NA Model 2 Saturn Audio Buzz

[naiaru]

So I have North American model 2 Sega Saturn that has a terrible audio buzz when using a SCART cable (I've tried two so far) that's been stopping me from using it as much as I'd like to. I've tried splitting the audio off from the cable and I got the buzz as you'd expect. I then tried adding RCA outputs for audio and wiring them seperately and soldered them to the points right under the output connector and the buzz got slightly better, but it was still really bad. I then tried soldering to the points TP2, TP3, and TP11 and the sound of the buzz changed a bit, but it was still just as loud and annoying. However, I noticed that if I unplugged the SCART cable at the Saturn side, the audio suddenly became really clean, though nothing happened if I unpugged it at the other end (i.e. unplugging it from the processor it's hooked up to did nothing if the cable was still connected to the Saturn itself). The audio was perfectly fine when I used to use an S-Video cable as well, BTW. Also, the buzz happens even when the power cable is disconnected. Should I buy a new cable? Is there someway I can change my current cable to not give me the buzz, or is there something I have to do to the Saturn itself?

Thanks in advance for any help!

EDIT: Also, I thought I'd mention that my Genesis and SNES are hooked up the same way (audio outputs seperate from their SCART cables and hooked up to the same switcher, processor, etc.) and they don't have this problem (the SNES buzzes just a little bit but it's not bad at all).

[RGB32E]

http://gamesx.com/wiki/doku.php?id=av:saturn_sp_dif

This is ultimately the best way to get buzz free audio - provided that you have a good external DAC or receiver to connect SPDIF to.

Alternatively you'd need a cable that has separate coaxes for the audio leads from the Saturn 10 pin mini din connector. Only composite video and s-video cables are built this way. When I was using s-video years ago I actually took a generic S-Video cable and turned it into a short breakout adapter for standard s-video & stereo RCA connections to get the best quality.

Even the official Sega SCART and RGB21 cables had some buzzing going on as they don't have a heavy enough outer shield/braid, and are too long. However, building a cable from a YAESU T9207451 works pretty well if kept under 5ft in length. Made mine with a 8MDIN plug for the XRGB-mini so no adapters would need to be used.

[naiaru]

Thanks RGB32E, but the S/PDIF mod is out of the question for me because I don't understand what the Notes section says (de-emphasis, EMPH, etc. might as well be Chinese to me) and I've never been able to get an explanation as to what it's saying actually needs to be done. I could live with a tiny bit of buzz, but the buzz is as bad as when you take powered computer speakers and touch your finger to the 3.5mm audio jack. So I take it you're saying the problem is with the cable's shielding and the only other option is to make my own cable?

[Ed Oscuro]

Alternatively you'd need a cable that has separate coaxes for the audio leads from the Saturn 10 pin mini din connector. Only composite video and s-video cables are built this way.

If there is some demand, I bet retro console accessories on eBay (RetroAccess here, I think) would build some.

[RGB32E]

1. Buy:
-CS8406 IC(s) (http://www.digikey.com/scripts/DkSearch ... =148064371)
-DIP Adapter board (http://www.schmartboard.com/index.asp?p ... dip&id=448)
-Couple of 0.1uF ceramic caps
-100uF electrolytic cap
-Single conductor wire (~26 AWG)
-374 ohm resistors
-90.9 ohm resistors
-RCA panel mount jack

2. Solder CS8406 to DIP adapter board
3. Link all CS8406 pins for +5VDC and GND respectively together (see gamesx diagram)
4. Add decoupling capacitors
5. Wire pins/test points described in the gamesx wiki to the respective CS8406 pins (dip adapter)
6. Add voltage divider resistors, and connect output to RCA connector, or track down an optical transmitter and go with that
7. Connect SPDIF to sound system and enjoy!

[RGB32E]

Alternatively you'd need a cable that has separate coaxes for the audio leads from the Saturn 10 pin mini din connector. Only composite video and s-video cables are built this way.

If there is some demand, I bet retro console accessories on eBay (RetroAccess here, I think) would build some.

