Rio

CEM3378 schematic

53 posts in this topic

1.Is there any CEM3378 schematic/connection diagramm for use with AOUT_LC, yet?

I only found this:

http://www.midibox.org/forum/index.php?topic=5538.0

I want control CEM3378's (max.4) with my upgraded MBSID2 in future.

2.Does every CEM3378 needs an own AOUT_LC (i have 2 AOUT_LCs yet)?

3.Does i need an external supply for the CEM3378? I've readen that +12V and -5V are needed for CEM3378 (Are they available from Reichelt or Conrad?)

4.What are the parts i need additional?

EDIT: I changed my questions in more detail in further posts below

Best Greets, Rio

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Hi Rio,

I can´t answer your questions - but:

If you don´t already have 3378s, think about using SSM2044 instead. These are also really nice one-chip filters (don´t know about sonic differences to the CEM, but I found some mp3s of it and it sounds great to my ears). And they are really cheap and easy to get. There´s one(?) guy on ebay calling himself either hongkongsuperseller or goodbuy711 (don´t know if there are more aliases). He regularly offers them and seems to have huge quantities. I just ordered 10 pieces for 75 USD from him, but he also offers 2 pieces for 19 USD. Prices are including worldwide shipping from Hongkong. I plan to use them in my new MBSID :)

Main advantage besides price and availability is that they can run on symmetrical supplies like e.g. the +/- 12 V you need for the AOUT anyway. So no need for the extra -5V.

Seppoman

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thx for info, but i've got 4x CEM3378..

so i needed detailed informations to use them with AOUT_LC ;)

Greets Rio.

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first i'll build up now a PSU for that, like in description of TK's AOUT_LC (bipolar)

+12V

-12V

and i'll get -5V with a 7905 too. So that the power supply should be allready.

But i still need a info about necessary parts for that schematic for a right connection from AOUT_LC to CEM3378.

I found that:http://www.synthtech.com/cem/c3378pdf.pdf

So i'll ask my questions more detailed now:

1. Which OPAmp should be choosen in that schematic ?

(Did someone has written down a complete partlist e.g. Shopping basket at Reichelt) I think i will first begin with 2x CEM3378.

2. Should CV#1 and CV#2 from AOUT_LC connected to CH.A and CH.B INPUT?

3. Should Freq, Resonanz, Gain, Balance controlled by Potentiometer or can MBSID handle this?

4. Does every CEM3378 needs an own AOUT_LC. Are 2x AOUT_LC + CEM3378 needed, to get start for Stereo-Filtering?

Greets, Rio.

PS: Please discuss build up's for SSM2044 further in a new thread.

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Some time ago I wrote down the schematic I used on a paper, but it's lost. So, no chance to reconstruct this without opening the Behringer case...

But basically the circuit was very simple: two outputs of AOUT_LC control CutOff and resonance. I added two trimpots against ground for an additional gain fineadjust. This was especially important for calibration of the four CEM3378 to ensure, that the same software driven cutoff/resonance value will result into the same effect at the analog side. MBSID supports software calibration (see ENV menu), but it's easier and more exact to do this with a pot, as a software calibration results into a reduced resolution! It doesn't matter to which CV outputs CutOff and Resonance are connected, as this can be configured in the setup_*.asm file of MBSID V2 anyhow, just read the comments. You could even control the outputs without the F2A (Filter-to-analog) option within the ensemble in order to address the filters seperately, and by doing so, you wouldn't need to do any change in the firmware - just select the right CV target in the modulation matrix and have fun.

This as background information, and to answer your questions:

1: I used a TL074

2: these are the audio inputs. The CV outputs are marked with "C.V. Frequency" and "C.V. Resonance" in the CEM3378 schematic

3: is it clear to you, what CV (control voltage) means?

4: how many CV inputs are you planning to control individually? The calculation is easy: each AOUT_LC module provides two CV outputs, with 2 modules you get 4 outputs. For an stereo effect it makes sense to control at least the cutoff parameter of two CEM3378 seperately, and maybe also the resonance or the VCA. But note, that the AOUT_LC module is used in 12/4 mode, which means; each first CV channel is working at 12bit resolution, each second at 4bit resolution.

Therefore in my own setup, I control CutOff with each first, and Resonance (where resolution doesn't matter) with each second output.

4 AOUT_LC modules are chained to control CutOff/Resonance of 4 CEM3378

In future I'm planning to replace the AOUT_LC modules of my "Behringer" by a AOUT_NG module due to the better resolution.

Best Regards, Thorsten.

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Hi Thorsten,

thanks for that huge information. Ok, everything is now a bit more clearly.

I added two trimpots against ground for an additional gain fineadjust.
You mean trimpots for filter and resonance? Do you adjust Gain or Balance on CEM3378 in any way?

If i understand it right, every SID Audio Output Channel should be Filtered through 1 CEM3378 seperatly to keep it stereo.

So i connect SID Output only at CH.A and CH.B wouldn't be used, because CEM 3378 provides at least only 1 Output? or i'm wrong?

If every CEM3378 needs 1 AOUT_LC, how can i connect 2 AOUT_LC on 1 CORE Module to have a stereo effect for CEM3378 on a MBSID2?

Does MBSID2-Application supports 2 AOUT_LCs to use them together with 2 SID on 1 Core?

