[time-nuts] Extron ADA 6 as 1/5/10 MHz DA
Charles P. Steinmetz
charles_steinmetz at lavabit.com
Wed May 22 13:59:37 EDT 2013
Following the recent discussion of using the Extron ADA 6 as a
distribution amplifier for 1/5/10 MHz reference signals, I dug out
the schematic of the amplifiers and typed up my notes re:
modifications (see attached).
Note that the ones I have are "plain" ADA 6's, not "MX" or
"MX-HV." I do not know if the MX or MX-HV units use this circuit or,
if they do, if the component numbers are the same. However, the
gain-switching circuitry is present on the "plain" ADA 6 PC cards
(but the switch itself is not), which leads me to believe that at
least the MX version was built with this same card.
There may be other Extron video DAs that use this circuit -- in
particular, models that have a PC card parallel to the rear panel and
mounted to it by the BNC connectors may do so.
There is another, discrete design that Extron apparently produced at
the same time, one example of which is the ADA 3 180. This design
cannot drive 50 ohm loads to +13dBm (1 Vrms) without severe
distortion (negative peak clipping), so you need to attenuate the
typical 1 Vrms input signal 6 dB to stay out of
clipping. Unfortunately, there is no easy way to modify this design
to drive +13dBm into 50 ohms (and, IMO, there is a lot not to like
about it for any use, including RGB video). I have a schematic of
that circuit, too, if anyone needs it.
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