DipakP

Help with Doubler versus Scaler?

Hello All,
This Is my first post to this tremendous community. I am relatively new the this venue but have a home theater in place. I will list my equipment at the bottom of this thread. My question is, given my setup, what is the best option for maximal picture quality, a doubler or a scaler?
What are the differences between them and can both be used at the same time?
Thanks in advance for your help.

Proceed AVP-S
Cal Audio CL2500 dvd/cd unit
proceed amp-5
proceed hpa-2
revel f-30's front right and left
revel c-30 center channel
rel storm III subwoofer (used with the fronts via neutrik connect and not independently)
Faroudja vp 201 doubler
Electrohome Marquee 8000 projector
Da-Late cinematech 1.3 gain 16:9 102" diag screen
b&w dm 603 series III for rears

D. Panigrahi, MD

scott>sau

Dr. Panigrahi,
Line doublers, and video scalers are just synonyms for advanced digital scan converters. Line doublers are worth using.
"Scan Rates and HDTV - The ability of a projector to display HDTV depends on its scanning capability. For example for a projector to line double standard NTSC signals (480i at 15.75kHz horizontal) from DVD, VCR or cable/ Satellite to 480p, requires 31.5 KHz of horizontal scan rate and enough bandwidth to handle twice the picture information. HDTV at 1080i requires a horizontal rate of 33.75 KHz and 50 MHz bandwidth. 720p requires a horizontal rate of 45 KHz with 50 MHz bandwidth." (www.crtcinema.com)
The above quote demonstrates the need for a doubler to get proper scan rates. I checked around and the Electrohome Marquee 8000 projector can accept a doubler, but does not have an internal doubler. I just wanted to make sure you needed it. As far as going to a line quadrupler and if this CRT can accept one, possibly try jumping to the "Display Devices" threads in this forum.

Greg_R

If your DVD player outputs a progressive format (480p), the line doubler is not worthwhile. A scaler is (potentially) capable of driving images with significantly higher resolutions (720p, etc.). For some digital PJs, the scaler can output exact resolutions (avoiding pixel aliasing). You do not want to drive 480i to your current PJ (the scan lines will be very obvious). A multiple of 480 is usually suggested (720p, 960p, etc.). Your CRT may be able to do 720p @ 48Hz w/o too much trouble.

I would hook up your DVD player to a scaler and then drive your EHome 8000 via RGB inputs. Key Digital has recently released their HD-Leeza scaler (which scales everything, including HD). Home Computers make excellent scalers and DVD players (if you have the technical know-how).

Greg
My DVD Collection

Guy Kuo

Both a doubler and scaler perform conversion of interlaced video to progressive scan video. A scaler adds the additional flexibility of scaling the resultant scan lines of video to other scan rates. A doubler can only output 480P.

A Marquee 8000, when properly set up, should produce a fine enough electron beam dot to use a higher line density than provided by a doubler. Depending on your screen's aspect ratio, I would expect it to produce good results with

4:3 screen (Quad rate AKA 960 Progressive lines)
16:9 screen (Triper rate AKA 720 Progressive lines)

Both are higher than the 480P which your doubler is currently supplying. The trick with CRT projectors is to supply a progressive scan signal with enough resolution such that the scan lines of the projector just barely touch each other vertically. A doubler simply doesn't give a good match to a Marquee 8000. Going to a scaler can provide you with a more continuous image and higher light output.

There are caveats:

1. Going to a scaler will require the projector be completely realigned and converged. Judging from you asking this level of question, I suspect you will need to have a professional installer or ISF technician perform that for you. Expect $500 or so of cost for the calibration. It may seem an exhorbitant fee, but the instrumentation and skill of a professional yields a result better than an inexperienced DIYer will be akin to the difference between an R1's first skin closure and that of a plastic surgeon.

2. Your Marquee 8000's age and condition can have an effect on its ability to sharply focus its electron beam. If you have over 5,000 or so hours on the unit, the tubes may well be worn beyond the point at which it can focus sharply enough to use the additional scan lines provided by a scaler. In such case, retubing the projector would be approx $2500. Most likely, you are not in this situation. As a rough check, go up to your screen and check if you can see separate scan lines. If so, you should be fine going to a scaler.

Guy Kuo
Director - Imaging Science Foundation Research Lab