Best Greets, Rio

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AOUT_NG module? Is this some future project? I searched the forum but couldn`t find anything regard NG module. If answer is positive, do you advise to wait for it rather than build AOUT_LC?

http://www.midibox.org/forum/index.php?topic=7830.msg68050#msg68050  ;D I advise to wait for it - I´m going to order proto PCBs this week, so I suppose it will be not more than 2 months until it is official. It won´t cost more than 4 AOUT_LCs (e.g. you need only one PCB instead of four) and will have better specs.

Seppoman

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@sasha and seppoman: nothing of your posts answered my questions! So please discuss only about relevant information in this thread.

i know also there is a AOUT_NG in development, but i got at home 2 AOUT_LC. I don't want to throw them away and i'm interessted in a MBSIDV2 + AOUT_LC solution too!

And i don't know yet, whether and how a MBSIDV2 will support seperated CEM3378 with AOUT_NG? Maybe if there is no way to use AOUT_LC i've to change to AOUT_NG.

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Rio, I know this didnt answered your questions, but it is pretty relevant to your topic. It is very hard to keep thread so specific. Take a look at my blog about Endorphin discussing about planes and carpets. I dont say it is ok, far from it, but not all slightly off topic posts means topic hijacking. Sorry if you feel that way, but our few posts didnt made you lose the answers. Eventually, somebody more relevant will answer you.

Peace!

PS. I removed all my previous postings from this topic to make it more clear.

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Rio, calm down a bit... Even if our discussion didn´t answer your personal questions, everything we´ve written is kind of on topic - at least for people reading here out of interest and/or having similar plans. I don´t recall you being chosen as a moderator, so I won´t remove anything - but if contributing to any of your topics brings the danger of getting negative vibes from you, I just simply won´t take part in any discussion involving you from now on...  :-X

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I don´t recall you being chosen as a moderator, so I won´t remove anything
who said that???

please calm down a bit too... i want to know, whether a solution with 2xAOUT_LC is possible for MBSIDV2 stereo feature (1Core -> 2SID) too. (if not, i have to change to a newer solution too, of course)..

Maybe only TK can give us a statement about that.

And don't understand me wrong, i appreciate every better solution. ;)

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So, apparently it works.  :)

ok my last questions so far:

1. you are always use only the CH.A input of CEM3378, i'm right?

2. To use the second AOUT_LC, i only need to chain the 2. AOUT_LC to J2 of first AOUT_LC, or?

I added two trimpots against ground for an additional gain fineadjust.

3. You mean trimpots for filter and resonance?

Do i need to adjust Gain or Balance on CEM3378 in any way?

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TK: I haven't heard that demo before! Very nice! Where is that MP3 linked to from the V2 manual??? (**edit** I found it!)

I'm deciding whether to design a PCB layout for the CEM3378/CEM3379 and get a small batch made... is there much interest from other people in such a PCB?

Even if I don't make a PCB, I still need a schematic for this filter to connect my SIDs to the CEMs. I've only got the one from the datasheet so far, so if anyone else progresses futher with a design, let me know. Or let us all know ;)

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TK: I haven't heard that demo before! Very nice! Where is that MP3 linked to from the V2 manual??? (**edit** I found it!)

I'm deciding whether to design a PCB layout for the CEM3378/CEM3379 and get a small batch made... is there much interest from other people in such a PCB?

Even if I don't make a PCB, I still need a schematic for this filter to connect my SIDs to the CEMs. I've only got the one from the datasheet so far, so if anyone else progresses futher with a design, let me know. Or let us all know ;)

Hi Wilba, I would be interested in a PCBfor either the CEM or the SSM chip seppoman was talking about earlier.

And if it would be also possible to control the values with pots instead of AOUT that would be cool too, if it isn't too much work.

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for the ssm2044 you can find a schematic here:

www.modular.fonik.de

greets...

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Rio: I've connected the SID audio output to both channels (A and B)

Best Regards, Thorsten.

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I'm deciding whether to design a PCB layout for the CEM3378/CEM3379 and get a small batch made... is there much interest from other people in such a PCB?

I'd be interested but those chips are expensive  :-\

Hi Wilba, I would be interested in a PCBfor either the CEM or the SSM chip seppoman was talking about earlier.

The rumour mill says that an SSM PCB is not so far away. A few of us got tubes from the bay.

And if it would be also possible to control the values with pots instead of AOUT that would be cool too, if it isn't too much work.

Is that so you can use it standalone? I'd think you could do that with switches on the CV ins?

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btw, i´m selling some cem3372/3378/3379  and ssm2044 on ebay right now...

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I'd be interested in PCBs for the CEM3379. I have eight of them that want to be used  ;)

Best regards, ilmenator

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btw, i´m selling some cem3372/3378/3379  and ssm2044 on ebay right now...

Where? You should post a link here and the fleamarket.. I searched but couldn't find anything except the usual HK sellers

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Now you know why I have SSMs ehhehee

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..and back to the theme:

@tk: Can you tell us, which parts (trimpots, capacitor types, etc?) you used in detail for a CEM3378 Schematic (Maybe you can open your Behringer Case again :-\).

Would it be meaningful to connect 2 external Potentiometer (as control knob) for Filter and Resonance additional - which type should then be possible?

I want to buy all parts at reichelt at end of the week.

Best Greets, Rio.

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