The State of DACs for the MiSTer and Direct Video

[Kuro Houou]

There has been a lot more discussion and questions around Direct Video lately, especially with the possibility of more Mister setups going dual sdram. With that said there is also a lot of bad information out there about the DACs themselves and the effects it has on the video output. DACs are a small but very important component and people deserve to know not all DACs are the same and the ones commonly recommended, based on the AG6200 are actually some of the worst out there. I took a lot of my time to analyze and try to identify just what makes a good DAC, and what people really should look for. If you have the time please take a look here, http://tinyurl.com/dacanalysis. The analysis section has many screen shots (more on Google drive) that really help visualize the state of DACs available today.

[callanabrown]

This was great! I was skeptical but I think I will try to seek out something better than the Rankie I have.

[jd213]

Has the ringing problem of the HD Fury 3 been fixed? I avoided it for that reason, currently using a Benfei cable. The Vention adapter looks like it would be good enough for me, might get that if it comes back in stock.

[akeley]

It's a nice write up, thanks a lot.

I think the "No one should use the AG6200 based DACs however unless you just can’t use anything else and the world depends on you getting a video signal of some kind." is a bit of an overdramatization though. I've been using one for over a year when I first got a MiSTer (with high quality TV sets), just like most other DV users, and I never really had a "it's too dark" problem in games, simply because I would tweak contrast/brightness when necessary. It might not result in a "reference level" image of course, but then, if you're into a CRT hobby you'd better get used to compromises.

In some cases (eg Castlevania) I actually prefer the crushed look, though that also depends on a day. Bottom line is, while far from perfect these AG6200 based DACs can also deliver a very enjoyable experience.

A big problem also is locating DACs with appropiate chips (and the fact that these sometimes change even though box might look the same). A quick search for that particular Vention around here in Europe did not return much, apart from their AG-based one. If somebody has links to reputable/confirmed sellers it would be most welcome.

[Armakuni]

The Cableader branded adaptors on Amazon for around £5 work great. Tried a couple over the past few years with no issues

[Kuro Houou]

It's a nice write up, thanks a lot.

I think the "No one should use the AG6200 based DACs however unless you just can’t use anything else and the world depends on you getting a video signal of some kind." is a bit of an overdramatization though. I've been using one for over a year when I first got a MiSTer (with high quality TV sets), just like most other DV users, and I never really had a "it's too dark" problem in games, simply because I would tweak contrast/brightness when necessary. It might not result in a "reference level" image of course, but then, if you're into a CRT hobby you'd better get used to compromises.

In some cases (eg Castlevania) I actually prefer the crushed look, though that also depends on a day. Bottom line is, while far from perfect these AG6200 based DACs can also deliver a very enjoyable experience.

A big problem also is locating DACs with appropiate chips (and the fact that these sometimes change even though box might look the same). A quick search for that particular Vention around here in Europe did not return much, apart from their AG-based one. If somebody has links to reputable/confirmed sellers it would be most welcome.

So two things, first, I am all for the you do you mentality, if something looks good to you, I am not going to judge. My biggest gripe is when people develop and sell products and not tell people the product is not meeting reference standards or show test results as I think every product should be properly tested and run at reference levels, that's just a given and no excuses there.

So in your case you have a AG6200, you tweaked your TV settings, bumping up brightness, which yeah can sort of get you where you want to be.. however, if you go plug in say a SNES or DVD player, now all those will looked washed out.. its why we have reference specs, so things will look right, no matter what you plug in. So there are trade offs.

But you also hit on another point, availability.. the Vention would be nice but its near impossible to find, I am looking for alternatives though and will post as soon as I find them! I have a couple coming I need to test... That said, there are still others out there better then the AG6200 DAC's that you could use in the meantime

But thanks for reading and your comments, appreciate all the feedback!

[Kuro Houou]

The Cableader branded adaptors on Amazon for around £5 work great. Tried a couple over the past few years with no issues

Do you have a link to this one?