It appeared to be tough enough for that seller to find 12C 28AWG cable stock with only outer shielding... I don't think they'll start using "real" SCART/RGB21 cable stock (separate coaxes for R/G/B/S/L/R).

[naiaru]

1. Buy:
-CS8406 IC(s) (http://www.digikey.com/scripts/DkSearch ... =148064371)
-DIP Adapter board (http://www.schmartboard.com/index.asp?p ... dip&id=448)
-Couple of 0.1uF ceramic caps
-100uF electrolytic cap
-Single conductor wire (~26 AWG)
-374 ohm resistors
-90.9 ohm resistors
-RCA panel mount jack

2. Solder CS8406 to DIP adapter board
3. Link all CS8406 pins for +5VDC and GND respectively together (see gamesx diagram)
4. Add decoupling capacitors
5. Wire pins/test points described in the gamesx wiki to the respective CS8406 pins (dip adapter)
6. Add voltage divider resistors, and connect output to RCA connector, or track down an optical transmitter and go with that
7. Connect SPDIF to sound system and enjoy!

Awesome! But what do I solder the caps and resistors you listed to?

[Ed Oscuro]

Alternatively you'd need a cable that has separate coaxes for the audio leads from the Saturn 10 pin mini din connector. Only composite video and s-video cables are built this way.

If there is some demand, I bet retro console accessories on eBay (RetroAccess here, I think) would build some.

It appeared to be tough enough for that seller to find 12C 28AWG cable stock with only outer shielding... I don't think they'll start using "real" SCART/RGB21 cable stock (separate coaxes for R/G/B/S/L/R).

So it's worth saying that one supplier, Retro Gaming Cables, reportedly is on record saying that shielding isn't important. I don't know if their stance would change if asked.

Retro Console Accessories was criticized in that thread for not shielding cables, but their current eBay listings say their cables are shielded (and grounded, I believe, when she responded to a question I asked here). She also stated that she is open to thoughts on improving audio quality on these cables, so by all means write her if you are interested.

I don't know what to say, personally, because spending more money on cabling isn't in the cards for me for a while, I don't think, but if I were buying more RGB cables I would definitely be interested in getting one with separate coaxes for the audio leads, as you suggest.

The S/PDIF mods seem interesting too, although that's a bit much investment for me personally (even though my headphones could benefit from it). I'm so cheap that I'm just plugging my headphones directly into an unamplified HD Audio on the back of my computer, anyways

[RGB32E]

1. Buy:
-CS8406 IC(s) (http://www.digikey.com/scripts/DkSearch ... =148064371)
-DIP Adapter board (http://www.schmartboard.com/index.asp?p ... dip&id=448)
-Couple of 0.1uF ceramic caps
-100uF electrolytic cap
-Single conductor wire (~26 AWG)
-374 ohm resistors
-90.9 ohm resistors
-RCA panel mount jack

2. Solder CS8406 to DIP adapter board
3. Link all CS8406 pins for +5VDC and GND respectively together (see gamesx diagram)
4. Add decoupling capacitors
5. Wire pins/test points described in the gamesx wiki to the respective CS8406 pins (dip adapter)
6. Add voltage divider resistors, and connect output to RCA connector, or track down an optical transmitter and go with that
7. Connect SPDIF to sound system and enjoy!

Awesome! But what do I solder the caps and resistors you listed to?

http://www.cirrus.com/en/pubs/proDatash ... 406_F6.pdf - Read through pages 27 through 31.

[naiaru]

1. Buy:
-CS8406 IC(s) (http://www.digikey.com/scripts/DkSearch ... =148064371)
-DIP Adapter board (http://www.schmartboard.com/index.asp?p ... dip&id=448)
-Couple of 0.1uF ceramic caps
-100uF electrolytic cap
-Single conductor wire (~26 AWG)
-374 ohm resistors
-90.9 ohm resistors
-RCA panel mount jack

2. Solder CS8406 to DIP adapter board
3. Link all CS8406 pins for +5VDC and GND respectively together (see gamesx diagram)
4. Add decoupling capacitors
5. Wire pins/test points described in the gamesx wiki to the respective CS8406 pins (dip adapter)
6. Add voltage divider resistors, and connect output to RCA connector, or track down an optical transmitter and go with that
7. Connect SPDIF to sound system and enjoy!

