^ nice , and it looks they are 4-5$ on eBay... is it correct to assume that if I want I can just connect the composite output of the EXP port and not have to worry whether c-sync is digital or not?
from TI's site I gather I feed it the 4 signals , put a 100nF cap between GND/Vs+ and on the output 75ohm resistors... Do I still need 100nF caps in the input signals?
Also will the 7374 be sufficient for the N64 too?
Last edited by keropi; 07-20-2012 at 05:45 PM.
The 7374 is superior to what I've been using in N64s from the looks of things. Not sure if it would produce a noticeably improved picture but it is sure worth trying out.
Damn shame Digi-Key doesn't stock the part.
This might prove more useful for the N64:
http://www.digikey.com/product-detai...4-2-ND/1905373
36mhz.
Though it requires 5.5v. Most people seem to want to run the THS7314 off 5v when it wants 3.3v. The datasheet says 5.5v is the maximum but that extra voltage has to go somewhere.
Last edited by APE; 07-20-2012 at 06:04 PM.
http://www.assemblergames.com/forums...ad.php?t=31524
My feedback thread, since it seems somewhat difficult for people to find.
Yes if you only intend to connect it via SCART. Most likely the composite signal won't be able to drive a TV directly, but you can use the 4th amplifier.Originally Posted by keropi
You can try without the input caps and see if it works. If it works definitely omit them. The reason I suggested it is because the bad circuit suggests that the DAC is biased towards V+ instead of GND, and if the level is too high the amplifier will clip while trying to amplify it. Using the capacitor is a sure way to remove the DC bias and it will have minimal effect on the video quality.from TI's site I gather I feed it the 4 signals , put a 100nF cap between GND/Vs+ and on the output 75ohm resistors... Do I still need 100nF caps in the input signals?
Absolutely, the bandwidth may not encompass all the DAC's frequency components like PCE, but "just" 60 MHz would be have excellent pixel edges much less 150 MHz.Also will the 7374 be sufficient for the N64 too?
Are you using the THS7314? If so on a TV maybe not, the '7314 is limited 8.5 MHz by its filter, which is probably the upper end of TV bandwidth. Newer broadcast monitors and arcade monitors could definitely benefit from the '7374.
36 MHz would be acceptable for N64, it passes the 5th harmonic allowing pixel edges this steep:36mhz.
http://www.paladinmicro.com/images/F...v5thHar-01.png
Over 60 MHz would capture the 9th harmonic which is this steep:
http://www.paladinmicro.com/images/F...v9thHar-01.png
The '7374 will have an extremely steep slope.
?? It doesn't REQUIRE 5.5V, it tolerates up to 5.5V but it will run off as low as 3V.Though it requires 5.5v.
?? It doesn't want 3.3V.Most people seem to want to run the THS7314 off 5v when it wants 3.3v.
?? It's not a voltage regulator, there's no consequence for using 5.5V over 3V, in many cases 5.5V will be NECESSARY. You WANT a wide rail to rail potential so your signal doesn't end up clipping. RGB signals are 0.7 V, composite is 1.1 V NEGLECTING any biasing. These amplifiers have a gain of 2, so the outputs must be able to swing 1.4 V and 2.2V respectively. At 3V there is very little headroom to account for any DC bias, plus the output signal cannot actually reach either rail, these modern IC amplifiers are able to get pretty close though, like 0.2 V or so. So at 3V amplifying composite you'd have no choice but to remove any DC offset. Typical bipolar outputs can clip at 0.7V even higher from either rail...The datasheet says 5.5v is the maximum but that extra voltage has to go somewhere.
Last edited by Calpis; 07-20-2012 at 09:52 PM.
those who can't make, mod
Keep in mind Caplis I'm still learning (logic design starts August 11!). The datasheet for for the 7314 claims to want 3.3v with a maximum of 5.5v. I've wired the 7314 for 5v and 3.3v without any noticeable difference on my Sony PVM displays.
Probably will try a 7374 in another however I'm not sure I'll be capable of seeing a difference on something almost 20 years old.
Or this:
http://www.digikey.com/product-detai...28-5-ND/948538
150mhz.
Last edited by APE; 07-20-2012 at 10:32 PM.
http://www.assemblergames.com/forums...ad.php?t=31524
My feedback thread, since it seems somewhat difficult for people to find.
"Wrong shouldn't have air quotes,"
It would have been incorrect to not place a qualifier around the word wrong. If I didn't it would've made my statement too open to misinterpretation. I had to avoid sounding like I was trying to debate dictionary definition of wrong.
"it literally is wrong"
I never said it otherwise.
"and yes it does mean intolerable and mediocre at least."
Context. Video quality that a user experiences is not necessarily intolerable and mediocre with wrong circuits. Instances of working or non-working are known to occur.
does this look like something that will work, or will it burn up when powered? (using or not the caps in C/R/G/B input depending if it works...)
Few people ever "finish" learning electronics. I'm 9 years in and I'm not halfway to where I want to be.
I've been checking CRT bandwidth figures:on something almost 20 years old.
-ancient PVM: 10 MHz
-late Wells Gardner 15 kHz: 15 MHz
-late Wells Gardner 15/24 kHz: 22 MHz
-late PVM (20L5): 24 MHz
-late BVM (20F1U): 30 MHz
-current Wei-ya 38" (!!!) tri-scan: 65 MHz
-late Wells Gardner tri-scan: 70 MHz
-current Wei-ya VGA: 135 MHz
Some consumer PC monitors are claiming up to 350 MHz... Not sure how valid that is since video signals must be amplified 50-150x to drive a CRT.