[Kuro Houou]

Has the ringing problem of the HD Fury 3 been fixed? I avoided it for that reason, currently using a Benfei cable. The Vention adapter looks like it would be good enough for me, might get that if it comes back in stock.

Curious what ringing your referring too.. I haven't notice any issues myself. Are their any examples of what it is? Happy to take a look.

[Armakuni]

The Cableader branded adaptors on Amazon for around £5 work great. Tried a couple over the past few years with no issues

Do you have a link to this one?

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

[callanabrown]

The Cableader branded adaptors on Amazon for around £5 work great. Tried a couple over the past few years with no issues

Do you have a link to this one?

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

Those look identical to the Rankie ones, and the whole point of the article was to show that they are not the best quality out there.

I noticed the StarTech HD2VGAE2 which is a ~$30 one uses a different chipset "IT6695FN", anyone have any experience with that one?

[Armakuni]

Do you have a link to this one?

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

Those look identical to the Rankie ones, and the whole point of the article was to show that they are not the best quality out there.

I noticed the StarTech HD2VGAE2 which is a ~$30 one uses a different chipset "IT6695FN", anyone have any experience with that one?

Lots of them look identical though, some dont even work. You cant tell just from the case or even ports on them sadly which is the best thing about Amazon returns policy

EDIT

for example look at these two. Nether are sold as Rankie branded but one works perfectly well and the other does not work at all.

nKpYqsQ.jpeg (1.82 MiB) Viewed 31357 times

[bricabrac]

There has been a lot more discussion and questions around Direct Video lately, especially with the possibility of more Mister setups going dual sdram. With that said there is also a lot of bad information out there about the DACs themselves and the effects it has on the video output. DACs are a small but very important component and people deserve to know not all DACs are the same and the ones commonly recommended, based on the AG6200 are actually some of the worst out there. I took a lot of my time to analyze and try to identify just what makes a good DAC, and what people really should look for. If you have the time please take a look here, http://tinyurl.com/dacanalysis. The analysis section has many screen shots (more on Google drive) that really help visualize the state of DACs available today.

Thank you so much for reaserch and analysis. That must have been a tremendous amount of work. It is very rare to see this kind of scientific approach nowadays. Your work has answered all my questions/doubts/unknowns about video DAC paired with MiSTer and I cannot thank enough.

And on a side note, you have specifically marked StarTech DAC as RGBHV, however as per the specification HDFury 3 is also RGBHV https://www.hdfury.eu/shop/hdfury3/. Or is it not? When did you buy yours if I may ask? The case of yours looks a little bit different than on the website so could they change something?

And regarding combining the H and V syncs did you just use BNC T Adapter or something more fancy?

[akeley]

My biggest gripe is when people develop and sell products and not tell people the product is not meeting reference standards or show test results as I think every product should be properly tested and run at reference levels, that's just a given and no excuses there.

I don't know which products you are referring to, but I'm pretty sure the ones from Ultimatemister were developed and sold without any bad intentions. I know Ricardo a little, and can vouch for his integrity as a seller, and as somebody who helped to test these cables know that he did try to do at least some due dilligence (I myself don't have neither machinery nor knowledge to help with such testing, and at the time we were trying to solve DV's core compatibility problems anyway).

It's worth remembering that MiSTer's CRT users are a niche within a niche. And so, the information regarding this subject is not easily available (or at least wasn't at the beginning) , often scattered around the web and hard to piece together. For a long time all the info regarding DV was the Wiki page, and since it mentioned AG6200, everyone went along with that. That in turn was also caused by the lottery factor when buying random DACs - large number of which wouldn't work (or at least was reported to not work in various people's setups) and so the AG one was at least something to aim for (though also not always with success). There are plenty of forum threads to attest to that.

