Balanced I/O board for SID MBFM etc...

Design Concepts
1

Ok, so here’s the Idea I am having. I want a Balanced I/O board for my MB sid V2 (using the base PCB of the MB6582) but it also could be suited for other uses MBFM, MBMixer, Standalone balanced/Unbalanced converter box, etc…

I am thinking of using the SSM2142 and 2143. Why, because I already have a tube of 2142’s, also these are pin compatible with some other line drivers on the market (ones made By THAT Corp. , maybe others too). I have attached the datasheets below

So Q’s and thoughts:

  1. Since I am already taking +/- 15V into my sid( EDIT here I am refering to the machine as a whole, not the SID module)to regulate down to +/-12V for AOUT and Seppoman’s filter module, and +9 for the 8580 sid’s I am using, should I supply the 2142/2143 with 15V? or is there no point when hooking up to the SID? of course I could leave the option for both, the chips will take up to +/-18V.

  2. Do i need any sort of buffer between the 2143 (balanced line reciever) and the SID input? I was thinking I may need a pad or variable attenuator to deal with high input levels, will this be sufficiewnt to protect the input?

  3. would anyone else be interested in this project when I am done? What else would you want to see on the board?

  4. there is also a SSM2141 reciever, only difference is the gain. the 2143 is designed as a unity gain transmission path when used with the 2142.

5)Insert points for feedback/effects? how to best do this? leave them as unbalanced and take them before this board?

  1. I was going to make one big 8 channel board, but for MBFM this would be overkill, of course components could be left out, I guess final board size will determine this.

  2. I am going to breadboard the output part of this circuit as soon as I get some remaining parts for the MB SID. I don’t have the reciever chips yet, waiting for feedback on #4 above before I decide which to order.

Thanks all,

Let mem know what you think.

[SSM2142[1].pdf](< base_url >/applications/core/interface/file/attachment.php?id=4486)

[SSM2143[1].pdf](< base_url >/applications/core/interface/file/attachment.php?id=4487)

[SSM2141[1].pdf](< base_url >/applications/core/interface/file/attachment.php?id=4488)

2

Your questions have me looking the SID module over.

Instead of answers, I have more questions.

You mentioned using this with the MBMixer.

Yes, it will work with that. But the MBMixer has support for balanced inputs and outputs already. It has had balanced support for almost four days now! :slight_smile:

(ok, I have got that off my chest, back to your questions)

Question 2 asks if you would need to attenuate the input level before going into the SID. Wow, I never knew the SID had an input! As a rule, inputs may never exceed the voltage range of the chip. So what’s your chip running at? Depending on the model, either 0 to 9 or 0 to 12 volts.

So ASSUMING that the audio input is biased between 0V and +9 or +12 V,(a fair assumption after seeing the schematic) you must keep the peak to peak voltage of the input below 9 or 12 volts.

You mentioned that you are taking + and - 15 volts into your SID.. but the prints I saw only showed +5 and either +9 or +12, depending on the model. Maybe I saw the wrong schematics. So my assumption above may be wrong.

Is this Sid Ver 2 based on the Sid board that Smash sells at his shop? I don’t see any negative voltages there. (He’s a really positive guy that way).

If it’s something else, where can I see a drawing?

Will your design provide Phantom power if needed? If you are looking for the most options, you might want to include that one.

Looks interesting!

LyleHaze

3

Your questions have me looking the SID module over.

Instead of answers, I have more questions.

You mentioned using this with the MBMixer.

Yes, it will work with that. But the MBMixer has support for balanced inputs and outputs already. It has had balanced support for almost four days now! :slight_smile:

(ok, I have got that off my chest, back to your questions)

Very nice, I see you are simply using two inverting opamps for your balanced line driver.

Question 2 asks if you would need to attenuate the input level before going into the SID. Wow, I never knew the SID had an input! As a rule, inputs may never exceed the voltage range of the chip. So what’s your chip running at? Depending on the model, either 0 to 9 or 0 to 12 volts.

I am using 8580’s which run at 9V

So ASSUMING that the audio input is biased between 0V and +9 or +12 V,(a fair assumption after seeing the schematic) you must keep the peak to peak voltage of the input below 9 or 12 volts.

OK

You mentioned that you are taking + and - 15 volts into your SID.. but the prints I saw only showed +5 and either +9 or +12, depending on the model. Maybe I saw the wrong schematics. So my assumption above may be wrong.

Is this Sid Ver 2 based on the Sid board that Smash sells at his shop? I don’t see any negative voltages there. (He’s a really positive guy that way).

If it’s something else, where can I see a drawing?

It is the mb6582 base pcb from smash TV’s webshop, which was mentioned in the second sentance of my opening post. I am using my own external supply that has +5V and +/-15V, inside the sid box i will be regulatimg down to +/-12V for use with seppomans ssm2044 filter board and AOUT modules, and +9 for my 8580 sids.

However, the ssm2142/2143 can operate at up to +/-18V, so I was wanting to know if  I gain any advantage in running them at a higher voltage than the SID? I am under the impression that this would allow me to take in a higher level of signal without clipping on the input side, but I am unsure wether I truly gain any advantage on the outputside.

Will your design provide Phantom power if needed? If you are looking for the most options, you might want to include that one.

Wasn’t thinking I’d ever need to hookup a condenser mic to my SID, but if there is interest in using the board for other purposes I could loook into it. I would then need to generate the 48V for phantom though.

Looks interesting!

LyleHaze

Thanks. As I said in my first post, I will know more once I have breadboarded the circuit.

4

there are some pin compatible that1200 's on ebay for cheap

5

Ok, still waiting on SID parts but I breadboarded the output circuit today. works nicely. Tested with my Korg ES-1. Left channel through the converter to one input on m,y DELTA 1010 (balanced inputs). the right channel I plugged straight into the 1010, unbalanced, so it shorts the -VE side of the balance3d input to Ground. the results? The expected 6dB increase on the right channel (OK, i didn’t measure, just recorded a few quick tracks into a stereo channel in Cubase). It had good clean signal, though I didn’t do stringent testing, maybe later.

Confirmed pin compatible parts from Burr-Brown(TI) and THAT Corp. so there will be options for other builders if anyone is interested.

I have some of the Burr Brown balanced line receivers in my parts box so I will breadboard the input circuit next. UI’ll let you know how it goes though  I am expecting it to go much the same as this last test. will be a busy weekend though so I may not have anything this weekend.

6

Props for doing this. I posted a link or two some time ago with schems for discrete balanced IO if you’re interested in doing one that doesn’t need obsolete chips.

7

The SSM’s may be obsolete (not sure, but mouser doesn’t have them), but the Burr-Brown, and THAT chips are still availible at mouser and are pin compatible (and better specs). I was going this road because I already have some chips. I would wonder how the discrete solution specs against the integrated ones? I could always look at doing both I suppose.

No progress this weekend, I barbecued 1000 pieces of chicken on saturday, and on sunday I broke out my stereo zoom microscope to practice SMD soldering. Some progress this week perhaps, though as usual I am working on this, an MB-6582, an MBFM, and MBSEQ in parallel.