Awesome! But what do I solder the caps and resistors you listed to?

http://www.cirrus.com/en/pubs/proDatash ... 406_F6.pdf - Read through pages 27 through 31.

Thank you! But on pg. 35, I'm not sure what that diagram is saying. Am I adding a 374 Ohm and 90.9 Ohm capacitor to TXP / pin 26?

Also, I think I understand what to do with the 0.1uf caps from pg. 31 "The VD and VL supplies should be decoupled with a 0.1uF capacitor to GND" But I can't seem to find the 100uf cap and Ctrl+F only finds "capacitors" in that one paragraph.

[naiaru]

Sorry to both bump an old thread and double post, but I only just now got all the parts that were listed and I was wondering if the caps' voltage ratings mattered and I'm still not sure where to solder the 100uf cap or the resistors after reading that link.

[RGB32E]

Sorry to both bump an old thread and double post, but I only just now got all the parts that were listed and I was wondering if the caps' voltage ratings mattered and I'm still not sure where to solder the 100uf cap or the resistors after reading that link.

Since the circuit uses 5VDC you should use capacitors rated for >5V (i.e. 6.3V or above).

For the 100uF cap I mentioned I have used 10V rated ones. I add it as an extra bypass capacitor on the circuit board within about 1" of either of the voltage input pins (+ to 5VDC and - to ground).

[naiaru]

All right, the 100uf cap has a 25v rating and the .1uf caps have a 50v rating so I guess I'm okay?

Here's what I'm going to do and I'd appreciate it if someone could tell me where I go wrong: I'll attach each pin on the CS8406 in the CS8406 column on the gamesx link to the PCM1710 pins in the PCM1710 column, adding a single 374 ohm resistor and a single 90.9 resistor both to the TXP pin that will then go to a RCA jack for output. Then I'll connect +5v and Ground together with a 100uf capacitor. I'll also connect both pin 6 and pin 23 (VD and VL) to pin 22 (GND) with a .1uf capacitor for each. I'll ignore everything in the Notes section. Also, I read something about hex inverters in a thread on racketboy, I take it I can ignore that stuff too?

[darcagn]

1. Buy:
-CS8406 IC(s) (http://www.digikey.com/scripts/DkSearch ... =148064371)
-DIP Adapter board (http://www.schmartboard.com/index.asp?p ... dip&id=448)
-Couple of 0.1uF ceramic caps
-100uF electrolytic cap
-Single conductor wire (~26 AWG)
-374 ohm resistors
-90.9 ohm resistors
-RCA panel mount jack

2. Solder CS8406 to DIP adapter board
3. Link all CS8406 pins for +5VDC and GND respectively together (see gamesx diagram)
4. Add decoupling capacitors
5. Wire pins/test points described in the gamesx wiki to the respective CS8406 pins (dip adapter)
6. Add voltage divider resistors, and connect output to RCA connector, or track down an optical transmitter and go with that
7. Connect SPDIF to sound system and enjoy!

Are you just leaving the emphasis line floating, grounded, or high? If so, won't the Cirrus chip expect the audio is pre-emphasized and will provide set the pre-emphasis flag where it isn't needed, leaving the receiver to de-emphasize audio that doesn't need de-emphasis? Or do I have this wrong? I just did the SPDIF mod to my Dreamcast recently, and I didn't have any parts to invert the emphasis line so I wired it straight through and even though it sounds great, but I'm worried I'm hearing it 'wrong' technically speaking since the receiver is likely de-emphasizing the audio, so I'll be adding an inverter to the circuit now that the proper ICs to do so have come in from Mouser.

[naiaru]

What ICs did you get? And it takes more than one to "invert" it?

[darcagn]

What ICs did you get? And it takes more than one to "invert" it?