I've been hunting for CRT info myself a lot during my first two years with MiSTer - including putting out a call for contributors while writing the Wiki's CRT Guide - and don't recall seeing any concrete info on the subject of your paper before. Otherwise I'd certainly have mentioned it (and it definitely should be included in this page's update, amongst other things). I suppose it was the same with Ricardo, and perhaps other sellers. People with in-depth knowledge of this subject are thin on the ground, at least around here, it seems. The other factor might've been availability too - the chip shortage was (is?) no joke... All in all, it's a hobbyist manufacturing so perhaps some leeway with mistakes should be allowed. Though I agree that relevant information should be always clearly stated.

So, again, big thanks for your work on the comprehensive testing and research you have done, it's definitely a valuable new resource. But, I wouldn't be (personally) telling everybody to chuck their poor ol' AG-based DVs into a bin yet At least not until affordable substitutes are easily available.

Myself, I would like to grab one of the good un's for sure, even though I haven't used DV in a long time - I prefer I/O board now for its 100% compatibility. Again, the trade offs, the trade offs...

[jd213]

Has the ringing problem of the HD Fury 3 been fixed? I avoided it for that reason, currently using a Benfei cable. The Vention adapter looks like it would be good enough for me, might get that if it comes back in stock.

Curious what ringing your referring too.. I haven't notice any issues myself. Are their any examples of what it is? Happy to take a look.

Sure, here's a link: https://junkerhq.net/xrgb/index.php?tit ... s_for_OSSC
It's not too bad, but for the premium price of an HD Fury I'd expect better.

[Kuro Houou]

Do you have a link to this one?

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

Those look identical to the Rankie ones, and the whole point of the article was to show that they are not the best quality out there.

I noticed the StarTech HD2VGAE2 which is a ~$30 one uses a different chipset "IT6695FN", anyone have any experience with that one?

I have this one inbound and will add it to the sheet in the next week or two

[Kuro Houou]

Has the ringing problem of the HD Fury 3 been fixed? I avoided it for that reason, currently using a Benfei cable. The Vention adapter looks like it would be good enough for me, might get that if it comes back in stock.

Curious what ringing your referring too.. I haven't notice any issues myself. Are their any examples of what it is? Happy to take a look.

Sure, here's a link: https://junkerhq.net/xrgb/index.php?tit ... s_for_OSSC
It's not too bad, but for the premium price of an HD Fury I'd expect better.

Hmm, I can't say I have ever noticed anything like that before, I also haven't heard anyone else that I know who has one mention it either.. maybe was a bad device or bad cable.. not sure exactly. I definitely have seen ghosting or artifacting like that with VGA devices in the past in general, usually from a lower grade cable or additional devices in the chain like switchers.. I've stared at a lot of test patters with the HDFury 3 and 4, using a microscope during calibrations.. never seen that though.

[Kuro Houou]

My biggest gripe is when people develop and sell products and not tell people the product is not meeting reference standards or show test results as I think every product should be properly tested and run at reference levels, that's just a given and no excuses there.

I don't know which products you are referring to, but I'm pretty sure the ones from Ultimatemister were developed and sold without any bad intentions. I know Ricardo a little, and can vouch for his integrity as a seller, and as somebody who helped to test these cables know that he did try to do at least some due dilligence (I myself don't have neither machinery nor knowledge to help with such testing, and at the time we were trying to solve DV's core compatibility problems anyway).

It's worth remembering that MiSTer's CRT users are a niche within a niche. And so, the information regarding this subject is not easily available (or at least wasn't at the beginning) , often scattered around the web and hard to piece together. For a long time all the info regarding DV was the Wiki page, and since it mentioned AG6200, everyone went along with that. That in turn was also caused by the lottery factor when buying random DACs - large number of which wouldn't work (or at least was reported to not work in various people's setups) and so the AG one was at least something to aim for (though also not always with success). There are plenty of forum threads to attest to that.

