've taken care of the seppoman boards and parts of the SSMs already. just need 2 more Aout_NGs then. and other stuff too, of course.

what i meant is J2 on the Aout_NG board. you connect the core to Aout_NG J1. while all other pins of J1 and J2 (Aout_NG) are connected, just the 4th pin of each go in the direction of the rest of the aout circuit, each on their appropriate side. so that's what lead me to the conclusion that both halves of the Aout_NG could receive their data from two different sources.

i have the feeling that i'll get deeper into the system and how it functions slowly, step by step.

but i hope i assume correctly that for example one SSM2164 quad VCA can have each of their quarters controlled by CVs source independent (from different Aout_NGs)

maybe i should make a quick drawing how i meant it would work....

yeah and pricey, sure! but wth, it's worth it!

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Hmm, I think you're on to something. Weird logik.png

J2 on the Aout board is for reading data/statuses etc back to the core. Or you could daisy-chain em: J2->J1 of Aout 2 u.s.w. But, that's not supported by the applications as of now.

But but but, if you want full stereo on each SID pair, you'll end up using 2x SSM2164 boards for octal VCA fun. For mono you could get away with mixing each SID pair and sending that to each VCA.

But, please draw away. I've been meaning to do something of that sort, but OLED and PSU first...

Burp!

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yep i'm planning 1 vca and 1 vcf per sid.

thanks for explaining that. so i'll definitely need 4 Aout_NGs.

i haven't yet tried the vca, that will be the next step now.

also i'm considering taking a control surface board from smashTV and the original panel from JulianF to speed things up a bit.

but the stereo sid with the seppoman filters sounds so good, i just have to do that with 6581. hard to imagine that 8x sound!

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Me again,

Hawkeye,I found this and would value your opinion on it http://www-fa.upc.es/websfa/lab/111/audio/audmixer.txt the reason I fancy this one is that I can follow the diagram easily which is what I need.

I will be adding seppomans' ssm 2044 (I built 3) into the equation at a later date and probably the ssm2164 (I built two) but thats down the road a while.

I thought about building one for the mbfm and one for the sid,any opinion on this?

Thanks in advance

Paul

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Hi Paul,

it will surely work, but I have no information on the quality of the transistor amplification, so in other words it could sound good or bad depending on your quality requirements :-).

If you want to go passive (no transistor amplification) first, you can at first build the top of the diagram only, just until below the 220K resistors for each channel and use 10K resistors for each channel instead and also try to omit C1-C3.

The MBSID output circuits have a fairly high signal level imho and you may not need the transistor amp part at all.

Best regards,

Peter

Edited by Hawkeye
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man, i wanted to recommend having a look at Ray Wilson's site for some easy active mixer circuits, but i thought no, they'll likely need bipolar supply!

doh!

if you use seppoman filters and vca you'll need bipolar supply anyway!!

so you could look over there, if you haven't already.

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  • 8 months later...
"The SID doesn't control the VCFs, that's done by the 4 core modules. Env and VCF data is local to each core (no, it's not shared from a "master" CPU via CAN) so you'll need one AOUT_NG per core if you want the full custom shine. AFAIK the AOUT_NG is connected using I2C SPI to the core, I don't think that's set up as a multi master bus as is. Perhaps TK, Wilba or one of the guru's can tell us if that will change later down the road?

The connection is: Core -> SID, Core -> Aout, SID Audio -> VCF/VCA, AOUT CV -> VCF/VCA. Plus control bits as necessary using the available port headers at each core."

If i understand well, to run my second ssm2044pcb on channel 2, i would need a second aout NG on core2?

Isn't it possible to use CV5>CV8 of first Aout NG wired on core1 to control my second SSM2044 PCB from channel 2?

What about using MBCV to control 2 SSM2044 pcb with only one aout NG by midi (channel 1>CV1234 and channel 2>CV5678)?

So adding one core add less cost than adding one AoutNG...

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If i understand well, to run my second ssm2044pcb on channel 2, i would need a second aout NG on core2?

Isn't it possible to use CV5>CV8 of first Aout NG wired on core1 to control my second SSM2044 PCB from channel 2?

What about using MBCV to control 2 SSM2044 pcb with only one aout NG by midi (channel 1>CV1234 and channel 2>CV5678)?

So adding one core add less cost than adding one AoutNG...

You are right. But what about interaction between MBSID and MBCV. Is there a way of sending CC from MBSID?

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