It only takes one to invert a signal, I just order multiples of most parts necessary to perform mods as it's almost always so cheap. The inverter chip I used is only $.38 apiece and I will likely end up modding multiple consoles for myself and others over time.

I opened the Dreamcast back up last night and inverted the signal. I can't really tell a difference, but I didn't listen with a side-by-side comparison or anything, regardless if this is the way it's supposed to be done, that's the way I want to do it. I used this IC to invert the signal. That's the surface mount version so it's really tiny, there's a DIP version as well but I don't have any problem soldering to tiny legs so I went with what's smaller. Using the chip should be easy if you look at the datasheet, you just need 4 pins, 5V, GND, emphasis signal in, and emphasis signal out. You could also use a transistor to make an inverter but this was just easier for me.

[naiaru]

The data sheet lists like 6 inputs and 6 outputs, which do you use?

[darcagn]

The data sheet lists like 6 inputs and 6 outputs, which do you use?

I used the first input/output, but it doesn't matter, you can use any input/output pair. They all do the same thing, the IC allows for inverting 6 independent signals.

[naiaru]

Will this work the same?

Also, when you did the mod on your Dreamcast, did you use an RCA jack or did you use optical? And if you used RCA, did you connect the TXP pin and the RCA jack with both a 374 ohm resistor and a 90.9 ohm resistor?

[darcagn]

Will this work the same?

Also, when you did the mod on your Dreamcast, did you use an RCA jack or did you use optical? And if you used RCA, did you connect the TXP pin and the RCA jack with both a 374 ohm resistor and a 90.9 ohm resistor?

Yes, that should work. Just remember, that's a surface mount version so it's quite tiny. Not like it's a big loss if you destroy it, and I didn't personally find it difficult to solder to, but just warning ya!

I use RCA jacks for mine. You can get them in S/PDIF orange style for $1.25 over at console5. TOSLINK jacks are usually like $10 so this is cheaper. For resistors, I used 330 and 91 ohm resistors as some tutorials say to use.

[naiaru]

Oh, could I ask what tutorials you used?

[darcagn]

Oh, could I ask what tutorials you used?

I used the same ones from gamesx.com that RGB32E posted above.

http://gamesx.com/wiki/doku.php?id=av:saturn_sp_dif
http://gamesx.com/wiki/doku.php?id=av:dreamcastda
http://gamesx.com/wiki/doku.php?id=av:snes_sp_dif

The SNES one doesn't use an inverter, though, I'm assuming they just leave EMPH high since the SNES doesn't play optical discs and therefore shouldn't have any content that uses emphasis.

[darcagn]

Went ahead and tackled this mod this morning. If you do decide to take it on let me know if you have any questions.

My Saturn had the TDA1386T chip. It's a V0.8 motherboard, modded with a region-free BIOS and a modchip.

Images of the mod:

Spoiler

It seems like there's 800 revisions of the Saturn's hardware...


The Saturn is spacious inside, but there's actually not too much good area to put a S/PDIF jack. I chose this small section next to the A/V connector as it seemed the best place near the other ports.




Everything soldered to the points on the Saturn


Turned out messier than I'd have liked, but it worked great on the first powerup and I decided to close 'er up. The small inverter chip is what's inside that heatshrink.


The final look on the outside.

[naiaru]

Thanks for posting those pics! I'm still waiting on those inverter chips to arrive, but what's the deal with the two wires to that surface-mount cap?

[darcagn]

Thanks for posting those pics! I'm still waiting on those inverter chips to arrive, but what's the deal with the two wires to that surface-mount cap?

It's a decoupling capacitor (connects 5V and ground). The 5V and ground wires for the Cirrus chip can come off anywhere there's 5V and ground on the motherboard, so I chose the pads that capacitor's legs were connected to, as they are bigger/easier pads than soldering to the legs on the chip, but still nearby so I'm not making (more of) a mess of wires everywhere. Also, the 5V and ground legs on the chip are on the same side as those other 4 wires, it was gonna be a more difficult soldering job to get so many wires on legs of the DAC IC without bumping stuff around.