I've been hunting for CRT info myself a lot during my first two years with MiSTer - including putting out a call for contributors while writing the Wiki's CRT Guide - and don't recall seeing any concrete info on the subject of your paper before. Otherwise I'd certainly have mentioned it (and it definitely should be included in this page's update, amongst other things). I suppose it was the same with Ricardo, and perhaps other sellers. People with in-depth knowledge of this subject are thin on the ground, at least around here, it seems. The other factor might've been availability too - the chip shortage was (is?) no joke... All in all, it's a hobbyist manufacturing so perhaps some leeway with mistakes should be allowed. Though I agree that relevant information should be always clearly stated.

So, again, big thanks for your work on the comprehensive testing and research you have done, it's definitely a valuable new resource. But, I wouldn't be (personally) telling everybody to chuck their poor ol' AG-based DVs into a bin yet At least not until affordable substitutes are easily available.

Myself, I would like to grab one of the good un's for sure, even though I haven't used DV in a long time - I prefer I/O board now for its 100% compatibility. Again, the trade offs, the trade offs...

Thanks for your feedback. Really it's not directed at anyone in particular, more so the industry as a whole who defaults to AG6200 DAC's or really any other DAC without testing because they are cheap and plentiful without realizing how bad they are. While Mister CRT users may be in the minority, I also think a lot of them really want high quality parts to get the most out of their $$ spent. Which is why I think when people are making products for the Mister or any device that needs an analog conversion, they should think twice about using higher quality IC's. I think most people would gladly pay another couple bucks more not to have blacks crushed over over exposure.

Also I fully realize the CRT group within the Mister group is a sub category and is often seen as a second class citizen.. but again, if your going to make and sell devices to those people, just take some time, do your research, hook it up to an oscilloscope and post your results so everyone can be informed.. that's all I ask really.

Again, this was really about education and getting information out there so everyone can make a more informed decision.

As for the AG6200's that exist.. that's each individuals choice, but as you will see in the DAC Test Sheet I have that goes along with the paper, there are better options for <$10 bucks out there. Might be worth the upgrade.

[jd213]

Curious what ringing your referring too.. I haven't notice any issues myself. Are their any examples of what it is? Happy to take a look.

Sure, here's a link: https://junkerhq.net/xrgb/index.php?tit ... s_for_OSSC
It's not too bad, but for the premium price of an HD Fury I'd expect better.

Hmm, I can't say I have ever noticed anything like that before, I also haven't heard anyone else that I know who has one mention it either.. maybe was a bad device or bad cable.. not sure exactly. I definitely have seen ghosting or artifacting like that with VGA devices in the past in general, usually from a lower grade cable or additional devices in the chain like switchers.. I've stared at a lot of test patters with the HDFury 3 and 4, using a microscope during calibrations.. never seen that though.

OK, that's promising, maybe it was fixed at some point (I still don't think I'd be willing to pay the going rate for an HDMI Fury 3 though). You might want to ask BuckoA51 about it, not sure what would be the best way to get in touch, maybe through https://videogameperfection.com/contact-us/

[justaguy]

Did you test the AG6200 DAC with hdmi_limited=2 set in MiSTer.ini? My understanding is that it was added to address this exact issue. I'd encourage people to buy standards-compliant products regardless, but if a workaround is available, that should be mentioned.

[Armakuni]

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

Those look identical to the Rankie ones, and the whole point of the article was to show that they are not the best quality out there.

I noticed the StarTech HD2VGAE2 which is a ~$30 one uses a different chipset "IT6695FN", anyone have any experience with that one?

I have this one inbound and will add it to the sheet in the next week or two

I had to time to take the case off and it's AG6201 based

1jTPu0L.jpg (153.93 KiB) Viewed 23652 times

[Armakuni]

Did you test the AG6200 DAC with hdmi_limited=2 set in MiSTer.ini? My understanding is that it was added to address this exact issue. I'd encourage people to buy standards-compliant products regardless, but if a workaround is available, that should be mentioned.

As far as I know that was added for DACs that were not AG6200 based ....

[rezb1t]

Did you test the AG6200 DAC with hdmi_limited=2 set in MiSTer.ini? My understanding is that it was added to address this exact issue. I'd encourage people to buy standards-compliant products regardless, but if a workaround is available, that should be mentioned.