Arcade monitors seem like the best compromise for purists. Not only do they have the best value, they're super elegant with their fully analog signal paths. Any HD video you'll be wanting to view on a fixed pixel/digital display anyway so they have the potential to be pretty much the end-all CRT. The only things pricy broadcast monitors have on them is color accuracy and geometry, but unless you get a self-calibrating one I think even that goes with time.
Right, but usually that's all thanks to the TV.
I think it'll work. You should get this http://www.ebay.com/itm/320900381229 and solder everything to the through-holes
those who can't make, mod
thanks again for the help, I'll order the parts and let you know when they arrive , I am most eager to try this on the n64 first, I don't think the current amp installed is a good one , it's just some transistors (got it pre-modded)
Right. The video artifacts never should've reached such prevalence. TV makers by that time had begun placing RGB inputs internationally. The right push may have convinced them it'd help standardize components used between regions, and hope word of mouth about RGB gaming's beauty would drive TV sales.
Cheaper console manufacturing and reduced design complexity is a benefit of RGB-only also. Less need to worry about encoders, color systems, or filtering. (apologies if this was mentioned before)
In the end it's somewhat redundant to apply a composite filter on RGB capable consoles. That's just trying to restore quality previously degraded. Cause and effect, start from s-video or RGB so you don't have composite artifacts as part of the signal chain to begin with.
Last edited by Lum; 07-22-2012 at 08:46 AM.
after all this time finally everything arrived... the TSSOP14 to DIP14 adapters and the amps themselves:
now I only need to solder the amps on the adapters, they are pretty small, any advice before I try it? or do I just flux the pads and heat with the iron with the IC in place (I think that's what I have to do) ?
awesome, thanks for the offer Bad_Ad84 , I'll try to solder them my self first and if I fail I will take up your kind gesture :)
well, unless the THS IC is super sensitive to heat I think I managed OK for a first time smd component soldering
will try the amps tomorrow and let you know how it goes
OK finally today I managed to do some testing:
it's a half-assed test mind you because the 100 and 200nf caps have not arrived yet. I used some 68nf caps for the test , so they are the wrong value. I also did not put a cap between gnd/vcc because I did not have another 68nf one.
I also did not connect to the GND the BYPASS+DISABLE+NC+NC pins, they are all just NC. I did not get a picture with them all connected to GND and I thought this was to blame LOL. But I found out later that without the caps there was no picture at all. With the 68nf ones I get this result:
I suppose when I try the 100 or 200nf the picture will improve...
edit: found another 68nf cap, put it in gnd/vcc but made no difference as expected... got some more shots though, I have moving pixels in the upper left , upper right and lower right corners of the logo box, where you can see the gfx errors.
Last edited by keropi; 08-20-2012 at 09:06 AM.
Remember that the PCE signal is nowhere near "broadcast compliant". I have a VCR and two LCD TVs that absolutely refuse to accept the signal my SGX generates, and another LCD monitor with video in that shows "flagging" for the first dozen lines of the display. So your glitches may have nothing to do with your circuit and everything to do with the timing your TV expects from the signal.
the monitor I tested with worked fine with the old rgb-amp that was discussed before , so I keep my hopes up that it will work with the 7374 too :)
I got some 100nf caps today, will try them later and report back!
100nf caps made a huge improvement (this time there is a cap between gnd/vcc and all unused pins are grounded) , there is still some discoloration effect mainly in the top and bottom parts of the screen though , and judging from the title screen there is also some kind of ghosting(?) when the color difference is great as it shows in the bottom corner of the logo box.
still waiting for the 220nf ceramic caps, but I can't help but wonder if 220nf is way too much...? maybe I need to search for some middle value (if it exists) ?
edit: also tried on a CRT tv, I get the same effect... when there is an object with great color difference it creates a horizontal "shadow" across the screen... for example the 1st moving platform in wonderboy creates a shadow that moves across the screen with the platform, seems like there is a luminance drop or something... also notice the grass on the ground, it has pink in it...
Last edited by keropi; 08-21-2012 at 07:01 AM.
The datasheet recommends 100 nF, and also specifies the input impedance to be 800k ohm. Together they make a high-pass filter corner frequency of 2 Hz... This is PLENTY low enough. You can use higher capacitors, but it won't make any difference.
You REALLY should follow the recommendations of: putting a 100 nF decoupling capacitor across GND and 5V, also a larger electrolytic, like 22 uF across them as well to minimize power supply ripple (not as necessary). They also specifically say to not leave the control signals floating! GND DISABLE and BYPASS.
Last edited by Calpis; 08-21-2012 at 02:14 PM.
those who can't make, mod
Thanks for the input Calpis but keep in mind that on the 2nd attempt I do have 100nf ceramic caps in all inputs, all extra pins are grounded together and there is a 100nf cap between GND+VCC , just like the rough drawing I did before:
it seems to me that it needs some slight tweaking to get it perfect on the PCE... but I have no idea what to try next
I don't think you should GND NC. Also your 100 nF decoupling is probably not effective (can't see how you wired it), you should solder the capacitor directly to pin 9 (GNDed) and pin 10.
The only way to know for sure what to do next is to use an oscilloscope on the signals... That way the levels could be verified in and out of the amplifier. I think they are fine though.. The interference is low frequency like a GND loop. Does the interference stay static or does it move around? Try larger capacitors at the input and see if that clears it up. If it doesn't I suggest decoupling 5V with the 22 uF cap.
those who can't make, mod
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