[naiaru]

Sorry for the noob questions but is it okay to use the same 5V pin for both the Cirrus chip and the hex inverter?

And which of these is pin 1? Is it the one next to the indent? And which pin is the last one? Is it the one above 1 on on the opposite corner?

[bobrocks95]

So it's worth saying that one supplier, Retro Gaming Cables, reportedly is on record saying that shielding isn't important. I don't know if their stance would change if asked.

I know it's not exactly the topic of the thread, but fwiw, the one Genesis 2 cable I bought from Retro Gaming Cables:
1) Wasn't shielded at all
2) Had horrible audio buzzing to the point where I HAD to use the Sega CD's rca out ports
3) Didn't have the ground pins wired for the R, G, B, and composite video lines, which translated to it not showing any video at all, so I had to daisy-chain the ground together myself (which believe me, with my horrible soldering skills, was not pretty).

[darcagn]

Sorry for the noob questions but is it okay to use the same 5V pin for both the Cirrus chip and the hex inverter?

Don't worry about the questions, I've been soldering in modchips and stuff since I was about 13, but that was all just following exact detailed instructions--literally all I know about this stuff beyond that I've learned in the past year, so I understand where you're coming from.

Yes, you can use the same point for 5V for both chips.

And which of these is pin 1? Is it the one next to the indent? And which pin is the last one? Is it the one above 1 on on the opposite corner?

The pin near the indent is pin 1, and the last pin is the pin directly opposite it, so the pin numbering goes around the chip like a U shape. When in doubt, just Google the chip's label + the word "datasheet"--datasheets should always have that info. Here's the datasheet for the PCM1710U, which has a diagram that shows the pin layout labelled.

I know it's not exactly the topic of the thread, but fwiw, the one Genesis 2 cable I bought from Retro Gaming Cables:
1) Wasn't shielded at all
2) Had horrible audio buzzing to the point where I HAD to use the Sega CD's rca out ports
3) Didn't have the ground pins wired for the R, G, B, and composite video lines, which translated to it not showing any video at all, so I had to daisy-chain the ground together myself (which believe me, with my horrible soldering skills, was not pretty).

That's been my experience with Retro Gaming Cables as well. I purchase all my cables from retro_console_accessories on eBay now. While her cables still have some buzz, it seems that all SCART cables inevitably have some buzz and hers seem to be made with the highest quality cabling she can find at a realistic price.

[naiaru]

I think this might be above my skill level. I can't connect the chip to the adapter board at all. It might be doable if say there were an adapter board with indents at the contact pads since the chip moves around whenever I put the iron to it. If I run my finger over the board I can feel the contact pads, so hopefully those don't count as indents.

Also, I was wondering, why would the shielding of the SCART cable matter for my buzzing audio problem if I wasn't using the SCART cable for audio?

[darcagn]

I think this might be above my skill level. I can't connect the chip to the adapter board at all. It might be doable if say there were an adapter board with indents at the contact pads since the chip moves around whenever I put the iron to it. If I run my finger over the board I can feel the contact pads, so hopefully those don't count as indents.

Place the adapter board on your tabletop, then place the chip on top of the adapter board. Using your left hand, hold the chip in place where it needs to be. Apply flux along the legs of the chip (I personally use a flux pen). Tin your soldering iron with solder, and while still holding the chip in place with your left hand, touch the iron to the legs on each corner of the chip. The solder will leave the tip of the iron and flow to the legs thanks to the flux. Once you have the corner legs soldered down, the chip won't move and you're free to solder as you are comfortable.

In general, it's frowned upon to apply solder directly from the tip of the iron to the component you're trying to solder to, because the flux will have already been burned off. But this technique works nicely for an application such as this, as long as you apply flux manually.

Also, I was wondering, why would the shielding of the SCART cable matter for my buzzing audio problem if I wasn't using the SCART cable for audio?

It won't matter, if you're not using the SCART cable for audio. I was responding to bobrocks95.