As far as I know that was added for DACs that were not AG6200 based ....

Not true, it was added specifically for AG6200 and AG6201 DACs

[Kuro Houou]

Do you have a link to this one?

Yeah sure https://www.amazon.co.uk/dp/B08HXRQGXM

Those look identical to the Rankie ones, and the whole point of the article was to show that they are not the best quality out there.

I noticed the StarTech HD2VGAE2 which is a ~$30 one uses a different chipset "IT6695FN", anyone have any experience with that one?

Just wanted to let you know I just added this one to the list, can find the results here, https://tinyurl.com/dactestresults.

One thing I wanted to point out as I was testing this, I did further analysis into how individual channel levels affect your calibration. It looks like a delta of about 5-10mV in Red or Blue color channels can cause a +1.0 error in your gray scale. In this case, it showed about 12mV delta in Red from Green at 100 IRE, resulting in an increase of +2.0 dE at 100 IRE!! all that work for a good calibration down the drain As always, use a quality DAC when connecting your video components!

[Kuro Houou]

Did you test the AG6200 DAC with hdmi_limited=2 set in MiSTer.ini? My understanding is that it was added to address this exact issue. I'd encourage people to buy standards-compliant products regardless, but if a workaround is available, that should be mentioned.

As far as I know that was added for DACs that were not AG6200 based ....

Not true, it was added specifically for AG6200 and AG6201 DACs

Or was it added for TV's that were calibrated for Limited Range like modern TV's setup for rec709 and calibrated for something like a BluRay?? Lots of variables, but at the end of the day it is a hack that can compress the grayscale range or a source that was supposed to be full, then hope the DAC de-compresses it properly. Or just buy a 10 dollar DAC that isn't a AG6200 and problem solved. At the end of the day any AG6200 DAC is a grenade.. they all crush blacks, they are a complete lottery on if you will get one with even decent video levels at 100 IRE, could be right on the money at 700mV, or it could be 750mV giving you insane luminance on white screens. Also could have horrible R/G/B voltage separation, making things look warmer or cooler then they should. Just not worth the trouble imo when there are better options at the same price point.

[FoxbatStargazer]

As far as I know that was added for DACs that were not AG6200 based ....

Not true, it was added specifically for AG6200 and AG6201 DACs

Or was it added for TV's that were calibrated for Limited Range like modern TV's setup for rec709 and calibrated for something like a BluRay??

limited=1 is for TVs, the standard limited range (16-235). limited=2 is specifically for certain VGA adapters, that are effectively looking for 16-255.

[Armakuni]

Did you test the AG6200 DAC with hdmi_limited=2 set in MiSTer.ini? My understanding is that it was added to address this exact issue. I'd encourage people to buy standards-compliant products regardless, but if a workaround is available, that should be mentioned.

As far as I know that was added for DACs that were not AG6200 based ....

Not true, it was added specifically for AG6200 and AG6201 DACs

Sorry my mistake i was going from memory and just checked the wiki. Apologies

[Armakuni]

One AIO i would like to see tested is the analogue output on the Ironclad ITX board as Roberto stated he spent some time getting the levels right.

From what i have used so far its the best analogue picture i have seen for MiSTer and one of the cleanest using a MD2 RGB scart cable

[Kuro Houou]

One AIO i would like to see tested is the analogue output on the Ironclad ITX board as Roberto stated he spent some time getting the levels right.

From what i have used so far its the best analogue picture i have seen for MiSTer and one of the cleanest using a MD2 RGB scart cable

Did he ever post his results? would love to see. Also would love to test one, but its very expensive and I fund all these purchases myself already. The hope is dev's will post their own results so we have something to reference

[Kuro Houou]

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

F5SA_j1XMAQc5Gw.jpg (360.14 KiB) Viewed 14690 times

[Armakuni]

Surely the suppliers of the stock IO boards just follow the open source designs ?