Sam440 audio connections

I have a Sam440ep-flex AmigaOS 4.1u2 system. I want to do some audio recording, and at present the motherboard audio expansion port (J12 on the motherboard) is not connected to anything.

Is there a readymade port with connections to connect at least LINE IN and MIC IN? Are these connections supported by the software?

Below are the pinouts for the J12 expansion port header on the motherboard.

1 ? 3.3 V
2 ? 5 V
3 ? SPDIFI
4 ? SPDIFO
5 ? MIC1
6 ? LINE_IN_L
7 ? JD0
8 ? JD2
9 ? MIC2
10 ? LINE_IN_R
11 ? SURR_L
12 ? PCIM_OUT
13 ? SURR_R
14 ? PCIM_IN
15 ? AUX_L
16 ? CEN_OUT
17 ? AUX_R
18 ? LFE_OUT
19 ? FMIC
20 ? VREFOUT
21 ? GND
22 ? GND

@mbrantley
I bought a SAM system that has what looks like mic and audio connectors that weren't even connected internally when I received the system. You would think that some detailed audio connection information should have been publidhed for the SAM. Without detailed info, I've been afaid of burning up the board if I just "guess" at what should be connected. I asked the same question as you have but never got a really good response.

@mbrantley

I connected pin 5, 9 and 21 to a microphone connector/jack, but I couldn?t get it to work. I was expecting to at least hear some hiss, if i turn up the amp and monitor in AHI, but it?s all quiet. HD-Rec doesn?t get any signal.

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Yes.

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I have asked ACube directly (I have a 440ep), but did not tested it yet:

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@ZeroG
You notice that Ismarty hooked up 3 wires to his MIC. I think that a lot of computer microphones are condenser types which require an input voltage. Your quote of ACube responses lists a 2-wire connection for the microphone and implies that a dynamic microphone should be used. What we need is some sort of clarification on this issue so that people aren't connecting the wrong type of external devices to their SAMs and frying the board.
I also wonder the line-in connections are designed for standard stereo impedance and voltage or if there is some different computer audio specification being used for those SAM inputs.

@lsmarty
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Be careful. If you connect a power line to the wrong microphone connectors, you could apply a voltage to the SAM MIC input which could damage your SAM. It sounds like you are trying to connect a 3-wire condenser microphone to the SAM but the specs that ZeroG quoted imply that a 2-wire dynamic microphone is required. The lack of specs (impedance & voltage levels) is the reason I haven't attempted to connect any audio devices to the SAM board. I think that there are also some battery powered microphones available which might overload the SAM MIC input if it's designed for a standard dynamic microphone.

@mbrantley
I'm not sure we're helping you much but without specific specifications for the SAM inputs (impedance & voltage) it's difficult to say how you should hook things up. Personally, I've encountered 3 types of microphones (condenser, dynamic and ceramic) all of which require a different type of connection or impedance circuitry. As I said in my previous post, the ACube response implies a dynamic microphone. However, if the input were designed for a ceramic microphone then the output of a dynamic microphone is likely to produce little or no sound when connected. Hopefully someone who knows more than I do will speak up and clarify the issue or correct my explanations.

@mbrantley
A little Internet search seems to indicate that my old stereo system based microphone info is a little outdated. Apparently, some sound cards expect an electret condenser microphone which requires a voltage bias on the signal input and sometimes have a special preamplifyer setting for dynamic microphones. Some microphones now have stereo input which would then presumably have 3 wires. You are probably unlikely to find a standard 3 wire condenser microphone used for computer sound cards.
The question that needs answered is what type of input is SAM designed to use? Surely someone has a SAM with working microphone input that could clarify the issue for me and everyone else.

@xenic

Thanks, everyone, for the help and to Xenic for looking into this. I'd ideally like to have MIC IN and LINE IN options for recording from the analog world, but I don't want to fry anything in the process of getting there. Perhaps a sound card would be the easiest way to get there? I have one more free PCI slot after installing my new Catweasel.

Of course, if I eventually swap out this board for a Sam460 it seems I will have fewer PCI slots. Not sure I'll be doing that but just thinking out loud. I wonder if the X1000 will come all wired up with audio inputs.

I've rehoused my AmigaKit Sam440 "complete system" into another case so I could fit the Catweasel and floppy(ies). Plus, I like my optical drives sitting flat, not vertically. But in any case (ha!) I was surprised to see the case AmigaKit chose didn't have all the audio connections made. For a "complete system" I expected this, but maybe there's some reason for it. The connectors don't fit so would have to be customized. Maybe it's the fault of the Sam board for not having standard connections for the audio bits.

Anyway, I'm not going to start plugging wires into my Sam board until I know someone else has blazed the trail before me and made it work. :)

@xenic

Don't know if it helps you:

The prototype I/O Extender from ACube:
link

Datasheet for the ALC655 used on the SAM:
link

I have connected a stereo-connector ("klinken-buchse" in German) to the pins and plugged in a cheap dynamic mic (mono). This combination usually worked when you had a PC-board instead of SAM. But as mentioned - AHI doesn?t seem to pick up any signal (and SAM is still working).

@lsmarty

Have you checked your Mixer settings?

@lsmarty
Dynamic microphones have much lower output than electret or condenser types. I think you either need an external preamplifier or a sound card with builtin preamp that can be turned on via the software that comes with the board. You might try another type of microphone and/or the Mixer settings as ZeroG has suggested.

@ZeroG
Do you know if that I/O extender ever made it past the prototype stage. It certainly would simplify audio interfacing on the SAM? I'll check out the datasheet link and see if that helps.

@xenic
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As far as i know it's still in prototype stage or has been dropped by ACube, i can't find any information about it on their webside.

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Thanks.

@ZeroG
I D/L the spec sheets and gave them a quick look. I can read simple circuit diagrams but the use of abbreviations and acronyms can be confusing. What's clear is that there is some interface circuitry required between the microphone and the MIC input on the board. The standard INTEL front panel I/O design shows a jack sensing circuit and bias voltage input. The impedance listed for the MIC inputs seems to indicate that a higher level signal like that produced by an electret microphone is required. It's unclear if any of the interface circuitry is included on the SAM board or if SAM's outputs match the header output shown in the data sheet. The one thing that is clear is that you don't want to connect a microphone directly to the MIC input on the SAM board. It's possible that AmiKits case front connector has the necessary interface circuitry but I have no way of knowing that. At the very least a capacitor is needed to prevent DC leakage into the MIC input. I doubt if connecting a dynamic microphone to the MIC input would damage the SAM (hopefully) but it's unlikely to produce a strong enough signal.
As has been the case with all OS4 hardware, you're probably better off (and safer) using a sound-card if you want the full benefit of computer audio capabilities.

@xenic

OK.
And what do you think about Line In, would it be save ?

Just a short note: when I wrote the driver, I had the same controller chip on a PCI card and am quite sure that recording was working with line-in and mic-in then.
I haven't had the ability to test it on my SAM by absence of the audio break-out board that was planned.

Hi,

we just published audio schematics of sam440ep and sam440ep-flex. You can download the file from both Sam440ep page and Sam440ep-flex page.

Or you can use this link:

Sam440ep audio schematics

Regards

@Lecta

Thank you for publishing that data, it will be very useful for developers.