The State of DACs for the MiSTer and Direct Video

[antoniovillena]

I had one more test for the day, I tested one of the Mister Addon's Analog I/O boards. To be clear there appears to be two versions of the Ref 6.1 analog I/O board, on the dac test results sheet, the Mister Multisystem shows what the what I call "high" version looks like. The Mister Addons board in the sheet shows the "low" version. A delta of 140mV at 100 IRE is just crazy imo for a "reference" design. I think the low version might actually be worse then the AG6200. It starts going darker sooner, at 50 IRE, then flatlines around 2.6-2.7 gamma, which is very dark! Also the highlights are darker as well, it maxes out around 83 nits at 100 IRE, again noticeably dark. Worst of all you don't know what you'll get, high or low voltage i/o board, its a lottery... we need vendors to step up and test their products and document what were getting, is that too much to ask?

https://tinyurl.com/dactestresults

Hi. I am interested to add my IO BOARD to the spreadsheet. I will send one unit. Please contact me by PM or email.

[CMR]

I wonder if the difference in IO boards might have something to do with the resistor packs not being soldered well enough. I had this issue with my first IO board (v5.5) with the audio not having stereo output. I managed to fix it by reflowing the resistors for it.

[thorr]

I am looking forward to seeing Antonio's tested. It should/might be better than all the others because it has full range RGB capabilities.

[Peredonov]

Probably useless for most MiSTer users, but it would be interesting also to see Jim Drew's (CBMStuff) IO board's analogue video tested. This board seems to be of better quality than the standard IO board, and the manual for it specifies "three 6-bit linear R2R ladders to provide a 18 bit (6-6-6) DAC color output. The each leg of the resistor ladder is connected directly to the FPGA chip."

[KnuckleheadFlow]

http://tinyurl.com/dacanalysis

Just wanted to say I appreciate your efforts here.

Canceled my order for the Tripp Lite P131-06N (didn’t know it’s the AG6200 and that can be had for less if I’m gonna settle). Tried to order a Vention HDMI to HDMI+VGA but apparently Vention won’t sell to Canada? On their Ali Express store it’s not available to be shipped to my address.
Found the last StarTech HD2VGAA2 on sale at BestBuy.ca for $32, so I hope it’ll be good enough.

Btw, any idea why the Vention with the Lontium does so much better than the Ontens with the same? Is that ‘_ex3’ a lower spec version or something?

[jd213]

I think the only Vention adapter known to have good measurements was the one with both VGA and HDMI outputs, and that one has been out of stock on Aliexpress for a while.

[KnuckleheadFlow]

I think the only Vention adapter known to have good measurements was the one with both VGA and HDMI outputs, and that one has been out of stock on Aliexpress for a while.

Ah ok. Yeah that’s the one I was going for. I thought it was some weird regional restriction when it said it can’t be shipped to me.

[KnuckleheadFlow]

So I finally got a StarTech HD2VGAA2 after some tomfoolery where the Best Buy seller didn’t ship the adapter for over a week and then shipped me some no name $10 amazon special instead (money refunded right away). Of course first thing I did was take the StarTech apart, not turn it on.

Seems this one has an ITE IT6693, instead of the IT6695. I can’t find much about it online. No mention of it in the 6695 data sheet I got from ITE, but the 6695 is mentioned as a drop in replacement for the 6693 in the dongle reference design they sent along with the data sheet. I emailed the rep that sent it about what the difference is, hope it’s not lower spec or anything. Maybe it just doesn’t have 5V tolerant inputs of the 6695?

Edit: No functional difference according to the rep: “IT6693 has been EOL, and replacement product is IT6695, the function is exactly the same”

Digital audio goes to what appears to be a Cirrus Logic CS4344 24 bit DAC. Don’t have any experience with that but it seems decent enough from a little quick googling.

[NuclearMonster]

Thank you for this analysis. I wanted the Icy Box IB-AC502 device based on the report and the only place to get it seems to be from grooves dot land in Germany. Fortunately it arrived here in Hawaii after just two weeks for only $4 in postage. I am surprised to see there are no screw terminals for the VGA side, but the Icy Box DAC works very well from a brief testing. It’s replacing the Rankie adapter in my direct video setup, which was so poorly shielded it made a terrible interference sound into the VGA-SCART cable every N milliseconds. This model of the Icy Box doesn’t carry audio, but that’s OK since I’ve switched to using optical and I’m happy to have better video quality and a video DAC that doesn’t require power.

[Sumolx]

I've also purchased the Icy Box IB-AC502 and it seems to be the Rev A model that I have received. However, I am running into an issue with my arcade monitor and that it does not lock onto the vertical sync with this adapter. Based on the spreadsheet, this adapter shouldn't require an mods, but I do see the picture rolling perfectly vertically.... i can almost lock onto it but with no success on the main menu. Same applies to when I start a game like Street Fighter Alpha 3. Via Analog IO module, everything is displayed correctly. Am I missing an ini setting besides enabling direct video?

[GeCe]

I've also purchased the Icy Box IB-AC502 and it seems to be the Rev A model that I have received. However, I am running into an issue with my arcade monitor and that it does not lock onto the vertical sync with this adapter. Based on the spreadsheet, this adapter shouldn't require an mods, but I do see the picture rolling perfectly vertically.... i can almost lock onto it but with no success on the main menu. Same applies to when I start a game like Street Fighter Alpha 3. Via Analog IO module, everything is displayed correctly. Am I missing an ini setting besides enabling direct video?

Enable composite sync if you don't combine H and V sync

[Sumolx]

I've also purchased the Icy Box IB-AC502 and it seems to be the Rev A model that I have received. However, I am running into an issue with my arcade monitor and that it does not lock onto the vertical sync with this adapter. Based on the spreadsheet, this adapter shouldn't require an mods, but I do see the picture rolling perfectly vertically.... i can almost lock onto it but with no success on the main menu. Same applies to when I start a game like Street Fighter Alpha 3. Via Analog IO module, everything is displayed correctly. Am I missing an ini setting besides enabling direct video?

Enable composite sync if you don't combine H and V sync

For the Jamma spec I have the settings set to rgb and composite sync and all works fine with analog io but when I enable direct video to use the hdmi to vga adapter the image just scrolls slowly across the screen and I'm unable to lock on.

If I was to describe it... it's like the direct video vertical sync is way off when compared to analog io. I have to adjust the v-hold quite a bit just to get the image to scroll slowly across the screen. This applies to the main menu and any core I load up. When the core loads up I then have to adjust v-hold again as it is significantly off as well.... I can get close to locking in but it is way off compared to analog io v-hold adjustment.

Edited...
Just purchased the ugreen adapter based off the ag6201 and going to see how it works.

Edit #2
Why does analog io and direct video resolutions differ?

IMG_5264.jpeg (5.79 MiB) Viewed 1421 times

[mr-box]

i just got the Icy Box does not work for component still need to add the diode (1N4148) and a 330ohm resistor which blows ass . anybody have any ideas how to make it work with out breaking the case on it

[Sumolx]

The ugreen ag6201 is also behaving the same way.... unable to lock in the vertical scrolling.... the direct video signaling is not identical to analog io so it's not usable for my setup which is an Arcade CGA monitor via RGBs.