Shinybow HD54-70 Review

The HD54-70 active matrix switch by Shinybow is shown above (case removed).  Inside, the product has three boards.  The front panel board is hidden in the image.  It contains the toggle buttons and control microprocessor.  The back panel board has the AV connectors.  The back panel board contains all the video & audio circuitry.

Construction:

    The video board is a standard two layer circuit board with fairly good ground & power routing.  The assembly quality appears to be standard quality, there was some stray hot glue trails, but they did not interfere with the electrical operation.

    The AV connectors are of average quality tin coated RCA connectors. 

Design:

    The active circuitry for the video path consists of two Asics (labels were removed) and an output current driver.  Investigation revealed that the asic was providing the matrix switching of video and audio as well as the required voltage gain.  The output current driver provides the current gain and source impedance for the video outputs.

    The performance of the asic can not be determined from the component datasheets, since the labels had been scraped off the device. 

    The output current driver is a single transistor configured as an emitter follower.  Unfortunately, this type of circuit is not highly linear over large voltage ranges.  It will introduce a fair amount of differential gain distortion.

Testing:

    The first thing we tested was the input resistance of the switch.
        Ron : 77.1 Ohms        (Pretty close to an ideal 75 ohms, most likely the contact resistance of the tin RCA jacks accounts for the deviation)

    Next we tested the bandwidth of the switch.  We used a 720p HDTV multiburst pattern so the test is a perfect representation of actual use.  The scope image shows the 30 Mhz section of the multiburst.

Top signal is source, bottom is HD54-70 output.  2 ft cables are used on both input and output.

The signal is 7.3 dB down at 30 Mhz.  At 15 Mhz, it is 5.2 dB down.  The actual measured -3 dB bandwidth was 9 Mhz.  According to their manual, they claim to have 250 Mhz!

This bandwidth is not even good enough for 480p.  480i should be ok. 

Here are the pictures taken of a portion of the multiburst image to illustrate the problem.  The camera used can actually capture the image very well, but enough to see how the fine line are completely missing on the shinybow output

Ideal image (if camera could capture properly)

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Direct connection to monitor

Connection through HD54-70

Notice how the lines disappear as the frequency increases.

Finally, we tested the crosstalk performance of the HD54-70.  Crosstalk is the amount of noise that an unselected signal can insert onto the desired signal.  It is basically interference.

The setup we used was white field on one input, and the multiburst (720p) on another.  The image below is the scope capture of the white field.  It should have less than 5mV of noise, since that is the noise floor of our test equipment.

The HD54-70 had over 90mV of interference from the unselected input.  This was with only a 400mV interfering signal!  With a full range inputs on the other channels as well, this could be even worse.  At 90mV, that is only 17dB isolation!  Shinybow claims >50dB in their manual.